Ontogenetic skull development and paleobiology of the tragulid Dorcatherium naui (Mammalia: Artiodactyla) from the early Late Miocene hominid locality Hammerschmiede (Germany)

Ontogenetic skull development and paleobiology of the tragulid Dorcatherium naui (Mammalia: Artiodactyla) from the early Late Miocene hominid locality Hammerschmiede (Germany) | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Ontogenetic skull development and paleobiology of the tragulid Dorcatherium naui (Mammalia: Artiodactyla) from the early Late Miocene hominid locality Hammerschmiede (Germany) Josephina Hartung, Madelaine Böhme This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9029355/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 9 You are reading this latest preprint version Abstract Ontogeny describes the individual developmental history of an organism across its lifetime. Comparative ontogenetic approaches can be applied to closely related taxa and provide a powerful framework for investigating evolutionary changes in morphology, life history, and developmental timing between fossil and extant relatives. This approach is particularly informative for the fossil chevrotain Dorcatherium naui and the extant African water chevrotain Hyemoschus aquaticus , which are consistently recovered as sister taxa in phylogenetic analyses. Until recently, the fossil record of D. naui was sparse, despite the fact that this species represents the type species of one of the most frequently cited fossil tragulid genera. Here we demonstrate that the life history and ecological characteristics, as sexual maturity, sexual size dimorphism, reproduction rate and maximum life span, inferred for fossil D. naui share numerous similarities with those of extant H. aquaticus , supporting a close phylogenetic relationship between both taxa. However, we find that D. naui might have lived in more open riparian woodlands, compared to its extant relative. In addition, our results provide evidence for a paedomorphic condition of cranial ornamentation in H. aquaticus relative to D. naui . Together, these findings support the use of H. aquaticus as a suitable modern analogue for fossil tragulids in general, and for Dorcatherium in particular. Moreover, the observed similarities between both taxa are consistent with a paleobiogeographic scenario involving a dispersal event of an ancestral form morphologically similar to D. naui from Eurasia into Africa during the Late Miocene, followed by independent evolution culminating in the emergence of H. aquaticus during the Pliocene. skull morphology population studies Artiodactyla life history habitat analysis Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Introduction Tragulids are a peculiar group of small ruminants and the sister group to Pecora. The group originated in Asia during the Late Eocene (Métais et al. 2001 ; Rössner 2007 ; Hassanin et al. 2012 ; Sanchéz et al. 2018 ; Mennecart et al. 2021 ) and survived until today, where they live in Asia and Africa. The extant taxa comprise three genera Moschiola , Tragulus (both from Asia), and Hyemoschus (from Africa). The fossil record shows, that tragulids were much more diverse during the Miocene (Rössner 2007 ; Khan and Akhtar 2013 ; Rössner and Heissig 2013 ; Sanchez et al. 2018; Koufos 2020 ; Guzmán and Rössner 2021 ; Musalizi et al. 2023 ) than today, with Dorcatherium and the type species D. naui being the most frequently studied genus and species; mainly known from central and southwestern Europe (e.g. Alba et al. 2011 ; Rössner and Heissig 2013 ; Aiglstorfer et al. 2014 ; Mennecart et al. 2018 ). However, the quality of the fossil record of D. naui was relatively limited comprising primarily teeth and isolated postcranial material, preventing detailed ontogenetic investigations. This situation has changed with the discovery of the Hammerschmiede hominid site (Böhme et al. 2019 ), yielding abundant skulls, partial skeletons, and a plethora of mandibles and postcranial bones (Hartung and Böhme 2022 ; Lechner and Böhme 2025 ), allowing now a detailed assessment of the paleobiology of this species. Fossil skulls represent a key source of information for understanding growth trajectories and sexual variation. The development of the artiodactyl skull follows a general vertebrate pattern (Whitmore 1953 ; Moyano et al. 2019 ), but in Pecora, the cranial morphology is strongly influenced by the development of headgear and can differ greatly among the sexes (Davis et al. 2011 ; Nasoori 2020 ) depending on body size (Calamari 2016 ) or whether females wear head gear at all (e.g. Bovidae Lundrigan 1996 ; Stankowich and Caro 2009 ). However, tragulids do not wear any type of head gear, but a strong ornamentation of the skull is visible in males of D. naui (Hartung and Böhme 2022 ). D. naui and the extant African water chevrotain H. aquaticus are recovered as sister taxa in phylogenetic parsimony analyses (Sánchez et al. 2015 ; 2018). Based on this close relationship, we investigate similarities between these two species regarding the overall biology and ecology. Recently, the cranial development of D. naui and the fossil tragulid Dorcabune crassum (genus affiliation according Musalizi et al. 2023 ), regarding the ornamentation of the skull with respect to sexual dimorphism was studied in Hartung and Böhme ( 2022 ). The study includes in total three skulls of males and females from Hammerschmiede and Eppelsheim (Germany). Here we study 10 additional well-preserved complete and partial skulls of D. naui from the Hammerschmiede locality and establish an ontogenetic series respecting males and females for the first time. We will test the hypothesis whether the ornamentation of the skull of male D. naui undergoes ontogenetic changes and we will discuss the correlation of the development of cranial ornamentation with the onset of sexual maturity. We than compare the data to the already known series of H. aquaticus studied in Hartung and Böhme ( 2024 ). Moreover, we analyze a set of isolated teeth and mandibles to conduct a mortality analysis and estimate the survivorship of D. naui from Hammerschmiede. Using this data set, we also calculate the mean body mass for males and females to test whether a sexual size dimorphism is present in D. naui . We use this data to give a comprehensive overview of the paleobiology and life history patterns. Geological and paleoenvironmental setting of the Hammerschmiede The Hammerschmiede is a clay pit belonging to the municipality of Pforzen. It is located in the southern part of the Northern Alpine Foreland Basin close to the town of Kaufbeuren (Allgäu, Bavaria). The locality contains fluvial and alluvial deposits from the Middle-to-Late Miocene Upper Series , the youngest lithostratigraphic unit of the Upper Freshwater Molasse (Doppler 1989 ; Doppler et al. 2005 ). Vertebrate finds are mainly restricted to the two fluvial channels HAM4 and HAM5 (Kirscher et al. 2016 ). The 11.58 Ma old HAM4 channel represents a larger meandering stream of up to 50 m width, whereas the 11.62 Ma old HAM5 channel is a smaller meandering rivulet or creek with a width of four to five meters (Lechner and Böhme 2025 ). Excavations are running since 2011 and until 2024 about 1.000 metric tons of lower point-bar and channel-lag sediments have been excavated in HAM4 and about 300 metric tons of sediment in HAM5 (Lechner and Böhme 2025 : Table 1 ). The locality is famous for its rich and diverse faunal content including bivalves and gastropods (Schneider and Prieto 2011 ), fishes, amphibians, reptiles, small mammals, large mammals (Fuss et al. 2015 ; Hartung et al. 2020 ; Kargopoulos et al. 2021a , b ; Hartung and Böhme 2022 ; Kargopoulos et al. 2022a , b ; Lechner and Böhme 2022 , 2023 ; Kampouridis et al. 2024 ; Kargopoulos et al. 2024 ; Böhme and Prieto 2025 ; Kargopoulos et al. 2025 ), and birds (Mayr et al. 2020a , b , 2023 ). It furthermore is renowned for the discovery of the associate skeletons of the hominid Danuvius guggenmosi (Böhme et al. 2019 , 2020 ) and the second syntopic hominid Buronius manfredschmidi (Böhme et al. 2024 ). The palaeoenvironmental conditions during deposition of both channels differ in respect to the openness of the surrounding vegetation (Lechner and Böhme 2025 ). The larger meandering HAM4 river has been flowing in a relatively open and fire-prone landscape, evidenced by higher abundance of micro- and macro-charcoal, less abundant rodents (dominated by the tree squirrel Csakvaromys ) and insectivore mammals, more abundant lagomorphs and scincomorph (lizards, scincs) reptiles. In contrast, the small HAM5 rivulet contains less charcoal, more rodents (dominated by the fossorial Anomalomys ) and insectivores, less abundant lagomorphs and scincomorphs, and is interpreted to be surrounded by more closed forest environment, relative to HAM4 (Lechner and Böhme 2025 ). This interpretation is supported by the syntopy of two hominids in HAM5 (Böhme et al. 2019 , 2024 ) and the presence of a chalicotheriine chalicothere, rather than schizotheriine chalicothere in HAM4 (Kampouridis et al. 2024 ). Material and methods The investigated material comprises 14 partial and complete skulls of D. naui . 13 are from the earliest Late Miocene Hammerschmiede locality (Tab. 1) and one is from the Middle to Late Miocene locality of Eppelsheim (both from Germany). The skulls GPIT/MA/17690, GPIT/MA/18000-01, SNSB-BSPG 2020 XCIV-3500, SNSB-BSPG 2020 XCIV-8518, SNSB-BSPG 2020 XCIV-2298, SNSB-BSPG 2020 XCIV-3566, SNSB-BSPG 2020 XCIV-8793, SNSB-BSPG 2020 XCIV-8970, GPIT/MA/17615, GPIT/MA/17841, and SNSB-BSPG 2020 XCIV-18870 were excavated from level HAM4. The level HAM5 produce the skull SNSB-BSPG 2020 XCV-474, as well as the skull fragments SNSB-BSPG 2020 XCV-380 and SNSB-BSPG 2020 XCV-357, which belong to one individuum and were excavated in close association. All Hammerschmiede specimens are presently housed in the Palaeontological collection of the University of Tuebingen (GPIT). GPIT/MA/17690 and GPIT/MA/18000-01 were already published in Hartung and Böhme (2022) and µCT scans of both specimens are available for study. Another complete skull with attached mandibles NHMUK PV OR 40632 from the type locality of D. naui , Eppelsheim, is housed at the NHMUK in London and was published in Kaup (1839b, a) and described in detail in Hartung and Böhme (2022). The skull terminology follows Whitmore (1953) and Zietzschmann et al. (1943) and the dental nomenclature follows Bärmann and Rössner (2011). Table 1: Skulls of Dorcatherium naui from the late Miocene locality of Hammerschmiede used for this study. Collection number Description Stratigraphic age Sex Wear stage SNSB-BSPG 2020 XCV-474 Complete skull HAM5 m 6 SNSB-BSPG 2020 XCV-357, 380 Complete skull HAM5 f 6 SNSB-BSPG 2020 XCIV-18870 Complete skull HAM4 m 6 SNSB-BSPG 2020 XCIV-3500 Complete skull HAM4 m 3-4 GPIT/MA/17690 Complete skull HAM4 m / GPIT/MA/17615 Partial skull, posterior part of skull roof HAM4 m / SNSB-BSPG 2020 XCIV-8518 Partial skull, skull roof HAM4 m / GPIT/MA/17841 Complete skull HAM4 f 6 GPIT/MA/1800-01 Complete skull HAM4 f 6 SNSB-BSPG 2020 XCIV-8970 Complete skull HAM4 f 4 SNSB-BSPG 2020 XCIV-2298 Posterior part of skull, occiput HAM4 f / SNSB-BSPG 2020 XCIV-3566 Posterior part of skull, occiput HAM4 f / SNSB-BSPG 2020 XCIV-8793 Posterior part of skull, occiput HAM4 f / In addition to the Hammerschmiede skulls 109 age-diagnostic mandibles and isolated teeth from level HAM4 and 17 teeth and mandibles from level HAM5 (all excavated between 2011 and 2024) were measured to investigate the mortality statistics, the survivorship rates, and the body mass distribution of D. naui . The studied dental material includes the following numbers of tooth positions: 40 M3, 26 dP4, 28 m3, and 24 dp4 from level HAM4, as well as two dP4, 11 M3, two dp4, and seven m3 from level HAM5 (teeth preserved within skulls and mandibles are included). Additionally, the length of the m1-m3 and of the m2 were measured to calculate the body mass (see below). In total, 13 mandibles from HAM4 and three mandibles from HAM5 were used. The assignment of the upper teeth into nine wear stages follows Hartung and Böhme (2024) with wear stage 0 being neonate, right after birth, wear stage 1 to wear stage 5 representing the juvenile stage, wear stage 6 and 7 representing the adult stage, and wear stage 8 including senile specimens (Fig. 1). The classification of the lower teeth into wear stages follows the same principle of the upper teeth and is based on the wear of the m3 and dp4 as well. At wear stage 0 the dp4 is erupted but unworn. In isolated dp4, the root is not preserved and only the thin enamel cap is visible. At wear stage 1, the dp4 is still unworn but the enamel is thicker than in w0 and a root is preserved. Wear stage 2 is characterized by the metaconid and the protoconid being slightly worn but the anteriolingual and anteriolabial as well as the entoconid and hypoconid being unworn. At wear stage 3 all cones show a wear facet and at wear stage 4 these cones are medium worn. At wear stage 5 the dp4 is heavily worn and the m3 is erupted but unworn. According to Hartung and Böhme (2024) we assume that the dp4 is shed at wear stage 6 and the m3 is worn at the metaconid, protoconid, as well as at the entoconid and hypoconid. The talonid basin (entoconulid and hypoconulid) is still unworn. At wear stage 7 all cones are medium worn and the talonid basin shows slight to medium wear facets. Wear stage 8 represents senile individuals with the m3 being highly worn so that in some specimens the selenodont pattern is almost not recognizable. For body mass estimates (in kg) on the combined HAM5 and HAM4 sample of mandibles we use the log-transformed regressions of Janis (1990) for lower molar length (m1-m3) and length of m2 for “ruminants only”: [log(BM) = 3.337 × log(SLML/10) + 1.118], [log(BM) = 3.352 × log(LMRL/10) − 0.604]; with SLML being the length of the m2 (mm) and LMRL being the length of the m1-m3 (mm). Mortality and survivorship were calculated from the minimum number of individuals (MNI), based on the abundance of left and right M3 and dP4, as well as m3 and dp4, for each wear stage, respectively. Survivorship was derived directly from the MNI per wear stage relative to the total number of individuals. A table including the exact measurements is provided in the appendix (SF1). The skulls GPIT/MA/17690, GPIT/MA/18000-01, SNSB-BSPG 2020 XCIV-3500, SNSB-BSPG 2020 XCIV-8970, SNSB-BSPG XCIV 2020-8518, SNSB-BSPG 2020 XCV-474, as well as GPIT/MA/17841 were scanned at the 3D Imaging Lab of the Senckenberg HEP at the Eberhard Karls University of Tübingen, Germany. The scans were acquired using the Nikon XTH 320 Reflection Target. For GPIT/MA/17690, the acceleration voltage was set to 190 kV and the resolution was 177 µA. A total of 4476 images were recorded and a 1 mm copper filter was inserted. For GPIT/MA/18000-01, a helical scan was acquired. The acceleration voltage was 195 kV and the resolution was set to 70 µA with a total of 7932 images. SNSB-BSPG 2020 XCIV-3500 and SNSB-BSPG 2020 XCIV-8970 were scanned with an acceleration voltage of 210 kV and a resolution of 90 µA. The number of total images was 4476 and a 0.1 mm copper filter was used for both specimen each. SNSB-BSPG XCIV 2020-8518 was scanned at 215 kV and 75 µA and SNSB-BSPG 2020 XCV-474, as well as GPIT/MA/17841 were scanned at 210 kV and 78 and 80 µA respectively. The scans were acquired using a 0.1 mm copper filter as for the other scans and a total number of 4476 images were taken. Images were processed using VG Studio Max 3.4.1. All scans are available at www.morphosource.org/projects/000810219?locale=en. Abbreviations GPIT: Geologisch-Paläontologisches Institut Tübingen; NHMUK: Natural History Museum of London; SNSB-BSPG: Staatliche Naturwissenschaftliche Sammlungen Bayerns-Bayerische Staatssammlung für Paläontologie und Geologie Systematic Paleontology MAMMALIA (Linnaeus 1758) ARTIODACTYLA (Owen 1848) RUMINANTIA (Scopoli 1777) TRAGULIDAE (Milne-Edwards 1864) Genus Dorcatherium (Kaup 1833) Type species: Dorcatherium naui Kaup, 1833 (Kaup 1833) Dorcatherium naui Kaup, 1833 (Kaup 1833) Locality and age of studied specimens: early Late Miocene locality of Hammerschmiede level HAM5 (11.62 Ma) and HAM4 (11.58 Ma) and middle to late Miocene locality of Eppelsheim in Germany. Referred Material: Partial and complete skulls from Hammerschmiede: GPIT/MA/17690 (HAM4), SNSB-BSPG 2020 XCV-474 (HAM5), SNSB-BSPG 2020 XCIV-3500 (HAM4),SNSB-BSPG 2020 XCIV-8518 (HAM4), GPIT/MA/17841 (HAM4), GPIT/MA/18000-01 (HAM4), SNSB-BSPG 2020 XCV-357, 380 (HAM5) SNSB-BSPG 2020 XCIV-8970 (HAM4), SNSB-BSPG 2020 XCIV-2298 (HAM4), SNSB-BSPG 2020 XCIV-3566 (HAM4),SNSB-BSPG 2020 XCIV-8793 (HAM4), SNSB-BSPG 2020 XCIV-18870 (HAM4) GPIT/MA/17615 (HAM4), as well as the complete skull NHMUK PV OR 40632 from Eppelsheim. 