Middle-upper Lochkovian (Lower Devonian) conodont succession in the section Segre 4 (Spanish central Pyrenees)

Middle-upper Lochkovian (Lower Devonian) conodont succession in the section Segre 4 (Spanish central Pyrenees) | 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 Middle-upper Lochkovian (Lower Devonian) conodont succession in the section Segre 4 (Spanish central Pyrenees) Jose Ignacio Valenzuela Rios, Jau-Chyn Liao This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9612481/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 4 You are reading this latest preprint version Abstract This study presents a detailed conodont-based biostratigraphic analysis of the Segre 4 section (Pyrenees), spanning the middle to upper Lochkovian. The section yields a continuous and well-preserved conodont succession comprising four globally recognized zones: the trigonicus–kutscheri and kutscheri–pandora β zones (middle Lochkovian), followed by the pandora β– gilberti and gilberti – steinachensis β zones (upper Lochkovian). The conodont assemblages include both cosmopolitan and regionally restricted taxa, allowing robust correlation with key Laurasian and peri-Gondwanan successions. The middle Lochkovian interval is characterized by high diversity and the radiation of the genera Ancyrodelloides , Lanea , and Flajsella , whereas the upper Lochkovian records the diversification of Masaraella and Pedavis . The Segre 4 section provides significant new data on the stratigraphic ranges of several taxa. Notably, Lanea omoalpha and L. eoeleonorae extend into the basal upper Lochkovian, representing the only known occurrences of these species above the middle Lochkovian. Additional relevant findings include the upward extension of Zieglerodina eladioi . The conodont succession also records a marked faunal turnover near the middle–upper Lochkovian boundary, followed by a progressive decline in diversity toward the top of the stage. Low-diversity assemblages dominated by Pedavis , Wurmiella , and Pseudooneotodus , reflecting a pronounced extinction interval, characterize the uppermost beds of the section. Lochkovian conodonts Pyrenees biostratigraphy correlation diversity faunal turnover Figures Figure 1 Figure 2 Figure 3 Figure 4 Introduction The Lochkovian Stage remains one of the few intervals of the Devonian for which a formal global subdivision has not yet been established. This situation may be related to the pronounced provincialism of Lochkovian conodont taxa, particularly in the lower part of the stage. Such provincialism restricted the global distribution of certain species (Klapper and Johnson 1980 ) and complicates the establishment of a globally applicable zonal framework for the entire Stage. Consequently, early Lochkovian conodont biostratigraphy was based on two principal reference areas: western North America and southwestern Europe (Spain), each characterized by distinct conodont successions that are difficult to correlate (Klapper 1977 ; Carls 1969 , 1975 ). Shortly thereafter, Klapper and Ziegler ( 1979 ) proposed an initial comparison between these successions and incorporated data from additional regions, including Germany, Austria, Ukraine, the Czech Republic, and Australia. The widely used global Lochkovian conodont succession is largely based on Klapper ( 1977 ), who explicitly noted that this biostratigraphic zonation was intended only for western North America (notably key sections from Central Nevada and the Yukon Territory) and the Canadian Artic Islands. However, many subsequent studies, applied Klapper’s zonation indiscriminately, even in the absence of the defining or characterising conodont taxa. As a result, the placement of local lower zonal boundaries in such cases is unreliable for correlation, and these interpretations should be treated with caution until supported by more robust stratigraphic evidence. Valenzuela-Ríos ( 1994a , b ) identified main global correlation issues arising from the widespread application of Klapper’s zonation and proposed several solutions, initially applied to the upper half of the Lochkovian. Subsequent zonation schemes following these principles were developed (Valenzuela-Ríos and Murphy 1997 ; Murphy and Valenzuela-Ríos 1999 ; Slavík et al. 2008 , 2012 ; Valenzuela-Ríos et al. 2015 ). Another relevant zonation (Corradini and Corriga 2012 ) exhibits, at least in part, some of the problems previously outlined by Valenzuela-Ríos ( 1994b ). Despite these challenges, the middle Lochkovian is characterized by the occurrence of cosmopolitan species associated with the radiation of three key genera- Ancyrodelloides , Lanea , and Flajsella -, which facilitates the establishment of a global zonation. These are followed in the upper Lochkovian by the radiation of Masaraella and Pedavis , further enabling accurate interregional correlations. In addition to these cosmopolitan taxa, other genera with more restricted distribution (e.g. Icriodus , Pelekysgnathus ) are used in regional zonation schemes (Carls and Gandl 1969 ; Carls 1987 ; Drygan and Szaniawsky 2012 ). The co-occurrence of cosmopolitan and endemic taxa in the Pyrenean sequences is particularly valuable for integrating regional biostratigraphic frameworks into a global scheme. As each stratigraphic section may provide unique and significant data for refining the global Lochkovian framework, it is essential that all potential sections are thoroughly investigated. Accordingly, we undertook a comprehensive study of the Segre 4 section. The main goal of this study is to analyse in detail the middle and upper Lochkovian conodont succession recorded in the Segre 4 section and to integrate these results into the global Lochkovian database. Additionally, we compare the stratigraphic ranges of key taxa with those documented in important Perigondwanan (Pyrenees, Prague Synform, Carnic Alps) and Laurasian (Central Nevada) sections. Material and Methodology The Segre 4 section is a part of a group of outcrops located on the right bank of the Segre river, near La Seu d’Urgell (Fig. 1 ). It is situated on the west flank of a faulted anticline and follows the route of the former national road N-260 between La Seu d’Urgell and Puigcerdà. The section is approximately 8 m thick and begins above a faulted base. It consists of well-bedded grey limestone interbedded with black and grey marls and shales. Up –section, the strata become thicker and display a pseudonodular appearance. These rocks correspond to the Rueda Formation and are assigned to the Compte Subfacies of the Southern Facies Area (Mey 1967 ; Zwart 1979 ; Valenzuela-Ríos and Liao 2006 ). A preliminary report on this section was presented at the Fourth International Conodont Symposium (ICOS IV) (Valenzuela Ríos et al. 2017), and a more detailed study is presented here. The strata dip steeply (approximately 75º) towards the southwest. Although the section is continuous, a minor fault- without significant disruption to the stratigraphic sequence- is present between beds 21 and 22. Minor displacements are occasionally observed, but the overall succession can be followed without difficulty. A total of 37 consecutive samples were collected, with a combined weight of approximately 200 kg (Table 1). Samples were processed using a 6–8% formic acid solution and subsequently washed by decantation. The residues were then dried in an oven at approximately 60ºC. Conodont elements and other microfossils were handpicked using a fine wet brush under a Leica MZ APO binocular microscope. Selected specimens were photographed using two Scanning Electron Microscopes (Philips Esem XL30 and Hitachi S4800) at the Microscopy Services of the University of Valencia, and the resulting images were digitally processed. Results and discussion All samples yielded conodonts. Among other microfossils observed in some samples fish scales, ostracods, and acrotetrids are the most common. Scarce crinoid stems, trilobite larvae, and possible fragments of phyllocarid jaws were also occasionally recovered in the residues. Macroremains observed in the field include orthoceratids, crinoids, trilobite fragments, and small shelly fauna (bivalves and brachiopods). Biostratigraphic interpretation The conodont succession begins in the middle parts of the middle Lochkovian ( trigonicus-kutscheri Zone) and extends to the uppermost Lochkovian ( gilberti - steinachensis β Zone), close below the base of the Pragian. It comprises four consecutive zones of global scope (Fig. 2 ). In our biostratigraphic interpretation, we follow the dual terminology proposed by Valenzuela-Ríos ( 1994b ), subsequently applied in Lochkovian studies (e.g. Valenzuela-Ríos and Murphy 1997 ; Murphy and Valenzuela-Ríos 1999 ; Valenzuela-Ríos and Liao, 2012 ; Valenzuela-Ríos et al. 2005 , 2015 , 2017 ) and summarized in Valenzuela-Ríos and Liao ( 2024 ). The definition of the middle Lochkovian trigonicus - kutscheri and kutscheri - pandora β zones, as well as the redefinition of the upper Lochkovian gilberti - steinachensis β Zone, were presented in Valenzuela-Ríos et al. ( 2015 ), whereas