Fin spine ontogeny in the Devonian shark Wellerodus priscus: Paleo-Evo-Devo insights into early chondrichthyan dermal skeleton development

Fin spine ontogeny in the Devonian shark Wellerodus priscus: Paleo-Evo-Devo insights into early chondrichthyan dermal skeleton development | 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 Fin spine ontogeny in the Devonian shark Wellerodus priscus: Paleo-Evo-Devo insights into early chondrichthyan dermal skeleton development Richard Flament, Nathaniel Bertrand-Maltais, Daniel Potvin-Leduc, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8895999/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 10 You are reading this latest preprint version Abstract Background Cartilaginous fishes (chondrichthyans) from the Devonian period (419 to 359 million years, Ma) are primarily known from fossilized isolated dermal elements such as teeth, scales, and fin spines. Although previous studies have described the morphology and the histology of these elements, their developmental patterns remain poorly understood. In this study, we propose to explore developmental patterns of fin spines by integrating analyses of ornamentation, morphology, and histology. Results We present the first description of the developmental patterns for the fin spines of the Middle Devonian shark Wellerodus priscus , from the Cairo Quarry Lagerstätte in New York State, USA. Based on the ornamentation pattern and paleohistological (thin sections and micro-computed tomography) characteristics, we identify two distinct growth axes in the pectoral and dorsal fin spines of W. priscus : a longitudinal (length wise) axis and a transverse (width wise) axis, each associated with specific zones of tissue production. Spine developmental patterns observed in Wellerodus are compared among Paleozoic chondrichthyans and their closest relatives, the “acanthodians” (extinct spiny sharks). Conclusions Our framework offers a new line of evidence for understanding the evolution of fin spine modular development by showing that fin spines in early chondrichthyans grow following two axes. It enhances our comprehension of developmental similarities between early chondrichthyans and more derived Carboniferous, Permian, and even extant chondrichthyans. The identified structural features enable well-supported inferences about developmental modularity. The histo-morphological criteria used to describe this developmental pattern provide characters potentially suitable for phylogenetic analyses. Vertebrate paleontology Chondrichthyes Paleohistology Growth Figures Figure 1 Figure 2 Introduction Our understanding of the morphology of Silurian and Early Devonian chondrichthyans has improved significantly in recent years 1 , 2 , 3 . However, knowledge of their developmental and growth patterns remains limited primarily owing to the fragmentary nature of their fossil record. Most early chondrichthyan fossils consist of isolated elements such as teeth, scales, and fin spines, while their largely cartilaginous skeletons are rarely preserved owing to the more delicate nature of the cartilage 4 . Articulated specimens are exceptionally rare and typically incomplete, such as Doliodus latispinosus from the Lower Devonian (Emsian; ca. 409 Ma) 5 . Despite these limitations, isolated dermal structures provide valuable developmental information 6 , 7 . Features such as the morphology (size and shape), ornamentation, and histology of fin spines—specifically tissue types and their organization—offer insights into growth patterns, even in the absence of an ontogenetic series 8 , 9 , 10 . Fin spines of several early chondrichthyans exhibit exceptional preservation, including Silurian sinacanthids from China 11 , the Emsian Doliodus latispinosus from New Brunswick, Canada 5 , 12 , and the Givetian Antarctilamna prisca from Antarctica 13 . Yet, none of these species have been studied in the context of fin spine development, a topic that has been explored primarily in “acanthodians” 14,8 and modern taxa such as chimaerids 15 and heterodontiform sharks 16 . Understanding the developmental and growth patterns of fin spines is used for aging extinct and extant sharks 17 , 10 , 18 , 19 , 20 or in reconstruction of paleoenvironments 21 . In addition, it could provide a foundation for phylogenetic comparisons, which is crucial in clarifying interrelationships between chondrichthyans and their closest relatives, the “acanthodians”, with whom they share the presence of fin spine 22 , 23 , 5 . The developmental patterns of fin spines in early chondrichthyans and most “acanthodians” remain poorly characterized, in contrast to our better understanding of spine growth in Carboniferous 24 and Permian sharks 10 . To fill this gap for Devonian taxa, we conducted an integrated morphological and histological analysis of fin spine development, similar to prior studies on xenacanth sharks 10 but with expanded analyses on the ornamentation pattern. Herein, this approach is applied to Wellerodus priscus , a mid Givetian shark from Cairo, New York State, USA, known from articulated specimens and isolated dermal elements including scales, teeth, and fin spines 25 . Material and methods The material of Wellerodus priscus comes from the Middle Devonian (mid Givetian) deposit of the Cairo quarry Lagerstätte (Plattekill Formation) in New York State, USA 25 (Potvin-Leduc et al. 2015). The material was prepared mechanically in the Laboratory of Paleontology and Evolutionary Biology at the University du Québec à Rimouski (UQAR), eastern Canada. All specimens are curated in the New York State Museum (NYSM), Albany, New York State, USA. A Leica MZ16 A was used to document the external morphology. Fin spine ornamentation was analysed using a JEOL JSM-6460LV SEM, especially on the apex of the spine to obtain more details of the denticles. One complete pectoral spine was used to prepare ten paleohistological sections from the distal to the proximal part based on the methodology used by Chevrinais et al. 22 . The tomography analyses were carried out with a SKYSCAN 1173 X-Ray Microtomography (Exposure time 5000 ms, voltage 130 kv, Source current 61 µA, Brass filter 0.25 mm, 0.2 degree rotation step) at UQAR on two pectoral and one dorsal fin spines. The resulting images were assembled in NRecon and visualized with Drishti-2.6.5. Results Fin spines, scale patches and teeth were found associated with disarticulated specimens present on multiple mudstone blocs (NYSM 19053 and 19052) extracted from the same stratigraphic layer of the Plattekill Formation 25 . This association of various dermal components correspond to a single species, Wellerodus priscus . Teeth and scales were unambiguously identified as W. priscus based on the striated bicuspid teeth and the polyodontode appositional ctenacanth-like scale ultrastructure described by Potvin-Leduc et al. 25 . Pectoral fin spine morphology The pectoral fin spine of specimen NYSM 19057 reaches a maximum length of 73 mm and a maximum basal width of 16 mm, tapering distally toward the apex. The insertion zone is 2 mm long, representing less than 3% of the total spine length. The outer surface of the insertion zone bears parallel longitudinal striations (see Supplementary Information). An open, concave pulp cavity is present on the proximal portion of the trailing (posterior) edge, extending for less than half the total spine length (Fig. 1 a, details of ventral view in Supplementary Information). Pectoral fin spine NYSM 19057 is curved along its distal half. The leading (anterior) edge is transversely rounded (Figs. 1 a, 2 ). Along the trailing edge, two rows of thorn-like denticles (see Supplementary Information) extend from the apex to the mid-length of the spine. These rows are restricted to the curved portion of the spine. Despite lateral taphonomic compression, pectoral fin spine NYSM 19057 is asymmetrical (see Supplementary Information). The ornamentation of specimen NYSM 19051 consists of sub-parallel tuberculated ridges diverging from the leading edge (Fig. 1 e, 1 f, 1 g, 1 h, 1 i, 1 j). Up to 14 ridges occur on each side of the spine proximally. The gap between ridges does not exceed the width of the tubercles and is ca. 1 mm deep. Toward the apex, ridges become smoother and individual tubercles are less distinct, whereas proximally the tubercle shapes are clearer. Each ridge bears 8 ± 1 tubercles per centimetre in specimens NYSM 19057 and NYSM 19051. The tubercles are diamond-shaped (Fig. 1 g) with concave edges, and each tubercle contacts the adjacent tubercle along the ridge. The apex of the tubercles is sharp, similar to an