117 teeth from level HAM4 and 22 teeth from level HAM5 including teeth preserved within skulls as well as in mandibles (for details see SF1 in the appendix). Remarks: The skulls and teeth can be attributed to D. naui based on characters of the dentition if applicable, such as (I) a high degree of selenodonty having a reduced external postmetacristid (sensu Bärmann and Rössner 2011) in the lower molars and well-developed cristids and flat main cusps (sensu Sánchez et al. 2011), (II) prominent sickle-shaped cones and conids (sensu Rössner and Heissig 2013) in combination with (III) the presence of the Dorcatherium-platform in the lower molars (sensu Alba et al. 2014), (IV) a complex posterior valley of the p4 (sensu Aiglstorfer et al. 2014), (V) lateral facing orbitae, (VI) prominent nuchal tubercle, and (VII) the presence of an occipital crest (Hartung and Böhme 2022). In addition to dental characters or if no teeth are preserved, the following characters apply, such as (A) well-developed parietal plateau, (B) well-developed frontoparietal bulges in males, (C) prominent nuchal tubercle, and (D) less-developed nuchal crests (Hartung and Böhme 2022). Description and comparison Sexual dimorphism in D. naui To investigate the ontogenetic skull development of D. naui , the specimens were separated into males and females based on characters published by Hartung and Böhme (2022). Males possess a unique skull morphology characterized by (I) a broad, concave and laterally expanding skull roof formed by the anterior frontal called the frontal plateau, (II) presence of frontoparietal bulges enclosing a well-developed parietal plateau, (III) a prominent, flat, and broad sagittal crest, (IV) large part of occipital participating in the formation of the sagittal crest, (V) strongly developed nuchal crests, (VI) large and prominent nuchal tubercle, (VII) laterally expanding part of ventral squamosal with only a slight depression, and (VIII) large saber-like upper canines. Females in contrast show delicate and fine cranial crests, no parietal plateau, and rudimentary, small upper canines (Hartung and Böhme 2022). GPIT/MA/17690 shows well-developed frontoparietal bulges enclosing a clearly constricted parietal plateau and a well-marked sagittal crest (Fig. 2A and 3A) and was already described in Hartung and Böhme (2022) as male. The same applies for NHMUK PV OR 40632 (Fig. 2C and 3C) which furthermore possesses large saber-like upper canines. SNSB-BSPG 2020 XCIV-3500 and SNSB-BSPG 2020 XCV-474 are comparable in their features with NHMUK PV OR 40632 and GPIT/MA/17690 but they are much more compressed dorsoventrally so that the bulges and crests appear more flattened (Fig. 2B, 2D and 3B, 3D). The frontal plateau is still enclosed by the frontoparietal bulges. The sagittal crests, as well as the nuchal crests are well-developed. Therefore, SNSB-BSPG 2020 XCIV-3500 and SNSB-BSPG 2020 XCV-474 are male specimens as well. GPIT/MA/17615 and SNSB-BSPG 2020 XCIV-8518 are morphologically very similar by possessing very fine and flat parietal bulges as typical for males (Fig. 2E and 3E). They appear much flatter than in SNSB-BSPG 2020 XCIV-3500 and SNSB-BSPG 2020 XCV-474. The frontal bulges are delicate but still visible in GPIT/MA/17615 as well as in SNSB-BSPG 2020 XCIV-8518 (Fig. 2E and 3E). GPIT/MA/18000-01 was published as female (Hartung and Böhme 2022) based on fine and delicate temporal lines, sagittal crests, and nuchal crests (Fig. 2G and 3G). Moreover, a small canine alveolus supported this statement. Like this specimen, the complete skull SNSB-BSPG 2020 XCIV-8970 (Fig. 2J and 3J), SNSB-BSPG 2020 XCIV-18870 (Fig. 2I and 3I), and GPIT/MA/17841 (Fig. 2F and 3F) are females as well. SNSB-BSPG 2020 XCV-357 and SNSB-BSPG 2020 XCV-380 (Fig. 2H) from level HAM5, are compressed dorsoventrally but the features of the skull are still visible. The temporal lines are fine confining in a narrow sagittal crest. The sagittal crest appears very high in lateral view (Fig. 3H); however, this is probably caused by compression. Therefore, this individual is also a female. The partial skulls SNSB-BSPG 2020 XCIV-2298 and SNSB-BSPG 2020 XCIV-8793 preserve the posterior part of the skull roof with a fine sagittal crest and temporal lines, typical for females. SNSB-BSPG 2020 XCIV-3566 preserves the left part of the parietal above the orbit and shows no bulges, but instead a flat parietal plateau and a fine temporal line are present. Therefore, this specimen is a female as well. Remarks on the dentition and ontogenetic stage of the complete skulls of D. naui The two ontogenetic youngest skulls containing teeth are the complete skulls SNSB-BSPG 2020 XCIV-3500 and SNSB-BSPG 2020 XCIV-8970 of wear stage 3-4 and wear stage 4 respectively. SNSB-BSPG 2020 XCIV-3500 exposes teeth from dP2–M2 on both sides (Fig. 4C). SNSB-BSPG 2020 XCIV-8970 (Fig. 4H) contains the right upper tooth row fromdP2 to the partially preserved M1. The teeth are brachyselenodont and contain a strong buccal relief. In SNSB-BSPG 2020 XCIV-3500, the part of the maxillary containing the canine is not preserved and the M3 is not formed yet, but a pocket is visible. In SNSB-BSPG 2020 XCIV-8970, the part lying mesial to the dP2 is missing and the distal half of the M1 and further teeth are not preserved. In occlusal view, the dP2 and dP3 are longer than wide containing three cones, which increase in size from mesial to distal. The dP2 is much more elongated than the dP3. The cones are oriented slightly buccodistally and especially the metacone and metaconule are pointing into buccodistal direction. In the dP2, the styles are weakly developed and in the dP3 the mesostyle is well-developed. The protocone and the metaconule are larger in the dP3 than in the dP2 and the dP3 contains a faint posterior cingulum that continues beneath the protocone. The dP4 is molariform and medium-worn in SNSB-BSPG 2020 XCIV-3500 and heavily-worn in SNSB-BSPG 2020 XCIV-8970. It contains strong para-and mesostyles. A strong lingual cingulum is visible and the postprotocrista does not reach the premetaconulecrista. It is smaller than the M1 and M2. The M1 of SNSB-BSPG 2020 XCIV-3500 is medium-worn and the M1 of SNSB-BSPG 2020 XCIV-8970 is heavily-worn. The M2 of SNSB-BSPG 2020 XCIV-3500 is slightly worn. The molars are almost as long as wide. They contain strong para-and mesostyles and have a well-developed, continuous lingual cingulum reaching from the distal side of the metaconule to the mesial side of the protocone. The postprotocrista is bent mesially and does not reach the premetaconulecrista. Based on the characteristics of the dentition and the cranial morphology, SNSB-BSPG 2020 XCIV-3500 represents a juvenile male between wear stage 3 and 4. SNSB-BSPG 2020 XCIV-8970 is a female skull of almost the same age representing wear stage 4. A detailed description of the permanent dentition of NHMUK PV OR 40632 and GPIT/MA/18000-01 was already published in Hartung and Böhme (2022). In NHMUK PV OR 40632, as well as in GPIT/MA/18000-01 and SNSB-BSPG 2020 XCIV-18870 the M3 is moderately worn representing wear stage 6, indicating that these specimens were about the same age (Fig. 4). In SNSB-BSPG 2020 XCV-357 from level HAM5 the M3 is slightly worn, fitting into wear stage 6 as well but being slightly younger than the skull from London and the adult female from level HAM4 of Hammerschmiede similar to SNSB-BSPG 2020 XCIV-18870. SNSB-BSPG 2020 XCV-474 and GPIT/MA/17841 are also adult specimens at wear stage 7 and 6 respectively, but in both of them the M3 is more worn (heavily worn in SNSB-BSPG 2020 XCV-474) than in the skull from London and GPIT/MA/18000-01, representing thus the oldest individuals of this ontogenetic series. In contrast, GPIT/MA/17690 preserves no teeth to determine the age, however the strong ossification, closed sutures, and the well-developed frontoparietal bulges indicate that the individual was adult. Accordingly, in SNSB-BSPG XCIV-2020 8518 the open midline suture between the parietals and the flat and faint frontoparietal bulges show, that this specimen was juvenile and compared to the still markable parietal bulges of SNSB-BSPG 2020 XCIV-3500 is even younger than the latter, probably corresponding to an early wear stage 3. In females of D. naui , the development of cranial crests is thus not as strongly correlated with ontogeny as in males. Comparative ontogenetic skull development of D. naui and the extant H. aquaticus In extant tragulids such as H. aquaticus , which is often used as a comparison to fossil tragulids, males also show well-developed large, saber-like upper canines in contrast to females, where the upper canines are reduced, similar to fossil tragulids (Rössner 2007). However, cranial ornamentation varies among adult males and females of this species (Hartung and Böhme 2024) and in the other extant tragulid genera, Moschiola and Tragulus , the cranial crests are reduced (Guzmán 2018; Mennecart et al. 2018 and own observations). Therefore, in the fossil tragulid D. naui the cranial ornamentation is much stronger developed than in H. aquaticus (fig, 1 and 2 in Hartung and Böhme 2024). The sagittal crest and the nuchal crests are comparable in their morphology to H. aquaticus , but they are much more constricted and offset in D. naui . The largest difference regarding cranial morphology of both species are the remarkable frontoparietal bulges of D. naui , which are formed by the temporal lines on the parietal and an extension of the latter onto the frontal, anterior to the orbit. They are large, bony bulges, and form the parietal part which constricts a parietal plateau. These bulges only develop in males of D. naui and are already present at wear stage 3-4 in SNSB-BSPG 2020 XCIV-3500 (Fig. 2D and 3D) or even earlier at an early wear stage 3 (SNSB-BSPG 2020 XCIV-8518, Fig. 2E and 3E). Cranial ornamentation in H. aquaticus are less remarkable at wear stage 3-4 (Hartung and Böhme 2024, fig. 1 and 2) where only the temporal lines are slightly enhanced and confine to form a sagittal crest. Fig. 5 shows that parietal bulges are pneumatized at wear stage 3-4 (SNSB-BSPG 2020 XCIV-3500, Fig. 5C) up to wear stage 6 (SNSB-BSPG 2020 XCV-474, Fig. 5B) showing a spongiose bone matrix surrounded by the external parietal bone dorsally and the internal wall of the latter (Fig. 5A, C, and D). These bulges are probably well-developed and pneumatized even in younger individuals, but adequate specimens preserving teeth are missing. SNSB-BSPG XCIV 2020-8518 preserves no teeth but might be younger than SNSB-BSPG 2020 XCIV-3500 based on flatter parietal and frontal bulges. It is noticeable that these structures are visible despite the dorsoventral compression of the specimen (compare Fig. 2D and 2E). Subadult, male D. naui , SNSB-BSPG 2020 XCIV-3500 and SNSB-BSPG 2020 XCIV- 8518, seem to have flatter parietal bulges and a less-developed frontal part of the bulges than the adult individuals, GPIT/MA/17690, SNSB-BSPG 2020 XCV-474, and NHMUK PV OR 40632 (Fig. 2A-C). However, these observations need to be taken with care, because of the different degrees of preservation of the fossil specimens. The parietal part of the bulges is especially visible throughout all ontogenetic stages, but the frontal part is very faint, probably due to compression. In the subadult specimens like SNSB-BSPG XCIV-2020 8518 and SNSB-BSPG 2020 XCIV-3500, a rugose surface is visible that forms the lateral part of the frontal in dorsal view (Fig. 2D and E). In contrast in females of D. naui of the same wear stage (Fig. 2J) this rugose surface is absent. The present ontogenetic series of D. naui indicates that during ontogeny an increase in size and progressive enhancement of frontoparietal bulges occurs in males of D. naui and that the latter possess strong sexual dimorphic features of the skull already relatively early in life if comparable to H. aquaticus . The bulges show allometric growth if compared to overall body size as typical for male sexual display features (Kodric-Brown et al. 2006). Females in contrast are much more similar to extant H. aquaticus by possessing delicate and fine sagittal and nuchal crests and no frontoparietal bulges. In females, the sagittal crest and crest-like temporal lines are already visible at wear stage 4 as in specimen SNSB-BSPG 2020 XCIV-8970 (Fig. 2J and 3J), and these crests are similar in development and morphology with adult specimens of wear stage 6 as in specimen SNSB-BSPG 2020 XCV-357, 380, GPIT/MA/17841, SNSB-BSPG 2020 XCIV-18870, and GPIT/MA/18000-01 (Fig. 2F-I and 3F-I). In the virtual cross sections, no pneumatization as in males is visible (Fig. 5E-G), although in specimen SNSB-BSPG 2020 XCIV-8970 (Fig. 5G) the temporal lines that form delicate crests appear like that, but the latter is caused by the lateral compression of the skull with the bone structure being distorted. This means that in contrast to males of D. naui , the cranial ornamentation of females does not develop or change in morphology during ontogeny and remarkable features like frontoparietal bulges are absent. Comparison of cranial ontogeny of Dorcatherium naui and Dorcabune crassum At present, there are only two other complete skulls known of another fossil tragulid, Dorcabune crassum . Guzmán (2018) describes a male skull of Db. crassum from Walda-2 in Germany and furthermore mentions another skull of the same species from the Upper Freshwater Molasse of Thierhaupten in Germany published by Seehuber (2015). Guzmán (2018), as well as Hartung and Böhme (2022) assign the skull from Thierhaupten to a female individual and describe a sexual dimorphism in Db. crassum that is comparable to D. naui . However, in Db. crassum , males have cranial ornamentation in form of bulges as well, but they differ in their morphology and are in general less markable if compared to D. naui . In Db. crassum , the frontal bulges are absent and only the posterior part of the parietal shows flatter bulges that confine to form a Y-structure with the sagittal crest (Guzmán 2018, fig. 4.5; Mennecart et al. 2018). This is different from D. naui , where the bulges encompass the entire parietal and continue onto the frontal to encompass a parietal plateau and cover the orbit (Hartung and Böhme 2022 and Fig. 2). In contrast, the female skull morphology of Db. crassum is rather similar to that of females of D. naui and both sexes of H. aquaticus , because it contains fine and delicate nuchal, temporal, and sagittal crests that follow the same morphology as in GPIT/MA/17841, GPIT/MA/18000-01, SNSB-BSPG 2020 XCIV-18870, as well as to SNSB-BSPG 2020 XCV-357 and SNSB-BSPG 2020 XCV-380 (all wear stage 6). Based on the wear stage of the teeth, the male skull of Db. crassum from Walda-2 is already senile, as there is no selenedont pattern visible anymore at the M3 (wear stage 8). It is therefore not directly comparable to any of the present specimens of D. naui and unfortunately the exact individual age of GPIT/MA/16790 is not known, although it can be assumed that this specimen is the ontogenetic oldest from the presented series. However, the difference in the development of the cranial ornamentation is still visible and it is very unlikely that after wear stage 6 a pattern as in Db. crassum will be present in senile males of D. naui , because the parietal and frontoparietal bulges are already well-developed and confine with the sagittal crest posteriorly. Interspecific heterochrony D. naui is closely related to the extant water chevrotain H. aquaticus . The exact relationships were studied last by Sánchez et al. (2015, 2018) were D. naui plotted as the sister taxon to H. aquaticus . However, phylogenetic relationships might have been much more complex due to the limit of the fossil record in Africa for example. Both species share similarities in cranial morphology and H. aquaticus shows the strongest cranial ornamentation among the extant tragulids, however, D . naui displays a markedly stronger and more intricate cranial ornamentation compared to the extant analogues, suggesting a heterochronic origin of this feature. To test this hypothesis, we apply the heterochrony model of Reilly et al. (1997), which investigates patterns of morphological change between ancestral and descendant taxa. For this purpose, the morphology of cranial ornamentation in Dorcatherium naui (Hartung and Böhme 2022) is defined as the “ancestral state”, whereas the cranial morphology of Hyemoschus aquaticus (Hartung and Böhme 2024) represents the “descendant state”, based on the currently available phylogenetic framework (see above). To incorporate a temporal dimension, we apply the age model established for H. aquaticus by Dubost (2016) to D. naui (Hartung and Böhme 2024) and reconstruct the ontogenetic trajectory of cranial ornamentation by establishing an ontogenetic series based on dental wear stages (Figs. 1 and 2). Dental wear stages follow the classification proposed by Hartung and Böhme (2024). We further assume that the onset of sexual maturity in D. naui and H. aquaticus was relatively similar, if not identical. This assumption allows a direct comparison of the somatic development of cranial ornamentation throughout ontogeny between both taxa. After Reilly et al. (1997) we observe a paedomorphic development of the cranial ornamentation (Fig. 6) in Hyemoschus aquaticus compared to D. naui , a truncation of the fossil ontogeny compared to the morphology of the extant analogue caused by a “deceleration” (after Reilly et al. 1997) of the development of the morphological character. This was already mentioned for Db. crassum (Mennecart et al. 2018), which likewise exhibits pronounced cranial crests that are morphologically similar to those of D. naui (Hartung and Böhme 2022). In contrast, H. aquaticus shows less developed cranial crests and bulges, as well as the absence of a parietal plateau, when compared to D. naui . We hypothesize that the onset of cranial ornamentation growth (α) is similar in both taxa, but that a higher developmental rate (−k) in D. naui results in more complex and developed cranial structures by the time developmental offset (β) is attained. It is also possible to argue for a post-displacement (positive onset, fig. 1 in Reilly et al. 1997) of the shape development, in which a delayed onset in the extant tragulid relative to the fossil one is present. In this scenario, the development of cranial crests starts earlier during ontogeny in D. naui and has therefore more time to develop. Thus, the initiation of cranial-crest growth in Hyemoschus would occur at a later time, resulting in a shortened developmental interval and reduced crest elaboration compared to D. naui (α->α 1 ). The developmental rate however, would be the same in contrast to a paedomorphosis and the onset time (β) would be similar. Weather this developmental process in D. naui is really beginning earlier if compared to H. aquaticus , cannot be conclusively said at the moment, because neonate to juvenile skulls of wear stage 0 to wear stage 2 are so far not present in D. naui or any other fossil tragulid. When comparing another fossil tragulid with well-known skulls, Db. crassum, to H. aquaticus , both taxa show greater morphological similarity to each other than to D. naui . In Db. crassum and H. aquaticus , the frontal component of the cranial bulges as well as the parietal plateau are absent. In addition, Db. crassum exhibits broader temporal lines and a more pronounced sagittal crest, forming the characteristic Y-shaped structure. This configuration has been interpreted as a hyperdeveloped condition relative to H. aquaticus according to Mennecart et al. (2018), which is consistent with a heterochronic shift involving post-displacement. Consequently, Db. crassum may reflect a heterochronic trajectory that differs from the pattern most likely inferred for H. aquaticus and D. naui . The morphological differences in the elaboration of cranial ornamentation and shape of the latter between D. naui and H. aquaticus are less-likely to be a result of hypomorphosis, because this would mean that the developmental process ends earlier in H. aquaticus , while D. naui extends even further, truncating the fossil ontogeny. Both taxa would have the same onset time, and the pathway of development would be similar, which is clearly not the case, because the cranial morphology in D. naui is different from H. aquaticus and even in juvenile male individuals of D. naui (SNSB-BSPG 2020 XCIV-3500 wear stage 3-4 and SNSB-BSPG 2020 XCIV-8518), the cranial bulges are morphologically clearly distinguishable from the extant tragulid. D. naui exhibits frontoparietal bulges that constrict a parietal plateau and form a strong broad sagittal crest (Hartung and Böhme 