the definition of the upper Lochkovian pandora β- gilberti Zone was already done by Valenzuela-Ríos ( 1994b ). trigonicus-kutscheri Zone The lowermost sample (Se 4/1a) was collected from the lower 22 cm of the basal bed of this section (Fig. 2 ). It already contains Ancyrodelloides trigonicus , together with A. transitans , A. asymmetricus , Lanea omoalpha , Flajsella stygia , and Wurmiella wurmi . This association is characteristic of the trigonicus-kutscheri Zone. Additionally, the coniform taxa Pseudooneotodus beckmanni and Panderodus unicostatus are recorded in this bed. The conodont assemblages from the overlying two samples (Se 4/1b and Se 4/2) are consistent with assignment to this zone (Fig. 2 , Tb. 1), and include L . eoeleanorae (sample Se 4/2). kutscheri - pandora β Zone The base of this zone is defined by the first appearance of A. kutscheri . In the Segre 4 section, this taxon first occurs in sample Se 4/3. This sample also yielded A . trigonicus , L . omoalpha , L . planilingua , and Ps . beckmanni . This zone extends up to the base of Bed 28, marked by the first occurrence of Masaraella pandora β. All taxa present in the underlying trigonicus - kutscheri Zone continue in this interval, along with additional taxa. The (eco)concurrence of A . transitans and Icriodus angustoides alcoleae in high abundance was used by Valenzuela-Ríos ( 1994a ) to subdivide this zone into lower and upper parts. This informal subdivision has also been applied in correlations between peri-Gondwana successions in the Spanish Pyrenees and the Prague Synform (Valenzuela-Ríos et al. 2015 ). The conodont record from the Segre 4 section allows the application of this informal subdivision, which is useful for regional correlation. The acme of these two taxa begins in Bed 15 and continues to Bed 20 (Tb. 1); thus, the base of Bed 15 marks the transition from the lower to the upper part of the kutscheri - pandora β Zone. The radiation of the genus Lanea is represented by three taxa: L. omoalpha , L. eoeleonorae , and L. telleri . L anea eleanorae is rare in the Pyrenean sections and has not been recorded in the Segre 4 section. In contrast, this section shows the widest known stratigraphic range of L . omoalpha and L . eoeleonorae . Both taxa extend into the upper Lochkovian pandora β- gilberti Zone, making this the only known section in which either taxon ranges above the middle Lochkovian. In most Pyrenean and Czech sections, both taxa are restricted to the lower kutscheri - pandora β Zone (Valenzuela-Ríos et al. 2015 ), and they do not reach the base of the trigonicus - kutscheri Zone in either Alpine (Corradini and Corriga 2012 ) or Nevadan sections (Murphy and Valenzuela-Ríos 1999 ). In the Segre 4 section, L . telleri has a limited stratigraphic range within the lower part of the kutscheri - pandora β Zone, between samples Se 4/5 and Se 4/13. This distribution is consistent with other Pyrenean sections and with records from Central Nevada (Murphy and Valenzuela-Ríos, 1999 ); although in Nevada its first occurrence lies in the upper part of the transitans - trigonicus Zone. Corradini and Corriga ( 2012 ) reported a broader stratigraphic range for this taxon, from the upper half of the transitans - trigonicus Zone to the top of the middle Lochkovian. Lanea telleri has not been recorded in the Prague-Synform (Valenzuela-Ríos et al. 2015 ) All species of Ancyrodelloides become extinct within this zone. Ancyrodelloides transitans disappears in Bed 20 following its acme. Ancyrodelloides asymmetricus becomes extinct within the lower part of the zone (sample Se 4/14a). Ancyrodellloides trigonicus has its last occurrence in Bed 22. Ancyrodelloides cruzae has a unique occurrence in Bed 7. Ancyrodelloides kutscheri has its last occurrence in the lower 20 cm of Bed 8 (sample Se 4/8a), whereas A . murphyi has a continuous record in the lower part of the zone (Beds 6a-8a). Thus, the radiation of the genus Ancyrodelloides is well represented in the Segre 4 section, with its upper range restricted to the middle Lochkovian. The earliest representative, A. carlsi , is absent, likely because the section begins in the upper part of the transitans - trigonicus Zone, after the disappearance of this species. No definitive specimens of A. sequeirosi were recorded; however, a transitional form between A. kutscheri and A. sequeirosi occurs in Bed 5 (Figs. 3j1, 3j2 ), supporting the high morphological plasticity of this group during its radiation in the middle Lochkovian. The cosmopolitan but rare genus Flajsella is represented by two fragmentary specimens in the upper part of the zone. The first, from Bed 16, is a Pa element fragment tentatively assigned to F. schulzei due to the preserved anterior carina bearing denticles of approximately the same high and a straight blade. The second, from Bed 22, is classified as F . cf. streptostygia based on the numerous denticles and their arrangement on the anterior blade (gradually ascending from the anterior end to the highest one located on the posterior half, Figs. 4e1, 4e2). Other notable taxa include I . a . alcoleae , recorded from Beds 12 to 20, with its acme in Bed 20 (35 specimens from a 4,3 kg sample; Tb. 1). L anea planilingua occurs sporadically (Beds 3 and 26), and Zieglerodina eladioi is represented by a single specimen in Bed 23 (Figs. 4h1, 4h2). The latter is noteworthy, as this taxon is otherwise common in lower and middle Lochkovian of the nearby Gerri and Segre sections (Valenzuela-Ríos 1994a ; Valenzuela-Ríos et al. 2015 ; Valenzuela-Ríos and Liao 2024 ) but does not typically extend in the upper part of the kutscheri - pandora β Zone. This occurrence therefore extends its known stratigraphic range upward. The absent of records in the underlying beds is puzzling. Kimognathus limbacarinatus is recorded from samples Se 4/14a to Se 4/16, spanning the lower to upper parts of the kutscheri - pandora β Zone. This extends its known range downward in the Pyrenees and aligns with records from Central Nevada, where K . limbacarinatus appears already in the upper beds of the transitans - trigonicus Zone (COP V-IV and SPVII sections) and in the kuscheri - pandora β Zone in the MC section (Murphy and Matti 1983 ). In the Carnic Alps its range fully coincides with that of A . kutscheri and, thus, it is restricted to the kuscheri - pandora β Zone. In the Prague Synform, the record in section Požár 3 starts with the lowest local record of A. trigonicus (a fragmentary specimen) and ends within the lower part of the kuscheri - pandora β Zone (Slavík et al. 2012 , Fig. 4 ; Valenzuela-Ríos et al. 2015 ). The upper beds of the middle Lochkovian are poor in conodonts, yielding only a few taxa, including the pectiniforms L . omoalpha , L. eoeleonorae , W . wurmi , Pelekysgnathus guadarramensis , L. planilingua , Masaraella pandora α, and the coniforms Ps. beckmani and Dvorakia . A notable feature is the acme of Ps . beckmanni in the uppermost bed of the zone (sample Se 4/27), with 108 specimens recovered. The extinction of most middle Lochkovian genera is followed by the radiation of a new genus, Masaraella , which diversifies in the upper Lochkovian and gives rise to Eognathodus at the beginning of the Pragian (Murphy et al. 1981 ; Murphy 2005 ). pandora β- gilberti Zone The base of this zone coincides with the base of the upper Lochkovian and is defined by the first evolutionary appearance of M asaraella pandora β (Valenzuela-Ríos 1994b ; Valenzuela-Ríos and Murphy 1997 ; Valenzuela-Ríos and Liao 2012 , 2024 ; Valenzuela-Ríos et al. 2015 ). In the Segre 4 section, M . pandora β first occurs in sample Se 4/28 (Figs. 4j1-j3), located within the lower 10 cm of Bed 28 (44 cm thick; Fig. 2 ). This sample also contains the last occurrences of L . omoalpha and L . eoeleonorae (Figs. 4 m, n, o; Fig. 5 a). These records represent the only known occurrence of these taxa in the upper Lochkovian worldwide. The four principal taxa involved in the Lochkovian radiation of Lanea ( L . omoalpha , L . eoeleonorae , L . eleanorae , and L. telleri ) became extinct during the middle Lochkovian in all know sections from Western North America, the Pyrenees, the Carnic Alps, and the Prague Synform. These basal upper Lochkovian occurrences in the Segre 4 section therefore constitute a notable exception, even at the regional scale, suggesting that these taxa locally survive the middle Lochkovian extinction event but disappear shortly thereafter. Within this zone, both morphotypes (α and β) of M . pandora disappear, with their last occurrence in sample Se 4/30, located in the lower 20 cm of Bed 30 (50 cm thick; Fig. 2 ). This extinction of Masaraella in the Segre 4 section coincides with the radiation of the genus Pedavis in the upper Lochkovian. In the same sample (Se 4/30), Ped . breviramus (Figs. 5b1-b3) and Ped . robertoi morphotype 1 of Valenzuela-Ríos 1994a (Figs. 5c1-c3) are recorded, while the overlying sample (Se 4/31) marks the first occurrence of Ped . pesavis (Figs. 5e1-e3). Wurmiella wurmi continues and Ps . beckmanni persist throughout this interval. The latter