arrowhead, and no surface streaks are present. Tubercle size decreases distally to approximately one tier of proximal dimension. Dorsal fin spine morphology Wellerodus priscus has one anterior dorsal fin spine that is shorter than the pectoral fin spine in specimen NYSM 19057. The dorsal fin spine of specimen NYSM 19051-2 reaches a maximum length of 65 mm and a maximum basal width of 9.5 mm, tapering distally to form an elongated triangular shape (see Supplementary Information). The insertion zone is similar to that of the pectoral fin spines: it is 2-mm long with parallel longitudinal striations on the surface. An open, concave pulp cavity is present on the proximal portion of the trailing edge, extending for less than half the spine length. Complete dorsal fin spine NYSM 19051-2 is straight, with an angular leading edge and a trailing edge lacking denticule rows (see Supplementary Information). Dorsal fin spines are bilaterally symmetrical. The ornamentation of the dorsal fin spine consists of sub-parallel tuberculated ridges diverging from the leading edge. In the longest specimen (NYSM 19051-2), up to 11 ridges occur on each side of the spine (see Supplementary Information). The gaps between ridges do not exceed the width of the tubercles and are less than 1 mm deep. Toward the apex (approximately the distal quarter), the ridges become smoother because individual tubercles are no longer clearly distinguishable. Each ridge bears 13 ± 1 tubercles per centimetre in the longest dorsal fin spine (see Supplementary Information). The tubercles are conical with circular bases, and their surfaces bear fine longitudinally striations. Dorsal spine tubercles are clearly demarcated and do not fuse into continuous ridges. Some tubercles along the leading edge possess a lateral notch. The size of the tubercles decreases distally, reaching approximately one tier of their proximal dimension. Histology Based on the paleohistological sections and the micro-CT-scans, the tissue organization within the pectoral and dorsal fin spines of Wellerodus priscus varies between the proximal and distal regions. The proximal part consists almost entirely of trabecular dentine (osteodentine) and is capped by a relatively thin layer of hypermineralized tissue covering the top of the tubercles along the leading edge (Fig. 1 a, 1 b). The trabecular dentine infill indicates substantial vascularization, at least within the first proximal tiers of the spine. This trabecular dentine surrounds an open concave pulp cavity (Fig. 1 a, 1 b) that extends up to the mid-length of the spine. Due to the state of preservation of the spine, dentine tubules are difficult to observe (see Supplementary Information). No other tissue types were observed in the proximal section of the spine. The distal part of the spine is more diversified histologically than the proximal part. It contains a smaller, central single pulp cavity surrounded by a circular layer of trabecular dentine (Fig. 1 c), which is itself encased by a layer of atrabecular dentine (Fig. 1 c). The outermost layer along the leading edge consists of more vascularized trabecular dentine layer compared to the internal layers, and this external layer extends into the tubercles (Fig. 1 d). A layer of hypermineralized tissue is also present (Fig. 1 d), thicker over the tubercles than in the proximal section, and restricted to the tubercles along the leading edge. The distal portion of the spines shows a concentric organization of dentine layers, reflecting the layered deposition of tissue during growth. Growth pattern The growth of the spines occurs along two axes: longitudinal and transverse. Longitudinal growth primarily takes place at the proximal part, which is the most vascularized region of the spine (Fig. 1 a). Tissue production in this area includes the formation of tubercles and ensures the continuity of the tuberculated ridges. Transverse expansion is most pronounced in the proximal part but is not limited to it; the spine also expands in width toward the distal end. This expansion originates from the leading edge, where multiple ridge lines diverge. A clear growth pattern emerges along these divergence lines: a single ridge splits into two ridges at the leading edge (Fig. 2 ). Of the two newly formed ridges, only one will diverge again, and this process continues in an alternating pattern: if the previous divergence occurred on the left side, the next occurs on the right side, and vice versa (Fig. 2 ). In total, up to eight divergences can be observed along the leading edge of a single spine. In specimen NYSM 19051, there are typically 4 to 6 tubercles between successive divergences. In specimen NYSM 19057, the number of tubercles varies between 4 and 6 along these intervals, with the observed sequence from proximal to distal being 6–6–5–4–6. Discussion The pectoral and dorsal fin spines of Wellerodus priscus exhibit a dual-axis growth pattern. Longitudinal growth occurs primarily at the proximal base near the insertion zone, whereas transverse growth is restricted to the leading edge, as indicated by divergence zones in the tuberculated ridges. Both growth axes are supported by the presence of highly vascularized tissue in their respective production areas. Fused tubercles at both the proximal and distal ends further suggest that widening continued throughout the organism's lifetime, even after proximal tubercles had formed. Width growth decreased distally but remained active, as shown by vascularized tissue localized within leading-edge tubercles near the apex. The presence of two distinct growth axes in the fin spines of Wellerodus priscus — longitudinal elongation and transverse widening — can be interpreted as reflecting a modular developmental organization. Tissue production in the highly vascularized basal region appears to drive lengthwise elongation, while separate activity along the leading-edge ridges promotes widening. Such compartmentalized growth is consistent with modular organization in extant chondrichthyans, where distinct tissue zones (e.g., trabecular vs lamellar dentine or cap vs body zones in tessellated cartilage) may grow at different rates or along partially independent axes 15 . In this framework, histological differentiation provides a mechanistic basis for the semi-independent control of spine morphology in Devonian sharks, linking localized tissue production to macroscopic ornamentation patterns and supporting a broader evo-devo perspective on early chondrichthyan skeletal evolution. A key feature of this developmental pattern is variation in inferred axial growth rates, estimated from the number of tubercles between successive divergence zones. In the proximal production area, tubercles form regularly, with one tubercle emerging per ridge simultaneously. If divergence zones at the leading edge formed at approximately regular intervals under continuous growth, then variation in tubercle number between divergences in specimen NYSM 19057 might implies variations in longitudinal growth rate. This pattern could reflect a slowdown in longitudinal growth (with widening maintained) or, alternatively, a period of accelerated elongation (as suggested by two series of six tubercles). Even if transverse growth alters tubercle sequences through time (e.g., by splitting tubercle rows), proportional relationships among successive tubercles should remain informative, supporting non-constant growth rates along the two axes. If comparable proportions of successive tubercles were observed within a single individual across dorsal and pectoral spines, it would be possible to reconstruct spine growth curves, and potentially identify autapomorphic spine characteristics (e.g., the ratio of successive tubercles) that may correlate with spine maturity. Such comparison could also help associate disarticulated spines belonging to the same individual. Conversely, if the sequences differ among spines within a single individual, this would suggest distinct axial growth regimes for different spines. At present, the absence of sufficiently articulated specimens of W. priscus prevents direct testing of these hypotheses. Among the rare basal shark species known from fin spines, some species exhibit similar ornamentation patterns comparable to W. priscus . W. priscus shares developmental similarities with Antarctilamna prisca 13 and certain fossil sharks from Bolivia 26 . The organization of ridge divergence zones at the leading edge suggests conserved developmental features, although tubercle shape and arrangement differ among taxa. These shared features may support a closer relationship