When snake vertebrae go to an extreme – revision, vertebral morphology, and intracolumnar variation of the enigmatic snake Cadurceryx Hoffstetter & Rage, 1972, from the Eocene of Europe
Abstract
We provide a thorough documentation of the vertebral morphology and intracolumnar variation of the enigmatic snake Cadurceryx Hoffstetter & Rage, 1972, from the Eocene of France. Based on abundant vertebrae, pertaining to practically all portions of the column, originating from the middle Eocene (MP 16) of Lavergne in the Phosphorites du Quercy, we conduct a revision of the taxon, provide an emended diagnosis, and highlight a number of distinctive vertebral features that differentiate it from all other snakes. Most prominently, Cadurceryx is characterized by the presence of additional apophyses throughout the trunk, cloacal, and caudal vertebrae, which form (at least partly) true articular joints linking neighbouring vertebrae (additional intervertebral articulations). These additional apophyses are: pterapophyses (present in all vertebrae), extensions of zygapophyses and neural spine, as well as extensions of pleurapophyses (present in caudal vertebrae). We further present additional trunk and/or caudal vertebrae from several other localities in the area of the Phosphorites du Quercy: the middle Eocene (MP 16) of Malpérié, the late Eocene (MP 17) of La Bouffie and Rosières 2, the late Eocene (MP 18) of Sainte Néboule, and from imprecise localities from the “old Quercy collections”. We further conduct a critical evaluation of the original description of the taxon. Based on all these, we conclude that a single species of Cadurceryx was present in France during the middle and late Eocene, i.e., the type species Cadurceryx filholi Hoffstetter & Rage, 1972. A second species of the genus, Cadurceryx pearchi Holman, Harrison & Ward, 2006, known exclusively from caudal vertebrae from the late Eocene (MP 17) of Hordle Cliff, England, is herein also assessed; based on a critical approach of the original publication that established the English species, coupled with the presentation of some new caudal vertebrae from its type locality, we consider that Cadurceryx pearchi represents a nomen dubium, with the material potentially pertaining to ?Cadurceryx sp. or some indeterminate erycid or charinaid snake. We provide a thorough overview of the geographic and stratigraphic distribution of Cadurceryx. Through a detailed comparison with extinct and extant snakes, we discard affinities of Cadurceryx with erycids or charinaids, taking also into consideration that this grouping, according to molecular data, is not monophyletic and that the evolution of complex caudal vertebral morphologies in erycids and charinaids is likely homoplastic. Accordingly, the shared distinctive features of Cadurceryx with erycids and charinaids (presence of additional apophyses in caudal vertebrae that form true articular joints linking neighbouring vertebrae) are herein also regarded as homoplastic. Instead, we show that Cadurceryx possesses a vertebral synapomorphy of tropidophiids, namely the prominent blade-like hypapophysis on trunk vertebrae, that in posterior trunk vertebrae possesses a distinct, straight anteroventral corner, plus additional shared vertebral features. Accordingly, we herein tentatively envisage Cadurceryx as a tropidophiid with convergently evolved apophyseal morphologies with erycids and charinaids. Finally, we attempt a speculative interpretation of the functional morphology of the complex structures of the vertebrae of Cadurceryx, tentatively suggesting that these true articular joints linking neighbouring vertebrae may have offered increased rigidity across the vertebral column and may have acted as an antipredator mechanism.
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Comptes Rendus Palevol est une revue en flux continu publiée par les Publications scientifiques du Muséum, Paris et l’Académie des sciences, Paris Comptes Rendus Palevol is a fast track journal published by the Museum Science Press, Paris and the Académie des sciences, Paris Les Publications scientifiques du Muséum publient aussi / The Museum Science Press also publish: Adansonia, Geodiversitas, Zoosystema, Anthropozoologica, European Journal of Taxonomy, Naturae, Cryptogamie sous-sections Algologie, Bryologie, Mycologie. L’Académie des sciences publie aussi / The Académie des sciences also publishes: Comptes Rendus Mathématique, Comptes Rendus Physique, Comptes Rendus Mécanique, Comptes Rendus Chimie, Comptes Rendus Géoscience, Comptes Rendus Biologies. Diffusion – Publications scientifiques Muséum national d’Histoire naturelle CP 41 – 57 rue Cuvier F-75231 Paris cedex 05 (France) Tél. : 33 (0)1 40 79 48 05 / Fax : 33 (0)1 40 79 38 40 [email protected] / https://sciencepress.mnhn.fr Académie des sciences, Institut de France, 23 quai de Conti, 75006 Paris. © This article is licensed under the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/) ISSN (imprimé / print) : 1631-0683/ ISSN (électronique / electronic) : 1777-571X Directeurs De la publication / Publication directors : Gilles Bloch, Président du Muséum national d’Histoire naturelle Étienne Ghys, Secrétaire perpétuel de l’Académie des sciences réDacteurs en chef / editors-in-chief : Michel Laurin (CNRS), Philippe Taquet (Académie des sciences) assistante De réDaction / assistant editor : Adenise Lopes (Académie des sciences ; [email protected]) Mise en page / Page layout : Audrina Neveu (Muséum national d’Histoire naturelle ; [email protected]) révisions linguistiques Des textes anglais / english language revisions : Kevin Padian (University of California at Berkeley) réDacteurs associés / associate editors (*, took charge of the editorial process of the article/a pris en charge le suivi éditorial de l’article) : Micropaléontologie/Micropalaeontology Lorenzo Consorti (Institute of Marine Sciences, Italian National Research Council, Trieste) Paléobotanique/Palaeobotany Cyrille Prestianni (Royal Belgian Institute of Natural Sciences, Brussels) Anaïs Boura (Sorbonne Université, Paris) Métazoaires/Metazoa Annalisa Ferretti (Università di Modena e Reggio Emilia, Modena) Paléoichthyologie/Palaeoichthyology Philippe Janvier (Muséum national d’Histoire naturelle, Académie des sciences, Paris) Amniotes du Mésozoïque/Mesozoic amniotes Hans-Dieter Sues (Smithsonian National Museum of Natural History, Washington) Tortues/Turtles Walter Joyce (Universität Freiburg, Switzerland) Lépidosauromorphes/Lepidosauromorphs Hussam Zaher* (Universidade de São Paulo) Oiseaux/Birds Jingmai O’Connor (Field Museum, Chicago) Paléomammalogie (mammifères de moyenne et grande taille)/Palaeomammalogy (large and mid-sized mammals) Grégoire Métais (CNRS, Muséum national d’Histoire naturelle, Sorbonne Université, Paris) Paléomammalogie (petits mammifères sauf Euarchontoglires)/Palaeomammalogy (small mammals except for Euarchontoglires) Robert Asher (Cambridge University, Cambridge) Paléomammalogie (Euarchontoglires)/Palaeomammalogy (Euarchontoglires) K. Christopher Beard (University of Kansas, Lawrence) Paléoanthropologie/Palaeoanthropology Aurélien Mounier (CNRS/Muséum national d’Histoire naturelle, Paris) Archéologie préhistorique (Paléolithique et Mésolithique)/Prehistoric archaeology (Palaeolithic and Mesolithic) Nicolas Teyssandier (CNRS/Université de Toulouse, Toulouse) Archéologie préhistorique (Néolithique et âge du bronze)/Prehistoric archaeology (Neolithic and Bronze Age) Marc Vander Linden (Bournemouth University, Bournemouth) référés / reviewers : https://sciencepress.mnhn.fr/fr/periodiques/comptes-rendus-palevol/referes-du-journal couverture / cover : Made from the Figures of the article. Comptes Rendus Palevol est indexé dans / Comptes Rendus Palevol is indexed by: – Cambridge Scientific Abstracts – Current Contents® Physical – Chemical, and Earth Sciences® – ISI Alerting Services® – Geoabstracts, Geobase, Georef, Inspec, Pascal – Science Citation Index®, Science Citation Index Expanded® – Scopus®. Les articles ainsi que les nouveautés nomenclaturales publiés dans Comptes Rendus Palevol sont référencés par / Articles and nomenclatural novelties published in Comptes Rendus Palevol are registered on: – ZooBank® (http://zoobank.org)
