taxonID	type	description	language	source
3F7E87D81D04FFE3FE84ED5F5D39FA6D.taxon	description	urn: lsid: zoobank. org: act: 447 C 8 D 95 - 2 A 3 D- 4 A 4 A-A 41 C-D 068 C 458797 A	en	Georgalis, Georgios L., Jones, Marc E. H. (2025): A new peculiar early diverging caenophidian snake (Serpentes) from the late Eocene of Hordle Cliff, England. Comptes Rendus Palevol 24 (25): 505-530, DOI: 10.5852/cr-palevol2025v24a25, URL: https://doi.org/10.5852/cr-palevol2025v24a25
3F7E87D81D04FFE3FE84ED5F5D39FA6D.taxon	type_taxon	TYPE SPECIES. — Paradoxophidion richardoweni n. gen., n. sp. DIAGNOSIS. — As for the type and only known species.	en	Georgalis, Georgios L., Jones, Marc E. H. (2025): A new peculiar early diverging caenophidian snake (Serpentes) from the late Eocene of Hordle Cliff, England. Comptes Rendus Palevol 24 (25): 505-530, DOI: 10.5852/cr-palevol2025v24a25, URL: https://doi.org/10.5852/cr-palevol2025v24a25
3F7E87D81D04FFE3FE84ED5F5D39FA6D.taxon	etymology	ETYMOLOGY. — The new genus name derives from the Greek words “ π ΑΡΆΔΟΞΟς ” (“ paradoxos ”) meaning “ paradox ” / “ weird ”, and “ ὀΦΊΔΙΟΝ ” (“ ophidion ”) meaning “ snake ”, in referral of the weird combination of vertebral features present in the new taxon. Gender of the new genus name is neuter.	en	Georgalis, Georgios L., Jones, Marc E. H. (2025): A new peculiar early diverging caenophidian snake (Serpentes) from the late Eocene of Hordle Cliff, England. Comptes Rendus Palevol 24 (25): 505-530, DOI: 10.5852/cr-palevol2025v24a25, URL: https://doi.org/10.5852/cr-palevol2025v24a25
3F7E87D81D04FFE9FCB9EC3F5C9DF860.taxon	description	(Figs 1 - 14; Appendices 1; 2) urn: lsid: zoobank. org: act: DF 7 D 9 EEA- 52 E 4 - 4 E 8 E- 8 DFC-AC 001 D 0 D 2 E 64	en	Georgalis, Georgios L., Jones, Marc E. H. (2025): A new peculiar early diverging caenophidian snake (Serpentes) from the late Eocene of Hordle Cliff, England. Comptes Rendus Palevol 24 (25): 505-530, DOI: 10.5852/cr-palevol2025v24a25, URL: https://doi.org/10.5852/cr-palevol2025v24a25
3F7E87D81D04FFE9FCB9EC3F5C9DF860.taxon	materials_examined	TYPE MATERIAL. — Holotype. England • 1 specimen (a trunk vertebra); Christchurch Bay, Hordle Cliff; Headon Hill Formation; 36.91 ± 0.326 Ma; MP 17, Priabonian (late Eocene); NHMUK PV R 10795 (Figs 1; 2). Paratype. England • 1 specimen (a trunk vertebra); Christchurch Bay, Hordle Cliff; Headon Hill Formation; 36.91 ± 0.326 Ma; MP 17, Priabonian (late Eocene); NHMUK PV R 10798 (Figs 3; 4). REFERRED SPECIMENS. — 18 trunk vertebrae (NHMUK PV R 10792, NHMUK PV R 10794, NHMUK PV R 10797, NHMUK PV R 38879, NHMUK PV R 38942, NHMUK PV R 38943, NHMUK PV R 38944, NHMUK PV R 38945, NHMUK PV R 38946, NHMUK PV R 38950, NHMUK PV R 38952 - NHMUK PV R 38954, and NHMUK PV R 38956 - NHMUK PV R 38960), two? cloacal vertebrae (NHMUK PV R 38947 and NHMUK PV R 38948), and nine caudal vertebrae (NHMUK PV R 10791, NHMUK PV R 10793, NHMUK PV R 10796, NHMUK PV R 10799, NHMUK PV R 10800, NHMUK PV R 38941, NHMUK PV R 38949, NHMUK PV R 38951, and NHMUK PV R 38955). TYPE LOCALITY AND AGE. — All specimens originate from the locality of Christchurch Bay at Hordle Cliff, Hampshire, England; Mammal Bed, Totland Bay Member, MP 17 (approximately 36.91 ± 0.326 Ma), late Eocene. GEOGRAPHIC AND STRATIGRAPHIC RANGE. — Taxon known exclusively from the type locality.	en	Georgalis, Georgios L., Jones, Marc E. H. (2025): A new peculiar early diverging caenophidian snake (Serpentes) from the late Eocene of Hordle Cliff, England. Comptes Rendus Palevol 24 (25): 505-530, DOI: 10.5852/cr-palevol2025v24a25, URL: https://doi.org/10.5852/cr-palevol2025v24a25