2022). In H. aquaticus , the temporal lines are enhanced and also the sagittal crest can be broad and strong, but the frontoparietal bulges, as well as the parietal plateau are absent. Moreover, the cranial ornamentation in H. aquaticus continues to grow even in senile specimen (fig. 2 in Hartung and Böhme 2022) and the same can be assumed for D. naui based on the morphology of GPIT/MA/17690 (Fig. 2A and 3A). Nevertheless, H. aquaticus appears unable to attain the degree of cranial complexity exhibited by D. naui and thus no hypomorphosis is present. Conclusively, D. naui already exhibits a strong sexual dimorphism relatively early in life similar to H. aquaticus , the only extant tragulid with noticeable cranial ornamentation. The development of these structures has a higher rate in the fossil relative. A comparison to other fossil subadult (wear stage 3-4) tragulids, such as Db. crassum , would be very interesting, however, no skulls of that age exist so far. It is noticeable, that the extend of cranial ornamentation of H. aquaticus varies among the sexes in such an extent, that it is not an inclusive feature to distinguish among the sexes and therefore upper canine size remains the most reliable character for sex differentiation in this species. This is a contrast to the fossils D. naui and Db. crassum and therefore comparison of skulls of Hyemoschus with D. naui as well as with Db. crassum need to be taken with care. Mortality analysis and survivorship rate of D. naui The mortality profile of D. naui individuals from Hammerschmiede was assessed based on the state of wear of the M3 and dP4, as well as of the lower equivalent m3 and dp4 according to wear stages established by Hartung and Böhme (2024). Based on the upper and lower teeth combined, in HAM4, the total number of individuals that died at a juvenile stage (w0-w5) is 22 and the number of individuals that died at an adult or senile stage (w6-w8) is 22 as well (Fig. 7). At HAM5, the sample size is much smaller and no dP4 of wear stage 0 and wear stage 1 are available. However, the pattern is similar to HAM4, because in HAM5, six individuals died at juvenile stage and seven at an adult stage respectively. The low number of juveniles, combined with the high total number of individuals (MNI=44) at HAM4, indicates that juvenile survivorship reached 50%, meaning that every second individual completes sexual maturity. The same can be attributed to the individuals from HAM5, but has to be taken with some care because of the lower sample size (MNI=13; Fig. 7). Body mass of D. naui For body mass estimates on the combined HAM5 and HAM4 sample we use the log-transformed regressions of Janis (1990) for lower molar length (m1-m3) and length of m2. Body mass according to lower molar length range from 29.1 to 35.4 kg (mean 32 kg, n=15) and for m2 length from 22.2 to 31.2 kg (mean 27.2 kg, n=21). A combined estimate using both regressions on 15 adult mandibles results in body mass between 26.2 and 31.7 kg, with a mean of 29.4 kg. The individual body mass estimates show a bimodal distribution with peaks at 28-29 kg and 30-31 kg (Fig. 7D). The female skull GPIT/MA/18000-01 contains a mandible as well, which was already published in Hartung and Böhme (2022). The estimated body mass of this female was estimated to 31.2 kg (32.6 kg using m1-m3 regression, 29.9 kg using m2 regression), suggesting to attribute the heavier mode to females and the lighter mode to male individuals. This attribution is corroborated by the even larger juvenile female skull SNSB-BSPG 2020 XCIV-08968, which includes both hemimandibles with dp1-m2. The size of their m2s are among the largest in our Hammerschmiede sample and indicate a body mass of 30.7 kg using the m2 regression (see appendix SF1). Discussion Influence of sexual dimorphism and intraspecific variability on skull ontogeny in D. naui and H. aquaticus Sexual cranial features develop in H. aquaticus within wear stage 3 between an age of 10-16 month (Hartung and Böhme 2024 and Dubost 2016). In males, development of testicle mass starts at 5-9 month (wear stage 1) and production of spermatozoa at 17-27 months during wear stage 5 (Dubost 2016). In D. naui , cranial sexual dimorphism is visible at wear stage 3-4 and it is likely that this morphology of the skull develops even earlier at early wear stage 3 as visible in the skull SNSB-BSPG 2020 XCIV-8518 (Fig. 2E) similar to H. aquaticus . The morphology of the cranial bulges in D. naui , however, is unique among both extant and fossil tragulids and differs markedly from that of H. aquaticus , even at comparable wear stages. This supports the hypothesis that the cranial structures in Hyemoschus are paedomorphic if compared to D. naui rather than being a result of post-displacement, where the development of cranial crests and bulges starts earlier but follows the same morphological trajectories (Reilly et al. 1997, Dubost 2016). However, the age of sexual maturity in H. aquaticus cannot be directly related to D. naui , but it might be possible that, following the pattern of Hartung and Böhme (2024, tab. 1 and Fig. 5), the sexual maturation starts when the cranial features develop. If this is the case, the onset of sexual maturation of D. naui could start at early wear stage 3 (or even earlier), similar to H. aquaticus , although the development of adult male sexual display features is much stronger in males of D. naui than in male H. aquaticus . In D. naui the characteristics of cranial crests are as important as the development of upper canines, as for example in specimen GPIT/MA/17690, where canines are not preserved, but the sex is unambiguous. However, the degree of variation within these crests is still unknown and needs to be evaluated in the future when more skulls are available. Limits of this study This model still leaves open questions, such as the morphology of the cranial features of fossil tragulids at wear stage 0-2, because no neonate or early juvenile skulls are available so far and it is questionable whether preservation of those specimens is even possible. Based on the strong development of cranial features in D. naui , it might be possible that some degree of ornamentation is already visible at wear stage 2, which is not the case in H. aquaticus . Moreover, the preservation of fossils, especially of juvenile individuals, is often deficient and can alter the identification of cranial structures and also makes comparison of any measurements difficult. For example, the virtual cross-sections of the fossil skulls (Fig. 5) show that bulges are present in all males: They show bone surface surrounding these structures, with pneumatized inner part. The strongest bulges are visible in GPIT/MA/17690, which is the oldest individual of the series (see description). However, in SNSB-BSPG 2020 XCV-474 from HAM5, the bulges are flattened and the inner structure is altered due to compression. Therefore, the spongiose part of the bone is barely visible, but the bony overhang is preserved, which is not the case in females, and the bulges are best visible in that specimen from external view (Fig. 2B). In GPIT/MA/18000-01, the skull roof shows longitudinal cracks due to the lateral compression, which alters the cranial morphology. However, it is clearly visible in Hartung and Böhme (2022), as well as in figure 2G that there are no such bulges visible as in males. Furthermore, age determination for extant and fossil individuals in this study follows the stages established by Dubost (2016) and subsequently adapted for fossil tragulids by Hartung and Böhme (2024). For the fossil specimens in particular, absolute individual ages are yet unknown, and the onset of sexual maturation remains uncertain and can only be inferred. Cranial ornamentation and upper canines as display features of D. naui The present ontogenetic series of D. naui indicates allometric growth pattern of the cranial ornamentation as typical for male display features (Kodric-Brown et al. 2006). Males of D. naui possess pronounced and well-developed display features of the skull already before the M3/m3 molar eruption at a relatively early ontogenetic stage at wear stage 3-4 (or even at an early wear stage 3 as in SNSB-BSPG 2020 XCIV-8518; Fig. 3E). In H. aquaticus the cranial crests (temporal lines and sagittal crest) are only fine and delicate and start to develop at wear stage 3-4, when the large upper canines already erupt. Thus, the enhancement and strong expression of this cranial trait in D. naui shows that the development of the trait might start relatively early in life, similar to the H. aquaticus . This may be because weapons or display features need to be ready as close to adult form as possible by the time they reach sexual maturity to compete successfully for mating (Calamari 2016). In H. aquaticus , sexual maturation in males starts at 5–9 months (wear stage 1) and completes at 17–27 months (wear stage 5), whereas in females sexual development starts after 10–16 months (wear stage 3) and reaches its maximum at 27 months (wear stage 5) (Dubost 2016; Hartung and Böhme 2024). The cranial features of males, however, develop at wear stage 3-4. However, it was stated in Hartung and Böhme (2024) that cranial ornamentation in H. aquaticus is not suitable for distinguishing among the sexes and might therefore not even be a display feature at all. Instead, upper permanent canines erupt at wear stage 3 when the small and cone-like deciduous upper canines are shed. This event occurs within the general time frame of sexual maturation in male H. aquaticus ; however, it cannot be considered a reliable proxy for the onset of sexual maturity alone. Maturation represents a gradual process extending from wear stage 1 to wear stage 5. In males, two main developmental milestones are observed at approximately 5–9 months (wear stage 1) and 17–27 months (wear stage 5), whereas in females major developmental changes occur between 10–16 months (wear stage 3), with full maturation reached at around 27 months (wear stage 5 according to Dubost 2016 and Hartung and Böhme 2024). In addition to the beforementioned strong cranial ornamentation, D. naui also possesses saber-like upper canines as visible in NHMUK PV OR 40632. This observation could, in turn, suggest that the intraspecific competition for females was relatively high and that the ecology of D. naui differs from H. aquaticus , possibly involving a more complex social structure than in the extant species, which lacks any hierarchical organization or strong territorial behavior and lives mainly solitary (Dubost 1975). Although, during mating season, extant males have short combats where they use their upper canines as weapons for stabbing or slashing. It might be possible that D. naui rather used frontoparietal bulges as display features than stabbing each other, leading to less fatal combat outcomes (Hartung & Böhme 2022). This would also be consistent with the theory of Calamari (2016), who states that complex sexual competition structures, like the described cranial ornamentation in D. naui , were used in non-lethal combat or ritualized male-male fights in contrast to simple structures that are commonly used for more violent fighting behavior, like the upper canines. Reproductive traits, life-history patterns, and habitats Results of the mortality analysis and the survivorship rate of the HAM4 population of D. naui (Fig. 7A, C) revealed that 50% of newborn tragulids (22 out of MNI=44) survive the juvenile stage (wear stage 0-5) and reach adulthood (wear stage 6-8). Survivorship (mortality) strongly decrease (increase) for prime adults (wear stage 6 and 7), and only one individual reached wear stage 8. In HAM5 the MNI is smaller (MNI=13) compared to HAM4, but still most individuals die at wear stage 6 similar to HAM4. The juvenile stage seems to be underrepresented in HAM5 with no individuals of wear stage 0 and wear stage 1. It is not surprising that most individuals in both horizons die at wear stage 6, because it covers a similar long period (approximately 27 Months to 4.5 years in Hyemoschus aquaticus , Dubost 2016) as all juvenile stages (wear stages 0-5) together. The relatively high survivorship of juveniles suggests that D. naui likely exhibited a low reproductive rate, potentially resulting from small litter sizes and a reduced number of reproductive events over the female life span. The litter size in Hyemoschus is very small with only one young per litter (Dubost 2016) and we assume the same for D. naui . Moreover, given the equal number of juveniles compared to adults (Fig. 7), it is possible that females of D. naui had only very few, possibly four, reproductive events throughout their life time resulting in a low reproductive rate. This may indicate that in D. naui senility is reached after an age of six years, which compares well with H. aquaticus (wear stage 8 at >6.5 years; Dubost 2016, Hartung & Böhme 2024), and may suggest that the maximum life span of both species was relatively short (maximum age in wild populations of H. aquaticus is normally eight years and potentially 11-13 years according to Meijaard (2011). Body size analysis in form of body mass calculations revealed that females tend to be larger than males, in which females of D. naui are on average approximately 2 kg or 7% heavier than males. The mean weight for males lies within a range of 28-29 kg and females reach a mass of 30-31 kg. Hyemoschus displays an even larger sexual size dimorphism (SSD) pattern where males have an average weight of 9.7 kg and females around 12 kg (Robin 1990; Nowak 1999). However, the most pronounced difference between both species is the absolute body mass, which in D. naui is more than twice as high as in H. aquaticus. This important biologic feature may reflect ecological adaptations in more seasonal and open deciduous broadleaf forests during the Miocene of Europe, compared to the thickets of African rainforests where Hyemoschus is living. Smaller body size in extant tragulids may facilitate concealment and escape from predators in densely vegetated habitats (Rössner 2007; Meijaard 2011). A preference of D. naui to more open riparian woodlands would be supported by the high numbers of individuals found in HAM4 (MNI=44), making here this species to the most abundant large mammal, whereas in the HAM5 level D. naui (MNI=13) is outcompeted by the deer Euprox furcatus (MNI=21). This female-biased SSD is common among mammals and is especially known from smaller mammals as for example Lagomorpha (Darwin 1871; Lindenfors et al. 2007; Tombak et al. 2024). This SSD is explained by a higher fecundity selection in small mammals (Darwin 1871), because of higher energetic demands on females like producing eggs in comparison to sperm, gestation, and lactation, and more space that is used for keeping the eggs. Therefore, female mammals of smaller species develop larger energy stores for high metabolic costs of gestation and lactation, ultimately promoting higher offspring survivorship and reproductive success. However, this theory does not always apply because male sexual selection strategy is often based on a larger body size in males compared to females, which is used for competition with other males (Darwin 1871; Alexander and Borgia 1979; Weckerly 1998; Lindenfors et al. 2007; Cassini 2020a, b, 2022, 2023). Potential paleobiogeographic scenario for Hyemoschus Several recent publications suggest a close phylogenetic relationship between the fossil Eurasian species Dorcatherium naui and the extant African Hyemoschus aquaticus (Geraads 2010; Sanchez et al. 2015, 2018), designated as ‘true Dorcatherium -clade’ by Sanchez et al. (2018). Dorcatherium naui is known from Western and Central Europe from the late Middle Miocene till the early Late Miocene, between 12.4 and ~9.5 Ma (Aiglstorfer et al. 2014), whereas the species occurs in Pakistan in the Chinji Formation in the late Middle Miocene (Guzman and Rössner 2021). Several potential, but badly known, European descendants of D. naui are known from later parts of the Late Miocene in southeastern Europe (e.g. Kostopoulos & Sen 2016), but after ~7.5 Ma the selenodont lineage of Dorcatherium , and the family Tragulidae at all, has disappeared from Western Eurasia and shortly after from Pakistan. In Africa, tragulids are common and diverse during the Early and Middle Miocene (e.g. Pickford 2001; Sanchez et al. 2015, 2018; Musalizi et al. 2023), but known from only one Late Miocene site (the 9 Ma old Ngeringerowa site in Kenya; Pickford 1991). After a four million years long gap for fossil tragulids in Africa, the family reappeared with the oldest fossil record of H. aquaticus, whichdates to the early Pliocene of the Mabaget Member at Tugen Hills in Kenya, Africa(5-4.5 Ma Pickford et al. 2004). Although this record is based on sparse dental material only, according to Geraads (2010) the upper molar resembles more closely the Late Miocene Dorcatherium from southeastern Europe than the extant water African chevrotain. The later part of the Late Miocene (Messinian) was a time of massive mammalian dispersals from Eurasia into Africa, triggered by transient hyperaridity events in Western Asia (Böhme et al. 2021). The dispersing genera have both a southern Asian and southeast European origin and we speculate that the ‘true Dorcatherium -clade’ may have been part of these dispersals as well. Conclusion In this study, we present the first ontogenetic series of a fossil tragulid based on 13 skulls from Hammerschmiede and one from Eppelsheim. The examined fossil sample of Dorcatherium naui , in comparison with the phylogenetically related extant African water chevrotain Hyemoschus aquaticus , reveals that (I) D. naui exhibits more pronounced cranial ornamentation than extant tragulids, allowing reliable distinction between males and females, particularly when upper canines are absent; (II) the development of distinct cranial crests in male D. naui begins relatively early in life (at least by wear stage 3-4, if not earlier), similar to H. aquaticus , indicating a comparable onset of sexual maturity; and (III) heterochronic changes in the development of cranial crests and bulges occurred in D. naui relative to Hyemoschus , resulting in paedomorphic traits of the latter. These findings suggest that D. naui likely exhibited a unique mating behavior compared to extant chevrotains, with males relying more on ritualized displays. Moreover, the pronounced body size difference between D. naui and H. aquaticus , with D. naui being more than twice as large, suggests that D. naui may have been adapted to more open habitats compared to the extant species. Additionally, a large dataset of isolated teeth and mandibles was used for a mortality analysis and body mass estimations. We observe very similar biological patterns in the fossil D. naui as in the extant H. aquaticus . Incorporating the early onset of sexual maturity, sexual size dimorphism in which females are larger than males, and large survivorship of juveniles, we conclude that D. naui probably had a low reproductive rate (one young per litter) and similar maximum life span compared to Hyemoschus . Abbreviations GPIT: Geologisch-Paläontologisches Institut Tübingen; NHMUK: Natural History Museum of London; SNSB-BSPG: Staatliche Naturwissenschaftliche Sammlungen Bayerns-Bayerische Staatssammlung für Paläontologie und Geologie Declarations Acknowledgements Here we greatly thank Emmanuel Gilissen (RMCA, Brussels) and Mathys Rotonda for access to the collection of Hyemoschus at the RMCA, Tervuren, Brussels. We moreover thank Frank Zachos (NHM Vienna) for comparative pictures of Moschiola . We also thank Gabriel Ferreira and Kristina Kyriakouli for their support and assistance with the µCT scans and Thomas Lechner (all Tübingen) for providing the MNI for Euprox furcatus . Statement of competing interests All authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest or non-financial interest in the subject matter or materials discussed in this manuscript. Funding statement Since 2020, the Hammerschmiede excavations and the associated research have been generously supported by the Bavarian State Parliament, the Bavarian State Ministry of Research and Art and the Bavarian Natural History Collections. Special thanks go to the Freie Wähler parliamentary group and its deputy chairman, Bernhard Pohl, member of the state parliament. Author Contribution J.H. and M.B. wrote the main manuscript and prepared, as well as provided the research data. J.H. prepared the figures. All authors reviewed the manuscript Data Availability µCT data were deposited into the Morphosource database under the project ID: ID: 000810219 and are available at the following URL: www.morphosource.org/projects/000810219?locale=en. References Aiglstorfer M, Rössner GE and Böhme M. (2014) Dorcatherium naui and pecoran ruminants from the late Middle Miocene Gratkorn locality (Austria). 