587 COMPTES RENDUS PALEVOL • 2025 • 24 (29) © Publications scientifiques du Muséum et/and Académie des sciences, Paris. www.cr-palevol.fr Zbigniew SZYNDLAR Georgios L. GEORGALIS Institute of Systematics and Evolution of Animals, Polish Academy of Sciences, Sławkowska 17, 31-016 Kraków (Poland) [email protected] (corresponding author) Submitted on 27 February 2025 | Accepted on 15 September 2025 | Published on 17 December 2025 When snake vertebrae go to an extreme – revision, vertebral morphology, and intracolumnar variation of the enigmatic snake Cadurceryx Hoffstetter & Rage, 1972, from the Eocene of Europe urn:lsid:zoobank.org:pub:D6A181E4-4B23-4875-B4D8-45BAFCEB202F Szyndlar Z. & Georgalis G. L. 2025. — When snake vertebrae go to an extreme – revision, vertebral morphology, and intracolumnar variation of the enigmatic snake Cadurceryx Hoffstetter & Rage, 1972, from the Eocene of Europe, in Georgalis G. L., Zaher H. & Laurin M. (eds), Snakes from the Cenozoic of Europe – towards a macroevolutionary and palaeobiogeographic synthesis. Comptes Rendus Palevol 24 (29): 587-620. https://doi.org/10.5852/cr-palevol2025v24a29 ABSTRACT We provide a thorough documentation of the vertebral morphology and intracolumnar variation of the enigmatic snake Cadurceryx Hoffstetter & Rage, 1972, from the Eocene of France. Based on abundant vertebrae, pertaining to practically all portions of the column, originating from the middle Eocene (MP 16) of Lavergne in the Phosphorites du Quercy, we conduct a revision of the taxon, provide an emended diagnosis, and highlight a number of distinctive vertebral features that differentiate it from all other snakes. Most prominently, Cadurceryx is characterized by the presence of additional apophyses throughout the trunk, cloacal, and caudal vertebrae, which form (at least partly) true articular joints linking neighbouring vertebrae (additional intervertebral articulations). These additional apophyses are: pterapophyses (present in all vertebrae), extensions of zygapophyses and neural spine, as well as extensions of pleurapophyses (present in caudal vertebrae). We further present additional trunk and/or caudal vertebrae from several other localities in the area of the Phosphorites du Quercy: the middle Eocene (MP 16) of Malpérié, the late Eocene (MP 17) of La Bouffie and Rosières 2, the late Eocene (MP 18) of Sainte Néboule, and from imprecise localities from the “old Quercy collections”. We further conduct a critical evaluation of the original description of the taxon. Based on all these, we conclude that a single species of Cadurceryx was present in France during the middle and late Eocene, i.e., the type species Cadurceryx filholi Hoffstetter & Rage, 1972. A second species of the genus, Cadurceryx pearchi Holman, Harrison & Ward, 2006, known exclusively from caudal vertebrae from the late Eocene (MP 17) of Hordle Cliff, England, is herein also assessed; based on a critical approach of the original publication that established the English species, coupled with the presentation of some new caudal vertebrae from
588 COMPTES RENDUS PALEVOL • 2025 • 24 (29) Szyndlar Z. & Georgalis G. L. its type locality, we consider that Cadurceryx pearchi represents a nomen dubium, with the material potentially pertaining to ?Cadurceryx sp. or some indeterminate erycid or charinaid snake. We provide a thorough overview of the geographic and stratigraphic distribution of Cadurceryx. Through a detailed comparison with extinct and extant snakes, we discard affinities of Cadurceryx with erycids or charinaids, taking also into consideration that this grouping, according to molecular data, is not monophyletic and that the evolution of complex caudal vertebral morphologies in erycids and charinaids is likely homoplastic. Accordingly, the shared distinctive features of Cadurceryx with erycids and charinaids (presence of additional apophyses in caudal vertebrae that form true articular joints linking neighbouring vertebrae) are herein also regarded as homoplastic. Instead, we show that Cadurceryx possesses a vertebral synapomorphy of tropidophiids, namely the prominent blade-like hypapophysis on trunk vertebrae, that in posterior trunk vertebrae possesses a distinct, straight anteroventral corner, plus additional shared vertebral features. Accordingly, we herein tentatively envisage Cadurceryx as a tropidophiid with convergently evolved apophyseal morphologies with erycids and charinaids. Finally, we attempt a speculative interpretation of the functional morphology of the complex structures of the vertebrae of Cadurceryx, tentatively suggesting that these true articular joints linking neighbouring vertebrae may have offered increased rigidity across the vertebral column and may have acted as an antipredator mechanism. RÉSUMÉ Quand les vertèbres des serpents atteignent l’extrême – révision, morphologie vertébrale et variation intracolonnaire du mystérieux serpent Cadurceryx Hoffstetter &Rage, 1972, de l’Éocène européen. Nous fournissons une documentation complète de la morphologie vertébrale et de la variation intracolonnaire du serpent énigmatique Cadurceryx Hoffstetter & Rage, 1972, de l’Eocène de France. Sur la base de vertèbres abondantes, appartenant à pratiquement toutes les parties de la colonne, originaires de l’Eocène moyen (MP 16) de Lavergne dans les Phosphorites du Quercy, nous effectuons une révision du taxon, fournissons une diagnose corrigée et mettons en évidence un certain nombre de caractéristiques vertébrales distinctives qui le différencient de tous les autres serpents. Plus particulièrement, Cadurceryx est caractérisé par la présence d’apophyses supplémentaires dans les vertèbres du tronc, du cloaque et de la caudale, qui forment (au moins en partie) de véritables articulations reliant les vertèbres voisines (articulations intervertébrales supplémentaires). Ces apophyses supplémentaires sont : des ptérapophyses (présentes dans toutes les vertèbres), des extensions de zygapophyses et d’épines neurales, ainsi que des extensions de pleurapophyses (présentes dans les vertèbres caudales). Nous présentons également des vertèbres tronculaires et/ou caudales supplémentaires provenant de plusieurs autres localités de la région des Phosphorites du Quercy : l’Eocène moyen (MP 16) de Malpérié, l’Eocène supérieur (MP 17) de La Bouffie et Rosières 2, l’Eocène supérieur (MP 18) de Sainte Néboule, et de localités imprécises des « anciennes collections du Quercy ». Nous effectuons également une évaluation critique de la description originale du taxon. Sur la base de tous ces éléments, nous concluons qu’une seule espèce de Cadurceryx était présente en France pendant l’Eocène moyen et supérieur, à savoir l’espèce type Cadurceryx filholi Hoffstetter & Rage, 1972. Une seconde espèce du genre, Cadurceryx pearchi Holman, Harrison & Ward, 2006, connue exclusivement à partir de vertèbres caudales de l’Eocène supérieur (MP 17) de Hordle Cliff, en Angleterre, est également évaluée ici ; sur la base d’une approche critique de la publication originale qui a établi l’espèce anglaise, couplée à la présentation de quelques nouvelles vertèbres caudales de sa localité type, nous considérons que Cadurceryx pearchi représente un nomen dubium, le matériel appartenant potentiellement à ?Cadurceryx sp. ou un serpent érycidé ou charinaid indéterminé. Nous fournissons un aperçu complet de la distribution géographique et stratigraphique de Cadurceryx. Grâce à une comparaison détaillée avec des serpents éteints et actuels, nous écartons les affinités de Cadurceryx avec les érycidés ou les charinaidés, prenant également en compte que ce groupement, selon les données moléculaires, n’est pas monophylétique et que l’évolution des morphologies vertébrales caudales complexes chez les érycidés et les charinaidés est probablement homoplasique. Par conséquent, les caractéristiques distinctives communes de Cadurceryx avec les érycidés et les charinaidés (présence d’apophyses supplémentaires dans les vertèbres caudales qui forment de véritables articulations reliant les vertèbres voisines) sont également considérées ici comme homoplasiques. Au lieu de cela, nous montrons que Cadurceryx possède une synapomorphie vertébrale des tropidophiidés, à savoir l’hypapophyse proéminente en forme de lame sur les vertèbres du tronc, qui, dans les vertèbres postérieures du tronc, possède un coin antéroventral droit distinct, ainsi que d’autres caractéristiques vertébrales communes. En conséquence, nous envisageons ici provisoirement Cadurceryx comme un tropidophiidé présentant des morphologies apophysaires convergentes avec les érycidés et les charinaidés. Enfin, nous proposons une interprétation spéculative de la morphologie fonctionnelle des structures complexes des vertèbres de Cadurceryx, suggérant provisoirement que ces véritables articulations reliant les vertèbres voisines auraient pu offrir une rigidité accrue à la colonne vertébrale et agir comme un mécanisme anti-prédateur. KEY WORDS Serpentes, vertebrae, skeletal description, Paleogene. MOTS CLÉS Serpentes, vertèbres, description du squelette, Paléogène.