among these forms. By contrast, Doliodus latispinosus , as well as Permian shark such as Sphenacanthus ignis and Bythiacanthus lopesi 27 , also display divergence zones indicative of width expansion; however, in these taxa the divergence zones are confined to the basal portion of the spine rather than concentrated along the leading edge 12 . Silurian sinacanthid sharks, particularly Sinacanthus , show a different pattern in which ridge divergences occur along the entire spine rather than being localized 11 . However, there is no indication that distal width growth persists through time in Sinacanthus ,because diverging tubercles are absent distally. Taken together, these comparisons suggest closer developmental affinities between W. priscus and A. prisca , whereas more divergent growth patterns occur in D. latispinosus and sinacanthids. Interestingly, W. priscus spine development also resembles that of stem-chondrichthyans such as gyracanthid “acanthodians” 28,29 , which show similar ridge orientations and divergence zones along the leading edge. However, gyracanthids exhibit a more extensive divergence area. These similarities in fin spine development are consistent with proposed phylogenetic affinities between early chondrichthyans and “acanthodians,” and may provide additional support for their relationships 22 . Further comparative histological analyses will be necessary to determine whether these external similarities correspond to shared internal tissue organization. Histologically, W. priscus shares features with xenacanth sharks, including the presence of trabecular dentine 10 , 18 , but differs in overall growth architecture. Xenacanth spines are typically round in cross-section, display smooth external ornamentation, and show prominent concentric growth lines surrounding a relatively large central pulp cavity 10 , 18 , features not observed in W. priscus . Although concentric growth lines are not visible in W. priscus , they may have been obscured, given the organization of dentine layers in the distal portion of the spine and the likelihood that diagenetic transformation of Cairo quarry material altered fine histological resolution 25 . W. priscus also shares similarities in internal organization with some extant sharks, such as heterodontiforms 9 , 16 , including the presence of a transitional layer or discontinuity marked by less vascularized tissue (e.g., the atrabecular dentine layer observed distally in W. priscus ). Nevertheless, comparisons with extant sharks remain limited due to the poorer preservation of fossil fin spines compared to those of extant taxa. Potvin-Leduc et al. 25 suggested that some W. priscus specimens from the Cairo quarry may represent juveniles. The histological structure of W. priscus spines resembles that of Antarctilamna prisca except for (1) the distribution of hypermineralized layers (restricted to tubercle tips in W. priscus ), and (2) the presence of a lamellar dentine layer surrounding the pulp cavity in A. prisca 12 . This difference is consistent with the hypothesis that lamellar dentine forms later in development and may serve as a marker of spine maturity in adult specimens 10 , 24 . Overall, the developmental characterization of Wellerodus priscus fin spines provides insight into both growth dynamics and comparative anatomy in early chondrichthyans. The dual-axis model, supported by localized vascularized tissue production, indicates a complex growth system that may vary through ontogeny. Similarities with A. prisca 13 suggest shared developmental patterns among some early chondrichthyans, whereas contrasts with D. latispinosus , S. ignis , and B. lopesi indicate distinct growth architectures. Comparisons with Silurian sinacanthids and xenacanth sharks further emphasize divergence in ornamentation and histological expression, while parallels with gyracanthids suggest developmental conservation across a broader assemblage of basal gnathostomes. At the histological level, comparisons with Carboniferous, Permian, and extant chondrichthyans reveal both shared features (e.g., trabecular dentine), and important differences in growth mode (including the apparent absence, or poorer preservation, of concentric growth lines in W. priscus ). More broadly, the consistent organization of tubercle systems across taxa supports the potential value of dermal structures for phylogenetic inference. Expanded sampling across early chondrichthyan fin spines, paired with comparable histological documentation, should refine assessments of morphological similarity and homology, improve phylogenetic reconstructions, and help test whether fin spines contain stronger phylogenetic signal than traditionally assumed for elements often considered of limited taxonomic utility 30 . Declarations Consent for publication Not applicable. Competing interests The authors declare no competing interests. Funding statement This work was supported by Natural Science and Engineering Research Council of Canada (NSERC) Discovery Grant 238612 and 2017–06200 to RC, by Quebec Center for Biodiversity Science (QCBS), and Research Laboratory in Paleontology and Evolutionary Biology (UQAR). Author Contribution R.F. realized observations, created the figures, made the data analysis and wrote the manuscript; D.P.L. collected most of the material, prepared the material, provided the original description of the material; N.B.M. prepared the paleohistological sections; R.C. conceived the project, organized the fieldwork, collected some of the specimens, reviewed the manuscript;all authors contributed to the final version. Acknowledgement We thank E. Landing, L.V. Hendrich, F. Mannolini (NYSM), C. Lavoie and C. Riley (UQAR) for their precious help during fieldwork seasons. We thank L. Amati (NYSM) for accessing the material to the collections from the Cairo quarry. Availability of data and materials All materials are hosted in New York State Museum (NYSM) in Albany (NY), United-States. The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request. 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Supplementary Files Supplementaryinformation.docx Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 06 Mar, 2026 Reviews received at journal 27 Feb, 2026 Reviews received at journal 24 Feb, 2026 Reviewers agreed at journal 21 Feb, 2026 Reviewers agreed at journal 18 Feb, 2026 Reviewers agreed at journal 18 Feb, 2026 Reviewers invited by journal 17 Feb, 2026 Editor assigned by journal 17 Feb, 2026 Submission checks completed at journal 17 Feb, 2026 First submitted to journal 16 Feb, 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. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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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-8895999","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":594029913,"identity":"1e419e6c-981c-447d-8ca8-b68cffe4dfb8","order_by":0,"name":"Richard Flament","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA/0lEQVRIiWNgGAWjYBAC+2YGNiDFzGB/HCIgR1CLwWGoFgNmCN+YsJYDaFoSGwhqOc787MHPPdZALcxPN3zc8Sd9w/HkZx8YauxwarFvZjM37HmWzmDPzGZ2c+YZg9wNZ54Zz2A4loxTix0zD5sEz4HDIIeZ3eZtA2q5kWDMwNjAjFOLMVCL5B+wFvZvt/+2GaQb3Ej/DNRSj1OLYTMPmzTEFh6z24xtBgkGN3JAthzG7f3DbGbSMgfSeYBaym72thkbzjzzppgh4dhx3FrOH34m+eaAtZwBe/u2Gz/b5OT5jqdvZvhQU41TCwzwILETwIgkQKr6UTAKRsEoGO4AAE3/T70/eOImAAAAAElFTkSuQmCC","orcid":"","institution":"Université du Québec à Rimouski","correspondingAuthor":true,"prefix":"","firstName":"Richard","middleName":"","lastName":"Flament","suffix":""},{"id":594029917,"identity":"102010e0-4171-49a6-9db9-e0b1abfb978c","order_by":1,"name":"Nathaniel Bertrand-Maltais","email":"","orcid":"","institution":"Université du Québec à Rimouski","correspondingAuthor":false,"prefix":"","firstName":"Nathaniel","middleName":"","lastName":"Bertrand-Maltais","suffix":""},{"id":594029918,"identity":"5a447c90-c9d8-4af8-a219-5dc0701da129","order_by":2,"name":"Daniel Potvin-Leduc","email":"","orcid":"","institution":"Université du Québec à Rimouski","correspondingAuthor":false,"prefix":"","firstName":"Daniel","middleName":"","lastName":"Potvin-Leduc","suffix":""},{"id":594029924,"identity":"a9f267c8-605f-40d2-98b0-848e9acee591","order_by":3,"name":"Richard Cloutier","email":"","orcid":"","institution":"Université du Québec à Rimouski","correspondingAuthor":false,"prefix":"","firstName":"Richard","middleName":"","lastName":"Cloutier","suffix":""}],"badges":[],"createdAt":"2026-02-16 20:23:10","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8895999/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8895999/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":103504274,"identity":"13c82eb5-4e8e-45ad-ac00-254edcd581da","added_by":"auto","created_at":"2026-02-26 13:18:54","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":173535,"visible":true,"origin":"","legend":"\u003cp\u003eMiddle Devonian shark, \u003cem\u003eWellerodus priscus\u003c/em\u003e, pectoral fin spines; (A) proximal section of a pectoral fin spine NYSM 19057; (B) NYSM 19057 close up proximal section; (C) NYSM 19057 distal section; (D) NYSM 19057 leading edge tubercles section; (E) NYSM 19051 from micro-CT scan tomography, dorsal view; (F) NYSM 19051 dorsal view; (G) fused tubercles at the leading edge of NYSM 19051; (H) fused tubercles at the leading edge of NYSM 19051 under tomography by micro CT-scan; (I) unfused tubercles at the leading edge of NYSM 19051; (J) unfused tubercles at the leading edge of NYSM19051 under tomography by micro-CT scan; abbreviations: td, trabecular dentine; cpc, central pulp cavity; en, enameloid; ad, atrabecular dentine; t, tubercles; da, divergence area. Scale bar (A), (C) = 1 mm; (B), (D) = 500 µm; (E), (F) = 1 cm; (G), (H), (I), (J) = 1 mm.