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Geological Survey Professional Paper: 117–159 Zietzschmann O, Ackerknecht E and Grau H (1943) Handbuch der vergleichenen Anatomie der Haustiere, Springer Berlin Heidelberg , Berlin Additional Declarations No competing interests reported. Supplementary Files SF1HartungBhme.xlsx Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 05 May, 2026 Reviews received at journal 04 May, 2026 Reviews received at journal 08 Apr, 2026 Reviewers agreed at journal 19 Mar, 2026 Reviewers agreed at journal 19 Mar, 2026 Reviewers invited by journal 17 Mar, 2026 Editor assigned by journal 13 Mar, 2026 Submission checks completed at journal 13 Mar, 2026 First submitted to journal 04 Mar, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9029355","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":607460084,"identity":"96f42070-9ba0-4b89-be99-6bcdc920e924","order_by":0,"name":"Josephina Hartung","email":"data:image/png;base64,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","orcid":"","institution":"Eberhard Karls University","correspondingAuthor":true,"prefix":"","firstName":"Josephina","middleName":"","lastName":"Hartung","suffix":""},{"id":607460086,"identity":"d13655d1-4f0c-4300-af95-a495f3a8fd2b","order_by":1,"name":"Madelaine Böhme","email":"","orcid":"","institution":"Eberhard Karls University","correspondingAuthor":false,"prefix":"","firstName":"Madelaine","middleName":"","lastName":"Böhme","suffix":""}],"badges":[],"createdAt":"2026-03-04 10:54:26","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9029355/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9029355/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":105035866,"identity":"e0b12b7a-b3ad-4c1f-9a76-27155ffced74","added_by":"auto","created_at":"2026-03-20 07:26:47","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":113418,"visible":true,"origin":"","legend":"\u003cp\u003eOcclusal pattern of the lower dp4 and m3 showing\u003cstrong\u003e \u003c/strong\u003ewear stages from w0 to w8 according to (Hartung and Böhme 2024) of \u003cem\u003eDorcatherium naui\u003c/em\u003e from the Hammerschmiede locality (Germany). Wear stages 0-5 represent the juvenile stage, wear stage 6 to 7 are the adult stage, and wear stage 8 represents the senile age category. Size of the teeth are not to scale\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-9029355/v1/406c4a17f9600edfc49f4e9e.png"},{"id":105009871,"identity":"5450f2bc-c384-453c-859a-319ee49e2ef2","added_by":"auto","created_at":"2026-03-19 19:59:42","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":479366,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eDorcatherium naui\u003c/em\u003e from the late Miocene Hammerschmiede locality level HAM4 and HAM5, as well as from the middle to late Miocene locality of Eppelsheim. Adult and juvenile males and females in dorsal view. \u003cstrong\u003eA-E\u003c/strong\u003emales, \u003cstrong\u003eA)\u003c/strong\u003e adult without teeth GPIT/MA/17690 from Hammerschmiede level HAM4, \u003cstrong\u003eB)\u003c/strong\u003e adult SNSB-BSPG 2020 XCV-474 at wear stage 7 from Hammerschmiede level HAM5, \u003cstrong\u003eC)\u003c/strong\u003e adult NHMUK PV OR 40632 at wear stage 6 from Eppelsheim, \u003cstrong\u003eD)\u003c/strong\u003e juvenile SNSB-BSPG 2020 XCIV-3500 at wear stage 3-4 from Hammerschmiede level HAM4, \u003cstrong\u003eE) \u003c/strong\u003eSNSB-BSPG 2020 XCIV-8518 unknown wear stage from Hammerschmiede level HAM4. Based on weak morphology of the cranial crests, the skull is younger than wear stage 3-4, probably early wear stage 3, \u003cstrong\u003eF-I\u003c/strong\u003efemales of determined age, \u003cstrong\u003eF) \u003c/strong\u003eadult GPIT/MA/17841 at wear stage 6 from Hammerschmiede level HAM4,\u003cstrong\u003e G) \u003c/strong\u003eadult GPIT/MA/18000-01 at wear stage 6 from Hammerschmiede level HAM4, \u003cstrong\u003eH)\u003c/strong\u003e adult SNSB-BSPG 2020 XCV-357 at wear stage 6 from Hammerschmiede level HAM5, \u003cstrong\u003eI) \u003c/strong\u003eadult\u003cstrong\u003e \u003c/strong\u003eSNSB-BSPG 2020 XCIV-18870 at wear stage 6 from Hammerschmiede level HAM4, \u003cdel\u003e\u0026nbsp;\u003c/del\u003e\u003cstrong\u003eJ)\u003c/strong\u003e SNSB-BSPG 2020 XCIV-8970 at wear stage 4 from Hammerschmiede level HAM4. \u003cstrong\u003eAbbreviations\u003c/strong\u003e: w=wear stage\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-9029355/v1/7e62abc06d0082a0e1ec438b.png"},{"id":105035674,"identity":"2f5f1646-8716-4272-b24a-f0ef388a47f9","added_by":"auto","created_at":"2026-03-20 07:26:26","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":381797,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eDorcatherium naui\u003c/em\u003e from the late Miocene Hammerschmiede locality level HAM4 and HAM5, as well as from the middle to late Miocene locality of Eppelsheim. Adult and juvenile males and females in lateral view. \u003cstrong\u003eA-E\u003c/strong\u003emales, \u003cstrong\u003eA)\u003c/strong\u003e adult without teeth GPIT/MA/17690 from Hammerschmiede level HAM 4, \u003cstrong\u003eB)\u003c/strong\u003e adult SNSB-BSPG 2020 XCV-474 mirrored at wear stage 7 from Hammerschmiede level HAM5, \u003cstrong\u003eC)\u003c/strong\u003e adult NHMUK PV OR 40632 at wear stage 6 from Eppelsheim, \u003cstrong\u003eD)\u003c/strong\u003e juvenile SNSB-BSPG 2020 XCIV-3500 at wear stage 3-4 from Hammerschmiede level HAM4, \u003cstrong\u003eE)\u003c/strong\u003e SNSB-BSPG 2020 XCIV-8518 unknown wear stage from Hammerschmiede level HAM4. Based on weak morphology of the cranial crests, the skull is younger than wear stage 3-4, probably early wear stage 3, \u003cstrong\u003eF-I\u003c/strong\u003efemales with determined age, \u003cstrong\u003eF)\u003c/strong\u003e adult GPIT/MA/17841 mirrored at wear stage 6 from Hammerschmiede level HAM4, \u003cstrong\u003eG) \u003c/strong\u003eadult GPIT/MA/18000-01 mirrored at wear stage 6 from Hammerschmiede level HAM4, \u003cstrong\u003eH)\u003c/strong\u003e adult SNSB-BSPG 2020 XCV-357 and SNSB-BSPG 2020 XCV-380 mirrored at wear stage 6 from Hammerschmiede level HAM5, \u003cstrong\u003eI)\u003c/strong\u003e adult SNSB-BSPG 2020 XCIV-18870 at wear stage 6 from Hammerschmiede level HAM4, \u003cstrong\u003eJ)\u003c/strong\u003e SNSB-BSPG 2020 XCIV-8970 mirrored at wear stage 4 from Hammerschmiede level HAM4. \u003cstrong\u003eAbbreviations\u003c/strong\u003e: w=wear stage\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-9029355/v1/f5500741df25af535610b631.png"},{"id":105009869,"identity":"3d6e4e9e-32ad-485c-8559-5aad3567f255","added_by":"auto","created_at":"2026-03-19 19:59:42","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":362339,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cem\u003eDorcatherium naui\u003c/em\u003e from the late Miocene Hammerschmiede locality level HAM4 and HAM5, as well as from the middle to late Miocene locality of Eppelsheim. Adult and juvenile males and females in ventral view. \u003cstrong\u003eA-C\u003c/strong\u003emales, \u003cstrong\u003eA)\u003c/strong\u003e adult SNSB-BSPG 2020 XCV-474 at wear stage 7 from Hammerschmiede level HAM5, \u003cstrong\u003eB)\u003c/strong\u003e adult NHMUK PV OR 40632 at wear stage 6 from Eppelsheim, upper right tooth row virtually isolated based from µCT scan, \u003cstrong\u003eC)\u003c/strong\u003ejuvenile SNSB-BSPG 2020 XCIV-3500 at wear stage 3-4 from Hammerschmiede level HAM4. \u003cstrong\u003eD-G\u003c/strong\u003e females, \u003cstrong\u003eD)\u003c/strong\u003e adult GPIT/MA/17841 at wear stage 6 from Hammerschmiede level HAM4, \u003cstrong\u003eE) \u003c/strong\u003eadult GPIT/MA/18000-01 at wear stage 6 from Hammerschmiede level HAM4, \u003cstrong\u003eF)\u003c/strong\u003e adult SNSB-BSPG 2020 XCV-357 and 380 at wear stage 6 from Hammerschmiede level HAM5, \u003cstrong\u003eG)\u003c/strong\u003e adult SNSB-BSPG 2020 XCIV-18870 at wear stage 6 from Hammerschmiede level HAM 4, \u003cstrong\u003eH)\u003c/strong\u003e SNSB-BSPG 2020 XCIV-8970 at wear stage 4 from Hammerschmiede level HAM4. \u003cstrong\u003eAbbreviations\u003c/strong\u003e: w=wear stage\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-9029355/v1/e837893c2f0c355af6a42ef7.png"},{"id":105009876,"identity":"7b5851f7-9fd3-4bdb-960f-b01049def628","added_by":"auto","created_at":"2026-03-19 19:59:43","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":259769,"visible":true,"origin":"","legend":"\u003cp\u003eVirtual cross sections of \u003cem\u003eDorcatherium naui\u003c/em\u003e from Hammerschmiede level HAM4 showing the pneumatized inner morphology of frontoparietal bulges in males \u003cstrong\u003eA-D\u003c/strong\u003e. These structures are absent in females \u003cstrong\u003eE-G\u003c/strong\u003e. \u003cstrong\u003eA)\u003c/strong\u003e adult GPIT/MA/17690, \u003cstrong\u003eB)\u003c/strong\u003e adult SNSB-BSPG 2020 XCV-474, \u003cstrong\u003eC)\u003c/strong\u003e subadult SNSB-BSPG 2020 XCIV-3500, \u003cstrong\u003eD)\u003c/strong\u003e SNSB-BSPG XCIV 2020-8518, \u003cstrong\u003eE)\u003c/strong\u003e adult GPIT/MA/17841, \u003cstrong\u003eF)\u003c/strong\u003e adult female GPIT/MA/18000-01, \u003cstrong\u003eG)\u003c/strong\u003e subadult female SNSB-BSPG 2020 XCIV-8970. Colors are inverted and contrast was adjusted for better visibility. Surface models are not to scale\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-9029355/v1/98c4928a8f6c6dc0df85d396.png"},{"id":105009873,"identity":"989b3435-ebdf-4ca3-9d97-a99d544d0972","added_by":"auto","created_at":"2026-03-19 19:59:43","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":71838,"visible":true,"origin":"","legend":"\u003cp\u003eHeterochronic process of \u003cem\u003eD. naui\u003c/em\u003e (ancestor) and \u003cem\u003eH. aquaticus\u003c/em\u003e (descendent) after (Reilly et al. 1997). \u003cem\u003eD. naui\u003c/em\u003e shows a hyperdevelopment of cranial crests and bulges if compared to the descendent leading to a paedomorphic state (deceleration and truncation of ancestral development) of the cranial ornamentation in \u003cem\u003eH. aquaticus\u003c/em\u003e. \u003cstrong\u003eAbbreviations\u003c/strong\u003e: α=age of onset of growth of morphological structure (here cranial ornamentation like e.g. frontoparietal bulges), a=ancestor (here: \u003cem\u003eDorcatherium naui\u003c/em\u003e), β=age when offset shape of morphological structure is attained, d=descendent (here: \u003cem\u003eHyemoschus aquaticus\u003c/em\u003e), k=rate of shape development\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-9029355/v1/9f6884c72ec822378815d7d6.png"},{"id":105562588,"identity":"9e2cd07c-a819-4b5e-9d60-825e31a478eb","added_by":"auto","created_at":"2026-03-27 12:43:16","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":109222,"visible":true,"origin":"","legend":"\u003cp\u003eResults of the mortality analysis and body mass estimations for individuals of \u003cem\u003eD. naui\u003c/em\u003e from Hammerschmiede (HAM4 and HAM5). \u003cstrong\u003eA)\u003c/strong\u003e Results of the combined mortality study based on the upper M3, dP4, as well as on the lower m3 and dp4 for HAM4 and \u003cstrong\u003eB)\u003c/strong\u003e for HAM5; \u003cstrong\u003eC)\u003c/strong\u003e Survivorship for HAM4 based on the combined mortality analysis and \u003cstrong\u003eD)\u003c/strong\u003e Body mass estimations based on the length of m1-m3 and m2 combined showing a bimodality with skulls attributed to females falling within the heavier range. \u003cstrong\u003eAbbreviations\u003c/strong\u003e: w=wear stage\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-9029355/v1/d2ba0f5766501cd950a95ac7.png"},{"id":105568638,"identity":"5aaeec93-c23d-4b88-84b8-8908624d60a3","added_by":"auto","created_at":"2026-03-27 13:10:00","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3001738,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9029355/v1/ff0e65fc-53f7-4dff-8f97-04dc1672588d.pdf"},{"id":105035731,"identity":"069d1a63-7557-4c0a-82dc-45c031d4e0ec","added_by":"auto","created_at":"2026-03-20 07:26:32","extension":"xlsx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":115489,"visible":true,"origin":"","legend":"","description":"","filename":"SF1HartungBhme.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-9029355/v1/37b9c24aa722a6194fcb3fb8.xlsx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Ontogenetic skull development and paleobiology of the tragulid Dorcatherium naui (Mammalia: Artiodactyla) from the early Late Miocene hominid locality Hammerschmiede (Germany)","fulltext":[{"header":"Introduction","content":"\u003cp\u003eTragulids are a peculiar group of small ruminants and the sister group to Pecora. The group originated in Asia during the Late Eocene (M\u0026eacute;tais et al. \u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e2001\u003c/span\u003e; R\u0026ouml;ssner \u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Hassanin et al. \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Sanch\u0026eacute;z et al. \u003cspan citationid=\"CR71\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Mennecart et al. \u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) and survived until today, where they live in Asia and Africa. The extant taxa comprise three genera \u003cem\u003eMoschiola\u003c/em\u003e, \u003cem\u003eTragulus\u003c/em\u003e (both from Asia), and \u003cem\u003eHyemoschus\u003c/em\u003e (from Africa). The fossil record shows, that tragulids were much more diverse during the Miocene (R\u0026ouml;ssner \u003cspan citationid=\"CR69\" class=\"CitationRef\"\u003e2007\u003c/span\u003e; Khan and Akhtar \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; R\u0026ouml;ssner and Heissig \u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Sanchez et al. 2018; Koufos \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Guzm\u0026aacute;n and R\u0026ouml;ssner \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Musalizi et al. \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) than today, with \u003cem\u003eDorcatherium\u003c/em\u003e and the type species \u003cem\u003eD. naui\u003c/em\u003e being the most frequently studied genus and species; mainly known from central and southwestern Europe (e.g. Alba et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; R\u0026ouml;ssner and Heissig \u003cspan citationid=\"CR70\" class=\"CitationRef\"\u003e2013\u003c/span\u003e; Aiglstorfer et al. \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Mennecart et al. \u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). However, the quality of the fossil record of \u003cem\u003eD. naui\u003c/em\u003e was relatively limited comprising primarily teeth and isolated postcranial material, preventing detailed ontogenetic investigations. This situation has changed with the discovery of the Hammerschmiede hominid site (B\u0026ouml;hme et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2019\u003c/span\u003e), yielding abundant skulls, partial skeletons, and a plethora of mandibles and postcranial bones (Hartung and B\u0026ouml;hme \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Lechner and B\u0026ouml;hme \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2025\u003c/span\u003e), allowing now a detailed assessment of the paleobiology of this species.\u003c/p\u003e \u003cp\u003eFossil skulls represent a key source of information for understanding growth trajectories and sexual variation. The development of the artiodactyl skull follows a general vertebrate pattern (Whitmore \u003cspan citationid=\"CR80\" class=\"CitationRef\"\u003e1953\u003c/span\u003e; Moyano et al. \u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e2019\u003c/span\u003e), but in Pecora, the cranial morphology is strongly influenced by the development of headgear and can differ greatly among the sexes (Davis et al. \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Nasoori \u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) depending on body size (Calamari \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2016\u003c/span\u003e) or whether females wear head gear at all (e.g. Bovidae Lundrigan \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e1996\u003c/span\u003e; Stankowich and Caro \u003cspan citationid=\"CR77\" class=\"CitationRef\"\u003e2009\u003c/span\u003e). However, tragulids do not wear any type of head gear, but a strong ornamentation of the skull is visible in males of \u003cem\u003eD. naui\u003c/em\u003e (Hartung and B\u0026ouml;hme \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cem\u003eD. naui\u003c/em\u003e and the extant African water chevrotain \u003cem\u003eH. aquaticus\u003c/em\u003e are recovered as sister taxa in phylogenetic parsimony analyses (S\u0026aacute;nchez et al. \u003cspan citationid=\"CR73\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; 2018). Based on this close relationship, we investigate similarities between these two species regarding the overall biology and ecology.