exhibits a second acme in Bed 30, with 56 specimens, coinciding with the last occurrence of Pa . unicostatus . gilberti - steinachensis β Zone The base of this zone is defined by the first occurrence of Ped . gilberti (Valenzuela-Ríos 1994b ; Valenzuela-Ríos et al. 2015 ). The radiation of Pedavis continues with the appearance of two additional taxa, Ped. gilberti (Figs. 5f1-f3) and Ped . robertoi morphotype 2 of Valenzuela-Ríos 1994a (Figs. 5d1-d3). Together with the long-ranging taxa W . wurmi and Ps . beckmanni , these are the only conodonts recorded in the uppermost exposed beds (samples Se 4/32 and Se 4/33). This low diversity reflects the upper Lochkovian conodont decline in Europe, which appears particularly pronounced in the Segre 4 section. In contrast, other Pyrenean sections assigned to this zone contain more diverse assemblages, with up to 12 taxa, including representatives of Pedavis , Masaraella , Icriodus , Pelekysgnathus , Wurmiella , and “ Ozarkodina ” pi (Valenzuela-Ríos and Liao 2024 ). This contrast, together with the unusual upward range extension of the two species of Lanea in the underlying pandora β- gilberti Zone, makes the upper Lochkovian interval in the Segre 4 section particularly noteworthy and somewhat enigmatic in terms of conodont diversity and evolutionary patterns. Conclusions The conodont assemblage from the Segre 4 section comprises 13 genera including Ancyrodelloides , Lanea , Flajsella, Masaraella , Zieglerodina , Wurmiella , Kimognathus , Pedavis , Icriodus , Pelekysgnathus , Pseudooneotodus , Panderodus , and Dvorakia . The Segre 4 section provides a continuous and biostratigraphically well-constrained record of the middle to upper Lochkovian, allowing recognition of four standard conodont zones of global significance. The successive first appearances of index species allow recognition of the middle Lochkovian trigonicus-kutscheri and kutscheri - pandora β zones, as well as the upper Lochkovian pandora β- gilberti and gilberti - steinachensis β zones. The concurrent acme of I . angustoides alcoleae and A . transitans permits subdivision of the kutscheri - pandora β Zone into lower and upper parts, improving regional correlation. The conodont fauna is predominantly cosmopolitan, facilitating reliable correlation with both Laurasian and peri-Gondwanan regions and contributing to refinement of the global Lochkovian biostratigraphic framework. The occurrence of Lanea omoalpha and L. eoeleanorae in the basal upper Lochkovian represents a unique extension of their known stratigraphic ranges, suggesting local survival beyond the middle Lochkovian extinction event. The middle Lochkovian is characterized by peak conodont diversity associated with the radiation of Ancyrodelloides , Lanea , and Flajsella , followed by a major faunal turnover near the base of the upper Lochkovian. The upper Lochkovian records a decline in diversity and the replacement of middle Lochkovian faunas by the radiation of Masaraella and Pedavis , culminating in a significant extinction interval toward the top of the stage. The Segre 4 section highlights both global evolutionary patterns and local anomalies, making it a key reference section for improving the understanding of Lochkovian conodont biostratigraphy and evolution. Declarations Conflict of interest: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Funding: the UCM Research Grant PR 12/24-31569 supports this work. J.-C. L. is supported by José Castillejo Fellow (MICCIN-MIU, CAS24/00333). Author contributions: Jos é Ignacio Valenzuela-Ríos : Conceptualization, Fieldwork, Formal analysis, Investigation, Methodology, Project administration, Supervision, Writing – original draft, Writing – review & editing. Jau-Chyn Liao : Conceptualization, Fieldwork, Photography of published specimens, Funding acquisition, Investigation, Methodology, Writing – original draft, Writing – review & editing. Acknowledgements We dedicate this contribution to our esteemed and beloved friend, mentor and master, the unique Prof. Dr. Peter Carls, whose guidance and inspiration were fundamental during the early stages of our careers and thorough our professional development. His insight and generosity continue to influence our work. The UCM Research Grant PR12/24-31569 supported this research. It is a contribution to the Research groups GIUV2017-395 and PERIGONDWANA UCM 910231. The technical help of Central Services for Experimental Research (SCSIE), Field Emission Electron Microscope, are acknowledged, in special the advice and care of Javier Badillo. Data availability: The complete conodont collection used in this work is housed in the micropaleontological collection NACHO VALENZUELA of the Department of Botany and Geology, University of València, Spain References Carls, P. (1969). 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Leidse Geologische Mededelingen , 50 , 1–74. Supplementary Files Tabla1def.xlsx Table 1 Records of main conodont taxa in Segre 4 section indicating the zonal boundaries. Only Pa and I elements are considered here for the pectiniforms; there are many ramiforms of the Spathognatodontidae and coniforms of the Icriodontidae and Pedavisae not included in this table. Cite Share Download PDF Status: Under Review Version 1 posted Reviewers agreed at journal 07 May, 2026 Reviewers invited by journal 06 May, 2026 Editor assigned by journal 06 May, 2026 First submitted to journal 05 May, 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. 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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-9612481","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":635491868,"identity":"fbbdf281-56a0-4c29-977e-85decafb9ae4","order_by":0,"name":"Jose Ignacio Valenzuela Rios","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABAklEQVRIiWNgGAWjYBACxgYQaQDE7BABGQb2BmK1MEMEeBh4DhBrH1yLRAIBhe3tDx8wFDAk9jczH3v4s82Gh3/mGzMJhoo63A7rOWNsAHRY4ozDbOkGkm1pPBK3c4BazhzGrWVGDpsEUIsxw2EeMwnDtsM8DLdzjA0Y23B7iHFG+vMfIC3yh/m/SSS2/eeRvwm0l/EfHofNSDADhZicwWEeNomDbQd4DG7wGD5gbGDG6xeJBAMJOcPDbGaSDeeSeQzPpBU+SDiG2y+GwBD78OGPDY/c8eZnkj/K7OTkjh/ecOBDDW6HGTYAiQQGCTThBJwaGBjk8ciNglEwCkbBKIAAAP3PSnIoW4S4AAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0002-9431-5673","institution":"Universitat de Valéncia","correspondingAuthor":true,"prefix":"","firstName":"Jose","middleName":"Ignacio Valenzuela","lastName":"Rios","suffix":""},{"id":635491870,"identity":"41aad7a6-49d0-4783-81ff-851db5ce049b","order_by":1,"name":"Jau-Chyn Liao","email":"","orcid":"","institution":"Complutense University of Madrid: Universidad Complutense de Madrid","correspondingAuthor":false,"prefix":"","firstName":"Jau-Chyn","middleName":"","lastName":"Liao","suffix":""}],"badges":[],"createdAt":"2026-05-04 23:19:24","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9612481/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9612481/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":109324938,"identity":"125834e2-d178-4f9f-994e-46520af067a1","added_by":"auto","created_at":"2026-05-15 14:31:39","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":3068605,"visible":true,"origin":"","legend":"\u003cp\u003eGeographical and geological location of the Segre 4 section in the Spanish Pyrenees. A. Geographical position of Segre 4 section (red start). B. Geological context of the Segre 4 section in the Compte Subfacies. This map shows the facial distribution and subdivision of the Devonian and Carboniferous rocks in the Southern Facies Area (Mey 1967; Zwart 1979). Based on Valenzuela-Ríos et al. 2015.\u003c/p\u003e","description":"","filename":"Fig1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9612481/v1/809af6e05dffbc8362acedfe.jpg"},{"id":109324939,"identity":"f74dcdfa-0b6c-4f2a-8cb4-8d7fc9a702a3","added_by":"auto","created_at":"2026-05-15 14:31:39","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1898177,"visible":true,"origin":"","legend":"\u003cp\u003eBiostratigraphic distribution of conodont taxa from section Segre 4 including biostratigraphic and chronostratigraphic interpretations. Taxa acronyms: \u003cem\u003eF.\u003c/em\u003e: \u003cem\u003eFlajsella\u003c/em\u003e; \u003cem\u003eA\u003c/em\u003e.: \u003cem\u003eAncyrodelloides\u003c/em\u003e; \u003cem\u003eL.\u003c/em\u003e \u003cem\u003eLanea\u003c/em\u003e; \u003cem\u003ePa\u003c/em\u003e.: \u003cem\u003ePanderodus\u003c/em\u003e; \u003cem\u003eW\u003c/em\u003e.: \u003cem\u003eWurmiella\u003c/em\u003e; \u003cem\u003ePs\u003c/em\u003e.: \u003cem\u003ePseudooneotodus\u003c/em\u003e; \u003cem\u003eI\u003c/em\u003e.: \u003cem\u003eIcriodus\u003c/em\u003e; \u003cem\u003ea\u003c/em\u003e.: \u003cem\u003eangustoides\u003c/em\u003e; \u003cem\u003eK\u003c/em\u003e.: \u003cem\u003eKimognathus\u003c/em\u003e; \u003cem\u003eZ\u003c/em\u003e.: \u003cem\u003eZieglerodina\u003c/em\u003e; \u003cem\u003ePel\u003c/em\u003e.: \u003cem\u003ePelekysgnathus\u003c/em\u003e; \u003cem\u003eM\u003c/em\u003e.: \u003cem\u003eMasaraella\u003c/em\u003e; \u003cem\u003ePed\u003c/em\u003e.: \u003cem\u003ePedavis\u003c/em\u003e.