\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8895999/v1/9628145b7238e59bc0d6ee36.jpg"},{"id":103061534,"identity":"1e02ab56-6334-4b1e-a7db-b169f8111f3d","added_by":"auto","created_at":"2026-02-20 10:09:30","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":84425,"visible":true,"origin":"","legend":"\u003cp\u003eReconstruction of \u003cem\u003eWellerodus priscus\u003c/em\u003e pectoral fin spine in dorsal view with proximal and distal cuts. The green line shows the divergences pattern of the tuberculated ornamentation.\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-8895999/v1/a15b29a2dd42b82a3ad8c1ec.jpg"},{"id":103510611,"identity":"9f7a9995-8f01-44aa-bad4-e60e7073f659","added_by":"auto","created_at":"2026-02-26 14:06:31","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":762546,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8895999/v1/ad52abec-513c-46ce-a66a-73508d8379fe.pdf"},{"id":103061532,"identity":"f3ed22b0-453f-45e4-8601-9f6031531fb5","added_by":"auto","created_at":"2026-02-20 10:09:29","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":2542642,"visible":true,"origin":"","legend":"","description":"","filename":"Supplementaryinformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-8895999/v1/f849334d31f4dbf888c16810.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Fin spine ontogeny in the Devonian shark Wellerodus priscus: Paleo-Evo-Devo insights into early chondrichthyan dermal skeleton development","fulltext":[{"header":"Introduction","content":"\u003cp\u003eOur understanding of the morphology of Silurian and Early Devonian chondrichthyans has improved significantly in recent years\u003csup\u003e\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e,\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e,\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e\u003c/sup\u003e. However, knowledge of their developmental and growth patterns remains limited primarily owing to the fragmentary nature of their fossil record. Most early chondrichthyan fossils consist of isolated elements such as teeth, scales, and fin spines, while their largely cartilaginous skeletons are rarely preserved owing to the more delicate nature of the cartilage\u003csup\u003e\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e\u003c/sup\u003e. Articulated specimens are exceptionally rare and typically incomplete, such as \u003cem\u003eDoliodus latispinosus\u003c/em\u003e from the Lower Devonian (Emsian; ca. 409 Ma)\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eDespite these limitations, isolated dermal structures provide valuable developmental information\u003csup\u003e\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e,\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e\u003c/sup\u003e. Features such as the morphology (size and shape), ornamentation, and histology of fin spines\u0026mdash;specifically tissue types and their organization\u0026mdash;offer insights into growth patterns, even in the absence of an ontogenetic series\u003csup\u003e\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e,\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eFin spines of several early chondrichthyans exhibit exceptional preservation, including Silurian sinacanthids from China\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e, the Emsian \u003cem\u003eDoliodus latispinosus\u003c/em\u003e from New Brunswick, Canada\u003csup\u003e\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e,\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e, and the Givetian \u003cem\u003eAntarctilamna prisca\u003c/em\u003e from Antarctica\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e. Yet, none of these species have been studied in the context of fin spine development, a topic that has been explored primarily in \u0026ldquo;acanthodians\u0026rdquo;\u003csup\u003e14,8\u003c/sup\u003e and modern taxa such as chimaerids\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e and heterodontiform sharks\u003csup\u003e\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eUnderstanding the developmental and growth patterns of fin spines is used for aging extinct and extant sharks\u003csup\u003e\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e,\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e,\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e,\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e,\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u003c/sup\u003e or in reconstruction of paleoenvironments\u003csup\u003e\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e\u003c/sup\u003e. In addition, it could provide a foundation for phylogenetic comparisons, which is crucial in clarifying interrelationships between chondrichthyans and their closest relatives, the \u0026ldquo;acanthodians\u0026rdquo;, with whom they share the presence of fin spine\u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e,\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e,\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eThe developmental patterns of fin spines in early chondrichthyans and most \u0026ldquo;acanthodians\u0026rdquo; remain poorly characterized, in contrast to our better understanding of spine growth in Carboniferous\u003csup\u003e\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e and Permian sharks\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e. To fill this gap for Devonian taxa, we conducted an integrated morphological and histological analysis of fin spine development, similar to prior studies on xenacanth sharks\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e\u003c/sup\u003e but with expanded analyses on the ornamentation pattern. Herein, this approach is applied to \u003cem\u003eWellerodus priscus\u003c/em\u003e, a mid Givetian shark from Cairo, New York State, USA, known from articulated specimens and isolated dermal elements including scales, teeth, and fin spines\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e"},{"header":"Material and methods","content":"\u003cp\u003eThe material of \u003cem\u003eWellerodus priscus\u003c/em\u003e comes from the Middle Devonian (mid Givetian) deposit of the Cairo quarry Lagerst\u0026auml;tte (Plattekill Formation) in New York State, USA\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e (Potvin-Leduc et al. 2015). The material was prepared mechanically in the Laboratory of Paleontology and Evolutionary Biology at the University du Qu\u0026eacute;bec \u0026agrave; Rimouski (UQAR), eastern Canada. All specimens are curated in the New York State Museum (NYSM), Albany, New York State, USA.\u003c/p\u003e \u003cp\u003eA Leica MZ16 A was used to document the external morphology. Fin spine ornamentation was analysed using a JEOL JSM-6460LV SEM, especially on the apex of the spine to obtain more details of the denticles. One complete pectoral spine was used to prepare ten paleohistological sections from the distal to the proximal part based on the methodology used by Chevrinais et al.\u003csup\u003e22\u003c/sup\u003e. The tomography analyses were carried out with a SKYSCAN 1173 X-Ray Microtomography (Exposure time 5000 ms, voltage 130 kv, Source current 61 \u0026micro;A, Brass filter 0.25 mm, 0.2 degree rotation step) at UQAR on two pectoral and one dorsal fin spines. The resulting images were assembled in NRecon and visualized with Drishti-2.6.5.