589 Revision of the snake Cadurceryx COMPTES RENDUS PALEVOL • 2025 • 24 (29) INTRODUCTION Snake vertebrae are characterized by a combination of unique anatomical features, including a distinctive zygosphenezygantrum articulation, that can readily differentiate them from all other squamates (Auffenberg 1963; Hoffstetter & Gasc 1969; Rage 1984b; Szyndlar 1984; Szyndlar & Georgalis 2023). Besides the basic structures observed across snakes, additional, bizarre anatomical structures or protuberances can also be observed across distantly related groups, such as the pterapophyses of palaeophiids (Rage 1983; Rage etal. 2003; Georgalis etal. 2021b; Georgalis 2023; Datta & Bajpai 2025), the distinct zygapophyseal expansions observed across an array of distantly related caenophidians (e.g. Hoffstetter 1939; Smith 1943; Bogert 1964; Fritts & Smith 1969; Hoffstetter & Gasc 1969; Slowinski 1994; Sheil 1998; Sheil & Grant 2001; Zaher etal. 2019), or the highly complex caudal vertebrae of erycids and charinaids (Bogert 1968a; Szyndlar 1994; Szyndlar & Georgalis 2023). Particularly for the latter, these rather complex structures on their caudal vertebrae, have been one of the principal characters that have in the past united the Old World Erycidae Bonaparte, 1831 (sensu Pyron etal. 2014) and the New World Charinaidae Gray, 1849 (sensu Burbrink etal. 2020). Indeed, this taxonomic arrangement uniting the Old Word erycids and the New World charinaids into an expanded concept of Erycidae or Erycinae Bonaparte, 1831 had practically met the almost absolute consensus across snake researchers during the second half of the 20th century (e.g. Hoffstetter 1955; Romer 1956; Kuhn 1966; Underwood 1967, 1976; Bogert 1968a; Hoffstetter & Rage 1972; Rage 1984b; McDowell 1987; Szyndlar 1987, 1991; Kluge 1993; Szyndlar & Schleich 1994; Holman 2000). Phylogenetic analyses based on morphology have found support of this grouping (e.g. Kluge 1993; Gauthier etal. 2012; Scanferla etal. 2016; Smith & Scanferla 2021), with its monophyly being primarily based on the caudal vertebral apophyses as synapomorphies (e.g. Gauthier etal. 2012). However, molecular data robustly and universally reject monophyly of Erycidae + Charinaidae, placing instead the latter as the sister group of ungaliophiids (Lawson etal. 2004; Vidal etal. 2007; Lynch & Wagner 2009; Wiens etal. 2012; Pyron etal. 2013; Reynolds etal. 2014; Hsiang etal. 2015; Figueroa etal. 2016; Harrington & Reeder 2017; Burbrink etal. 2020), a topology recovered also in total evidence (morphology + molecules) phylogenies (Zaher etal. 2023; Palci etal. 2024; Croghan etal. 2025). A number of fossil forms, primarily from the Paleogene and Neogene of Europe and North America, has been referred to either of these two extant families (or even to the extant genera Eryx Daudin, 1803b, Charina Gray, 1849, and Lichanura Cope, 1861), a taxonomic assignment facilitated also by the presence of these complex structures on the caudal vertebral region (e.g. Szyndlar 1991; Szyndlar & Schleich 1994; Smith & Scanferla 2021). Nevertheless, certain extinct taxa from the Paleogene and Neogene of Europe and North America with distinctive caudal vertebral morphology (e.g. Hoffstetter & Rage 1972; Rage 1977; Zerova 1989) cannot be confidently assigned to either erycids and charinaids and, taking into consideration that this grouping is a polyphyletic accumulation of non-related snakes, they have been tentatively collectively lumped as “erycines” (see Smith & Georgalis 2022). One such prominent case of a bizarre “erycine” of imprecise affinities is the genus Cadurceryx Hoffstetter & Rage, 1972, from the Eocene of Western Europe. The genus was originally established by Hoffstetter & Rage (1972) in order to accommodate the species Cadurceryx filholi Hoffstetter & Rage, 1972, based on vertebral material from the Eocene of the Phosphorites du Quercy, France. The taxon was characterized by unique vertebral morphology, most prominently the presence of bizarre additional apophyses. A few additional fossil vertebrae, either identified to the species level (as Cadurceryx filholi), or only tentatively to the same species (as Cadurceryx cf. filholi), or only to the genus level (as Cadurceryx sp.), were subsequently described and illustrated from some further middle and late Eocene localities in France (Hoffstetter & Rage 1972; Rage 1984b, 1988, 2013). Furthermore, a second species of the genus, Cadurceryx pearchi Holman, Harrison & Ward, 2006, was later established upon material from the late Eocene (MP 17) of Hordle Cliff, England, by Holman etal. (2006), thus expanding significantly the geographic distribution, as well as the taxonomic diversity, of the genus. Nevertheless, even though vertebrae of Cadurceryx have always appeared as bizarre to several ophidian palaeontologists in the past more than 50 years, a proper knowledge of the vertebral morphology and intracolumnar variation of this enigmatic and intriguing taxon is lacking. In the present paper, we document in detail abundant vertebrae of Cadurceryx filholi, pertaining to practically all portions of the vertebral column, from the middle Eocene (MP 16) locality of Lavergne in the Phosphorites du Quercy, France. We provide detailed descriptions and figures, focusing on the additional vertebral apophyses of this snake and its intracolumnar variation. We provide photographs of the holotype vertebra for the first time and present also additional vertebrae from certain other localities from Quercy. A critical evaluation of the original description of the taxon by Hoffstetter & Rage (1972) is conducted. We also revise the status of the English taxon Cadurceryx pearchi, based on its original description by Holman etal. (2006) but also on new caudal vertebrae from its type locality. Through detailed comparisons with several extinct and extant snakes, we finally discuss the potential taxonomic affinities of Cadurceryx within other snakes. MATERIAL AND METHODS The new fossil material from the middle Eocene (MP 16) of Lavergne described herein pertains to the collections of SU. In addition, we re-document previously published specimens from the “old collections” of Quercy, the middle Eocene (MP 16) of Malpérié, and the late Eocene (MP 17) of Rosières 2, from the collections of MNHN, NHMW, and UM. Finally, we provide figures of previously undescribed vertebrae of Cadurceryx filholi from the Quercy late Eocene
590 COMPTES RENDUS PALEVOL • 2025 • 24 (29) Szyndlar Z. & Georgalis G. L. localities of La Bouffie (MP 17) and Sainte Néboule (MP 18), from the collections of UM, plus of Cadurceryx pearchi from the late Eocene (MP 17A) of Christchurch Bay at Hordle Cliff, England, from the collections of NHMUK. The UM Cadurceryx material from Sainte-Néboule and La Bouffie was collected by palaeontologists from UM and other French institutes (Monique Vianey-Liaud, Jean Sudre, Louis De Bonis, Jean-Yves Crochet, Bernard Sigé, and Bernard Marandat) in expeditions held during the 1970s-1980s. The single NHMW specimen from the “old collections” of Quercy belongs to a long “forgotten” collection of reptiles and amphibians that were acquired by the NHMW in the 19th century and only recently (2019) rediscovered by GLG; they all originate from imprecise localities, with the age of the specimen of the present study probably lying somewhen the middle and late Eocene (for details on the herpetofaunal elements of this NHMW collection, see Georgalis etal. 2021a, c, 2023). The NHMUK specimens from Christchurch Bay at Hordle Cliff, England, were collected by Roy Gardner in 1981. The drawings of the vertebrae from Lavergne, Malpérié, and Rosières 2, were made by ZS. Photographs were made by