\u003c/p\u003e \u003cp\u003eRecently, the cranial development of \u003cem\u003eD. naui\u003c/em\u003e and the fossil tragulid \u003cem\u003eDorcabune crassum\u003c/em\u003e (genus affiliation according Musalizi et al. \u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), regarding the ornamentation of the skull with respect to sexual dimorphism was studied in Hartung and B\u0026ouml;hme (\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2022\u003c/span\u003e). The study includes in total three skulls of males and females from Hammerschmiede and Eppelsheim (Germany). Here we study 10 additional well-preserved complete and partial skulls of \u003cem\u003eD. naui\u003c/em\u003e from the Hammerschmiede locality and establish an ontogenetic series respecting males and females for the first time. We will test the hypothesis whether the ornamentation of the skull of male \u003cem\u003eD. naui\u003c/em\u003e undergoes ontogenetic changes and we will discuss the correlation of the development of cranial ornamentation with the onset of sexual maturity. We than compare the data to the already known series of \u003cem\u003eH. aquaticus\u003c/em\u003e studied in Hartung and B\u0026ouml;hme (\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eMoreover, we analyze a set of isolated teeth and mandibles to conduct a mortality analysis and estimate the survivorship of \u003cem\u003eD. naui\u003c/em\u003e from Hammerschmiede. Using this data set, we also calculate the mean body mass for males and females to test whether a sexual size dimorphism is present in \u003cem\u003eD. naui\u003c/em\u003e. We use this data to give a comprehensive overview of the paleobiology and life history patterns.\u003c/p\u003e\n\u003ch3\u003eGeological and paleoenvironmental setting of the Hammerschmiede\u003c/h3\u003e\n\u003cp\u003eThe Hammerschmiede is a clay pit belonging to the municipality of Pforzen. It is located in the southern part of the Northern Alpine Foreland Basin close to the town of Kaufbeuren (Allg\u0026auml;u, Bavaria). The locality contains fluvial and alluvial deposits from the Middle-to-Late Miocene \u003cem\u003eUpper Series\u003c/em\u003e, the youngest lithostratigraphic unit of the Upper Freshwater Molasse (Doppler \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e1989\u003c/span\u003e; Doppler et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2005\u003c/span\u003e). Vertebrate finds are mainly restricted to the two fluvial channels HAM4 and HAM5 (Kirscher et al. \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). The 11.58 Ma old HAM4 channel represents a larger meandering stream of up to 50 m width, whereas the 11.62 Ma old HAM5 channel is a smaller meandering rivulet or creek with a width of four to five meters (Lechner and B\u0026ouml;hme \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). Excavations are running since 2011 and until 2024 about 1.000 metric tons of lower point-bar and channel-lag sediments have been excavated in HAM4 and about 300 metric tons of sediment in HAM5 (Lechner and B\u0026ouml;hme \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2025\u003c/span\u003e: Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe locality is famous for its rich and diverse faunal content including bivalves and gastropods (Schneider and Prieto \u003cspan citationid=\"CR74\" class=\"CitationRef\"\u003e2011\u003c/span\u003e), fishes, amphibians, reptiles, small mammals, large mammals (Fuss et al. \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Hartung et al. \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Kargopoulos et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2021a\u003c/span\u003e, \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003eb\u003c/span\u003e; Hartung and B\u0026ouml;hme \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Kargopoulos et al. \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2022a\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003eb\u003c/span\u003e; Lechner and B\u0026ouml;hme \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2022\u003c/span\u003e, \u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Kampouridis et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Kargopoulos et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; B\u0026ouml;hme and Prieto \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2025\u003c/span\u003e; Kargopoulos et al. \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2025\u003c/span\u003e), and birds (Mayr et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2020a\u003c/span\u003e, \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003eb\u003c/span\u003e, \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). It furthermore is renowned for the discovery of the associate skeletons of the hominid \u003cem\u003eDanuvius guggenmosi\u003c/em\u003e (B\u0026ouml;hme et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2019\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) and the second syntopic hominid \u003cem\u003eBuronius manfredschmidi\u003c/em\u003e (B\u0026ouml;hme et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe palaeoenvironmental conditions during deposition of both channels differ in respect to the openness of the surrounding vegetation (Lechner and B\u0026ouml;hme \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). The larger meandering HAM4 river has been flowing in a relatively open and fire-prone landscape, evidenced by higher abundance of micro- and macro-charcoal, less abundant rodents (dominated by the tree squirrel \u003cem\u003eCsakvaromys\u003c/em\u003e) and insectivore mammals, more abundant lagomorphs and scincomorph (lizards, scincs) reptiles. In contrast, the small HAM5 rivulet contains less charcoal, more rodents (dominated by the fossorial \u003cem\u003eAnomalomys\u003c/em\u003e) and insectivores, less abundant lagomorphs and scincomorphs, and is interpreted to be surrounded by more closed forest environment, relative to HAM4 (Lechner and B\u0026ouml;hme \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). This interpretation is supported by the syntopy of two hominids in HAM5 (B\u0026ouml;hme et al. \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2019\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2024\u003c/span\u003e) and the presence of a chalicotheriine chalicothere, rather than schizotheriine chalicothere in HAM4 (Kampouridis et al. \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e"},{"header":"Material and methods","content":"\u003cp\u003eThe investigated material comprises 14 partial and complete skulls of \u003cem\u003eD. naui\u003c/em\u003e. 13 are from the earliest Late Miocene Hammerschmiede locality (Tab. 1) and one is from the Middle to Late Miocene locality of Eppelsheim (both from Germany). The skulls GPIT/MA/17690, GPIT/MA/18000-01, SNSB-BSPG 2020 XCIV-3500, SNSB-BSPG 2020 XCIV-8518, SNSB-BSPG 2020 XCIV-2298, SNSB-BSPG 2020 XCIV-3566, SNSB-BSPG 2020 XCIV-8793, SNSB-BSPG 2020 XCIV-8970, GPIT/MA/17615, GPIT/MA/17841, and SNSB-BSPG 2020 XCIV-18870 were excavated from level HAM4. The level HAM5 produce the skull SNSB-BSPG 2020 XCV-474, as well as the skull fragments SNSB-BSPG 2020 XCV-380 and SNSB-BSPG 2020 XCV-357, which belong to one individuum and were excavated in close association. All Hammerschmiede specimens are presently housed in the Palaeontological collection of the University of Tuebingen (GPIT). GPIT/MA/17690 and GPIT/MA/18000-01 were already published in Hartung and Böhme (2022) and µCT scans of both specimens are available for study. Another complete skull with attached mandibles NHMUK PV OR 40632 from the type locality of \u003cem\u003eD. naui\u003c/em\u003e, Eppelsheim, is housed at the NHMUK in London and was published in Kaup (1839b, a) and described in detail in Hartung and Böhme (2022). The skull terminology follows Whitmore (1953) and Zietzschmann et al. (1943)\u0026nbsp;and the dental nomenclature follows Bärmann and Rössner (2011).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1:\u0026nbsp;\u003c/strong\u003eSkulls of \u003cem\u003eDorcatherium naui\u003c/em\u003e from the late Miocene locality of Hammerschmiede used for this study.\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eCollection number\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eDescription\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eStratigraphic age\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eSex\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e\u003cstrong\u003eWear stage\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eSNSB-BSPG 2020 XCV-474\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eComplete skull\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eHAM5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003em\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eSNSB-BSPG 2020 XCV-357, 380\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eComplete skull\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eHAM5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003ef\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eSNSB-BSPG 2020 XCIV-18870\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eComplete skull\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eHAM4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003em\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eSNSB-BSPG 2020 XCIV-3500\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eComplete skull\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eHAM4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003em\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e3-4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eGPIT/MA/17690\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eComplete skull\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eHAM4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003em\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eGPIT/MA/17615\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003ePartial skull, posterior part of skull roof\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eHAM4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003em\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eSNSB-BSPG 2020 XCIV-8518\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003ePartial skull, skull roof\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eHAM4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003em\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eGPIT/MA/17841\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eComplete skull\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eHAM4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003ef\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eGPIT/MA/1800-01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eComplete skull\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eHAM4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003ef\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eSNSB-BSPG 2020 XCIV-8970\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eComplete skull\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eHAM4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003ef\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eSNSB-BSPG 2020 XCIV-2298\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003ePosterior part of skull, occiput\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eHAM4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003ef\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eSNSB-BSPG 2020 XCIV-3566\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003ePosterior part of skull, occiput\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eHAM4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003ef\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eSNSB-BSPG 2020 XCIV-8793\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003ePosterior part of skull, occiput\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eHAM4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003ef\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003e/\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003eIn addition to the Hammerschmiede skulls 109 age-diagnostic mandibles and isolated teeth from level HAM4 and 17 teeth and mandibles from level HAM5 (all excavated between 2011 and 2024) were measured to investigate the mortality statistics, the survivorship rates, and the body mass distribution of \u003cem\u003eD. naui\u003c/em\u003e. The studied dental material includes the following numbers of tooth positions: 40 M3, 26 dP4, 28 m3, and 24 dp4 from level HAM4, as well as two dP4, 11 M3, two dp4, and seven m3 from level HAM5 (teeth preserved within skulls and mandibles are included). Additionally, the length of the m1-m3 and of the m2 were measured to calculate the body mass (see below). In total, 13 mandibles from HAM4 and three mandibles from HAM5 were used.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe assignment of the upper teeth into nine wear stages follows Hartung and Böhme (2024) with wear stage 0 being neonate, right after birth, wear stage 1 to wear stage 5 representing the juvenile stage, wear stage 6 and 7 representing the adult stage, and wear stage 8 including senile specimens (Fig. 1). The classification of the lower teeth into wear stages follows the same principle of the upper teeth and is based on the wear of the m3 and dp4 as well. At wear stage 0 the dp4 is erupted but unworn. In isolated dp4, the root is not preserved and only the thin enamel cap is visible. At wear stage 1, the dp4 is still unworn but the enamel is thicker than in w0 and a root is preserved. Wear stage 2 is characterized by the metaconid and the protoconid being slightly worn but the anteriolingual and anteriolabial as well as the entoconid and hypoconid being unworn. At wear stage 3 all cones show a wear facet and at wear stage 4 these cones are medium worn. At wear stage 5 the dp4 is heavily worn and the m3 is erupted but unworn. According to Hartung and Böhme (2024) we assume that the dp4 is shed at wear stage 6 and the m3 is worn at the metaconid, protoconid, as well as at the entoconid and hypoconid. The talonid basin (entoconulid and hypoconulid) is still unworn. At wear stage 7 all cones are medium worn and the talonid basin shows slight to medium wear facets. Wear stage 8 represents senile individuals with the m3 being highly worn so that in some specimens the selenodont pattern is almost not recognizable.\u003c/p\u003e\n\u003cp\u003eFor body mass estimates (in kg) on the combined HAM5 and HAM4 sample of mandibles we use the log-transformed regressions of Janis (1990) for lower molar length (m1-m3) and length of m2\u0026nbsp;for “ruminants only”: [log(BM) = 3.337 × log(SLML/10) + 1.118], [log(BM) = 3.352 × log(LMRL/10) − 0.604]; with SLML being the length of the m2 (mm) and LMRL being the length of the m1-m3 (mm).\u003c/p\u003e\n\u003cp\u003eMortality and survivorship were calculated from the minimum number of individuals (MNI), based on the abundance of left and right M3 and dP4, as well as m3 and dp4, for each wear stage, respectively. Survivorship was derived directly from the MNI per wear stage relative to the total number of individuals.\u0026nbsp;A table including the exact measurements is provided in the appendix (SF1).\u003c/p\u003e\n\u003cp\u003eThe skulls GPIT/MA/17690, GPIT/MA/18000-01,\u0026nbsp;SNSB-BSPG 2020 XCIV-3500, SNSB-BSPG 2020 XCIV-8970, SNSB-BSPG XCIV 2020-8518, SNSB-BSPG 2020 XCV-474, as well as GPIT/MA/17841 were scanned at the 3D Imaging Lab of the Senckenberg HEP at the Eberhard Karls University of Tübingen, Germany. The scans were acquired using the Nikon XTH 320 Reflection Target. For GPIT/MA/17690, the acceleration voltage was set to 190 kV and the resolution was 177 µA. A total of 4476 images were recorded and a 1 mm copper filter was inserted. For GPIT/MA/18000-01, a helical scan was acquired. The acceleration voltage was 195 kV and the resolution was set to 70 µA with a total of 7932 images. SNSB-BSPG 2020 XCIV-3500 and SNSB-BSPG 2020 XCIV-8970 were scanned with an acceleration voltage of 210 kV and a resolution of 90 µA. The number of total images was 4476 and a 0.1 mm copper filter was used for both specimen each. \u0026nbsp;SNSB-BSPG XCIV 2020-8518 was scanned at 215 kV and 75 µA and SNSB-BSPG 2020 XCV-474, as well as GPIT/MA/17841 were scanned at 210 kV and 78 and 80 µA respectively. The scans were acquired using a 0.1 mm copper filter as for the other scans and a total number of 4476 images were taken. Images were processed using VG Studio Max 3.4.1. All scans are available at\u0026nbsp;www.morphosource.org/projects/000810219?locale=en.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cu\u003eAbbreviations\u003c/u\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eGPIT: Geologisch-Paläontologisches Institut Tübingen; NHMUK: Natural History Museum of London; SNSB-BSPG: Staatliche Naturwissenschaftliche Sammlungen Bayerns-Bayerische Staatssammlung für Paläontologie und Geologie\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cu\u003eSystematic Paleontology\u003c/u\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eMAMMALIA (Linnaeus 1758)\u003c/p\u003e\n\u003cp\u003eARTIODACTYLA (Owen 1848)\u003c/p\u003e\n\u003cp\u003eRUMINANTIA (Scopoli 1777)\u003c/p\u003e\n\u003cp\u003eTRAGULIDAE (Milne-Edwards 1864)\u003c/p\u003e\n\u003cp\u003eGenus \u003cem\u003eDorcatherium\u0026nbsp;\u003c/em\u003e(Kaup 1833)\u003c/p\u003e\n\u003cp\u003eType species: \u003cem\u003eDorcatherium naui\u0026nbsp;\u003c/em\u003eKaup, 1833 (Kaup 1833)\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eDorcatherium naui\u0026nbsp;\u003c/em\u003eKaup, 1833 (Kaup 1833)\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eLocality and age of studied specimens:\u0026nbsp;\u003c/strong\u003eearly Late Miocene locality of Hammerschmiede level HAM5 (11.62 Ma) and HAM4 (11.58 Ma) and middle to late Miocene locality of Eppelsheim in Germany.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eReferred Material:\u0026nbsp;\u003c/strong\u003ePartial and complete skulls from Hammerschmiede: GPIT/MA/17690 (HAM4), SNSB-BSPG 2020 XCV-474 (HAM5), SNSB-BSPG 2020 XCIV-3500 (HAM4),SNSB-BSPG \u0026nbsp;2020 XCIV-8518 (HAM4), GPIT/MA/17841 (HAM4), GPIT/MA/18000-01 (HAM4), SNSB-BSPG 2020 XCV-357, 380 (HAM5) SNSB-BSPG 2020 XCIV-8970 (HAM4), SNSB-BSPG 2020 XCIV-2298 (HAM4), SNSB-BSPG 2020 XCIV-3566 (HAM4),SNSB-BSPG 2020 XCIV-8793 (HAM4), SNSB-BSPG 2020 XCIV-18870 (HAM4) GPIT/MA/17615 (HAM4), as well as the complete skull NHMUK PV OR 40632 from Eppelsheim. 