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eFin spines, scale patches and teeth were found associated with disarticulated specimens present on multiple mudstone blocs (NYSM 19053 and 19052) extracted from the same stratigraphic layer of the Plattekill Formation\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e. This association of various dermal components correspond to a single species, \u003cem\u003eWellerodus priscus\u003c/em\u003e. Teeth and scales were unambiguously identified as \u003cem\u003eW. priscus\u003c/em\u003e based on the striated bicuspid teeth and the polyodontode appositional ctenacanth-like scale ultrastructure described by Potvin-Leduc et al.\u003csup\u003e25\u003c/sup\u003e.\u003c/p\u003e\n\u003ch3\u003ePectoral fin spine morphology\u003c/h3\u003e\n\u003cp\u003eThe pectoral fin spine of specimen NYSM 19057 reaches a maximum length of 73 mm and a maximum basal width of 16 mm, tapering distally toward the apex. The insertion zone is 2 mm long, representing less than 3% of the total spine length. The outer surface of the insertion zone bears parallel longitudinal striations (see Supplementary Information). An open, concave pulp cavity is present on the proximal portion of the trailing (posterior) edge, extending for less than half the total spine length (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea, details of ventral view in Supplementary Information).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003ePectoral fin spine NYSM 19057 is curved along its distal half. The leading (anterior) edge is transversely rounded (Figs.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea, \u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Along the trailing edge, two rows of thorn-like denticles (see Supplementary Information) extend from the apex to the mid-length of the spine. These rows are restricted to the curved portion of the spine. Despite lateral taphonomic compression, pectoral fin spine NYSM 19057 is asymmetrical (see Supplementary Information).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe ornamentation of specimen NYSM 19051 consists of sub-parallel tuberculated ridges diverging from the leading edge (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ee, \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ef, \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eg, \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eh, \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ei, \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ej). Up to 14 ridges occur on each side of the spine proximally. The gap between ridges does not exceed the width of the tubercles and is ca. 1 mm deep. Toward the apex, ridges become smoother and individual tubercles are less distinct, whereas proximally the tubercle shapes are clearer. Each ridge bears 8\u0026thinsp;\u003cb\u003e\u0026plusmn;\u003c/b\u003e\u0026thinsp;1 tubercles per centimetre in specimens NYSM 19057 and NYSM 19051. The tubercles are diamond-shaped (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eg) with concave edges, and each tubercle contacts the adjacent tubercle along the ridge. The apex of the tubercles is sharp, similar to an arrowhead, and no surface streaks are present. Tubercle size decreases distally to approximately one tier of proximal dimension.\u003c/p\u003e\n\u003ch3\u003eDorsal fin spine morphology\u003c/h3\u003e\n\u003cp\u003e \u003cem\u003eWellerodus priscus\u003c/em\u003e has one anterior dorsal fin spine that is shorter than the pectoral fin spine in specimen NYSM 19057. The dorsal fin spine of specimen NYSM 19051-2 reaches a maximum length of 65 mm and a maximum basal width of 9.5 mm, tapering distally to form an elongated triangular shape (see Supplementary Information). The insertion zone is similar to that of the pectoral fin spines: it is 2-mm long with parallel longitudinal striations on the surface. An open, concave pulp cavity is present on the proximal portion of the trailing edge, extending for less than half the spine length. Complete dorsal fin spine NYSM 19051-2 is straight, with an angular leading edge and a trailing edge lacking denticule rows (see Supplementary Information). Dorsal fin spines are bilaterally symmetrical.\u003c/p\u003e \u003cp\u003eThe ornamentation of the dorsal fin spine consists of sub-parallel tuberculated ridges diverging from the leading edge. In the longest specimen (NYSM 19051-2), up to 11 ridges occur on each side of the spine (see Supplementary Information). The gaps between ridges do not exceed the width of the tubercles and are less than 1 mm deep. Toward the apex (approximately the distal quarter), the ridges become smoother because individual tubercles are no longer clearly distinguishable.\u003c/p\u003e \u003cp\u003eEach ridge bears 13\u0026thinsp;\u0026plusmn;\u0026thinsp;1 tubercles per centimetre in the longest dorsal fin spine (see Supplementary Information). The tubercles are conical with circular bases, and their surfaces bear fine longitudinally striations. Dorsal spine tubercles are clearly demarcated and do not fuse into continuous ridges. Some tubercles along the leading edge possess a lateral notch. The size of the tubercles decreases distally, reaching approximately one tier of their proximal dimension.\u003c/p\u003e\n\u003ch3\u003eHistology\u003c/h3\u003e\n\u003cp\u003eBased on the paleohistological sections and the micro-CT-scans, the tissue organization within the pectoral and dorsal fin spines of \u003cem\u003eWellerodus priscus\u003c/em\u003e varies between the proximal and distal regions.\u003c/p\u003e \u003cp\u003eThe proximal part consists almost entirely of trabecular dentine (osteodentine) and is capped by a relatively thin layer of hypermineralized tissue covering the top of the tubercles along the leading edge (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea, \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb). The trabecular dentine infill indicates substantial vascularization, at least within the first proximal tiers of the spine. This trabecular dentine surrounds an open concave pulp cavity (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea, \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb) that extends up to the mid-length of the spine. Due to the state of preservation of the spine, dentine tubules are difficult to observe (see Supplementary Information). No other tissue types were observed in the proximal section of the spine.\u003c/p\u003e \u003cp\u003eThe distal part of the spine is more diversified histologically than the proximal part. It contains a smaller, central single pulp cavity surrounded by a circular layer of trabecular dentine (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec), which is itself encased by a layer of atrabecular dentine (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec). The outermost layer along the leading edge consists of more vascularized trabecular dentine layer compared to the internal layers, and this external layer extends into the tubercles (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed). A layer of hypermineralized tissue is also present (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed), thicker over the tubercles than in the proximal section, and restricted to the tubercles along the leading edge. The distal portion of the spines shows a concentric organization of dentine layers, reflecting the layered deposition of tissue during growth.\u003c/p\u003e\n\u003ch3\u003eGrowth pattern\u003c/h3\u003e\n\u003cp\u003eThe growth of the spines occurs along two axes: longitudinal and transverse. Longitudinal growth primarily takes place at the proximal part, which is the most vascularized region of the spine (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea). Tissue production in this area includes the formation of tubercles and ensures the continuity of the tuberculated ridges.\u003c/p\u003e \u003cp\u003eTransverse expansion is most pronounced in the proximal part but is not limited to it; the spine also expands in width toward the distal end. This expansion originates from the leading edge, where multiple ridge lines diverge. A clear growth pattern emerges along these divergence lines: a single ridge splits into two ridges at the leading edge (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Of the two newly formed ridges, only one will diverge again, and this process continues in an alternating pattern: if the previous divergence occurred on the left side, the next occurs on the right side, and vice versa (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn total, up to eight divergences can be observed along the leading edge of a single spine. In specimen NYSM 19051, there are typically 4 to 6 tubercles between successive divergences. In specimen NYSM 19057, the number of tubercles varies between 4 and 6 along these intervals, with the observed sequence from proximal to distal being 6\u0026ndash;6\u0026ndash;5\u0026ndash;4\u0026ndash;6.