GLG. Terminology of snake vertebrae follows Szyndlar & Georgalis (2023). In particular for vertebrae of erycid and charinaid snakes, it follows Szyndlar (1994) and Szyndlar & Georgalis (2023). InstItutIonal abbrevIatIons ICPS Institut Català de Paleontologia Miquel Crusafont, Sabadell; MNHN Muséum national d’Histoire naturelle, Paris; MSUVP Michigan State University Museum of Vertebrate Paleontology, East Lansing, Michigan; NHMUK Natural History Museum, London; NHMW Naturhistorisches Museum Wien, Vienna; SU (formerly UPVI) Sorbonne Université, Paris (formerly Université de Paris VI); UM Institut des Sciences de l’Évolution, Université de Montpellier. SYSTEMATIC PALAEONTOLOGY SERPENTES Linnaeus, 1758 ALETHINOPHIDIA Nopcsa, 1923 ?TROPIDOPHIIDAE Brongersma, 1951 Cadurceryx Hoffstetter & Rage, 1972 Cadurceryx Hoffstetter & Rage, 1972: 91. type specIes. — Cadurceryx filholi Hoffstetter & Rage, 1972. other valId specIes. — None (for details, see below). emended dIagnosIs. — Cadurceryx can be differentiated from all other snakes by the presence of additional apophyses throughout the trunk, cloacal, and caudal vertebrae, which form (at least partly) true articular joints linking neighbouring vertebrae (additional intervertebral articulations). These additional apophyses are: pterapophyses (present in all vertebrae), extensions of zygapophyses and neural spine, as well as extensions of pleurapophyses (present in caudal vertebrae). Moreover, there is a progressive increase of the complexity of succeeding vertebrae in the trunk portion of the column, from relatively simple anterior trunk vertebrae to moderately complex mid-trunk vertebrae, finally followed by highly complex vertebrae (“Posterior trunk vertebrae”). Cadurceryx is further diagnosed by the combination of the following features: centrum distinctly wider than long; presence of broad hypapophyses throughout the trunk and anterior cloacal vertebrae, which in posterior trunk vertebrae becomes even broader and possesses a distinct anteroventral corner forming approximately a right angle; presence of haemapophyses on more posterior caudal vertebrae; pterapophyses more prominent in midand posterior trunk vertebrae; pterapophyses extending forwards and backwards in trunk vertebrae, but extending almost exclusively forwards in caudal vertebrae; presence of a rather thick and occasionally anteriorly bifurcated neural spine in dorsal view; distinct interzygapophyseal connections present in trunk vertebrae but completely absent in cloacal and caudal vertebrae; in posterior trunk vertebrae, the posterior extensions of prezygapophyses and anterior extensions of postzygapophyses fuse with each other forming a thick bar; absence of paracotylar foramina. Cadurceryx filholi Hoffstetter & Rage, 1972 (Figs 1-18) Cadurceryx filholi Hoffstetter & Rage, 1972: 91. taxonomIc hIstory. — Cadurceryx filholi Hoffstetter & Rage, 1972 (new genus and species). Note that the “Taxonomic history” section here deals only with novel nomenclatural acts, new taxonomic combinations, or novel taxonomic renderings of the taxon, similarly to the style proposed in other recent reptilian papers (e.g. Joyce 2016; Georgalis & Joyce 2017; Georgalis etal. 2021c; Georgalis 2025). type materIal. — Holotype. France • 1 specimen (a posterior trunk ver tebra [not anterior cloacal vertebra as stated by Rage 1984b]); Phosphorites du Quercy (imprecise locality); probably between middle and late Eocene; MNHN.F.QU16301 (formerly MNHN Qu 301) (Hoffstetter & Rage 1972: fig. 6a, pl. I.1; Rage 1984b: fig. 16e; this paper, Fig. 1). t ype localIty and age . — Similar to most other fossil specimens from the so called “old collections” of Quercy, there are no precise locality data for the holotype of Cadurceryx filholi, apart from the general information that it originates from the area of the Phosphorites du Quercy. However, this information is rather general, taking into consideration that the Phosphorites du Quercy include at least 170 fissure filling localities, distributed over a broad geographic area, encompassing large parts of the current Departments of Lot, Tarn-et-Garonne, Tarn, and Aveyron, all in the administrative region of Occitanie (Rage 2006; Sigé & Hugueney 2006; Georgalis etal. 2021a, c; Pelissié etal. 2021). They also stratigraphically span over a considerable time period, from the early Eocene (MP 8+9) until the Early Miocene (MN 3); however, most of the respective fossiliferous localities range between the late middle Eocene (MP 16) and the late Oligocene (MP 28) (Rage 2006; Sigé & Hugueney 2006; Georgalis etal. 2021a, c; Pelissié etal. 2021). new and other materIal studIed hereIn. — Lavergne (MP 16): two pairs of two fused mid-trunk vertebrae (SU.PAL.2019.0.303.1 and SU.PAL.2019.0.303.12), two anterior trunk vertebrae (SU. PAL.2019.0.303.4 and SU.PAL.2019.0.303.5), two mid-trunk vertebrae (SU.PAL.2019.0.303.6 and SU.PAL.2019.0.303.7), one posterior trunk vertebra (SU.PAL.2019.0.303.8), two cloacal vertebrae (SU. PAL.2019.0.303.9 and SU.PAL.2019.0.303.10), nine caudal vertebrae
591 Revision of the snake Cadurceryx COMPTES RENDUS PALEVOL • 2025 • 24 (29) (SU.PAL.2019.0.303.11 - SU.PAL.2019.0.303.19), two fused caudal vertebrae (SU.PAL.2019.0.303.3), and 70 vertebrae (of which 13 trunk, 8 cloacal, and 49 caudal vertebrae; SU.PAL.2019.0.303.20 - SU.PAL.2019.0.303.89). Malpérié (MP16): two caudal vertebrae (UM MAL 501 and UM MAL 503). LaBouffie (MP 17): 51 trunk vertebrae (UM BFI 3011 - UM BFI 3048, UM BFI 3082, UM BFI 3104, UM BFI 3117, UM BFI 3151 – UM BFI 3158, UM BFI 3160, and UM BFI 3161), one ?cloacal (or anterior caudal) vertebra (UM BFI 3159), and seven caudal vertebrae (UM BFI 3049 - UM BFI 3051, UM BFI 3115, UM BFI 3116, UM BFI 3119, and UM BFI 3121). Rosières 2 (MP 17): one caudal vertebra (UM ROS2 266). Sainte Néboule (MP 18): 10 caudal vertebrae (UM SNB 5135 - UM SNB 5142, UM SNB 5233, and UM SNB 5234). “Old collections” of Quercy (localities imprecisely known, middle or late Eocene): two trunk vertebrae (MNHN.F.QU16304 and NHMW 2019/0064/0001). localItIes and age. — All localities of Lavergne, Malpérié, La Bouffie, Rosières 2, and Sainte Néboule are situated in the area of the Phosphorites du Quercy in southern France. Lavergne and Malpérié are the oldest among them, pertaining to the MP 16 zone of the middle Eocene, while Rosières 2 and Sainte Néboule are late Eocene, with Rosières 2 (MP 17) slightly older than Sainte Néboule (MP 18) (Biochrom’97 1997). As for the two vertebrae from the “old collections” of Quercy (MNHN.F.QU16304 and NHMW 2019/0064/0001), similarly to the case of the holotype, they originate from imprecisely known localities and therefore their age could lie anywhen within middle to late Eocene. geographIc and stratIfraphIc dIstrIbutIon. — Middle and late Eocene of France. For a detailed account of all known occurrences of the taxon, see Discussion below. emended dIagnosIs. — As for the genus (see above). descrIptIon The descriptions are based on the abundant vertebral sample from Lavergne. The vertebrae of Cadurceryx from Lavergne represent all major regions of the column (Figs 2; 3), except for anteriormost trunk (in particular atlas and axis) and possibly the last trunk vertebrae, i.e., those (or that) preceding immediately the cloacal region. All vertebrae, as characteristic of the so called constrictor snakes (i.e., booids and pythonoids), have centra distinctly wider than long. The vertebrae are relatively small, in a few largest trunk vertebrae the centrum length is 3.0 to 3.5 mm, centrum width 4.2 to 4.6 mm, whereas centrum length/neural arch width ratio 0.7 to 0.8. Apart from the vertebral structures found in all ophidians, virtually all vertebrae throughout the column possess additional apophyses providing (at least partly) articular joints between adjacent bones. These are: pterapophyses (present in all vertebrae), extensions of zygapophyses and neural spine, as well as extensions of pleurapophyses (in caudal vertebrae). fig. 1. — Holotype posterior trunk vertebra MNHN.F.QU16301 from the middle or late Eocene of the “Old Collections” of the Phosphorites du Quercy, in anterior (A), posterior (B), right lateral (C), left lateral (D), ventral (E), and dorsal (F) views. Scale bar: 2 mm. ABC D EF