3F7E87D81D04FFE9FCB9EC3F5C9DF860.taxon	diagnosis	DIAGNOSIS. — Paradoxophidion richardoweni n. gen., n. sp. is unique among all snakes in possessing the following characters: hypapophysis with a triangular shape in lateral view; vaulted neural arch with a peculiar dome-shaped arching; thick and transversely expanded zygantral roof (i. e., “ thickened posterior margin of the neural arch ” sensu Head 2021); and the contact of the paradiapophyses with the lateral margins of cotyle well dorsal to the level of its ventral margin. Paradoxophidion richardoweni n. gen., n. sp. can be further differentiated from all other snakes by the following combination of features: small vertebral size, with centrum length (CL) ranging around 2 mm; moderately (dorsoventrally) short neural spine that is almost strictly confined to the posteriormost portion of the neural arch; presence of hypapophysis across all trunk vertebrae, that is prominent and much ventrally expanded in lateral view and narrow in ventral view; presence of prominent prezygapophyseal buttresses that are compressed and form a more or less vertical ridge; presence of a small, pterapophysis-like, tubercle on each side of the neural arch; paradiapophyses not clearly divided into diapophyses and parapophyses; paradiapophyses facing ventrally in anterior view and reaching below the ventral level of the cotyle; absence of paracotylar foramina; very small and circular cotyle and condyle; absence of paracotylar ventrolateral processes; occasional presence of a short median ventral process / tubercle in the ventral margin of the cotyle; zygosphene very thin and always larger than the cotyle; very large neural canal; absence of parazygosphenal foramina; caudal vertebrae with elongated and slender pleurapophyses; anterior caudal vertebrae with a haemal keel; and mid-caudal and posterior caudal vertebrae with paired haemapophyses. For detailed comparisons with other snakes, see Discussion below.	en	Georgalis, Georgios L., Jones, Marc E. H. (2025): A new peculiar early diverging caenophidian snake (Serpentes) from the late Eocene of Hordle Cliff, England. Comptes Rendus Palevol 24 (25): 505-530, DOI: 10.5852/cr-palevol2025v24a25, URL: https://doi.org/10.5852/cr-palevol2025v24a25
3F7E87D81D04FFE9FCB9EC3F5C9DF860.taxon	etymology	ETYMOLOGY. — The new species name honours Sir Richard Owen (1804 - 1892), one of the greatest palaeontologists and comparative anatomists of all time. Richard Owen was the first to describe fossil remains of snakes from Hordle Cliff, as well as one of the first researchers that provided a thorough documentation of the snake vertebral column, focusing on its anatomical structures and the intracolumnar variation. Richard Owen was also the founder of the Natural History Museum in London (1881), where all known specimens of the new taxon are permanently curated. The name also alludes to the Richard Owen Fund of the Palaeontographical Society that was awarded to the first author (GLG) in 2023 and enabled him to study the fossil specimens of this new taxon at NHMUK.	en	Georgalis, Georgios L., Jones, Marc E. H. (2025): A new peculiar early diverging caenophidian snake (Serpentes) from the late Eocene of Hordle Cliff, England. Comptes Rendus Palevol 24 (25): 505-530, DOI: 10.5852/cr-palevol2025v24a25, URL: https://doi.org/10.5852/cr-palevol2025v24a25
3F7E87D81D04FFE9FCB9EC3F5C9DF860.taxon	description	DESCRIPTION Holotype (NHMUK PV R 10795) The holotype trunk vertebra NHMUK PV R 10795 of Paradoxophidion richardoweni n. gen., n. sp. is practically complete, with only some erosion observed in its right paradiapophysis and (perhaps also) the dorsalmost part of the neural spine (Figs 1; 2; Appendix 1). In anterior view (Figs 1 A; 2 A), the zygosphene is very thin and is much wider than the cotyle. The dorsal roof of the zygosphene is slightly convex. The neural canal is very large. The prezygapophyses are only slightly dorsally inclined. Prominent prezygapophyseal buttresses are present, forming a somehow vertical ridge; these commence dorsally from the level of the prezygapophyses and terminating ventrally towards the level of the paradiapophyses. The cotyle is very small and circular. There are no paracotylar foramina. There