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThe pectoral and dorsal fin spines of \u003cem\u003eWellerodus priscus\u003c/em\u003e exhibit a dual-axis growth pattern. Longitudinal growth occurs primarily at the proximal base near the insertion zone, whereas transverse growth is restricted to the leading edge, as indicated by divergence zones in the tuberculated ridges. Both growth axes are supported by the presence of highly vascularized tissue in their respective production areas. Fused tubercles at both the proximal and distal ends further suggest that widening continued throughout the organism's lifetime, even after proximal tubercles had formed. Width growth decreased distally but remained active, as shown by vascularized tissue localized within leading-edge tubercles near the apex.\u003c/p\u003e \u003cp\u003eThe presence of two distinct growth axes in the fin spines of \u003cem\u003eWellerodus priscus\u003c/em\u003e \u0026mdash; longitudinal elongation and transverse widening \u0026mdash; can be interpreted as reflecting a modular developmental organization. Tissue production in the highly vascularized basal region appears to drive lengthwise elongation, while separate activity along the leading-edge ridges promotes widening. Such compartmentalized growth is consistent with modular organization in extant chondrichthyans, where distinct tissue zones (e.g., trabecular vs lamellar dentine or cap vs body zones in tessellated cartilage) may grow at different rates or along partially independent axes\u003csup\u003e\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u003c/sup\u003e. In this framework, histological differentiation provides a mechanistic basis for the semi-independent control of spine morphology in Devonian sharks, linking localized tissue production to macroscopic ornamentation patterns and supporting a broader evo-devo perspective on early chondrichthyan skeletal evolution.\u003c/p\u003e \u003cp\u003eA key feature of this developmental pattern is variation in inferred axial growth rates, estimated from the number of tubercles between successive divergence zones. In the proximal production area, tubercles form regularly, with one tubercle emerging per ridge simultaneously. If divergence zones at the leading edge formed at approximately regular intervals under continuous growth, then variation in tubercle number between divergences in specimen NYSM 19057 might implies variations in longitudinal growth rate. This pattern could reflect a slowdown in longitudinal growth (with widening maintained) or, alternatively, a period of accelerated elongation (as suggested by two series of six tubercles). Even if transverse growth alters tubercle sequences through time (e.g., by splitting tubercle rows), proportional relationships among successive tubercles should remain informative, supporting non-constant growth rates along the two axes.\u003c/p\u003e \u003cp\u003eIf comparable proportions of successive tubercles were observed within a single individual across dorsal and pectoral spines, it would be possible to reconstruct spine growth curves, and potentially identify autapomorphic spine characteristics (e.g., the ratio of successive tubercles) that may correlate with spine maturity. Such comparison could also help associate disarticulated spines belonging to the same individual. Conversely, if the sequences differ among spines within a single individual, this would suggest distinct axial growth regimes for different spines. At present, the absence of sufficiently articulated specimens of \u003cem\u003eW. priscus\u003c/em\u003e prevents direct testing of these hypotheses.\u003c/p\u003e \u003cp\u003eAmong the rare basal shark species known from fin spines, some species exhibit similar ornamentation patterns comparable to \u003cem\u003eW. priscus\u003c/em\u003e. \u003cem\u003eW. priscus\u003c/em\u003e shares developmental similarities with \u003cem\u003eAntarctilamna prisca\u003c/em\u003e\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e and certain fossil sharks from Bolivia\u003csup\u003e\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e\u003c/sup\u003e. The organization of ridge divergence zones at the leading edge suggests conserved developmental features, although tubercle shape and arrangement differ among taxa. These shared features may support a closer relationship among these forms. By contrast, \u003cem\u003eDoliodus latispinosus\u003c/em\u003e, as well as Permian shark such as \u003cem\u003eSphenacanthus ignis\u003c/em\u003e and \u003cem\u003eBythiacanthus lopesi\u003c/em\u003e\u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e, also display divergence zones indicative of width expansion; however, in these taxa the divergence zones are confined to the basal portion of the spine rather than concentrated along the leading edge\u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eSilurian sinacanthid sharks, particularly \u003cem\u003eSinacanthus\u003c/em\u003e, show a different pattern in which ridge divergences occur along the entire spine rather than being localized\u003csup\u003e\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e\u003c/sup\u003e. However, there is no indication that distal width growth persists through time in \u003cem\u003eSinacanthus\u003c/em\u003e,because diverging tubercles are absent distally. Taken together, these comparisons suggest closer developmental affinities between \u003cem\u003eW. priscus\u003c/em\u003e and \u003cem\u003eA. prisca\u003c/em\u003e, whereas more divergent growth patterns occur in \u003cem\u003eD. latispinosus\u003c/em\u003e and sinacanthids.\u003c/p\u003e \u003cp\u003eInterestingly, \u003cem\u003eW. priscus\u003c/em\u003e spine development also resembles that of stem-chondrichthyans such as gyracanthid \u0026ldquo;acanthodians\u0026rdquo;\u003csup\u003e28,29\u003c/sup\u003e, which show similar ridge orientations and divergence zones along the leading edge. However, gyracanthids exhibit a more extensive divergence area. These similarities in fin spine development are consistent with proposed phylogenetic affinities between early chondrichthyans and \u0026ldquo;acanthodians,\u0026rdquo; and may provide additional support for their relationships\u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e. Further comparative histological analyses will be necessary to determine whether these external similarities correspond to shared internal tissue organization.\u003c/p\u003e \u003cp\u003eHistologically, \u003cem\u003eW. priscus\u003c/em\u003e shares features with xenacanth sharks, including the presence of trabecular dentine\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e,\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e, but differs in overall growth architecture. Xenacanth spines are typically round in cross-section, display smooth external ornamentation, and show prominent concentric growth lines surrounding a relatively large central pulp cavity\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e,\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e\u003c/sup\u003e, features not observed in \u003cem\u003eW. priscus\u003c/em\u003e. Although concentric growth lines are not visible in \u003cem\u003eW. priscus\u003c/em\u003e, they may have been obscured, given the organization of dentine layers in the distal portion of the spine and the likelihood that diagenetic transformation of Cairo quarry material altered fine histological resolution\u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003e \u003cem\u003eW. priscus\u003c/em\u003e also shares similarities in internal organization with some extant sharks, such as heterodontiforms\u003csup\u003e\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e,\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e\u003c/sup\u003e, including the presence of a transitional layer or discontinuity marked by less vascularized tissue (e.g., the atrabecular dentine layer observed distally in \u003cem\u003eW. priscus\u003c/em\u003e). Nevertheless, comparisons with extant sharks remain limited due to the poorer preservation of fossil fin spines compared to those of extant taxa.\u003c/p\u003e \u003cp\u003ePotvin-Leduc et al.