592 COMPTES RENDUS PALEVOL • 2025 • 24 (29) Szyndlar Z. & Georgalis G. L. The distinctive feature observed in the morphology of the trunk vertebrae of Cadurceryx is a progressive increase of the complexity of succeeding elements, from relatively simple anterior trunk vertebrae (see section “Anterior trunk vertebrae” below) to moderately complex mid-trunk vertebrae (“Mid-trunk vertebrae”), finally followed by highly complex vertebrae (“Posterior trunk vertebrae”). This unique morphological pattern (if we consider the morphology of additional apophyses) resembles closely the patterns characteristic of caudal (but not trunk!) portion of the column in both extant and extinct (the fossil genus Bransateryx Hoffstetter & Rage, 1972, at least) “erycine” snakes. The morphology of the post-trunk (i.e., cloacal and caudal) vertebrae, also provided with additional apophyses, is rather homogenous throughout the tail skeleton; in other words, there are no striking differences between the vertebrae coming from different parts of the cloacal/caudal portion of the column. Anterior trunk vertebrae (Fig. 4) We use this term to refer to a number (typically a few dozen in most alethinophidian snakes) of vertebrae located immediately behind the head and provided with distinct (but successively reduced in size) hypapophyses (taxa like elapids and natricids, provided with hypapophyses throughout the trunk portion of the column, are noteworthy exceptions). This trait is observed in 10 vertebrae from Lavergne, available for this study. The hypapophysis is subsquare in shape in lateral view and rather short; its posteroventral termination reaches the level of the condyle. Apart from the presence of the latter structure, the morphology of the anterior trunk vertebrae of Cadurceryx is relatively simple compared with those located more posteriorly. The anterior trunk vertebrae, however, possess small but distinct pterapophyses beginning atop the postzygapophyseal area of the neural arch and directed anteriorly. At first glance, these structures look like the postzygapophyseal wings observed in Eryx, rather than pterapophyses (cf. Szyndlar 1994: fig. 5A), because they have the form of spurs projecting forwards but not backwards. However, in more posterior vertebrae located close to the anterior/mid-trunk transition (attributed to this region due to the presence of reduced and much different-shaped hypapophyses) the pterapophyses are produced into a short spur projecting backwards, as well (Fig. 5A). The neural arch is moderately vaulted, but the difference between the vaulting of the arch of the anterior trunk vertebrae and of those located more posteriorly is not significant, unlike in most other snakes. The neural spine is as high as long in lateral view and not flattened dorsally. The subcentral ridges and subcentral grooves are prominent. The prezygapophyseal accessory processes are relatively short, strongly built, but are not expanded laterally or posteriorly. fig. 2. — Cadurceryx filholi Hoffstetter & Rage, 1972 from Lavergne: hypothesized sequence of vertebrae in the trunk portion of the column, in left lateral, dorsal, and anterior views. A, SU.PAL.2019.0.03.4; B, SU.PAL.2019.0.03.1; C, SU.PAL.2019.0.03.6; D, SU.PAL.2019.0.03.2; E, SU.PAL.2019.0.03.8. Scale bar: 5 mm. A BC DE
593 Revision of the snake Cadurceryx COMPTES RENDUS PALEVOL • 2025 • 24 (29) Mid-trunk vertebrae (Fig. 5) In the vertebrae immediately succeeding the anterior trunk ones, the hypapophysis has a rather different shape: this structure is prominent, thick, and moderately broad in ventral view, while in lateral view, this is relatively anteroposteriorly long. Behind the cotyle rim, there is a shallow (and rather indistinct) depression in the keel (Fig. 5F). The subcentral grooves, on both sides of the hypapophysis, are deep and accompanied by prominent subcentral ridges. In most (but not all) vertebrae, the ridges terminate sharply in the form of distinct spurs before reaching the condyle, the feature well seen in lateral view (Fig. 5E). These vertebrae are distinctly higher than long in lateral view and distinctly broader than long in ventral view. The neural arch is moderately depressed. The neural canal is significantly narrower than the suborbicular cotyle. The condyle is also rounded or slightly depressed. The paradiapophyses are relatively small, without distinct subdivision into paraand diapophyseal portions. The subcentral and lateral foramina are small but distinct (the latter, usually covered by post-prezygapophyseal structures, are hardly seen in lateral view). The neural spine, approximately as high as long, has its anterior margin slightly overhanging and the posterior margin usually strongly overhanging. The upper margin of the neural spine can be slightly depressed and sometimes slightly bifurcated anteriorly and posteriorly, in dorsal view; the bifurcations do not overlap in neighbouring vertebrae (Fig. 5A, C). The pterapophyses, well developed on both sides of the base of the neural spine, are elongate and protrude distinctly both anteriorly and posteriorly. As seen in the pairs of fused vertebrae, the anterior projections of pterapophyses of the more posteriorly located vertebra externally overlap the posterior projections of pterapophyses of the preceding vertebra (Fig. 5C, D). The prezygapophyses have prominent extensions: prezygapophyseal accessory processes and posterior extensions of prezygapophyses. The prezygapophyseal accessory processes, developed beneath the elongated prezygapophyseal articular facets in the form of long laminae, project forwards and backwards. The postzygapophyses, provided with subsquareshaped articular facets, are distinctly separated off the pterapophyses located above; anteriorly, the postzygapophyses are produced into more or less prominent anterior extensions. fig. 3 . — Cadurceryx filholi Hoffstetter & Rage, 1972 from Lavergne: hypothesized sequence of vertebrae in the cloacal and caudal portion of the column, in left lateral, dorsal, and anterior views. A, SU.PAL.2019.0.03.9; B, SU.PAL.2019.0.03.10; C, SU.PAL.2019.0.03.12 (mirror view of right lateral side); D, SU.PAL.2019.0.03.13; E, SU.PAL.2019.0.03.16 (mirror view of right lateral side); F, SU.PAL.2019.0.03.17. Scale bar: 5 mm. AB C D E F