117 teeth from level HAM4 and 22 teeth from level HAM5 including teeth preserved within skulls as well as in mandibles (for details see SF1 in the appendix).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eRemarks:\u0026nbsp;\u003c/strong\u003eThe skulls and teeth can be attributed to \u003cem\u003eD. naui\u003c/em\u003e based on characters of the dentition if applicable, such as (I) a high degree of selenodonty having a reduced external postmetacristid (sensu Bärmann and Rössner 2011) in the lower molars and well-developed cristids and flat main cusps (sensu Sánchez et al. 2011), (II) prominent sickle-shaped cones and conids (sensu Rössner and Heissig 2013) in combination with (III) the presence of the Dorcatherium-platform in the lower molars (sensu Alba et al. 2014), (IV) a complex posterior valley of the p4 (sensu Aiglstorfer et al. 2014), (V) lateral facing orbitae, (VI) prominent nuchal tubercle, and (VII) the presence of an occipital crest (Hartung and Böhme 2022). In addition to dental characters or if no teeth are preserved, the following characters apply, such as (A) well-developed parietal plateau, (B) well-developed frontoparietal bulges in males, (C) prominent nuchal tubercle, and (D) less-developed nuchal crests (Hartung and Böhme 2022).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cu\u003eDescription and comparison\u003c/u\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSexual dimorphism in \u003cem\u003eD. naui\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTo investigate the ontogenetic skull development of \u003cem\u003eD. naui\u003c/em\u003e, the specimens were separated into males and females based on characters published by Hartung and Böhme (2022). \u0026nbsp;Males possess a unique skull morphology characterized by (I) a broad, concave and laterally expanding skull roof formed by the anterior frontal called the frontal plateau, (II) presence of frontoparietal bulges enclosing a well-developed parietal plateau, (III) a prominent, flat, and broad sagittal crest, (IV) large part of occipital participating in the formation of the sagittal crest, (V) strongly developed nuchal crests, (VI) large and prominent nuchal tubercle, (VII) laterally expanding part of ventral squamosal with only a slight depression, and (VIII) large saber-like upper canines. Females in contrast show delicate and fine cranial crests, no parietal plateau, and rudimentary, small upper canines (Hartung and Böhme 2022).\u003c/p\u003e\n\u003cp\u003eGPIT/MA/17690 shows well-developed frontoparietal bulges enclosing a clearly constricted parietal plateau and a well-marked sagittal crest (Fig. 2A and 3A) and was already described in Hartung and Böhme (2022) as male. The same applies for NHMUK PV OR 40632 (Fig. 2C and 3C) which furthermore possesses large saber-like upper canines. SNSB-BSPG 2020 XCIV-3500 and SNSB-BSPG 2020 XCV-474 are comparable in their features with NHMUK PV OR 40632 and GPIT/MA/17690 but they are much more compressed dorsoventrally so that the bulges and crests appear more flattened (Fig. 2B, 2D and 3B, 3D). The frontal plateau is still enclosed by the frontoparietal bulges. The sagittal crests, as well as the nuchal crests are well-developed. Therefore, SNSB-BSPG 2020 XCIV-3500 and SNSB-BSPG 2020 XCV-474 are male specimens as well. GPIT/MA/17615 and SNSB-BSPG \u0026nbsp;2020 XCIV-8518 are morphologically very similar by possessing very fine and flat parietal bulges as typical for males (Fig. 2E and 3E). They appear much flatter than in SNSB-BSPG 2020 XCIV-3500 and SNSB-BSPG 2020 XCV-474. The frontal bulges are delicate but still visible in GPIT/MA/17615 as well as in SNSB-BSPG 2020 XCIV-8518 (Fig. 2E and 3E).\u003c/p\u003e\n\u003cp\u003eGPIT/MA/18000-01 was published as female (Hartung and Böhme 2022) based on fine and delicate temporal lines, sagittal crests, and nuchal crests (Fig. 2G and 3G). Moreover, a small canine alveolus supported this statement. Like this specimen, the complete skull SNSB-BSPG 2020 XCIV-8970 (Fig. 2J and 3J), SNSB-BSPG 2020 XCIV-18870 (Fig. 2I and 3I), and GPIT/MA/17841 (Fig. 2F and 3F) are females as well. SNSB-BSPG 2020 XCV-357 and SNSB-BSPG 2020 XCV-380 (Fig. 2H) from level HAM5, are compressed dorsoventrally but the features of the skull are still visible. The temporal lines are fine confining in a narrow sagittal crest. The sagittal crest appears very high in lateral view (Fig. 3H); however, this is probably caused by compression. Therefore, this individual is also a female. The partial skulls SNSB-BSPG 2020 XCIV-2298 and SNSB-BSPG 2020 XCIV-8793 preserve the posterior part of the skull roof with a fine sagittal crest and temporal lines, typical for females. SNSB-BSPG 2020 XCIV-3566\u0026nbsp;preserves the left part of the parietal above the orbit and shows no bulges, but instead a flat parietal plateau and a fine temporal line are present. Therefore, this specimen is a female as well.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eRemarks on the dentition and ontogenetic stage of the complete skulls of \u003cem\u003eD. naui\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe two ontogenetic youngest skulls containing teeth are the complete skulls SNSB-BSPG 2020 XCIV-3500 and SNSB-BSPG 2020 XCIV-8970 of wear stage 3-4 and wear stage 4 respectively. SNSB-BSPG 2020 XCIV-3500 exposes teeth from dP2–M2 on both sides (Fig. 4C). SNSB-BSPG 2020 XCIV-8970 (Fig. 4H) contains the right upper tooth row fromdP2 to the partially preserved M1. The teeth are brachyselenodont and contain a strong buccal relief. In SNSB-BSPG 2020 XCIV-3500, the part of the maxillary containing the canine is not preserved and the M3 is not formed yet, but a pocket is visible. In SNSB-BSPG 2020 XCIV-8970, the part lying mesial to the dP2 is missing and the distal half of the M1 and further teeth are not preserved. \u0026nbsp;In occlusal view, the dP2 and dP3 are longer than wide containing three cones, which increase in size from mesial to distal. The dP2 is much more elongated than the dP3. The cones are oriented slightly buccodistally and especially the metacone and metaconule are pointing into buccodistal direction. In the dP2, the styles are weakly developed and in the dP3 the mesostyle is well-developed. The protocone and the metaconule are larger in the dP3 than in the dP2 and the dP3 contains a faint posterior cingulum that continues beneath the protocone. The dP4 is molariform and medium-worn in SNSB-BSPG 2020 XCIV-3500 and heavily-worn in SNSB-BSPG 2020 XCIV-8970. It contains strong para-and mesostyles. A strong lingual cingulum is visible and the postprotocrista does not reach the premetaconulecrista. It is smaller than the M1 and M2. The M1 of SNSB-BSPG 2020 XCIV-3500 is medium-worn and the M1 of SNSB-BSPG 2020 XCIV-8970 is heavily-worn. The M2 of SNSB-BSPG 2020 XCIV-3500 is slightly worn. The molars are almost as long as wide. They contain strong para-and mesostyles and have a well-developed, continuous lingual cingulum reaching from the distal side of the metaconule to the mesial side of the protocone. The postprotocrista is bent mesially and does not reach the premetaconulecrista. Based on the characteristics of the dentition and the cranial morphology, SNSB-BSPG 2020 XCIV-3500 represents a juvenile male between wear stage 3 and 4. SNSB-BSPG 2020 XCIV-8970 is a female skull of almost the same age representing wear stage 4.\u003c/p\u003e\n\u003cp\u003eA detailed description of the permanent dentition of NHMUK PV OR 40632 and GPIT/MA/18000-01 was already published in Hartung and Böhme (2022). In NHMUK PV OR 40632, as well as in GPIT/MA/18000-01 and SNSB-BSPG 2020 XCIV-18870 the M3 is moderately worn representing wear stage 6, indicating that these specimens were about the same age (Fig. 4). In SNSB-BSPG 2020 XCV-357 from level HAM5 the M3 is slightly worn, fitting into wear stage 6 as well but being slightly younger than the skull from London and the adult female from level HAM4 of Hammerschmiede similar to SNSB-BSPG 2020 XCIV-18870. SNSB-BSPG 2020 XCV-474 and GPIT/MA/17841 are also adult specimens at wear stage 7 and 6 respectively, but in both of them the M3 is more worn (heavily worn in SNSB-BSPG 2020 XCV-474) than in the skull from London and GPIT/MA/18000-01, representing thus the oldest individuals of this ontogenetic series. In contrast, GPIT/MA/17690 preserves no teeth to determine the age, however the strong ossification, closed sutures, and the well-developed frontoparietal bulges indicate that the individual was adult. Accordingly, in SNSB-BSPG XCIV-2020 8518 the open midline suture between the parietals and the flat and faint frontoparietal bulges show, that this specimen was juvenile and compared to the still markable parietal bulges of SNSB-BSPG 2020 XCIV-3500 is even younger than the latter, probably corresponding to an early wear stage 3. In females of \u003cem\u003eD. naui\u003c/em\u003e, the development of cranial crests is thus not as strongly correlated with ontogeny as in males.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eComparative ontogenetic skull development of \u003cem\u003eD. naui\u0026nbsp;\u003c/em\u003eand the extant \u003cem\u003eH. aquaticus\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIn extant tragulids such as \u003cem\u003eH. aquaticus\u003c/em\u003e, which is often used as a comparison to fossil tragulids, males also show well-developed large, saber-like upper canines in contrast to females, where the upper canines are reduced, similar to fossil tragulids (Rössner 2007). However, cranial ornamentation varies among adult males and females of this species (Hartung and Böhme 2024) and in the other extant tragulid genera, \u003cem\u003eMoschiola\u0026nbsp;\u003c/em\u003eand \u003cem\u003eTragulus\u003c/em\u003e, the cranial crests are reduced (Guzmán 2018; Mennecart et al. 2018 and own observations). Therefore, in the fossil tragulid \u003cem\u003eD. naui\u003c/em\u003e the cranial ornamentation is much stronger developed than in \u003cem\u003eH. aquaticus\u0026nbsp;\u003c/em\u003e(fig, 1 and 2 in Hartung and Böhme 2024). The sagittal crest and the nuchal crests are comparable in their morphology to \u003cem\u003eH. aquaticus\u003c/em\u003e, but they are much more constricted and offset in \u003cem\u003eD. naui\u003c/em\u003e. The largest difference regarding cranial morphology of both species are the remarkable frontoparietal bulges of \u003cem\u003eD. naui\u003c/em\u003e, which are formed by the temporal lines on the parietal and an extension of the latter onto the frontal, anterior to the orbit. They are large, bony bulges, and form the parietal part which constricts a parietal plateau. These bulges only develop in males of \u003cem\u003eD. naui\u003c/em\u003e and are already present at wear stage 3-4 in SNSB-BSPG 2020 XCIV-3500 (Fig. 2D and 3D) or even earlier at an early wear stage 3 (SNSB-BSPG 2020 XCIV-8518, Fig. 2E and 3E). Cranial ornamentation in \u003cem\u003eH. aquaticus\u003c/em\u003e are less remarkable at wear stage 3-4 (Hartung and Böhme 2024, fig. 1 and 2) where only the temporal lines are slightly enhanced and confine to form a sagittal crest.\u003c/p\u003e\n\u003cp\u003eFig. 5 shows that parietal bulges are pneumatized at wear stage 3-4 (SNSB-BSPG 2020 XCIV-3500, Fig. 5C) up to wear stage 6 (SNSB-BSPG 2020 XCV-474, Fig. 5B) showing a spongiose bone matrix surrounded by the external parietal bone dorsally and the internal wall of the latter (Fig. 5A, C, and D). These bulges are probably well-developed and pneumatized even in younger individuals, but adequate specimens preserving teeth are missing. SNSB-BSPG XCIV 2020-8518 preserves no teeth but might be younger than SNSB-BSPG 2020 XCIV-3500 based on flatter parietal and frontal bulges. It is noticeable that these structures are visible despite the dorsoventral compression of the specimen (compare Fig. 2D and 2E). Subadult, male \u003cem\u003eD. naui\u003c/em\u003e, SNSB-BSPG 2020 XCIV-3500 and SNSB-BSPG 2020 XCIV- 8518, seem to have flatter parietal bulges and a less-developed frontal part of the bulges than the adult individuals, GPIT/MA/17690, SNSB-BSPG 2020 XCV-474, and NHMUK PV OR 40632 (Fig. 2A-C). However, these observations need to be taken with care, because of the different degrees of preservation of the fossil specimens. The parietal part of the bulges is especially visible throughout all ontogenetic stages, but the frontal part is very faint, probably due to compression. In the subadult specimens like SNSB-BSPG XCIV-2020 8518 and SNSB-BSPG 2020 XCIV-3500, a rugose surface is visible that forms the lateral part of the frontal in dorsal view (Fig. 2D and E). In contrast in females of \u003cem\u003eD.\u003c/em\u003e \u003cem\u003enaui\u003c/em\u003e of the same wear stage (Fig. 2J) this rugose surface is absent.\u003c/p\u003e\n\u003cp\u003eThe present ontogenetic series of \u003cem\u003eD. naui\u003c/em\u003e indicates that during ontogeny an increase in size and progressive enhancement of frontoparietal bulges occurs in males of \u003cem\u003eD. naui\u0026nbsp;\u003c/em\u003eand that the latter possess strong sexual dimorphic features of the skull already relatively early in life if comparable to \u003cem\u003eH. aquaticus\u003c/em\u003e. The bulges show allometric growth if compared to overall body size as typical for male sexual display features (Kodric-Brown et al. 2006). Females in contrast are much more similar to extant \u003cem\u003eH. aquaticus\u003c/em\u003e by possessing delicate and fine sagittal and nuchal crests and no frontoparietal bulges. In females, the sagittal crest and crest-like temporal lines are already visible at wear stage 4 as in specimen SNSB-BSPG 2020 XCIV-8970 (Fig. 2J and 3J), and these crests are similar in development and morphology with adult specimens of wear stage 6 as in specimen SNSB-BSPG 2020 XCV-357, 380, GPIT/MA/17841, SNSB-BSPG 2020 XCIV-18870, and GPIT/MA/18000-01 (Fig. 2F-I and 3F-I). In the virtual cross sections, no pneumatization as in males is visible (Fig. 5E-G), although in specimen SNSB-BSPG 2020 XCIV-8970 (Fig. 5G) the temporal lines that form delicate crests appear like that, but the latter is caused by the lateral compression of the skull with the bone structure being distorted.\u003c/p\u003e\n\u003cp\u003eThis means that in contrast to males of \u003cem\u003eD. naui\u003c/em\u003e, the cranial ornamentation of females does not develop or change in morphology during ontogeny and remarkable features like frontoparietal bulges are absent.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eComparison of cranial ontogeny of \u003cem\u003eDorcatherium naui\u003c/em\u003e and \u003cem\u003eDorcabune crassum\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAt present, there are only two other complete skulls known of another fossil tragulid, \u003cem\u003eDorcabune crassum\u003c/em\u003e. Guzmán (2018) describes a male skull of \u003cem\u003eDb. crassum\u003c/em\u003e from Walda-2 in Germany and furthermore mentions another skull of the same species from the Upper Freshwater Molasse of Thierhaupten in Germany published by Seehuber (2015). Guzmán (2018), as well as Hartung and Böhme (2022) assign the skull from Thierhaupten to a female individual and describe a sexual dimorphism in \u003cem\u003eDb. crassum\u003c/em\u003e that is comparable to \u003cem\u003eD. naui\u003c/em\u003e. However, in \u003cem\u003eDb. crassum\u003c/em\u003e, males have cranial ornamentation in form of bulges as well, but they differ in their morphology and are in general less markable if compared to \u003cem\u003eD. naui\u003c/em\u003e. In \u003cem\u003eDb. crassum\u003c/em\u003e, the frontal bulges are absent and only the posterior part of the parietal shows flatter bulges that confine to form a Y-structure with the sagittal crest (Guzmán 2018, fig. 4.5; Mennecart et al. 2018). This is different from \u003cem\u003eD. naui\u003c/em\u003e, where the bulges encompass the entire parietal and continue onto the frontal to encompass a parietal plateau and cover the orbit (Hartung and Böhme 2022 and Fig. 2). In contrast, the female skull morphology of \u003cem\u003eDb. crassum\u003c/em\u003e is rather similar to that of females of \u003cem\u003eD. naui\u003c/em\u003e and both sexes of \u003cem\u003eH. aquaticus\u003c/em\u003e, because it contains fine and delicate nuchal, temporal, and sagittal crests that follow the same morphology as in GPIT/MA/17841, GPIT/MA/18000-01, SNSB-BSPG 2020 XCIV-18870, as well as to SNSB-BSPG 2020 XCV-357 and SNSB-BSPG 2020 XCV-380 (all wear stage 6).\u003c/p\u003e\n\u003cp\u003eBased on the wear stage of the teeth, the male skull of \u003cem\u003eDb. crassum\u003c/em\u003e from Walda-2 is already senile, as there is no selenedont pattern visible anymore at the M3 (wear stage 8). It is therefore not directly comparable to any of the present specimens of \u003cem\u003eD. naui\u003c/em\u003e and unfortunately the exact individual age of GPIT/MA/16790 is not known, although it can be assumed that this specimen is the ontogenetic oldest from the presented series. However, the difference in the development of the cranial ornamentation is still visible and it is very unlikely that after wear stage 6 a pattern as in \u003cem\u003eDb. crassum\u003c/em\u003e will be present in senile males of \u003cem\u003eD. naui\u003c/em\u003e, because the parietal and frontoparietal bulges are already well-developed and confine with the sagittal crest posteriorly.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cu\u003eInterspecific heterochrony\u003c/u\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cem\u003eD. naui\u003c/em\u003e is closely related to the extant water chevrotain \u003cem\u003eH. aquaticus\u003c/em\u003e. The exact relationships were studied last by Sánchez et al. (2015, 2018) were \u003cem\u003eD. naui\u003c/em\u003e plotted as the sister taxon to \u003cem\u003eH. aquaticus\u003c/em\u003e. However, phylogenetic relationships might have been much more complex due to the limit of the fossil record in Africa for example. Both species share similarities in cranial morphology and \u003cem\u003eH. aquaticus\u003c/em\u003e shows the strongest cranial ornamentation among the extant tragulids, however, \u003cem\u003eD\u003c/em\u003e. \u003cem\u003enaui\u003c/em\u003e displays a markedly stronger and more intricate cranial ornamentation compared to the extant analogues, suggesting a heterochronic origin of this feature. To test this hypothesis, we apply the heterochrony model of Reilly et al. (1997), which investigates patterns of morphological change between ancestral and descendant taxa. For this purpose, the morphology of cranial ornamentation in \u003cem\u003eDorcatherium naui\u0026nbsp;\u003c/em\u003e(Hartung and Böhme 2022) is defined as the “ancestral state”, whereas the cranial morphology of \u003cem\u003eHyemoschus aquaticus\u003c/em\u003e (Hartung and Böhme 2024) represents the “descendant state”, based on the currently available phylogenetic framework (see above). To incorporate a temporal dimension, we apply the age model established for \u003cem\u003eH. aquaticus\u003c/em\u003e by Dubost (2016) to \u003cem\u003eD. naui\u003c/em\u003e (Hartung and Böhme 2024) and reconstruct the ontogenetic trajectory of cranial ornamentation by establishing an ontogenetic series based on dental wear stages (Figs. 1 and 2). Dental wear stages follow the classification proposed by Hartung and Böhme (2024). We further assume that the onset of sexual maturity in \u003cem\u003eD. naui\u003c/em\u003e and \u003cem\u003eH. aquaticus\u003c/em\u003e was relatively similar, if not identical. This assumption allows a direct comparison of the somatic development of cranial ornamentation throughout ontogeny between both taxa.