\u003c/p\u003e","description":"","filename":"Fig2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-9612481/v1/2f543c48c6f3d40747d6e5d2.jpg"},{"id":109405578,"identity":"caa0ffa4-bac9-4ecc-baf6-e889331746c6","added_by":"auto","created_at":"2026-05-17 13:19:13","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":3159604,"visible":true,"origin":"","legend":"\u003cp\u003eConodonts from the Segre 4 section. a: \u003cem\u003eFlajsella stygia\u003c/em\u003e, a1 upper view; a2 lateral view; Bed 1a, bar scale 300 μm. b: \u003cem\u003eAncyrodelloides asymmetricus\u003c/em\u003e, b1 upper view; b2 lower view; b3 lateral view; Bed 1a; bar scale b1 and b2 500 μm; b3 200 μm. c: \u003cem\u003eAncyrodelloides transitans\u003c/em\u003e, c1 upper view; c2 lower view; c3 lateral view; Bed 1a; bar scale c1 –c3 200 μm. d: \u003cem\u003eLanea eoeleanorae\u003c/em\u003e, d1 upper view; d2 lower view; d3 lateral view; Bed 2; bar scale d1-d3 200 μm. e: \u003cem\u003eWurmiella wurmi\u003c/em\u003e, e1 upper view; e2 lower view; e3 lateral view; Bed 2; bar scale e1-e3 200 μm. f: \u003cem\u003eLanea planilingua\u003c/em\u003e, f1 upper view; f2 lower view; f3 lateral view; Bed 3; bar scale f1-f3 500 μm. g: \u003cem\u003eAncyrodelloides kutscheri\u003c/em\u003e, initial state derived from \u003cem\u003eA. trigonicus\u003c/em\u003e, g1 lower view; g2 upper view; Bed 3; bar scale g1 and g2 500 μm. h: \u003cem\u003eAncyrodelloides trigonicus\u003c/em\u003e, h1 upper view, h2 lower view; Bed 4; bar scale h1 and h2 500 μm. i: \u003cem\u003eAncyrodelloides kutscheri\u003c/em\u003e, lower view; Bed 4; bar scale 500 μm. j: \u003cem\u003eAncyrodelloides kutscheri\u003c/em\u003e showing incipient bifurcation leading to \u003cem\u003eA. sequeirosi\u003c/em\u003e, j1 lower view; j2 upper view; Bed 5; bar scale j1 and j2 500 μm. k: fragmentary specimen of \u003cem\u003eAncyrodelloides cruzae\u003c/em\u003e; upper view; Bed 7; bar scale 200 μm. l: \u003cem\u003eAncyrodelloides murphyi\u003c/em\u003e, l1 lower view; l2 upper view; Bed 7; bar scale l1 and l2 200 μm. m: \u003cem\u003eAncyrodelloides trigonicus\u003c/em\u003e, m1 lower view, m2 upper view; Bed 11; bar scale m1 and m2 200 μm. n: \u003cem\u003eLanea telleri\u003c/em\u003e, n1 upper view; n2 lower view; n3 lateral view; Bed 13; bar scale n1 200 μm; n2 and n3 500 μm.\u003c/p\u003e","description":"","filename":"Fig3.png","url":"https://assets-eu.researchsquare.com/files/rs-9612481/v1/c3a317546abc798dd564320d.png"},{"id":109324942,"identity":"4de8ae23-5abe-4324-ad43-48f67f783f2c","added_by":"auto","created_at":"2026-05-15 14:31:39","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":3424540,"visible":true,"origin":"","legend":"\u003cp\u003eConodonts from the Segre 4 section. a: \u003cem\u003eIcriodus angustoides alcoleae\u003c/em\u003e, a1 upper view; a2 lateral view; Bed 16; bar scale a1 and a2 400 μm. b: \u003cem\u003eAncyrodelloides transitans\u003c/em\u003e, upper view; Bed 16; bar scale 200 μm. c: \u003cem\u003eKimognathus limbacarinatus\u003c/em\u003e, c1 upper view; c2 lateral view; Bed 16; bar scale c1 and c2 200 μm. d: \u003cem\u003eAncyrodelloides trigonicus\u003c/em\u003e, upper view; Bed 22; bar scale 500 μm. e: \u003cem\u003eFlajsella\u003c/em\u003e cf.\u003cem\u003e streptostygia\u003c/em\u003e, e1 upper view; e2 lateral view; Bed 22; bar scale e1 and e2 300 μm. f: \u003cem\u003eMasaraella pandora\u003c/em\u003e alpha, f1 upper view; f2 lower view; Bed 27; bar scale f1 and f2 200 μm. g: \u003cem\u003eLanea omoalpha\u003c/em\u003e, g1 upper view; g2 lateral view; Bed 23; bar scale g1 and g2 500 μm. h: \u003cem\u003eZieglerodina eladioi\u003c/em\u003e, h1 upper view; h2 lateral view; Bed 23; bar scale h1 and h2 200 μm. i: \u003cem\u003eLanea omoalpha\u003c/em\u003e, i1 upper view; i2 lateral view; Bed 26; bar scale i1 and i2 500 μm. j: \u003cem\u003eMasaraella pandora\u003c/em\u003e beta, j1 lower view; j2 upper view; j3 lateral view; Bed 28; bar scale j1-j3 200 μm. k: \u003cem\u003ePelekysgnathus guadarramensis\u003c/em\u003e, k1 lower view; k2 upper view; k3 lateral view; Bed 27; bar scale k1-k3 200 μm. l: \u003cem\u003eLanea omoalpha\u003c/em\u003e, l1 upper view; l2 lower view; l3 lateral view; Bed 27; bar scale l1-l3 200 μm. m: \u003cem\u003eLanea omoalpha\u003c/em\u003e, m1 upper view; m2 lateral view; m3 lower view; Bed 28; bar scale 400 μm. n: \u003cem\u003eLanea eoeleanorae\u003c/em\u003e, n1 upper view; n2 lateral view; n3 lower view; Bed 28; bar scale n1-n3 500 μm. o: very fragmentary specimen showing main characteristics of \u003cem\u003eLanea eoeleanorae\u003c/em\u003e, o1 upper view; o2 lateral view; o3 lower view; Bed 28; bar scale o1-o3 300 μm. Specimens of \u003cem\u003eLanea\u003c/em\u003e from the basal bed of the upper Lochkovian, Bed 28, show a broad range of morphological variation including two taxa, \u003cem\u003eL. omoalpha\u003c/em\u003e and \u003cem\u003eL. eoeleonorae\u003c/em\u003e. Here, and Fig 5 a, we document an example of this spectrum.\u003c/p\u003e","description":"","filename":"Fig4.png","url":"https://assets-eu.researchsquare.com/files/rs-9612481/v1/ec2f79e348abfcda37647951.png"},{"id":109405413,"identity":"337428e2-02ed-40c9-a11a-f7ab7b5b249a","added_by":"auto","created_at":"2026-05-17 13:17:55","extension":"xlsx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":45634,"visible":true,"origin":"","legend":"\u003cp\u003eTable 1\u003c/p\u003e\n\u003cp\u003eRecords of main conodont taxa in Segre 4 section indicating the zonal boundaries. Only Pa and I elements are considered here for the pectiniforms; there are many ramiforms of the Spathognatodontidae and coniforms of the Icriodontidae and Pedavisae not included in this table.\u003c/p\u003e","description":"","filename":"Tabla1def.xlsx","url":"https://assets-eu.researchsquare.com/files/rs-9612481/v1/4b8048e4e7408f75b697b89d.xlsx"}],"financialInterests":"","formattedTitle":"Middle-upper Lochkovian (Lower Devonian) conodont succession in the section Segre 4 (Spanish central Pyrenees)","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe Lochkovian Stage remains one of the few intervals of the Devonian for which a formal global subdivision has not yet been established. This situation may be related to the pronounced provincialism of Lochkovian conodont taxa, particularly in the lower part of the stage. Such provincialism restricted the global distribution of certain species (Klapper and Johnson \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e1980\u003c/span\u003e) and complicates the establishment of a globally applicable zonal framework for the entire Stage.\u003c/p\u003e \u003cp\u003eConsequently, early Lochkovian conodont biostratigraphy was based on two principal reference areas: western North America and southwestern Europe (Spain), each characterized by distinct conodont successions that are difficult to correlate (Klapper \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e1977\u003c/span\u003e; Carls \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e1969\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e1975\u003c/span\u003e). Shortly thereafter, Klapper and Ziegler (\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e1979\u003c/span\u003e) proposed an initial comparison between these successions and incorporated data from additional regions, including Germany, Austria, Ukraine, the Czech Republic, and Australia.\u003c/p\u003e \u003cp\u003eThe widely used global Lochkovian conodont succession is largely based on Klapper (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e1977\u003c/span\u003e), who explicitly noted that this biostratigraphic zonation was intended only for western North America (notably key sections from Central Nevada and the Yukon Territory) and the Canadian Artic Islands. However, many subsequent studies, applied Klapper\u0026rsquo;s zonation indiscriminately, even in the absence of the defining or characterising conodont taxa. As a result, the placement of local lower zonal boundaries in such cases is unreliable for correlation, and these interpretations should be treated with caution until supported by more robust stratigraphic evidence.