600 COMPTES RENDUS PALEVOL • 2025 • 24 (29) Szyndlar Z. & Georgalis G. L. addItIonal materIal of CadurCeryx Filholi from the phosphorItes du Quercy Besides the abundant vertebral material from Lavergne described above, which pertains to practically almost all portions of the column, we present here additional vertebrae of Cadurceryx filholi from other localities in the area of the Phosphorites du Quercy. These include caudal vertebrae from Malpérié (MP 16; Fig. 11A-J) and Rosières 2 (MP 17; Fig. 11K-M) that were previously described and figured by Hoffstetter & Rage (1972), plus several undescribed trunk and caudal vertebrae from La Bouffie (MP 17; Figs 12-16), and a few caudal vertebrae from Sainte Néboule (MP 18; Fig. 17). Moreover, we present also two further trunk vertebrae from the “old collections” of Quercy: one vertebra (MNHN.F.QU16304; Fig. 18A-F), originally described and figured by Hoffstetter & Rage (1972: fig. 6B), and one previously undescribed vertebra from the collections of NHMW (NHMW 2019/0064/0001; Fig. 18G-L). All these vertebrae match well with the morphology and intracolumnar variation observed in the above documented Lavergne sample. We therefore assign all of them to Cadurceryx filholi. This resemblance further prompts us to consider that a single species of Cadurceryx, i.e., the type species Cadurceryx filholi, was present in all these studied localities and perhaps, in general in France during the middle and late Eocene. It is further worth noting that the snake sample from Sainte Néboule, although it comprised vertebrae of several other snake taxa (GLG, personal observation), yielded only caudal vertebrae of Cadurceryx but not a single trunk one (see also Discussion below). a crItIcal approach of hoffstetter & rage’s (1972) orIgInal descrIptIon and other early documentatIons of CadurCeryx The genus Cadurceryx, with the type (and then only known) species Cadurceryx filholi, was originally described by Hoffstetter fig. 11. — Cadurceryx filholi Hoffstetter & Rage, 1972 from Malpérié (A-J) and Rosières 2 (K-M), caudal vertebrae: A-D, UM MAL 501 in right lateral (A), left lateral (B), anterior (C), and dorsal (D) views; E-J, UM MAL 503 in left lateral (E), right lateral (F), anterior (G), posterior (H), dorsal (I), and ventral (J) views; K-M, UM ROS2 266 in left lateral (K), anterior (L), and dorsal (M) views. Scale bar: 5 mm. AB C D E F G H IJ KLM
601 Revision of the snake Cadurceryx COMPTES RENDUS PALEVOL • 2025 • 24 (29) fig. 12. — Cadurceryx filholi Hoffstetter & Rage, 1972 from La Bouffie, trunk vertebrae: A-E, UM BFI 3019 in anterior (A), posterior (B), left lateral (C), dorsal (D), and ventral (E) views; F-J, UM BFI 3041 in anterior (F), posterior (G), left lateral (H), dorsal (I), and ventral (J) views; K-O, UM BFI 3014 in anterior (K), posterior (L), right lateral (M), dorsal (N), and ventral (O) views; P-T, UM BFI 3044 in anterior (P), posterior (Q), left lateral (R), dorsal (S), and ventral (T) views; U-Y, UM BFI 3028 in anterior (U), posterior (V), right lateral (W), dorsal (X), and ventral (Y) views; Z-AD, UM BFI 3043 in anterior (Z), posterior (AA), left lateral (AB), dorsal (AC), and ventral (AD) views. Scale bars: 2 mm. ABCD E FGHI J KLMN O PQRST UVWX Y ZAAABAC AD
602 COMPTES RENDUS PALEVOL • 2025 • 24 (29) Szyndlar Z. & Georgalis G. L. fig. 13. — Cadurceryx filholi Hoffstetter & Rage, 1972 from La Bouffie, trunk vertebrae: A-E, UM BFI 3013 in anterior (A), posterior (B), right lateral (C), dorsal (D), and ventral (E) views; F-J, UM BFI 3030 in anterior (F), posterior (G), left lateral (H), dorsal (I), and ventral (J) views; K-O, UM BFI 3016 in anterior (K), posterior (L), right lateral (M), dorsal (N), and ventral (O) views; P-T, UM BFI 3045 in anterior (P), posterior (Q), left lateral (R), dorsal (S), and ventral (T) views; U-Y, UM BFI 3082 in anterior (U), posterior (V), left lateral (W), dorsal (X), and ventral (Y) views; Z-AB, UM BFI 3034 in anterior (Z), dorsal (AA), and left lateral (AB) views; AC, AD, UM BFI 3033 in posterior (AC) and ventral (AD) views. Scale bars: 2mm. ABCD E FGHI J KLMN O PQRS T UV W X Y ZAAABACAD
603 Revision of the snake Cadurceryx COMPTES RENDUS PALEVOL • 2025 • 24 (29) & Rage (1972), based on remains (exclusively isolated vertebrae) coming from several Eocene sites of France. The holotype vertebra (MNHN.F.QU16301), originating from an unidentified locality in the Phosphorites du Quercy (“anciennes collections”), was defined by Hoffstetter & Rage (1972) as “une vertèbre complexe à tubercules costaux”, owing to its complex morphology, as originating from the posterior portion of the column; subsequently Rage (1984b) treated the holotype as a probably anterior cloacal vertebra. The astonishing statement of Rage (1984b) that the holotype vertebra of Cadurceryx filholi may have come from the cloacal region of the column seems apparently to be an unintentional mistake (although certainly difficult to be explained how the mistake was made)! Jean-Claude Rage, who on many occasions in the 1990s and early 2000s was discussing with ZS about Cadurceryx, never actually supported the above opinion; what is more, the only figure of a trunk vertebra of Cadurceryx (UM [formerly USTL] LAV 1275), morphologically not differing from the holotype, published by Rage (2013: fig. 3h, i) was described in the caption as just “trunk vertebra”. In any case, as we demonstrated in the descriptions above, the morphology of the holotype specimen matches that of a posterior trunk vertebra. Eight other trunk vertebrae, also belonging to the old collections of the Phosphorites du Quercy, were referred to C. filholi, as well (Hoffstetter & Rage 1972). Of them, four vertebrae display the complex morphology (MNHN.F.QU16304; Hoffstetter fig. 14. — Cadurceryx filholi Hoffstetter & Rage, 1972 from La Bouffie, trunk vertebrae: A-E, UM BFI 3117 in anterior (A), posterior (B), left lateral (C), dorsal (D), and ventral (E) views; F-J, UM BFI 3012 in anterior (F), posterior (G), left lateral (H), dorsal (I), and ventral (J) views; K-O, UM BFI 3104 in anterior (K), posterior (L), left lateral (M), dorsal (N), and ventral (O) views; P-T, UM BFI 3017 in anterior (P), posterior (Q), right lateral (R), dorsal (S), and ventral (T) views; U-Y, UM BFI 3151 in anterior (U), posterior (V), right lateral (W), dorsal (X), and ventral (Y) views. Scale bars: 2 mm. ABCD E FGHI J KLM NO PQRS T UVWX Y
604 COMPTES RENDUS PALEVOL • 2025 • 24 (29) Szyndlar Z. & Georgalis G. L. & Rage 1972: fig. 6B; this paper, Fig. 17A-F), similarly to the holotype, whereas four others (MNHN.F.QU16306; Hoffstetter & Rage 1972: fig. 6C) are simply built, devoid of any additional apophyses (“vertèbres dorsales typiques”). Hoffstetter & Rage (1972) attributed the latter vertebrae to the anterior trunk portion of the column of C. filholi, justifying that decision with their similarity to trunk vertebrae of the extant “erycine” snakes (“présentent le style des Erycinae”), in which they envisaged Cadurceryx to pertain. Hoffstetter & Rage (1972) noticed that, at first glance, the complexity pattern of the trunk vertebrae of Cadurceryx closely resembles (but not in all aspects) that characteristic of caudal vertebrae of the living erycids and charinaids. Apart from the remains belonging to the “old collections” from the Phosphorites du Quercy, Hoffstetter & Rage (1972) described also a number of vertebrae from precisely dated Eocene localities in France. These were identified as either Cadurceryx cf. filholi or Cadurceryx sp., and originated from the middle Eocene (MP 16) of Robiac and the late Eocene (MP 17) Quercy localities of Malpérié and Les Pradigues. Among them, Hoffstetter & Rage (1972) found a few complex caudal (or cloacal) vertebrae (“vertèbres caudales typiques”) (UM MAL 501 and UM MAL 503; Hoffstetter & Rage 1972: 95, fig. 6D, pl. I fig. 4; this paper, Fig. 11A-J). They noticed that these vertebrae are less complex than the preceding trunk vertebrae (“vertèbres complexes à tubercules costaux”) and identified them as belonging to Cadurceryx sp. (and not C. filholi). At least one vertebra from Malpérié (UM MAL 502), described briefly and illustrated by Hoffstetter & Rage (1972: pl. I, fig. 3), with reduced protruding elements accompanying the zygapophyses and provided with a distinct (and small anteroposteriorly) hypapophysis, apparently pertained (in the light of our present study; see above) to the anterior trunk portion of the column. Hoffstetter & Rage (1972), however, referred it as a “vertèbre complexe à tubercules costaux”, therefore as coming from the posterior trunk portion of the column, whereas its hypapophysis (short but distinct) was unexpectedly considered a haemal keel (“carène hémale”). This (rather strange) judgement may have resulted from the absolute (?) conviction of these authors that all anterior trunk vertebrae of Cadurceryx were simply built, therefore the vertebra in question should have originated from another region of the column. In the section devoted to the fossils from Malpérié, Hoffstetter & Rage (1972: 95) mentioned the presence of vertebrae provided with cloacal hypapophyses (“hypapophyse « cloacale » ou « précloacale »”), the feature characteristic of posteriormost fig. 15. — Cadurceryx filholi Hoffstetter & Rage, 1972 from La Bouffie, caudal vertebrae: A-E, UM BFI 3048 in anterior (A), posterior (B), left lateral (C), dorsal (D), and ventral (E) views; F-J, UM BFI 3049 in anterior (F), posterior (G), right lateral (H), dorsal (I), and ventral (J) views; K-O, UM BFI 3050 in anterior (K), posterior (L), right lateral (M), dorsal (N), and ventral (O) views. Scale bars: 2 mm. ABC DE FGHIJ K LM N O