\u003c/p\u003e\n\u003cp\u003eAfter Reilly et al. (1997) we observe a paedomorphic development of the cranial ornamentation (Fig. 6) in \u003cem\u003eHyemoschus aquaticus\u003c/em\u003e compared to \u003cem\u003eD. naui\u003c/em\u003e, a truncation of the fossil ontogeny compared to the morphology of the extant analogue caused by a “deceleration” (after Reilly et al. 1997) of the development of the morphological character. This was already mentioned for \u003cem\u003eDb. crassum\u003c/em\u003e (Mennecart et al. 2018), which likewise exhibits pronounced cranial crests that are morphologically similar to those of \u003cem\u003eD. naui\u0026nbsp;\u003c/em\u003e(Hartung and Böhme 2022). In contrast, \u003cem\u003eH. aquaticus\u003c/em\u003e shows less developed cranial crests and bulges, as well as the absence of a parietal plateau, when compared to \u003cem\u003eD. naui\u003c/em\u003e. We hypothesize that the onset of cranial ornamentation growth (α) is similar in both taxa, but that a higher developmental rate (−k) in \u003cem\u003eD. naui\u003c/em\u003e results in more complex and developed cranial structures by the time developmental offset (β) is attained.\u003c/p\u003e\n\u003cp\u003eIt is also possible to argue for a post-displacement (positive onset, fig. 1 in Reilly et al. 1997) of the shape development, in which a delayed onset in the extant tragulid relative to the fossil one is present. \u0026nbsp;In this scenario, the development of cranial crests starts earlier during ontogeny in \u003cem\u003eD. naui\u003c/em\u003e and has therefore more time to develop. Thus, the initiation of cranial-crest growth in \u003cem\u003eHyemoschus\u003c/em\u003e would occur at a later time, resulting in a shortened developmental interval and reduced crest elaboration compared to \u003cem\u003eD. naui\u003c/em\u003e (α-\u0026gt;α\u003csub\u003e1\u003c/sub\u003e). The developmental rate however, would be the same in contrast to a paedomorphosis and the onset time (β) would be similar. Weather this developmental process in \u003cem\u003eD. naui\u003c/em\u003e is really beginning earlier if compared to \u003cem\u003eH. aquaticus\u003c/em\u003e, cannot be conclusively said at the moment, because neonate to juvenile skulls of wear stage 0 to wear stage 2 are so far not present in \u003cem\u003eD. naui\u003c/em\u003e or any other fossil tragulid.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eWhen comparing another fossil tragulid with well-known skulls, \u003cem\u003eDb. crassum,\u003c/em\u003e to \u003cem\u003eH. aquaticus\u003c/em\u003e, both taxa show greater morphological similarity to each other than to \u003cem\u003eD. naui\u003c/em\u003e. In \u003cem\u003eDb. crassum\u003c/em\u003e and \u003cem\u003eH. aquaticus\u003c/em\u003e, the frontal component of the cranial bulges as well as the parietal plateau are absent. In addition, \u003cem\u003eDb. crassum\u003c/em\u003e exhibits broader temporal lines and a more pronounced sagittal crest, forming the characteristic Y-shaped structure. This configuration has been interpreted as a hyperdeveloped condition relative to \u003cem\u003eH. aquaticus\u003c/em\u003e according to Mennecart et al. (2018), which is consistent with a heterochronic shift involving post-displacement. Consequently, \u003cem\u003eDb. crassum\u003c/em\u003e may reflect a heterochronic trajectory that differs from the pattern most likely inferred for \u003cem\u003eH. aquaticus\u003c/em\u003e and \u003cem\u003eD. naui\u003c/em\u003e.\u003c/p\u003e\n\u003cp\u003eThe morphological differences in the elaboration of cranial ornamentation and shape of the latter between \u003cem\u003eD. naui\u003c/em\u003e and \u003cem\u003eH. aquaticus\u003c/em\u003e are less-likely to be a result of hypomorphosis, because this would mean that the developmental process ends earlier in \u003cem\u003eH. aquaticus\u003c/em\u003e, while \u003cem\u003eD. naui\u003c/em\u003e extends even further, truncating the fossil ontogeny. Both taxa would have the same onset time, and the pathway of development would be similar, which is clearly not the case, because the cranial morphology in \u003cem\u003eD. naui\u003c/em\u003e is different from \u003cem\u003eH. aquaticus\u003c/em\u003e and even in juvenile male individuals of \u003cem\u003eD. naui\u003c/em\u003e (SNSB-BSPG 2020 XCIV-3500 wear stage 3-4 and SNSB-BSPG 2020 XCIV-8518), the cranial bulges are morphologically clearly distinguishable from the extant tragulid. \u003cem\u003eD. naui\u003c/em\u003e exhibits frontoparietal bulges that constrict a parietal plateau and form a strong broad sagittal crest (Hartung and Böhme 2022). In \u003cem\u003eH. aquaticus\u003c/em\u003e, the temporal lines are enhanced and also the sagittal crest can be broad and strong, but the frontoparietal bulges, as well as the parietal plateau are absent. Moreover, the cranial ornamentation in \u003cem\u003eH. aquaticus\u003c/em\u003e continues to grow even in senile specimen (fig. 2 in Hartung and Böhme 2022) and the same can be assumed for \u003cem\u003eD. naui\u003c/em\u003e based on the morphology of GPIT/MA/17690 (Fig. 2A and 3A). Nevertheless, \u003cem\u003eH. aquaticus\u003c/em\u003e appears unable to attain the degree of cranial complexity exhibited by \u003cem\u003eD. naui\u003c/em\u003e and thus no hypomorphosis is present.\u003c/p\u003e\n\u003cp\u003eConclusively, \u003cem\u003eD. naui\u003c/em\u003e already exhibits a strong sexual dimorphism relatively early in life similar to \u003cem\u003eH. aquaticus\u003c/em\u003e, the only extant tragulid with noticeable cranial ornamentation. The development of these structures has a higher rate in the fossil relative. A comparison to other fossil subadult (wear stage 3-4) tragulids, such as \u003cem\u003eDb. crassum\u003c/em\u003e, would be very interesting, however, no skulls of that age exist so far. It is noticeable, that the extend of cranial ornamentation of \u003cem\u003eH. aquaticus\u003c/em\u003e varies among the sexes in such an extent, that it is not an inclusive feature to distinguish among the sexes and therefore upper canine size remains the most reliable character for sex differentiation in this species. This is a contrast to the fossils \u003cem\u003eD. naui\u003c/em\u003e and \u003cem\u003eDb. crassum\u003c/em\u003e and therefore comparison of skulls of \u003cem\u003eHyemoschus\u003c/em\u003e with \u003cem\u003eD. naui\u003c/em\u003e as well as with \u003cem\u003eDb. crassum\u003c/em\u003e need to be taken with care.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cu\u003eMortality analysis and survivorship rate of \u003cem\u003eD. naui\u003c/em\u003e\u003c/u\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe mortality profile of \u003cem\u003eD. naui\u003c/em\u003e individuals from Hammerschmiede was assessed based on the state of wear of the M3 and dP4, as well as of the lower equivalent m3 and dp4 according to wear stages established by Hartung and Böhme (2024). Based on the upper and lower teeth combined, in HAM4, the total number of individuals that died at a juvenile stage (w0-w5) is 22 and the number of individuals that died at an adult or senile stage (w6-w8) is 22 as well (Fig. 7). At HAM5, the sample size is much smaller and no dP4 of wear stage 0 and wear stage 1 are available. However, the pattern is similar to HAM4, because in HAM5, six individuals died at juvenile stage and seven at an adult stage respectively. The low number of juveniles, combined with the high total number of individuals (MNI=44) at HAM4, indicates that juvenile survivorship reached 50%, meaning that every second individual completes sexual maturity. The same can be attributed to the individuals from HAM5, but has to be taken with some care because of the lower sample size (MNI=13; Fig. 7).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cu\u003eBody mass of \u003cem\u003eD. naui\u003c/em\u003e\u003c/u\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFor body mass estimates on the combined HAM5 and HAM4 sample we use the log-transformed regressions of Janis (1990) for lower molar length (m1-m3) and length of m2. Body mass according to lower molar length range from 29.1 to 35.4 kg (mean 32 kg, n=15) and for m2 length from 22.2 to 31.2 kg (mean 27.2 kg, n=21). A combined estimate using both regressions on 15 adult mandibles results in body mass between 26.2 and 31.7 kg, with a mean of 29.4 kg. The individual body mass estimates show a bimodal distribution with peaks at 28-29 kg and 30-31 kg (Fig. 7D). The female skull GPIT/MA/18000-01 contains a mandible as well, which was already published in Hartung and Böhme (2022). The estimated body mass of this female was estimated to 31.2 kg (32.6 kg using m1-m3 regression, 29.9 kg using m2 regression), suggesting to attribute the heavier mode to females and the lighter mode to male individuals. This attribution is corroborated by the even larger juvenile female skull SNSB-BSPG 2020 XCIV-08968, which includes both hemimandibles with dp1-m2. The size of their m2s are among the largest in our Hammerschmiede sample and indicate a body mass of 30.7 kg using the m2 regression (see appendix SF1).\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003e\u003cstrong\u003eInfluence of sexual dimorphism and intraspecific variability on skull ontogeny in \u003cem\u003eD. naui\u003c/em\u003e and \u003cem\u003eH. aquaticus\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSexual cranial features develop in \u003cem\u003eH. aquaticus\u003c/em\u003e within wear stage 3 between an age of 10-16 month (Hartung and Böhme 2024 and Dubost 2016). In males, development of testicle mass starts at 5-9 month (wear stage 1) and production of spermatozoa at 17-27 months during wear stage 5 (Dubost 2016). In \u003cem\u003eD. naui\u003c/em\u003e, cranial sexual dimorphism is visible at wear stage 3-4 and it is likely that this morphology of the skull develops even earlier at early wear stage 3 as visible in the skull SNSB-BSPG 2020 XCIV-8518 (Fig. 2E) similar to \u003cem\u003eH. aquaticus\u003c/em\u003e. The morphology of the cranial bulges in \u003cem\u003eD. naui\u003c/em\u003e, however, is unique among both extant and fossil tragulids and differs markedly from that of \u003cem\u003eH. aquaticus\u003c/em\u003e, even at comparable wear stages. This supports the hypothesis that the cranial structures in \u003cem\u003eHyemoschus\u003c/em\u003e are paedomorphic if compared to \u003cem\u003eD. naui\u003c/em\u003e rather than being a result of post-displacement, where the development of cranial crests and bulges starts earlier but follows the same morphological trajectories (Reilly et al. 1997, Dubost 2016). However, the age of sexual maturity in \u003cem\u003eH. aquaticus\u003c/em\u003e cannot be directly related to \u003cem\u003eD. naui\u003c/em\u003e, but it might be possible that, following the pattern of Hartung and Böhme (2024, tab. 1 and Fig. 5), the sexual maturation starts when the cranial features develop. If this is the case, the onset of sexual maturation of \u003cem\u003eD. naui\u003c/em\u003e could start at early wear stage 3 (or even earlier), similar to \u003cem\u003eH.\u003c/em\u003e \u003cem\u003eaquaticus\u003c/em\u003e, although the development of adult male sexual display features is much stronger in males of \u003cem\u003eD. naui\u003c/em\u003e than in male \u003cem\u003eH. aquaticus\u003c/em\u003e. In \u003cem\u003eD. naui\u003c/em\u003e the characteristics of cranial crests are as important as the development of upper canines, as for example in specimen GPIT/MA/17690, where canines are not preserved, but the sex is unambiguous. However, the degree of variation within these crests is still unknown and needs to be evaluated in the future when more skulls are available.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eLimits of this study\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis model still leaves open questions, such as the morphology of the cranial features of fossil tragulids at wear stage 0-2, because no neonate or early juvenile skulls are available so far and it is questionable whether preservation of those specimens is even possible. Based on the strong development of cranial features in \u003cem\u003eD. naui\u003c/em\u003e, it might be possible that some degree of ornamentation is already visible at wear stage 2, which is not the case in \u003cem\u003eH. aquaticus\u003c/em\u003e.\u003c/p\u003e\n\u003cp\u003eMoreover, the preservation of fossils, especially of juvenile individuals, is often deficient and can alter the identification of cranial structures and also makes comparison of any measurements difficult. For example, the virtual cross-sections of the fossil skulls (Fig. 5) show that bulges are present in all males: They show bone surface surrounding these structures, with pneumatized inner part. The strongest bulges are visible in GPIT/MA/17690, which is the oldest individual of the series (see description). However, in SNSB-BSPG 2020 XCV-474 from HAM5, the bulges are flattened and the inner structure is altered due to compression. Therefore, the spongiose part of the bone is barely visible, but the bony overhang is preserved, which is not the case in females, and the bulges are best visible in that specimen from external view (Fig. 2B). In GPIT/MA/18000-01, the skull roof shows longitudinal cracks due to the lateral compression, which alters the cranial morphology. However, it is clearly visible in Hartung and Böhme (2022), as well as in figure 2G that there are no such bulges visible as in males.\u003c/p\u003e\n\u003cp\u003eFurthermore, age determination for extant and fossil individuals in this study follows the stages established by Dubost (2016) and subsequently adapted for fossil tragulids by Hartung and Böhme (2024). For the fossil specimens in particular, absolute individual ages are yet unknown, and the onset of sexual maturation remains uncertain and can only be inferred.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCranial ornamentation and upper canines as display features of \u003cem\u003eD. naui\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe present ontogenetic series of \u003cem\u003eD. naui\u003c/em\u003e indicates allometric growth pattern of the cranial ornamentation as typical for male display features (Kodric-Brown et al. 2006). Males of \u003cem\u003eD. naui\u003c/em\u003e possess pronounced and well-developed display features of the skull already before the M3/m3 molar eruption at a relatively early ontogenetic stage at wear stage 3-4 (or even at an early wear stage 3 as in SNSB-BSPG 2020 XCIV-8518; Fig. 3E). In \u003cem\u003eH. aquaticus\u003c/em\u003e the cranial crests (temporal lines and sagittal crest) are only fine and delicate and start to develop at wear stage 3-4, when the large upper canines already erupt. Thus, the enhancement and strong expression of this cranial trait in \u003cem\u003eD. naui\u003c/em\u003e shows that the development of the trait might start relatively early in life, similar to the \u003cem\u003eH. aquaticus\u003c/em\u003e. This may be because weapons or display features need to be ready as close to adult form as possible by the time they reach sexual maturity to compete successfully for mating (Calamari 2016). In \u003cem\u003eH. aquaticus\u003c/em\u003e, sexual maturation in males starts at 5–9 months (wear stage 1) and completes at 17–27 months (wear stage 5), whereas in females sexual development starts after 10–16 months (wear stage 3) and reaches its maximum at 27 months (wear stage 5) (Dubost 2016; Hartung and Böhme 2024). The cranial features of males, however, develop at wear stage 3-4.\u003c/p\u003e\n\u003cp\u003eHowever, it was stated in Hartung and Böhme (2024) that cranial ornamentation in \u003cem\u003eH. aquaticus\u003c/em\u003e is not suitable for distinguishing among the sexes and might therefore not even be a display feature at all. Instead, upper permanent canines erupt at wear stage 3 when the small and cone-like deciduous upper canines are shed. This event occurs within the general time frame of sexual maturation in male \u003cem\u003eH. aquaticus\u003c/em\u003e; however, it cannot be considered a reliable proxy for the onset of sexual maturity alone. Maturation represents a gradual process extending from wear stage 1 to wear stage 5. In males, two main developmental milestones are observed at approximately 5–9 months (wear stage 1) and 17–27 months (wear stage 5), whereas in females major developmental changes occur between 10–16 months (wear stage 3), with full maturation reached at around 27 months (wear stage 5 according to Dubost 2016 and Hartung and Böhme 2024).\u003c/p\u003e\n\u003cp\u003eIn addition to the beforementioned strong cranial ornamentation,\u003cem\u003e\u0026nbsp;D. naui\u003c/em\u003e also possesses saber-like upper canines as visible in NHMUK PV OR 40632. This observation could, in turn, suggest that the intraspecific competition for females was relatively high and that the ecology of \u003cem\u003eD. naui\u0026nbsp;\u003c/em\u003ediffers from \u003cem\u003eH. aquaticus\u003c/em\u003e, possibly involving a more complex social structure than in the extant species, which lacks any hierarchical organization or strong territorial behavior and lives mainly solitary (Dubost 1975). Although, during mating season, extant males have short combats where they use their upper canines as weapons for stabbing or slashing. It might be possible that \u003cem\u003eD. naui\u003c/em\u003e rather used frontoparietal bulges as display features than stabbing each other, leading to less fatal combat outcomes (Hartung \u0026amp; Böhme 2022). This would also be consistent with the theory of Calamari (2016), who states that complex sexual competition structures, like the described cranial ornamentation in \u003cem\u003eD. naui\u003c/em\u003e, were used in non-lethal combat or ritualized male-male fights in contrast to simple structures that are commonly used for more violent fighting behavior, like the upper canines.