\u003c/p\u003e \u003cp\u003eValenzuela-R\u0026iacute;os (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e1994a\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003eb\u003c/span\u003e) identified main global correlation issues arising from the widespread application of Klapper\u0026rsquo;s zonation and proposed several solutions, initially applied to the upper half of the Lochkovian. Subsequent zonation schemes following these principles were developed (Valenzuela-R\u0026iacute;os and Murphy \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e1997\u003c/span\u003e; Murphy and Valenzuela-R\u0026iacute;os \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Slav\u0026iacute;k et al. \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2008\u003c/span\u003e, \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Valenzuela-R\u0026iacute;os et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Another relevant zonation (Corradini and Corriga \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) exhibits, at least in part, some of the problems previously outlined by Valenzuela-R\u0026iacute;os (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1994b\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eDespite these challenges, the middle Lochkovian is characterized by the occurrence of cosmopolitan species associated with the radiation of three key genera- \u003cem\u003eAncyrodelloides\u003c/em\u003e, \u003cem\u003eLanea\u003c/em\u003e, and \u003cem\u003eFlajsella\u003c/em\u003e-, which facilitates the establishment of a global zonation. These are followed in the upper Lochkovian by the radiation of \u003cem\u003eMasaraella\u003c/em\u003e and \u003cem\u003ePedavis\u003c/em\u003e, further enabling accurate interregional correlations. In addition to these cosmopolitan taxa, other genera with more restricted distribution (e.g. \u003cem\u003eIcriodus\u003c/em\u003e, \u003cem\u003ePelekysgnathus\u003c/em\u003e) are used in regional zonation schemes (Carls and Gandl \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e1969\u003c/span\u003e; Carls \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e1987\u003c/span\u003e; Drygan and Szaniawsky \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2012\u003c/span\u003e). The co-occurrence of cosmopolitan and endemic taxa in the Pyrenean sequences is particularly valuable for integrating regional biostratigraphic frameworks into a global scheme.\u003c/p\u003e \u003cp\u003eAs each stratigraphic section may provide unique and significant data for refining the global Lochkovian framework, it is essential that all potential sections are thoroughly investigated. Accordingly, we undertook a comprehensive study of the Segre 4 section.\u003c/p\u003e \u003cp\u003eThe main goal of this study is to analyse in detail the middle and upper Lochkovian conodont succession recorded in the Segre 4 section and to integrate these results into the global Lochkovian database. Additionally, we compare the stratigraphic ranges of key taxa with those documented in important Perigondwanan (Pyrenees, Prague Synform, Carnic Alps) and Laurasian (Central Nevada) sections.\u003c/p\u003e"},{"header":"Material and Methodology","content":"\u003cp\u003eThe Segre 4 section is a part of a group of outcrops located on the right bank of the Segre river, near La Seu d\u0026rsquo;Urgell (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). It is situated on the west flank of a faulted anticline and follows the route of the former national road N-260 between La Seu d\u0026rsquo;Urgell and Puigcerd\u0026agrave;.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe section is approximately 8 m thick and begins above a faulted base. It consists of well-bedded grey limestone interbedded with black and grey marls and shales. Up \u0026ndash;section, the strata become thicker and display a pseudonodular appearance. These rocks correspond to the Rueda Formation and are assigned to the Compte Subfacies of the Southern Facies Area (Mey \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e1967\u003c/span\u003e; Zwart \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e1979\u003c/span\u003e; Valenzuela-R\u0026iacute;os and Liao \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2006\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eA preliminary report on this section was presented at the Fourth International Conodont Symposium (ICOS IV) (Valenzuela R\u0026iacute;os et al. 2017), and a more detailed study is presented here. The strata dip steeply (approximately 75\u0026ordm;) towards the southwest. Although the section is continuous, a minor fault- without significant disruption to the stratigraphic sequence- is present between beds 21 and 22. Minor displacements are occasionally observed, but the overall succession can be followed without difficulty.\u003c/p\u003e \u003cp\u003eA total of 37 consecutive samples were collected, with a combined weight of approximately 200 kg (Table\u0026nbsp;1). Samples were processed using a 6\u0026ndash;8% formic acid solution and subsequently washed by decantation. The residues were then dried in an oven at approximately 60\u0026ordm;C. Conodont elements and other microfossils were handpicked using a fine wet brush under a Leica MZ APO binocular microscope. Selected specimens were photographed using two Scanning Electron Microscopes (Philips Esem XL30 and Hitachi S4800) at the Microscopy Services of the University of Valencia, and the resulting images were digitally processed.\u003c/p\u003e"},{"header":"Results and discussion","content":"\u003cp\u003eAll samples yielded conodonts. Among other microfossils observed in some samples fish scales, ostracods, and acrotetrids are the most common. Scarce crinoid stems, trilobite larvae, and possible fragments of phyllocarid jaws were also occasionally recovered in the residues. Macroremains observed in the field include orthoceratids, crinoids, trilobite fragments, and small shelly fauna (bivalves and brachiopods).\u003c/p\u003e\n\u003ch3\u003eBiostratigraphic interpretation\u003c/h3\u003e\n\u003cp\u003eThe conodont succession begins in the middle parts of the middle Lochkovian (\u003cem\u003etrigonicus-kutscheri\u003c/em\u003e Zone) and extends to the uppermost Lochkovian (\u003cem\u003egilberti\u003c/em\u003e-\u003cem\u003esteinachensis\u003c/em\u003e β Zone), close below the base of the Pragian. It comprises four consecutive zones of global scope (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eIn our biostratigraphic interpretation, we follow the dual terminology proposed by Valenzuela-R\u0026iacute;os (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1994b\u003c/span\u003e), subsequently applied in Lochkovian studies (e.g. Valenzuela-R\u0026iacute;os and Murphy \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e1997\u003c/span\u003e; Murphy and Valenzuela-R\u0026iacute;os \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e1999\u003c/span\u003e; Valenzuela-R\u0026iacute;os and Liao, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2012\u003c/span\u003e; Valenzuela-R\u0026iacute;os et al. \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2005\u003c/span\u003e, \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2015\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2017\u003c/span\u003e) and summarized in Valenzuela-R\u0026iacute;os and Liao (\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). The definition of the middle Lochkovian \u003cem\u003etrigonicus\u003c/em\u003e-\u003cem\u003ekutscheri\u003c/em\u003e and \u003cem\u003ekutscheri\u003c/em\u003e-\u003cem\u003epandora\u003c/em\u003e β zones, as well as the redefinition of the upper Lochkovian \u003cem\u003egilberti\u003c/em\u003e-\u003cem\u003esteinachensis\u003c/em\u003e β Zone, were presented in Valenzuela-R\u0026iacute;os et al. (\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2015\u003c/span\u003e), whereas the definition of the upper Lochkovian \u003cem\u003epandora\u003c/em\u003e β-\u003cem\u003egilberti\u003c/em\u003e Zone was already done by Valenzuela-R\u0026iacute;os (\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1994b\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cem\u003etrigonicus-kutscheri\u003c/em\u003e Zone\u003c/p\u003e \u003cp\u003eThe lowermost sample (Se 4/1a) was collected from the lower 22 cm of the basal bed of this section (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). It already contains \u003cem\u003eAncyrodelloides trigonicus\u003c/em\u003e, together with \u003cem\u003eA. transitans\u003c/em\u003e, \u003cem\u003eA. asymmetricus\u003c/em\u003e, \u003cem\u003eLanea omoalpha\u003c/em\u003e, \u003cem\u003eFlajsella stygia\u003c/em\u003e, and \u003cem\u003eWurmiella wurmi\u003c/em\u003e. This association is characteristic of the \u003cem\u003etrigonicus-kutscheri\u003c/em\u003e Zone.\u003c/p\u003e \u003cp\u003eAdditionally, the coniform taxa \u003cem\u003ePseudooneotodus beckmanni\u003c/em\u003e and \u003cem\u003ePanderodus unicostatus\u003c/em\u003e are recorded in this bed. The conodont assemblages from the overlying two samples (Se 4/1b and Se 4/2) are consistent with assignment to this zone (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e, Tb. 1), and include \u003cem\u003eL\u003c/em\u003e. \u003cem\u003eeoeleanorae\u003c/em\u003e (sample Se 4/2).\u003c/p\u003e \u003cp\u003e \u003cem\u003ekutscheri\u003c/em\u003e-\u003cem\u003epandora\u003c/em\u003e β Zone\u003c/p\u003e \u003cp\u003eThe base of this zone is defined by the first appearance of \u003cem\u003eA. kutscheri\u003c/em\u003e. In the Segre 4 section, this taxon first occurs in sample Se 4/3. This sample also yielded \u003cem\u003eA\u003c/em\u003e. \u003cem\u003etrigonicus\u003c/em\u003e, \u003cem\u003eL\u003c/em\u003e. \u003cem\u003eomoalpha\u003c/em\u003e, \u003cem\u003eL\u003c/em\u003e. \u003cem\u003eplanilingua\u003c/em\u003e, and \u003cem\u003ePs\u003c/em\u003e. \u003cem\u003ebeckmanni\u003c/em\u003e. This zone extends up to the base of Bed 28, marked by the first occurrence of \u003cem\u003eMasaraella pandora\u003c/em\u003e β. All taxa present in the underlying \u003cem\u003etrigonicus\u003c/em\u003e-\u003cem\u003ekutscheri\u003c/em\u003e Zone continue in this interval, along with additional taxa.