605 Revision of the snake Cadurceryx COMPTES RENDUS PALEVOL • 2025 • 24 (29) trunk vertebrae, i.e., those located immediately before cloacal vertebrae. It is not certain, based on Hoffstetter & Rage’s (1972) text, whether these vertebrae belonged to the fossils coming from Malpérié or another locality; we have been unable to trace these vertebrae. The caudal vertebrae from Malpérié (originally referred to Cadurceryx sp.) attracted a special attention of Hoffstetter & Rage (1972: 95), who observed (considering this fact as curious) that they are a little less complex (“un peu moins complexes”) than the preceding (i.e., trunk) ones. These authors also noticed that the arrangement of additional apophyses surmounting the caudal vertebrae differs from that observed in the trunk vertebrae, in particular “les ptérapophyses sont confondues avec la lame qui surmonte les postzygapophyses [= anterior extensions of postzygapophyses]” (Hoffstetter & Rage 1972: 95). It is difficult, however, to guess from the above statement which of the either two structures is lacking. In our opinion, the anterior extensions of postzygapophyses are the elements missing in the caudal (and also cloacal) vertebrae, whereas the prominent pterapophyses are maintained in the entire posttrunk portion of the column. This explains the absence of interzygapophyseal fusions in post-trunk vertebrae (see below). Subsequently to this 1972 original description, Cadurceryx was mentioned (but not described in detail) from several Eocene localities in the Phosphorites du Quercy (see also Discussion below). In the literature, there exist illustrations of three previously undescribed vertebrae. Of them, two caudal vertebrae were illustrated: Cadurceryx cf. filholi from Le Bretou (MP 16) (UM BRT 1317; Rage 1988: fig. 17) and Cadurceryx filholi from Rosières 2 (MP 17) (UM ROS2 266; Rage 1984b: fig. 16D; this paper, Fig. 11K-M). As revealed by our current study, these two vertebrae rather “deviate” from the morphology “typical” of Cadurceryx filholi; it is unclear if this deviation could reflect some species level distinction, but we tentatively treat it here as some kind of intraspecific variation. The third illustrated specimen (shown in anterior and dorsal views) is a trunk vertebra from Lavergne (UM [formerly USTL] LAV 1275; Rage 2013: fig. 3h, i). Finally, Szyndlar & Rage (2003), based on unpublished observations, briefly reported that additional apophyses in Cadurceryx were not restricted to the posterior trunk portion of the column but that they were also present on more anteriorly located trunk vertebrae. As a further note, based on the herein documentation that Cadurceryx possessed complex structures and additional apophyses throughout its vertebral column, from its beginning to the end of the tail, it is evident that the trunk vertebrae devoid of additional apophyses that were presented in the original Hoffstetter & Rage (1972) publication (“vertèbres fig. 16. — Cadurceryx filholi Hoffstetter & Rage, 1972 from La Bouffie, caudal vertebrae: A-E, UM BFI 3115 in anterior (A), posterior (B), right lateral (C), dorsal (D), and ventral (E) views; F-J, UM BFI 3119 in anterior (F), posterior (G), right lateral (H), dorsal (I), and ventral (J) views; K-O, UM BFI 3121 in anterior (K), posterior (L), right lateral (M), dorsal (N), and ventral (O) views. Scale bars: 2 mm. AB CD E FG HI J KL MN O
606 COMPTES RENDUS PALEVOL • 2025 • 24 (29) Szyndlar Z. & Georgalis G. L. fig. 17. — Cadurceryx filholi Hoffstetter & Rage, 1972 from Sainte Néboule, caudal vertebrae: A-E, UM SNB 5136 in anterior (A), posterior (B), left lateral (C), dorsal (D), and ventral (E) views; F-J, UM SNB 5137 in anterior (F), posterior (G), right lateral (H), dorsal (I), and ventral (J) views; K-O, UM SNB 5138 in anterior (K), posterior (L), right lateral (M), dorsal (N), and ventral (O) views; P-T, UM SNB 5139 in anterior (P), posterior (Q), right lateral (R), dorsal (S), and ventral (T) views; U-Y, UM SNB 5140 in anterior (U), posterior (V), right lateral (W), dorsal (X), and ventral (Y) views. Scale bars: 2 mm. ABC DE FGH I J KLMN O PQ R ST UV W XY
607 Revision of the snake Cadurceryx COMPTES RENDUS PALEVOL • 2025 • 24 (29) fig. 18. — Cadurceryx filholi Hoffstetter & Rage, 1972 from the “old collections” of Quercy (locality[ies] imprecisely known, middle or late Eocene), trunk vertebrae: A-F, MNHN.F.QU16304 in anterior (A), posterior (B), right lateral (C), dorsal (D), ventral (E), and left lateral (F) views; G-L, NHMW 2019/0064/0001 in anterior (G), posterior (H), right lateral (I), dorsal (J), ventral (K), and left lateral (L) views. Scale bars: 2 mm. dorsales typiques” of Hoffstetter & Rage 1972; e.g. specimens MNHN.F.QU16306; see Hoffstetter & Rage 1972: fig. 6C) cannot belong to this taxon and instead they are here reidentified as belonging to some other snake (provisionally referred here as Constrictores indet.). status of the englIsh materIal referred to CadurCeryx The first snake remains identified as Cadurceryx outside of France were reported from the Eocene of England. The oldest fossil, a single “Cadurceryx-like caudal vertebra”, ABC D E F GHI JKL
608 COMPTES RENDUS PALEVOL • 2025 • 24 (29) Szyndlar Z. & Georgalis G. L. was reported from the middle Eocene locality of Creechbarrow (MP 16) by Hooker (1986), with this record being reproduced as Cadurceryx sp. by Milner (1986) and cf. Cadurceryxsp. indet. by Benton & Spencer (1995). Unfortunately, these were all simple mentions and no description or figure or that material was published. The presence of other material of Cadurceryx sp. was mentioned also from the late Eocene of Hordle Cliff (MP 17) by Milner (1986); also in this case, no information about the above fossil(s) was provided. Nevertheless, other excavations in Hordle Cliff, starting at the 1990s, yielded new fossil ophidian remains, which were eventually housed in the collections of MSUVP. Of them, five caudal vertebrae from the collections of MSUVP were described as the new species Cadurceryx pearchi by Holman etal. (2006). Interestingly, the above paper did not include any mention about possible presence or absence of trunk vertebrae in the examined MSUVP material, while four other snake papers that were also based on the Hordle Cliff material from the MSUVP collections (Holman 1993, 1996; Holman & Harrison 1998a, b), provided no evidence for the existence of trunk vertebrae of Cadurceryx. Accordingly, there is no evidence whether trunk vertebrae were actually absent in this MSUVP collection or they (if present) were ignored by the above