\u003csup\u003e25\u003c/sup\u003e suggested that some \u003cem\u003eW. priscus\u003c/em\u003e specimens from the Cairo quarry may represent juveniles. The histological structure of \u003cem\u003eW. priscus\u003c/em\u003e spines resembles that of \u003cem\u003eAntarctilamna prisca\u003c/em\u003e except for (1) the distribution of hypermineralized layers (restricted to tubercle tips in \u003cem\u003eW. priscus\u003c/em\u003e), and (2) the presence of a lamellar dentine layer surrounding the pulp cavity in \u003cem\u003eA. prisca\u003c/em\u003e \u003csup\u003e\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e\u003c/sup\u003e. This difference is consistent with the hypothesis that lamellar dentine forms later in development and may serve as a marker of spine maturity in adult specimens\u003csup\u003e\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e,\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eOverall, the developmental characterization of \u003cem\u003eWellerodus priscus\u003c/em\u003e fin spines provides insight into both growth dynamics and comparative anatomy in early chondrichthyans. The dual-axis model, supported by localized vascularized tissue production, indicates a complex growth system that may vary through ontogeny. Similarities with \u003cem\u003eA. prisca\u003c/em\u003e\u003csup\u003e\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e\u003c/sup\u003e suggest shared developmental patterns among some early chondrichthyans, whereas contrasts with \u003cem\u003eD. latispinosus\u003c/em\u003e, \u003cem\u003eS. ignis\u003c/em\u003e, and \u003cem\u003eB. lopesi\u003c/em\u003e indicate distinct growth architectures. Comparisons with Silurian sinacanthids and xenacanth sharks further emphasize divergence in ornamentation and histological expression, while parallels with gyracanthids suggest developmental conservation across a broader assemblage of basal gnathostomes.\u003c/p\u003e \u003cp\u003eAt the histological level, comparisons with Carboniferous, Permian, and extant chondrichthyans reveal both shared features (e.g., trabecular dentine), and important differences in growth mode (including the apparent absence, or poorer preservation, of concentric growth lines in \u003cem\u003eW. priscus\u003c/em\u003e). More broadly, the consistent organization of tubercle systems across taxa supports the potential value of dermal structures for phylogenetic inference. Expanded sampling across early chondrichthyan fin spines, paired with comparable histological documentation, should refine assessments of morphological similarity and homology, improve phylogenetic reconstructions, and help test whether fin spines contain stronger phylogenetic signal than traditionally assumed for elements often considered of limited taxonomic utility\u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003cstrong\u003eConsent for publication\u003c/strong\u003e \u003cp\u003eNot applicable.\u003c/p\u003e \u003c/p\u003e\u003cp\u003e \u003ch2\u003eCompeting interests\u003c/h2\u003e \u003cp\u003eThe authors declare no competing interests.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding statement\u003c/h2\u003e \u003cp\u003eThis work was supported by Natural Science and Engineering Research Council of Canada (NSERC) Discovery Grant 238612 and 2017\u0026ndash;06200 to RC, by Quebec Center for Biodiversity Science (QCBS), and Research Laboratory in Paleontology and Evolutionary Biology (UQAR).\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eR.F. realized observations, created the figures, made the data analysis and wrote the manuscript; D.P.L. collected most of the material, prepared the material, provided the original description of the material; N.B.M. prepared the paleohistological sections; R.C. conceived the project, organized the fieldwork, collected some of the specimens, reviewed the manuscript;all authors contributed to the final version.\u003c/p\u003e\u003ch2\u003eAcknowledgement\u003c/h2\u003e\u003cp\u003eWe thank E. Landing, L.V. Hendrich, F. Mannolini (NYSM), C. Lavoie and C. Riley (UQAR) for their precious help during fieldwork seasons. We thank L. Amati (NYSM) for accessing the material to the collections from the Cairo quarry.\u003c/p\u003e\u003ch2\u003eAvailability of data and materials\u003c/h2\u003e \u003cp\u003eAll materials are hosted in New York State Museum (NYSM) in Albany (NY), United-States. The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request. All data generated or analyzed during this study are included in this published article and its supplementary information files.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eLong JA, Burrow CJ, Ginter M, Maisey JG, Trinajstic KM, Coates MI, Young GC, Senden TJ. First shark from the Late Devonian (Frasnian) Gogo Formation, Western Australia sheds new light on the development of tessellated calcified cartilage. Nat Commun. 2015;6:1\u0026ndash;10.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCoates MI, Finarelli JA, Sansom IJ, Andreev PS, Criswell KE, Tietjen K, Rivers MJ, La Riviere PJ. (2018). An early chondrichthyan and the evolutionary assembly of a shark body plan. \u003cem\u003eProceedings of the Royal Society B: Biological Sciences\u003c/em\u003e, 285(1870), e20172418.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAndreev PS, Zhao W, Wang N-Z, Smith MM, Li Q, Cui X, Zhu M, Sansom IJ, Wong WO. (2020). Early Silurian chondrichthyans from the Tarim Basin (Xinjiang, China). PLoS ONE, 15(2), e0228589.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSchnetz L, Butler RJ, Coates MI, Sansom IJ. (2024). The skeletal completeness of the Palaeozoic chondrichthyan fossil record. Royal Soc Open Sci, 11(1), e231451.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMiller RF, Cloutier R, Turner S. The oldest articulated chondrichthyan from the Early Devonian period. Nature. 2003;425(6957):501\u0026ndash;4.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCloutier R. The fossil record of fish ontogenies: insights into developmental patterns and processes. Semin Cell Dev Biol. 2010;21(4):400\u0026ndash;13.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCui X, Qu Q, Andreev PS, Li Q, Mai H, Zhu M. (2021). Modeling scale morphogenesis in a Devonian chondrichthyan and scale growth patterns in crown gnathostomes. J Vertebr Paleontol, 41(2), e1930018.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJerve A, Bremer O, Sanchez S, Ahlberg PE. (2017). Morphology and histology of acanthodian fin spines from the late Silurian Rams\u0026aring;sa E locality, Sk\u0026aring;ne, Sweden. Palaeontologia Electronica, 20(3).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMaisey JG. Finspine morphogenesis in squalid and heterodontid sharks. Zool J Linn Soc. 1979;66(2):161\u0026ndash;83.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBeck KG, Soler-Gij\u0026oacute;n R, Carlucci JR, Willis RE. Morphology and histology of dorsal spines of the xenacanthid shark \u003cem\u003eOrthacanthus platypternus\u003c/em\u003e from the Lower Permian of Texas, USA: palaeobiological and palaeoenvironmental implications. Acta Palaeontol Pol. 2016;61(1):97\u0026ndash;117.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLiu YL, Yin JY, Fan RY, Zong RW, Gong YM. New data on Silurian (Llandovery) sinacanthids from Wuhan, South China and their biostratigraphic and paleobiogeographic implications. Palaeoworld. 2024;33(5):1242\u0026ndash;55.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBurrow CJ, Turner S, Maisey JG, Desbiens S, Miller RF. Spines of the stem chondrichthyan \u003cem\u003eDoliodus latispinosus\u003c/em\u003e (Whiteaves) comb. nov. from the Lower Devonian of eastern Canada. Can J Earth Sci. 2017;54(12):1248\u0026ndash;62.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eYoung GC. Devonian sharks from south-eastern Australia and Antarctica. Palaeontology. 1982;25(4):817\u0026ndash;43.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBotella H, Mart\u0026iacute;nez-P\u0026eacute;rez C, Soler-Gij\u0026oacute;n R. \u003cem\u003eMachaeracanthus goujeti\u003c/em\u003e n. sp. (Acanthodii) from the Lower Devonian of Spain and northwest France, with special reference to spine histology. Geodiversitas. 2012;34(4):761\u0026ndash;83.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJerve A, Johanson Z, Ahlberg P, Boisvert C. Embryonic development of fin spines in \u003cem\u003eCallorhinchus milii\u003c/em\u003e (Holocephali): implications for chondrichthyan fin spine evolution. Evol Dev. 2014;16(6):339\u0026ndash;53.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTovar-\u0026Aacute;vila J, Izzo C, Walker TI, Braccini JM, Day RW. Dorsal-fin spine growth of \u003cem\u003eHeterodontus portusjacksoni\u003c/em\u003e: a general model that applies to dorsal-fin spines of chondrichthyans. Can J Fish Aquat Sci. 2008;65(1):74\u0026ndash;82.