\u003c/p\u003e \u003cp\u003eThe (eco)concurrence of \u003cem\u003eA\u003c/em\u003e. \u003cem\u003etransitans\u003c/em\u003e and \u003cem\u003eIcriodus angustoides alcoleae\u003c/em\u003e in high abundance was used by Valenzuela-R\u0026iacute;os (\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e1994a\u003c/span\u003e) to subdivide this zone into lower and upper parts. This informal subdivision has also been applied in correlations between peri-Gondwana successions in the Spanish Pyrenees and the Prague Synform (Valenzuela-R\u0026iacute;os et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2015\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eThe conodont record from the Segre 4 section allows the application of this informal subdivision, which is useful for regional correlation. The acme of these two taxa begins in Bed 15 and continues to Bed 20 (Tb. 1); thus, the base of Bed 15 marks the transition from the lower to the upper part of the \u003cem\u003ekutscheri\u003c/em\u003e-\u003cem\u003epandora\u003c/em\u003e β Zone.\u003c/p\u003e \u003cp\u003eThe radiation of the genus \u003cem\u003eLanea\u003c/em\u003e is represented by three taxa: \u003cem\u003eL. omoalpha\u003c/em\u003e, \u003cem\u003eL. eoeleonorae\u003c/em\u003e, and \u003cem\u003eL. telleri\u003c/em\u003e. \u003cem\u003eL\u003c/em\u003eanea \u003cem\u003eeleanorae\u003c/em\u003e is rare in the Pyrenean sections and has not been recorded in the Segre 4 section. In contrast, this section shows the widest known stratigraphic range of \u003cem\u003eL\u003c/em\u003e. \u003cem\u003eomoalpha\u003c/em\u003e and \u003cem\u003eL\u003c/em\u003e. \u003cem\u003eeoeleonorae\u003c/em\u003e. Both taxa extend into the upper Lochkovian \u003cem\u003epandora\u003c/em\u003e β-\u003cem\u003egilberti\u003c/em\u003e Zone, making this the only known section in which either taxon ranges above the middle Lochkovian.\u003c/p\u003e \u003cp\u003eIn most Pyrenean and Czech sections, both taxa are restricted to the lower \u003cem\u003ekutscheri\u003c/em\u003e-\u003cem\u003epandora\u003c/em\u003e β Zone (Valenzuela-R\u0026iacute;os et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2015\u003c/span\u003e), and they do not reach the base of the \u003cem\u003etrigonicus\u003c/em\u003e-\u003cem\u003ekutscheri\u003c/em\u003e Zone in either Alpine (Corradini and Corriga \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) or Nevadan sections (Murphy and Valenzuela-R\u0026iacute;os \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e1999\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn the Segre 4 section, \u003cem\u003eL\u003c/em\u003e. \u003cem\u003etelleri\u003c/em\u003e has a limited stratigraphic range within the lower part of the \u003cem\u003ekutscheri\u003c/em\u003e-\u003cem\u003epandora\u003c/em\u003e β Zone, between samples Se 4/5 and Se 4/13. This distribution is consistent with other Pyrenean sections and with records from Central Nevada (Murphy and Valenzuela-R\u0026iacute;os, \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e1999\u003c/span\u003e); although in Nevada its first occurrence lies in the upper part of the \u003cem\u003etransitans\u003c/em\u003e-\u003cem\u003etrigonicus\u003c/em\u003e Zone. Corradini and Corriga (\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2012\u003c/span\u003e) reported a broader stratigraphic range for this taxon, from the upper half of the \u003cem\u003etransitans\u003c/em\u003e-\u003cem\u003etrigonicus\u003c/em\u003e Zone to the top of the middle Lochkovian. \u003cem\u003eLanea telleri\u003c/em\u003e has not been recorded in the Prague-Synform (Valenzuela-R\u0026iacute;os et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2015\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eAll species of \u003cem\u003eAncyrodelloides\u003c/em\u003e become extinct within this zone. \u003cem\u003eAncyrodelloides transitans\u003c/em\u003e disappears in Bed 20 following its acme. \u003cem\u003eAncyrodelloides asymmetricus\u003c/em\u003e becomes extinct within the lower part of the zone (sample Se 4/14a). \u003cem\u003eAncyrodellloides trigonicus\u003c/em\u003e has its last occurrence in Bed 22. \u003cem\u003eAncyrodelloides cruzae\u003c/em\u003e has a unique occurrence in Bed 7. \u003cem\u003eAncyrodelloides kutscheri\u003c/em\u003e has its last occurrence in the lower 20 cm of Bed 8 (sample Se 4/8a), whereas \u003cem\u003eA\u003c/em\u003e. \u003cem\u003emurphyi\u003c/em\u003e has a continuous record in the lower part of the zone (Beds 6a-8a). Thus, the radiation of the genus \u003cem\u003eAncyrodelloides\u003c/em\u003e is well represented in the Segre 4 section, with its upper range restricted to the middle Lochkovian. The earliest representative, \u003cem\u003eA. carlsi\u003c/em\u003e, is absent, likely because the section begins in the upper part of the \u003cem\u003etransitans\u003c/em\u003e-\u003cem\u003etrigonicus\u003c/em\u003e Zone, after the disappearance of this species. No definitive specimens of \u003cem\u003eA. sequeirosi\u003c/em\u003e were recorded; however, a transitional form between \u003cem\u003eA. kutscheri\u003c/em\u003e and \u003cem\u003eA. sequeirosi\u003c/em\u003e occurs in Bed 5 (Figs.\u0026nbsp;3j1, 3j2 ), supporting the high morphological plasticity of this group during its radiation in the middle Lochkovian.\u003c/p\u003e \u003cp\u003eThe cosmopolitan but rare genus \u003cem\u003eFlajsella\u003c/em\u003e is represented by two fragmentary specimens in the upper part of the zone. The first, from Bed 16, is a Pa element fragment tentatively assigned to \u003cem\u003eF. schulzei\u003c/em\u003e due to the preserved anterior carina bearing denticles of approximately the same high and a straight blade. The second, from Bed 22, is classified as \u003cem\u003eF\u003c/em\u003e. cf. \u003cem\u003estreptostygia\u003c/em\u003e based on the numerous denticles and their arrangement on the anterior blade (gradually ascending from the anterior end to the highest one located on the posterior half, Figs.\u0026nbsp;4e1, 4e2).\u003c/p\u003e \u003cp\u003eOther notable taxa include \u003cem\u003eI\u003c/em\u003e. \u003cem\u003ea\u003c/em\u003e. \u003cem\u003ealcoleae\u003c/em\u003e, recorded from Beds 12 to 20, with its acme in Bed 20 (35 specimens from a 4,3 kg sample; Tb. 1). \u003cem\u003eL\u003c/em\u003eanea \u003cem\u003eplanilingua\u003c/em\u003e occurs sporadically (Beds 3 and 26), and \u003cem\u003eZieglerodina eladioi\u003c/em\u003e is represented by a single specimen in Bed 23 (Figs.\u0026nbsp;4h1, 4h2). The latter is noteworthy, as this taxon is otherwise common in lower and middle Lochkovian of the nearby Gerri and Segre sections (Valenzuela-R\u0026iacute;os \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e1994a\u003c/span\u003e; Valenzuela-R\u0026iacute;os et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2015\u003c/span\u003e; Valenzuela-R\u0026iacute;os and Liao \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2024\u003c/span\u003e) but does not typically extend in the upper part of the \u003cem\u003ekutscheri\u003c/em\u003e-\u003cem\u003epandora\u003c/em\u003e β Zone. This occurrence therefore extends its known stratigraphic range upward. The absent of records in the underlying beds is puzzling.\u003c/p\u003e \u003cp\u003e \u003cem\u003eKimognathus limbacarinatus\u003c/em\u003e is recorded from samples Se 4/14a to Se 4/16, spanning the lower to upper parts of the \u003cem\u003ekutscheri\u003c/em\u003e-\u003cem\u003epandora\u003c/em\u003e β Zone. This extends its known range downward in the Pyrenees and aligns with records from Central Nevada, where \u003cem\u003eK\u003c/em\u003e. \u003cem\u003elimbacarinatus\u003c/em\u003e appears already in the upper beds of the \u003cem\u003etransitans\u003c/em\u003e-\u003cem\u003etrigonicus\u003c/em\u003e Zone (COP V-IV and SPVII sections) and in the \u003cem\u003ekuscheri\u003c/em\u003e-\u003cem\u003epandora\u003c/em\u003e β Zone in the MC section (Murphy and Matti \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e1983\u003c/span\u003e). In the Carnic Alps its range fully coincides with that of \u003cem\u003eA\u003c/em\u003e. \u003cem\u003ekutscheri\u003c/em\u003e and, thus, it is restricted to the \u003cem\u003ekuscheri\u003c/em\u003e-\u003cem\u003epandora\u003c/em\u003e β Zone. In the Prague Synform, the record in section Pož\u0026aacute;r 3 starts with the lowest local record of \u003cem\u003eA. trigonicus\u003c/em\u003e (a fragmentary specimen) and ends within the lower part of the \u003cem\u003ekuscheri\u003c/em\u003e-\u003cem\u003epandora\u003c/em\u003e β Zone (Slav\u0026iacute;k et al. \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2012\u003c/span\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003e; Valenzuela-R\u0026iacute;os et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2015\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe upper beds of the middle Lochkovian are poor in conodonts, yielding only a few taxa, including the pectiniforms \u003cem\u003eL\u003c/em\u003e. \u003cem\u003eomoalpha\u003c/em\u003e, \u003cem\u003eL. eoeleonorae\u003c/em\u003e, \u003cem\u003eW\u003c/em\u003e. \u003cem\u003ewurmi\u003c/em\u003e, \u003cem\u003ePelekysgnathus guadarramensis\u003c/em\u003e, \u003cem\u003eL. planilingua\u003c/em\u003e, \u003cem\u003eMasaraella pandora\u003c/em\u003e α, and the coniforms \u003cem\u003ePs. beckmani\u003c/em\u003e and \u003cem\u003eDvorakia\u003c/em\u003e. A notable feature is the acme of \u003cem\u003ePs\u003c/em\u003e. \u003cem\u003ebeckmanni\u003c/em\u003e in the uppermost bed of the zone (sample Se 4/27), with 108 specimens recovered.