authors. Anyway, possible absence of trunk vertebrae in the situation when caudals are present, seems astonishing (but this is anyway not the only such case for this taxon; see also Discussion below). Apparently, in order to compare the newly erected species Cadurceryx pearchi with the type species Cadurceryx filholi, Holman etal. (2006) used only one illustration of a caudal vertebra referred to the latter species, published in the snake volume of Handbuch der Paläoherpetologie by Rage (1984b: fig. 16D; this paper, Fig. 11K-M). The choice of this vertebra (UM ROS2 266; originating from Rosières 2) seems unfortunate, because its morphology, especially in the anterior aspect, notably deviates from that characteristic of most caudal vertebrae of Cadurceryx. However, the reason for which Holman etal. (2006) chose just this vertebra seems quite clear: it was (and so far still is!) the only illustrated caudal vertebra identified to the species level as Cadurceryx filholi. At those times, illustrations of three other caudal vertebrae referred to Cadurceryx were available in the literature (two from Malpérié: UM MAL 501 and UM MAL 503; Hoffstetter & Rage 1972: fig. 6D; pl. I, fig. 4; this paper, Figs 11A-D, E-H; and one from Le Bretou: UM BRT 1317; Rage 1988: fig. 17), but they were ignored by Holman etal. (2006), probably because they were identified either only to the genus level for the material of Malpérié (Cadurceryx sp. of Hoffstetter & Rage 1972) or were not confidently identified anyway to the species level (Cadurceryx cf. filholi of Rage 1988). Ironically, the two vertebrae from Malpérié (as we can state today) display clearly the morphology characteristic of the species C.filholi, unlike the caudal one from Rosières 2. Hence, the diagnosis of Cadurceryx pearchi seems inaccurate, because it reflects exclusively the differences between the single vertebra from Rosières 2 and the English holotype (MSUVP 2061; Holman etal. 2006: figs 2, 3), stating that: 1) C. pearchi has the cotyle larger than the neural canal, while in C. filholi vice versa; and 2) the prezygapophyses of C. pearchi are produced into knoblike tubercles, absent in C.filholi. However, the relatively broad neural canal in the Rosières fossil (feature 1) apparently results from the juvenile age of the snake (e.g. Georgalis & Scheyer 2019; Szyndlar & Georgalis 2023). Regarding the second diagnostic trait of C. filholi (feature 2), namely the “anterior ends of prezygapophyses […] produced into knoblike tubercles”, it is very difficult to guess what the latter term means based on Holman’s etal. (2006: 58) text and figures. The only reasonable explanation is that the authors used the term “knoblike tubercle” as a synonym of “prezygapophyseal accessory process”. The prezygapophyseal accessory processes (prominent in most cases), however, occur in caudal vertebrae of C.filholi; no doubt, their absence in the vertebra from Rosières results again from the juvenile age of the snake. To close the comments on the paper by Holman etal. (2006), we should add that one of the paratypes of Cadurceryx pearchi (MSUVP 2059) was listed as “Caudal [sic] vertebrae of Pterygoboa sp. indet. (MSUVP 2059)” on their caption of the drawing of the specimen (Holman etal. 2006: 57, fig. 3i-l), although the same (single) vertebra was described as “Caudal [sic] vertebrae of Cadurceryx pearchi sp. nov. paratype (MSUVP 2059)” on their caption of the photograph of the specimen (Holman etal. 2006: 56, fig. 2g-i). This is most probably a misspelling, as we see no reason why Holman etal. (2006) regarded this particular specimen as belonging to Pterygoboa. In any case, there is so far no evidence that the genus Pterygoboa Holman, 1976, a bizarre “erycine” from the Oligo-Miocene of North America was ever present in England or Europe in general; besides, the vertebral morphology of Pterygoboa (that is also characterized by the presence of additional apophyses) is drastically different from Cadurceryx ( Holman 1976, 1998; Mead & Schubert 2013). Here we present a few caudal vertebrae from the late Eocene (MP 17A) of Christchurch Bay at Hordle Cliff (Mammal Bed, Totland Bay Member), England, from the collections of NHMUK (Figs 19-21). These specimens are apparently the same ones mentioned in the faunal list of Milner (1986). Interestingly, in this NHMUK sample, among numerous vertebrae of several other snake taxa from Hordle Cliff, there were only a few Cadurceryx-like caudal vertebrae available and not a single trunk vertebra. Nevertheless, the vertebrae still seem to pertain to different regions of the caudal vertebral column, as it can be attested by the differences regarding the anteroposterior length and dorsoventral height across the specimens (Figs 19-21). In any case, the new English caudal vertebrae bear practically no important differences from the known caudal vertebrae of Cadurceryx filholi from the Phosphorites du Quercy. These being said, to summarize, the English form from Hordle Cliff seems to could potentially belong to Cadurceryx, although the absence of any trunk vertebra renders such
609 Revision of the snake Cadurceryx COMPTES RENDUS PALEVOL • 2025 • 24 (29) taxonomic identification as tentative (at max). Nevertheless, based on the diagnosis of Holman etal. (2006), coupled with the observation of the NHMUK caudal vertebrae, a species level distinction of the English Cadurceryx from the French species Cadurceryx filholi (although possible) cannot be demonstrated with certainty. The holotype of Cadurceryx pearchi and all known specimens from England are all incomplete caudal vertebrae and the diagnosis proposed by Holman etal. (2006) refers to variable features. Accordingly, Cadurceryx pearchi is considered to be a nomen dubium, with the material potentially pertaining to an indeterminate species of Cadurceryx (i.e., ?Cadurceryxsp.). Only new and more complete material from the Eocene of England, ideally comprising also trunk vertebrae, will eventually show whether indeed a distinct species of this genus was inhabiting England or whether they are conspecific with the French species Cadurceryx filholi or even whether these “puzzling” caudal vertebrae from Hordle pertain instead to a (different) taxon (potentially an erycid or a charinaid). DISCUSSION taxonomIc affInItIes of CadurCeryx wIthIn snakes Ever since its original establishment by Hoffstetter & Rage (1972), Cadurceryx has met a relatively frequent appearance in the literature (e.g. Rage 1973, 1974, 1975, 1977, 1978, 1984a, b, 1987, 1988, 2006, 2012, 2013; Underwood 1976; Holman 1977, 1998; Estes & Hutchison 1980; Rage & Ford 1980; Crochet etal. 1981; Hooker 1986; Milner 1986; McDowell 1987; Carroll 1988; Zerova 1989; Kluge 1993; Rage & Augé 1993; Szyndlar 1994; Szyndlar & Schleich 1994; Benton & Spencer 1995; Duffaud & Rage 1997; Szyndlar & Rage 2003; Szyndlar & Alférez 2005; Holman etal. 2006; Wallach etal. 2014; Boundy 2021; Georgalis etal. 2021a, c; Smith & Scanferla 2021; Smith & Georgalis 2022; Villa etal. 2022; Shi etal. 2023; Szyndlar & Georgalis 2023; Lemierre & Georgalis 2025). Nevertheless, almost all of these frequent appearances consisted of simple mentions of the name or reviews of what fig. 19. — ?Cadurceryx sp. from Hordle Cliff, caudal vertebrae: A-E, NHMUK PV R 10803 in anterior (A), posterior (B), right (ventro)lateral (C), dorsal (D), and ventral (E) views; F-J, NHMUK PV R 10805 in anterior (F), posterior (G), left lateral (H), dorsal (I), and ventral (J) views; K-O, NHMUK PV R 10804 in anterior (K), posterior (L), right lateral (M), (postero)dorsal (N), and ventral (O) views. Scale bars: 2 mm. ABCD E FG HI J KL MN O
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