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eReproductive traits, life-history patterns, and habitats\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eResults of the mortality analysis and the survivorship rate of the HAM4 population of \u003cem\u003eD. naui\u003c/em\u003e (Fig. 7A, C) revealed that 50% of newborn tragulids (22 out of MNI=44) survive the juvenile stage (wear stage 0-5) and reach adulthood (wear stage 6-8). Survivorship (mortality) strongly decrease (increase) for prime adults (wear stage 6 and 7), and only one individual reached wear stage 8. In HAM5 the MNI is smaller (MNI=13) compared to HAM4, but still most individuals die at wear stage 6 similar to HAM4. The juvenile stage seems to be underrepresented in HAM5 with no individuals of wear stage 0 and wear stage 1. It is not surprising that most individuals in both horizons die at wear stage 6, because it covers a similar long period (approximately 27 Months to 4.5 years in \u003cem\u003eHyemoschus aquaticus\u003c/em\u003e, Dubost 2016) as all juvenile stages (wear stages 0-5) together.\u003c/p\u003e\n\u003cp\u003eThe relatively high survivorship of juveniles suggests that \u003cem\u003eD. naui\u003c/em\u003e likely exhibited a low reproductive rate, potentially resulting from small litter sizes and a reduced number of reproductive events over the female life span. The litter size in \u003cem\u003eHyemoschus\u003c/em\u003e is very small with only one young per litter (Dubost 2016) and we assume the same for \u003cem\u003eD. naui\u003c/em\u003e. Moreover, given the equal number of juveniles compared to adults (Fig. 7), it is possible that females of \u003cem\u003eD. naui\u003c/em\u003e had only very few, possibly four, reproductive events throughout their life time resulting in a low reproductive rate. This may indicate that in \u003cem\u003eD. naui\u003c/em\u003e senility is reached after an age of six years, which compares well with \u003cem\u003eH. aquaticus\u003c/em\u003e (wear stage 8 at \u0026gt;6.5 years; Dubost 2016, Hartung \u0026amp; Böhme 2024), and may suggest that the maximum life span of both species was relatively short (maximum age in wild populations of \u003cem\u003eH. aquaticus\u0026nbsp;\u003c/em\u003eis normally eight years and potentially 11-13 years according to Meijaard (2011).\u003c/p\u003e\n\u003cp\u003eBody size analysis in form of body mass calculations revealed that females tend to be larger than males, in which females of \u003cem\u003eD. naui\u003c/em\u003e are on average approximately 2 kg or 7% heavier than males. The mean weight for males lies within a range of 28-29 kg and females reach a mass of 30-31 kg. \u003cem\u003eHyemoschus\u003c/em\u003e displays an even larger sexual size dimorphism (SSD) pattern where males have an average weight of 9.7 kg and females around 12 kg (Robin 1990; Nowak 1999). However, the most pronounced difference between both species is the absolute body mass, which in \u003cem\u003eD. naui\u003c/em\u003e is more than twice as high as in \u003cem\u003eH. aquaticus.\u003c/em\u003e This important biologic feature may reflect ecological adaptations in more seasonal and open deciduous broadleaf forests during the Miocene of Europe, compared to the thickets of African rainforests where \u003cem\u003eHyemoschus\u003c/em\u003e is living. Smaller body size in extant tragulids may facilitate concealment and escape from predators in densely vegetated habitats (Rössner 2007; Meijaard 2011). A preference of \u003cem\u003eD. naui\u003c/em\u003e to more open riparian woodlands would be supported by the high numbers of individuals found in HAM4 (MNI=44), making here this species to the most abundant large mammal, whereas in the HAM5 level \u003cem\u003eD. naui\u003c/em\u003e (MNI=13) is outcompeted by the deer \u003cem\u003eEuprox furcatus\u003c/em\u003e (MNI=21).\u003c/p\u003e\n\u003cp\u003eThis female-biased SSD is common among mammals and is especially known from smaller mammals as for example Lagomorpha (Darwin 1871; Lindenfors et al. 2007; Tombak et al. 2024). This SSD is explained by a higher fecundity selection in small mammals (Darwin 1871), because of higher energetic demands on females like producing eggs in comparison to sperm, gestation, and lactation, and more space that is used for keeping the eggs. Therefore, female mammals of smaller species develop larger energy stores for high metabolic costs of gestation and lactation, ultimately promoting higher offspring survivorship and reproductive success. However, this theory does not always apply because male sexual selection strategy is often based on a larger body size in males compared to females, which is used for competition with other males (Darwin 1871; Alexander and Borgia 1979; Weckerly 1998; Lindenfors et al. 2007; Cassini 2020a, b, 2022, 2023).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePotential paleobiogeographic scenario for \u003cem\u003eHyemoschus\u003c/em\u003e\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSeveral recent publications suggest a close phylogenetic relationship between the fossil Eurasian species \u003cem\u003eDorcatherium naui\u003c/em\u003e and the extant African \u003cem\u003eHyemoschus aquaticus\u003c/em\u003e (Geraads 2010; Sanchez et al. 2015, 2018), designated as ‘true \u003cem\u003eDorcatherium\u003c/em\u003e-clade’ by Sanchez et al. (2018). \u003cem\u003eDorcatherium naui\u003c/em\u003e is known from Western and Central Europe from the late Middle Miocene till the early Late Miocene, between 12.4 and ~9.5 Ma (Aiglstorfer et al. 2014), whereas the species occurs in Pakistan in the Chinji Formation in the late Middle Miocene (Guzman and Rössner 2021). Several potential, but badly known, European descendants of \u003cem\u003eD. naui\u003c/em\u003e are known from later parts of the Late Miocene in southeastern Europe (e.g. Kostopoulos \u0026amp; Sen 2016), but after ~7.5 Ma the selenodont lineage of \u003cem\u003eDorcatherium\u003c/em\u003e, and the family Tragulidae at all, has disappeared from Western Eurasia and shortly after from Pakistan.\u003c/p\u003e\n\u003cp\u003eIn Africa, tragulids are common and diverse during the Early and Middle Miocene (e.g. Pickford 2001; Sanchez et al. 2015, 2018; Musalizi et al. 2023), but known from only one Late Miocene site (the 9 Ma old Ngeringerowa site in Kenya; Pickford 1991). After a four million years long gap for fossil tragulids in Africa, the family reappeared with the oldest fossil record\u003cem\u003e\u0026nbsp;of H. aquaticus,\u0026nbsp;\u003c/em\u003ewhichdates to the early Pliocene of the Mabaget Member at Tugen Hills in Kenya, Africa(5-4.5 Ma Pickford et al. 2004). Although this record is based on sparse dental material only, according to Geraads (2010) the upper molar resembles more closely the Late Miocene \u003cem\u003eDorcatherium\u003c/em\u003e from southeastern Europe than the extant water African chevrotain.\u003c/p\u003e\n\u003cp\u003eThe later part of the Late Miocene (Messinian) was a time of massive mammalian dispersals from Eurasia into Africa, triggered by transient hyperaridity events in Western Asia (Böhme et al. 2021). The dispersing genera have both a southern Asian and southeast European origin and we speculate that the ‘true \u003cem\u003eDorcatherium\u003c/em\u003e-clade’ may have been part of these dispersals as well.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn this study, we present the first ontogenetic series of a fossil tragulid based on 13 skulls from Hammerschmiede and one from Eppelsheim. The examined fossil sample of \u003cem\u003eDorcatherium naui\u003c/em\u003e, in comparison with the phylogenetically related extant African water chevrotain \u003cem\u003eHyemoschus aquaticus\u003c/em\u003e, reveals that (I) \u003cem\u003eD. naui\u003c/em\u003e exhibits more pronounced cranial ornamentation than extant tragulids, allowing reliable distinction between males and females, particularly when upper canines are absent; (II) the development of distinct cranial crests in male \u003cem\u003eD. naui\u003c/em\u003e begins relatively early in life (at least by wear stage 3-4, if not earlier), similar to \u003cem\u003eH. aquaticus\u003c/em\u003e, indicating a comparable onset of sexual maturity; and (III) heterochronic changes in the development of cranial crests and bulges occurred in \u003cem\u003eD. naui\u003c/em\u003e relative to \u003cem\u003eHyemoschus\u003c/em\u003e, resulting in paedomorphic traits of the latter. These findings suggest that \u003cem\u003eD. naui\u003c/em\u003e likely exhibited a unique mating behavior compared to extant chevrotains, with males relying more on ritualized displays. Moreover, the pronounced body size difference between \u003cem\u003eD. naui\u003c/em\u003e and \u003cem\u003eH. aquaticus\u003c/em\u003e, with \u003cem\u003eD. naui\u003c/em\u003e being more than twice as large, suggests that \u003cem\u003eD. naui\u003c/em\u003e may have been adapted to more open habitats compared to the extant species.\u003c/p\u003e\n\u003cp\u003eAdditionally, a large dataset of isolated teeth and mandibles was used for a mortality analysis and body mass estimations. We observe very similar biological patterns in the fossil \u003cem\u003eD. naui\u003c/em\u003e as in the extant \u003cem\u003eH. aquaticus\u003c/em\u003e. Incorporating the early onset of sexual maturity, sexual size dimorphism in which females are larger than males, and large survivorship of juveniles, we conclude that \u003cem\u003eD. naui\u003c/em\u003e probably had a low reproductive rate (one young per litter) and similar maximum life span compared to \u003cem\u003eHyemoschus\u003c/em\u003e.\u0026nbsp;\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eGPIT: Geologisch-Pal\u0026auml;ontologisches Institut T\u0026uuml;bingen; NHMUK: Natural History Museum of London; SNSB-BSPG: Staatliche Naturwissenschaftliche Sammlungen Bayerns-Bayerische Staatssammlung f\u0026uuml;r Pal\u0026auml;ontologie und Geologie\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eHere we greatly thank Emmanuel Gilissen (RMCA, Brussels) and Mathys Rotonda for access to the collection of \u003cem\u003eHyemoschus\u003c/em\u003e at the RMCA, Tervuren, Brussels. We moreover thank Frank Zachos (NHM Vienna) for comparative pictures of \u003cem\u003eMoschiola\u003c/em\u003e. We also thank Gabriel Ferreira and Kristina Kyriakouli for their support and assistance with the µCT scans and Thomas Lechner (all Tübingen) for providing the MNI for \u003cem\u003eEuprox furcatus\u003c/em\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStatement of competing interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors certify that they have no affiliations with or involvement in any organization or entity with any financial interest or non-financial interest in the subject matter or materials discussed in this manuscript.\u003c/p\u003e\n\u003ch2\u003eFunding statement\u003c/h2\u003e\n\u003cp\u003eSince 2020, the Hammerschmiede excavations and the associated research have been generously supported by the Bavarian State Parliament, the Bavarian State Ministry of Research and Art and the Bavarian Natural History Collections. Special thanks go to the Freie Wähler parliamentary group and its deputy chairman, Bernhard Pohl, member of the state parliament.\u003c/p\u003e\n\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\n\u003cp\u003eJ.H. and M.B. wrote the main manuscript and prepared, as well as provided the research data. J.H. prepared the figures. All authors reviewed the manuscript\u003c/p\u003e\n\u003ch2\u003eData Availability\u003c/h2\u003e\n\u003cp\u003eµCT data were deposited into the Morphosource database under the project ID: ID: 000810219 and are available at the following URL: www.morphosource.org/projects/000810219?locale=en.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eAiglstorfer M, R\u0026ouml;ssner GE and B\u0026ouml;hme M. (2014) \u003cem\u003eDorcatherium naui\u003c/em\u003e and pecoran ruminants from the late Middle Miocene Gratkorn locality (Austria). 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Communications of the Geological Survey of Namibia 19: 110\u0026ndash;122\u003c/li\u003e\n\u003cli\u003eS\u0026aacute;nchez IM, Quiralte V and Morales J (2011) Solving an old dispute: anatomical differences between the European Miocene chevrotains \u003cem\u003eDorcatherium crassum\u003c/em\u003e (Lartet, 1839) and \u003cem\u003eDorcatherium naui\u003c/em\u003e Kaup \u0026amp; Scholl, 1834 (Mammalia, Ruminantia, Tragulidae). Paleontologia i Evolucio: 343\u0026ndash;347\u003c/li\u003e\n\u003cli\u003eS\u0026aacute;nchez IM, Quiralte V, Rios M, Morales J and Pickford M (2015) First African record of the Miocene Asian mouse-deer \u003cem\u003eSiamotragulus\u003c/em\u003e (Mammalia, Ruminantia, Tragulidae): implications for the phylogeny and evolutionary history of the advanced selenodont tragulids. 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Proceedings of the Royal Society B: Biological Sciences 276: 4329\u0026ndash;4334\u003c/li\u003e\n\u003cli\u003eTombak KJ, Hex SBSW and Rubenstein DI (2024) New estimates indicate that males are not larger than females in most mammal species. Nat Commun 15: 1872\u003c/li\u003e\n\u003cli\u003eWeckerly FW (1998) Sexual-size dimorphism: influence of mass and mating systems in the most dimorphic mammals. Journal of Mammology 79: 33\u0026ndash;52\u003c/li\u003e\n\u003cli\u003eWhitmore FC (1953) Cranial morphology of some Oligocene Artiodactyles. Geological Survey Professional Paper: 117\u0026ndash;159\u003c/li\u003e\n\u003cli\u003eZietzschmann O, Ackerknecht E and Grau H (1943) Handbuch der vergleichenen Anatomie der Haustiere,\u003cem\u003e \u003c/em\u003eSpringer Berlin Heidelberg\u003cem\u003e, \u003c/em\u003eBerlin\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"journal-of-mammalian-evolution","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jomm","sideBox":"Learn more about [Journal of Mammalian Evolution](http://link.springer.com/journal/10914)","snPcode":"10914","submissionUrl":"https://submission.nature.com/new-submission/10914/3","title":"Journal of Mammalian Evolution","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"skull morphology, population studies, Artiodactyla, life history, habitat analysis","lastPublishedDoi":"10.21203/rs.3.rs-9029355/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9029355/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eOntogeny describes the individual developmental history of an organism across its lifetime. Comparative ontogenetic approaches can be applied to closely related taxa and provide a powerful framework for investigating evolutionary changes in morphology, life history, and developmental timing between fossil and extant relatives. This approach is particularly informative for the fossil chevrotain \u003cem\u003eDorcatherium naui\u003c/em\u003e and the extant African water chevrotain \u003cem\u003eHyemoschus aquaticus\u003c/em\u003e, which are consistently recovered as sister taxa in phylogenetic analyses. Until recently, the fossil record of \u003cem\u003eD. naui\u003c/em\u003e was sparse, despite the fact that this species represents the type species of one of the most frequently cited fossil tragulid genera. Here we demonstrate that the life history and ecological characteristics, as sexual maturity, sexual size dimorphism, reproduction rate and maximum life span, inferred for fossil \u003cem\u003eD. naui\u003c/em\u003e share numerous similarities with those of extant \u003cem\u003eH. aquaticus\u003c/em\u003e, supporting a close phylogenetic relationship between both taxa. However, we find that \u003cem\u003eD. naui\u003c/em\u003e might have lived in more open riparian woodlands, compared to its extant relative. In addition, our results provide evidence for a paedomorphic condition of cranial ornamentation in \u003cem\u003eH. aquaticus\u003c/em\u003e relative to \u003cem\u003eD. naui\u003c/em\u003e. Together, these findings support the use of \u003cem\u003eH. aquaticus\u003c/em\u003e as a suitable modern analogue for fossil tragulids in general, and for \u003cem\u003eDorcatherium\u003c/em\u003e in particular. Moreover, the observed similarities between both taxa are consistent with a paleobiogeographic scenario involving a dispersal event of an ancestral form morphologically similar to \u003cem\u003eD. naui\u003c/em\u003e from Eurasia into Africa during the Late Miocene, followed by independent evolution culminating in the emergence of \u003cem\u003eH. aquaticus\u003c/em\u003e during the Pliocene.\u003c/p\u003e","manuscriptTitle":"Ontogenetic skull development and paleobiology of the tragulid Dorcatherium naui (Mammalia: Artiodactyla) from the early Late Miocene hominid locality Hammerschmiede (Germany)","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-19 19:59:33","doi":"10.21203/rs.3.rs-9029355/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-05-05T06:55:52+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-05T02:13:17+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-08T15:48:18+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"335388526050557249581168756158769272147","date":"2026-03-19T13:53:49+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"113101162400174523697328495091188013934","date":"2026-03-19T09:28:52+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-03-17T08:56:20+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-03-13T04:22:49+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-03-13T04:22:42+00:00","index":"","fulltext":""},{"type":"submitted","content":"Journal of Mammalian Evolution","date":"2026-03-04T10:46:52+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"journal-of-mammalian-evolution","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"jomm","sideBox":"Learn more about [Journal of Mammalian Evolution](http://link.springer.com/journal/10914)","snPcode":"10914","submissionUrl":"https://submission.nature.com/new-submission/10914/3","title":"Journal of Mammalian Evolution","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"884728cb-0664-41df-84be-d93998fab5ec","owner":[],"postedDate":"March 19th, 2026","published":true,"recentEditorialEvents":[{"type":"decision","content":"Revision requested","date":"2026-05-05T06:55:52+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-05T02:13:17+00:00","index":13,"fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-05-17T09:23:17+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-19 19:59:33","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9029355","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9029355","identity":"rs-9029355","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}