\u003c/p\u003e \u003cp\u003eThe extinction of most middle Lochkovian genera is followed by the radiation of a new genus, \u003cem\u003eMasaraella\u003c/em\u003e, which diversifies in the upper Lochkovian and gives rise to \u003cem\u003eEognathodus\u003c/em\u003e at the beginning of the Pragian (Murphy et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e1981\u003c/span\u003e; Murphy \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2005\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cem\u003epandora\u003c/em\u003e β-\u003cem\u003egilberti\u003c/em\u003e Zone\u003c/p\u003e \u003cp\u003eThe base of this zone coincides with the base of the upper Lochkovian and is defined by the first evolutionary appearance of \u003cem\u003eM\u003c/em\u003easaraella \u003cem\u003epandora\u003c/em\u003e β (Valenzuela-R\u0026iacute;os \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1994b\u003c/span\u003e; Valenzuela-R\u0026iacute;os and Murphy \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e1997\u003c/span\u003e; Valenzuela-R\u0026iacute;os and Liao \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2012\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2024\u003c/span\u003e; Valenzuela-R\u0026iacute;os et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2015\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eIn the Segre 4 section, \u003cem\u003eM\u003c/em\u003e. \u003cem\u003epandora\u003c/em\u003e β first occurs in sample Se 4/28 (Figs.\u0026nbsp;4j1-j3), located within the lower 10 cm of Bed 28 (44 cm thick; Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). This sample also contains the last occurrences of \u003cem\u003eL\u003c/em\u003e. \u003cem\u003eomoalpha\u003c/em\u003e and \u003cem\u003eL\u003c/em\u003e. eoeleonorae (Figs.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003em, n, o; Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003ea). These records represent the only known occurrence of these taxa in the upper Lochkovian worldwide. The four principal taxa involved in the Lochkovian radiation of \u003cem\u003eLanea\u003c/em\u003e (\u003cem\u003eL\u003c/em\u003e. \u003cem\u003eomoalpha\u003c/em\u003e, \u003cem\u003eL\u003c/em\u003e. \u003cem\u003eeoeleonorae\u003c/em\u003e, \u003cem\u003eL\u003c/em\u003e. \u003cem\u003eeleanorae\u003c/em\u003e, and \u003cem\u003eL. telleri\u003c/em\u003e) became extinct during the middle Lochkovian in all know sections from Western North America, the Pyrenees, the Carnic Alps, and the Prague Synform. These basal upper Lochkovian occurrences in the Segre 4 section therefore constitute a notable exception, even at the regional scale, suggesting that these taxa locally survive the middle Lochkovian extinction event but disappear shortly thereafter.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eWithin this zone, both morphotypes (α and β) of \u003cem\u003eM\u003c/em\u003e. \u003cem\u003epandora\u003c/em\u003e disappear, with their last occurrence in sample Se 4/30, located in the lower 20 cm of Bed 30 (50 cm thick; Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). This extinction of \u003cem\u003eMasaraella\u003c/em\u003e in the Segre 4 section coincides with the radiation of the genus \u003cem\u003ePedavis\u003c/em\u003e in the upper Lochkovian.\u003c/p\u003e \u003cp\u003eIn the same sample (Se 4/30), \u003cem\u003ePed\u003c/em\u003e. \u003cem\u003ebreviramus\u003c/em\u003e (Figs.\u0026nbsp;5b1-b3) and \u003cem\u003ePed\u003c/em\u003e. \u003cem\u003erobertoi\u003c/em\u003e morphotype 1 of Valenzuela-R\u0026iacute;os \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e1994a\u003c/span\u003e (Figs.\u0026nbsp;5c1-c3) are recorded, while the overlying sample (Se 4/31) marks the first occurrence of \u003cem\u003ePed\u003c/em\u003e. \u003cem\u003epesavis\u003c/em\u003e (Figs.\u0026nbsp;5e1-e3). \u003cem\u003eWurmiella wurmi\u003c/em\u003e continues and \u003cem\u003ePs\u003c/em\u003e. \u003cem\u003ebeckmanni\u003c/em\u003e persist throughout this interval. The latter exhibits a second acme in Bed 30, with 56 specimens, coinciding with the last occurrence of \u003cem\u003ePa\u003c/em\u003e. \u003cem\u003eunicostatus\u003c/em\u003e.\u003c/p\u003e \u003cp\u003e \u003cem\u003egilberti\u003c/em\u003e-\u003cem\u003esteinachensis\u003c/em\u003e β Zone\u003c/p\u003e \u003cp\u003eThe base of this zone is defined by the first occurrence of \u003cem\u003ePed\u003c/em\u003e. \u003cem\u003egilberti\u003c/em\u003e (Valenzuela-R\u0026iacute;os \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1994b\u003c/span\u003e; Valenzuela-R\u0026iacute;os et al. \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). The radiation of \u003cem\u003ePedavis\u003c/em\u003e continues with the appearance of two additional taxa, \u003cem\u003ePed. gilberti\u003c/em\u003e (Figs.\u0026nbsp;5f1-f3) and \u003cem\u003ePed\u003c/em\u003e. \u003cem\u003erobertoi\u003c/em\u003e morphotype 2 of Valenzuela-R\u0026iacute;os \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e1994a\u003c/span\u003e (Figs.\u0026nbsp;5d1-d3).\u003c/p\u003e \u003cp\u003eTogether with the long-ranging taxa \u003cem\u003eW\u003c/em\u003e. \u003cem\u003ewurmi\u003c/em\u003e and \u003cem\u003ePs\u003c/em\u003e. \u003cem\u003ebeckmanni\u003c/em\u003e, these are the only conodonts recorded in the uppermost exposed beds (samples Se 4/32 and Se 4/33). This low diversity reflects the upper Lochkovian conodont decline in Europe, which appears particularly pronounced in the Segre 4 section.\u003c/p\u003e \u003cp\u003eIn contrast, other Pyrenean sections assigned to this zone contain more diverse assemblages, with up to 12 taxa, including representatives of \u003cem\u003ePedavis\u003c/em\u003e, \u003cem\u003eMasaraella\u003c/em\u003e, \u003cem\u003eIcriodus\u003c/em\u003e, \u003cem\u003ePelekysgnathus\u003c/em\u003e, \u003cem\u003eWurmiella\u003c/em\u003e, and \u0026ldquo;\u003cem\u003eOzarkodina\u003c/em\u003e\u0026rdquo; \u003cem\u003epi\u003c/em\u003e (Valenzuela-R\u0026iacute;os and Liao \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). This contrast, together with the unusual upward range extension of the two species of \u003cem\u003eLanea\u003c/em\u003e in the underlying \u003cem\u003epandora\u003c/em\u003e β-\u003cem\u003egilberti\u003c/em\u003e Zone, makes the upper Lochkovian interval in the Segre 4 section particularly noteworthy and somewhat enigmatic in terms of conodont diversity and evolutionary patterns.\u003c/p\u003e"},{"header":"Conclusions","content":"\u003cp\u003eThe conodont assemblage from the Segre 4 section comprises 13 genera including \u003cem\u003eAncyrodelloides\u003c/em\u003e, \u003cem\u003eLanea\u003c/em\u003e, \u003cem\u003eFlajsella, Masaraella\u003c/em\u003e, \u003cem\u003eZieglerodina\u003c/em\u003e, \u003cem\u003eWurmiella\u003c/em\u003e, \u003cem\u003eKimognathus\u003c/em\u003e, \u003cem\u003ePedavis\u003c/em\u003e, \u003cem\u003eIcriodus\u003c/em\u003e, \u003cem\u003ePelekysgnathus\u003c/em\u003e, \u003cem\u003ePseudooneotodus\u003c/em\u003e, \u003cem\u003ePanderodus\u003c/em\u003e, and \u003cem\u003eDvorakia\u003c/em\u003e.\u003c/p\u003e \u003cp\u003eThe Segre 4 section provides a continuous and biostratigraphically well-constrained record of the middle to upper Lochkovian, allowing recognition of four standard conodont zones of global significance.\u003c/p\u003e \u003cp\u003eThe successive first appearances of index species allow recognition of the middle Lochkovian \u003cem\u003etrigonicus-kutscheri\u003c/em\u003e and \u003cem\u003ekutscheri\u003c/em\u003e-\u003cem\u003epandora\u003c/em\u003e β zones, as well as the upper Lochkovian \u003cem\u003epandora\u003c/em\u003e β-\u003cem\u003egilberti\u003c/em\u003e and \u003cem\u003egilberti\u003c/em\u003e-\u003cem\u003esteinachensis\u003c/em\u003e β zones. The concurrent acme of \u003cem\u003eI\u003c/em\u003e. \u003cem\u003eangustoides alcoleae\u003c/em\u003e and \u003cem\u003eA\u003c/em\u003e. \u003cem\u003etransitans\u003c/em\u003e permits subdivision of the \u003cem\u003ekutscheri\u003c/em\u003e-\u003cem\u003epandora\u003c/em\u003e β Zone into lower and upper parts, improving regional correlation.\u003c/p\u003e \u003cp\u003eThe conodont fauna is predominantly cosmopolitan, facilitating reliable correlation with both Laurasian and peri-Gondwanan regions and contributing to refinement of the global Lochkovian biostratigraphic framework.