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGoldman KJ, Cailliet GM, Andrews AH, Natanson LJ. Age determination and validation in chondrichthyan fishes. In: Carrier JC, Musick JA, Heithaus MR, editors. Biology of Sharks and Their Relatives. 2nd ed. Boca Raton, Florida: CRC; 2012. pp. 423\u0026ndash;51.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSoler-Gij\u0026oacute;n R. Development and growth in xenacanth sharks: new data from Upper Carboniferous of Bohemia. In: Arratia G, Wilson MVH, Cloutier R, editors. Recent Advances in the Origin and Early Radiation of Vertebrates. M\u0026uuml;nchen: Verlag Dr. Friedrich Pfeil; 2004. pp. 533\u0026ndash;62.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eIrvine SB, Stevens JD, Laurenson LJ. Surface bands on deepwater squalid dorsal-fin spines: an alternative method for ageing \u003cem\u003eCentroselachus crepidater\u003c/em\u003e. Can J Fish Aquat Sci. 2006;63(3):617\u0026ndash;27.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHedeholm R, Qvist T, Frausing M, Olsen J, Nielsen J, Gr\u0026oslash;nkj\u0026aelig;r P. Age of black dogfish (\u003cem\u003eCentroscyllium fabricii\u003c/em\u003e) estimated from fin spine growth bands and eye lens bomb radiocarbon dating. Polar Biol. 2021;44:751\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eLuccisano V, Cuny G, Pradel A, Fourel F, L\u0026eacute;cuyer C, Pouillon JM, Amiot R. Palaeoenvironmental and palaeoecological reconstructions based on oxygen, carbon and sulfur isotopes of Early Permian shark spines from the French Massif Central. Palaeogeogr Palaeoclimatol Palaeoecol. 2023;628:e111760.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eChevrinais M, Sire JY, Cloutier R. (2017). From body scale ontogeny to species ontogeny: histological and morphological assessment of the Late Devonian acanthodian \u003cem\u003eTriazeugacanthus affinis\u003c/em\u003e from Miguasha, Canada. PLoS ONE, 12(4), e0174655.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBrazeau MD. The braincase and jaws of a Devonian \u0026lsquo;acanthodian\u0026rsquo; and modern gnathostome origins. Nature. 2009;457(7227):305\u0026ndash;8.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSoler-Gij\u0026oacute;n R. Occipital spine of \u003cem\u003eOrthacanthus\u003c/em\u003e (Xenacanthidae, Elasmobranchii): structure and growth. J Morphol. 1999;242(1):1\u0026ndash;45.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePotvin-Leduc D, Cloutier R, Landing E, Hernick LV, Mannolini F. (2015). Givetian (Middle Devonian) sharks from Cairo, New York (USA): evidence of early cosmopolitanism. \u003cem\u003eActa Palaeontologica Polonica\u003c/em\u003e, 60(1), 183\u0026ndash;200.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eRichter M, Bosetti EP, Horodyski RS. Early Devonian (Late Emsian) shark fin remains (Chondrichthyes) from the Paran\u0026aacute; Basin, southern Brazil. An Acad Bras Cienc. 2017;89:103\u0026ndash;18.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFigueroa RT, Gallo V. New chondrichthyan fin spines from the Pedra de Fogo Formation, Brazil. J S Am Earth Sci. 2017;76:389\u0026ndash;96.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGess RW, Burrow CJ. (2023). A new gyracanthid (stem Chondrichthyes) from the Late Devonian (Famennian) of the Eastern Cape, South Africa. J Vertebr Paleontol, 43(4), e2305888.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBurrow CJ, Turner S, Desbiens S, Miller RF. Early Devonian putative gyracanthid acanthodians from eastern Canada. Can J Earth Sci. 2008;45(8):897\u0026ndash;908.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eGess RW, Coates MI. Fossil juvenile coelacanths from the Devonian of South Africa shed light on the order of character acquisition in actinistians. Zool J Linn Soc. 2015;175(2):360\u0026ndash;83.\u003c/span\u003e\u003c/li\u003e\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":"developmental-biology-advances","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"evod","sideBox":"Learn more about [EvoDevo](http://evodevojournal.biomedcentral.com/)","snPcode":"13227","submissionUrl":"https://submission.nature.com/new-submission/13227/3","title":"Developmental Biology Advances","twitterHandle":"@BioMedCentral","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Vertebrate paleontology, Chondrichthyes, Paleohistology, Growth","lastPublishedDoi":"10.21203/rs.3.rs-8895999/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8895999/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003ch2\u003eBackground\u003c/h2\u003e \u003cp\u003eCartilaginous fishes (chondrichthyans) from the Devonian period (419 to 359\u0026nbsp;million years, Ma) are primarily known from fossilized isolated dermal elements such as teeth, scales, and fin spines. Although previous studies have described the morphology and the histology of these elements, their developmental patterns remain poorly understood. In this study, we propose to explore developmental patterns of fin spines by integrating analyses of ornamentation, morphology, and histology.\u003c/p\u003e\u003ch2\u003eResults\u003c/h2\u003e \u003cp\u003eWe present the first description of the developmental patterns for the fin spines of the Middle Devonian shark \u003cem\u003eWellerodus priscus\u003c/em\u003e, from the Cairo Quarry Lagerst\u0026auml;tte in New York State, USA. Based on the ornamentation pattern and paleohistological (thin sections and micro-computed tomography) characteristics, we identify two distinct growth axes in the pectoral and dorsal fin spines of \u003cem\u003eW. priscus\u003c/em\u003e: a longitudinal (length wise) axis and a transverse (width wise) axis, each associated with specific zones of tissue production. Spine developmental patterns observed in \u003cem\u003eWellerodus\u003c/em\u003e are compared among Paleozoic chondrichthyans and their closest relatives, the \u0026ldquo;acanthodians\u0026rdquo; (extinct spiny sharks).\u003c/p\u003e\u003ch2\u003eConclusions\u003c/h2\u003e \u003cp\u003eOur framework offers a new line of evidence for understanding the evolution of fin spine modular development by showing that fin spines in early chondrichthyans grow following two axes. It enhances our comprehension of developmental similarities between early chondrichthyans and more derived Carboniferous, Permian, and even extant chondrichthyans. The identified structural features enable well-supported inferences about developmental modularity. The histo-morphological criteria used to describe this developmental pattern provide characters potentially suitable for phylogenetic analyses.\u003c/p\u003e","manuscriptTitle":"Fin spine ontogeny in the Devonian shark Wellerodus priscus: Paleo-Evo-Devo insights into early chondrichthyan dermal skeleton development","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-20 10:09:17","doi":"10.21203/rs.3.rs-8895999/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-03-07T01:01:14+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-02-27T15:47:06+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-02-24T16:27:15+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"61541511445082679455708829216945156762","date":"2026-02-22T04:34:20+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"217372364677614886224935147536461096701","date":"2026-02-18T14:12:26+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"120839243745182141138671605576555745930","date":"2026-02-18T09:53:09+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-02-18T02:46:27+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-02-17T21:01:10+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-02-17T18:21:54+00:00","index":"","fulltext":""},{"type":"submitted","content":"Developmental Biology Advances","date":"2026-02-16T20:18:49+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"developmental-biology-advances","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"evod","sideBox":"Learn more about [EvoDevo](http://evodevojournal.biomedcentral.com/)","snPcode":"13227","submissionUrl":"https://submission.nature.com/new-submission/13227/3","title":"Developmental Biology Advances","twitterHandle":"@BioMedCentral","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"abb37593-2a53-4369-ac1e-fe91aed4fe71","owner":[],"postedDate":"February 20th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-05-05T21:38:31+00:00","versionOfRecord":[],"versionCreatedAt":"2026-02-20 10:09:17","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8895999","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8895999","identity":"rs-8895999","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}