\u003c/p\u003e \u003cp\u003eThe occurrence of \u003cem\u003eLanea omoalpha\u003c/em\u003e and \u003cem\u003eL. eoeleanorae\u003c/em\u003e in the basal upper Lochkovian represents a unique extension of their known stratigraphic ranges, suggesting local survival beyond the middle Lochkovian extinction event.\u003c/p\u003e \u003cp\u003eThe middle Lochkovian is characterized by peak conodont diversity associated with the radiation of \u003cem\u003eAncyrodelloides\u003c/em\u003e, \u003cem\u003eLanea\u003c/em\u003e, and \u003cem\u003eFlajsella\u003c/em\u003e, followed by a major faunal turnover near the base of the upper Lochkovian.\u003c/p\u003e \u003cp\u003eThe upper Lochkovian records a decline in diversity and the replacement of middle Lochkovian faunas by the radiation of \u003cem\u003eMasaraella\u003c/em\u003e and \u003cem\u003ePedavis\u003c/em\u003e, culminating in a significant extinction interval toward the top of the stage.\u003c/p\u003e \u003cp\u003eThe Segre 4 section highlights both global evolutionary patterns and local anomalies, making it a key reference section for improving the understanding of Lochkovian conodont biostratigraphy and evolution.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e \u003ch2\u003eConflict of interest:\u003c/h2\u003e \u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e \u003c/p\u003e\u003ch2\u003eFunding:\u003c/h2\u003e \u003cp\u003ethe UCM Research Grant PR 12/24-31569 supports this work. J.-C. L. is supported by Jos\u0026eacute; Castillejo Fellow (MICCIN-MIU, CAS24/00333).\u003c/p\u003e\u003ch2\u003eAuthor contributions:\u003c/h2\u003e \u003cp\u003e \u003cb\u003eJos\u003c/b\u003e\u0026eacute; \u003cb\u003eIgnacio Valenzuela-R\u0026iacute;os\u003c/b\u003e: Conceptualization, Fieldwork, Formal analysis, Investigation, Methodology, Project administration, Supervision, Writing \u0026ndash; original draft, Writing \u0026ndash; review \u0026amp; editing. \u003cb\u003eJau-Chyn Liao\u003c/b\u003e: Conceptualization, Fieldwork, Photography of published specimens, Funding acquisition, Investigation, Methodology, Writing \u0026ndash; original draft, Writing \u0026ndash; review \u0026amp; editing.\u003c/p\u003e\u003ch2\u003eAcknowledgements\u003c/h2\u003e \u003cp\u003eWe dedicate this contribution to our esteemed and beloved friend, mentor and master, the unique Prof. Dr. Peter Carls, whose guidance and inspiration were fundamental during the early stages of our careers and thorough our professional development. His insight and generosity continue to influence our work.\u003c/p\u003e \u003cp\u003eThe UCM Research Grant PR12/24-31569 supported this research. It is a contribution to the Research groups GIUV2017-395 and PERIGONDWANA UCM 910231. The technical help of Central Services for Experimental Research (SCSIE), Field Emission Electron Microscope, are acknowledged, in special the advice and care of Javier Badillo.\u003c/p\u003e\u003ch2\u003eData availability:\u003c/h2\u003e \u003cp\u003eThe complete conodont collection used in this work is housed in the micropaleontological collection NACHO VALENZUELA of the Department of Botany and Geology, University of Val\u0026egrave;ncia, Spain\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eCarls, P. (1969). 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The middle and upper Lochkovian (Lower Devonian) conodont successions in peri-Gondwana key localities (Spanish Central Pyrenees and Prague Synform) and their relevance for global correlations. \u003cem\u003eTerra Nova\u003c/em\u003e, \u003cem\u003e27\u003c/em\u003e, 409\u0026ndash;415. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003e10.1111/ter.12172\u003c/span\u003e\u003cspan address=\"10.1111/ter.12172\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eValenzuela-R\u0026iacute;os, J. I., Liao, J. C., \u0026amp; Calvo, H. (2017). Middle and upper Lochkovian (Lower Devonian) at Segre 4 section. \u003cem\u003eBerichte des Institutes f\u0026uuml;r Erdwissenschaften\u003c/em\u003e. \u003cem\u003eKarls-Franzes-Universit\u0026auml;t Graz\u003c/em\u003e, \u003cem\u003e23\u003c/em\u003e, 61\u0026ndash;64.\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eZwart, H. J. (1979). The Geology of the Central Pyrenees. \u003cem\u003eLeidse Geologische Mededelingen\u003c/em\u003e, \u003cem\u003e50\u003c/em\u003e, 1\u0026ndash;74.\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":false,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"palaeobiodiversity-and-palaeoenvironments","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"pbpe","sideBox":"Learn more about [Palaeobiodiversity and Palaeoenvironments](https://www.springer.com/journal/12549)","snPcode":"12549","submissionUrl":"https://www.editorialmanager.com/pbpe/default2.aspx","title":"Palaeobiodiversity and Palaeoenvironments","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Lochkovian conodonts, Pyrenees, biostratigraphy, correlation, diversity, faunal turnover","lastPublishedDoi":"10.21203/rs.3.rs-9612481/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9612481/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThis study presents a detailed conodont-based biostratigraphic analysis of the Segre 4 section (Pyrenees), spanning the middle to upper Lochkovian. The section yields a continuous and well-preserved conodont succession comprising four globally recognized zones: the \u003cem\u003etrigonicus\u0026ndash;kutscheri\u003c/em\u003e and \u003cem\u003ekutscheri\u0026ndash;pandora\u003c/em\u003e β zones (middle Lochkovian), followed by the \u003cem\u003epandora\u003c/em\u003e β\u0026ndash;\u003cem\u003egilberti\u003c/em\u003e and \u003cem\u003egilberti\u003c/em\u003e\u0026ndash;\u003cem\u003esteinachensis\u003c/em\u003e β zones (upper Lochkovian).\u003c/p\u003e \u003cp\u003eThe conodont assemblages include both cosmopolitan and regionally restricted taxa, allowing robust correlation with key Laurasian and peri-Gondwanan successions. The middle Lochkovian interval is characterized by high diversity and the radiation of the genera \u003cem\u003eAncyrodelloides\u003c/em\u003e, \u003cem\u003eLanea\u003c/em\u003e, and \u003cem\u003eFlajsella\u003c/em\u003e, whereas the upper Lochkovian records the diversification of \u003cem\u003eMasaraella\u003c/em\u003e and \u003cem\u003ePedavis\u003c/em\u003e.\u003c/p\u003e \u003cp\u003eThe Segre 4 section provides significant new data on the stratigraphic ranges of several taxa. Notably, \u003cem\u003eLanea omoalpha\u003c/em\u003e and \u003cem\u003eL. eoeleonorae\u003c/em\u003e extend into the basal upper Lochkovian, representing the only known occurrences of these species above the middle Lochkovian. Additional relevant findings include the upward extension of \u003cem\u003eZieglerodina eladioi\u003c/em\u003e.\u003c/p\u003e \u003cp\u003eThe conodont succession also records a marked faunal turnover near the middle\u0026ndash;upper Lochkovian boundary, followed by a progressive decline in diversity toward the top of the stage. Low-diversity assemblages dominated by \u003cem\u003ePedavis\u003c/em\u003e, \u003cem\u003eWurmiella\u003c/em\u003e, and \u003cem\u003ePseudooneotodus\u003c/em\u003e, reflecting a pronounced extinction interval, characterize the uppermost beds of the section.\u003c/p\u003e","manuscriptTitle":"Middle-upper Lochkovian (Lower Devonian) conodont succession in the section Segre 4 (Spanish central Pyrenees)","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-05-15 14:31:32","doi":"10.21203/rs.3.rs-9612481/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2026-05-07T07:30:11+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-05-06T12:10:03+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-05-06T09:42:54+00:00","index":"","fulltext":""},{"type":"submitted","content":"Palaeobiodiversity and Palaeoenvironments","date":"2026-05-05T08:14:48+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"palaeobiodiversity-and-palaeoenvironments","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"pbpe","sideBox":"Learn more about [Palaeobiodiversity and Palaeoenvironments](https://www.springer.com/journal/12549)","snPcode":"12549","submissionUrl":"https://www.editorialmanager.com/pbpe/default2.aspx","title":"Palaeobiodiversity and Palaeoenvironments","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"f57fc2fb-48e3-48d0-85d4-0ebd9690cf93","owner":[],"postedDate":"May 15th, 2026","published":true,"recentEditorialEvents":[{"type":"reviewerAgreed","content":"","date":"2026-05-07T07:30:11+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-05-06T12:10:03+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-05-06T09:42:54+00:00","index":"","fulltext":""},{"type":"submitted","content":"Palaeobiodiversity and Palaeoenvironments","date":"2026-05-05T08:14:48+00:00","index":"","fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-05-15T14:31:32+00:00","versionOfRecord":[],"versionCreatedAt":"2026-05-15 14:31:32","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9612481","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9612481","identity":"rs-9612481","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}