are no paracotylar ventrolateral processes. The paradiapophyses are distinct from the centrum and extend ventrally, below the level of the ventral lip of the cotyle; the paradiapophyses contact the lateral margins of the cotyle well above the level of its ventral margin. The hypapophysis is relatively thick and is very elongated, extending much ventrally. In posterior view (Figs 1 B; 2 I), the zygantral roof is very thick (i. e., “ thickened posterior margin of the neural arch ” sensu Head 2021). The neural arch is moderately vaulted, with a vaulting ratio (sensu Georgalis et al. 2021 b) equal to 0.42, and possesses a peculiar dome-shaped arching. The condyle is small and circular. The paradiapophyses (only the left one is almost complete, with a slight breakage in its parapophyseal surface; the right one is eroded), are massive and they seem not to be divided into diapophyseal and parapophyseal portions. In dorsal view (Figs 1 D; 2 E), the base of the neural spine is strictly confined to the posterior half of the neural arch. The zygosphene possesses two distinct lateral lobes. The prezygapophyses are small, slightly extending anterolaterally. The prezygapophyseal articular facets are relatively small and oval. The interzygapophyseal constriction is moderately deep. A posterior median notch of the neural arch is almost absent. In ventral view (Figs 1 E; 2 M), the centrum is slightly wider than long (CL / NAW = 0.95). The hypapophysis extends across most of the midline of the centrum, commencing anteriorly from the base of the cotyle and terminating posteriorly well before the condyle. The condyle is situated in a distinct condylar neck. The subcentral grooves are deep. The postzygapophyses are moderately large and somewhat triangular. There are no prezygapophyseal accessory processes, however, small, russellophiid-like spines are present below the prezygapophyseal articular facets. In lateral view (Figs 1 C; 2 H, L), the neural spine is relatively dorsoventrally short, while it is slender and anteroposteriorly relatively short; it abruptly commences augmenting in height in the posterior half of the centrum and is much posteriorly inclined. A small, pterapophysis-like, tubercle is present posteriorly on each side of the neural arch. A large lateral foramen is situated below the interzygapophyseal ridges. The subcentral ridges are strongly convex. The hypapophysis is large and almost triangular; it commences anteriorly from the tip of the cotyle but it is mostly developed towards the posterior half of the centrum, where it becomes prominent and extends rather ventrally. Paratype and referred specimens – intracolumnar variation All available trunk vertebrae of Paradoxophidion richardoweni n. gen., n. sp. are rather small, with CL ranging around 2 mm or even less (Figs 3 - 9). The paratype (NHMUK PV R 10798; Figs 3; 4) and all referred specimens share with the holotype a rather similar vertebral morphology, though some differences can be observed, which can be attributed to intracolumnar variation. The centrum is anteroposteriorly short and relatively wide in all trunk vertebrae. Among them, notably, NHMUK PV R 38943 (Fig. 8 K-O) is rather anteroposteriorly short and laterally wide, i. e., wider than every other available vertebra of the species (CL / NAW = 0.77). This shape is probably due to intracolumnar variation, as this vertebra (NHMUK PV R 38943) is also characterized by a much vaulted neural arch (vaulting ratio sensu Georgalis et al. 2021 b equal to 0.48). Still though, even this vertebra has a prominent hypapophysis, while all other distinctive features (e. g. shape and thickness of the zygantrum, paradiapophyses being distinct from the centrum and ventrally expanded, posterior confinement and size of the neural spine) perfectly match the morphology of the remaining vertebrae. The zygosphene in trunk vertebrae most usually possesses two (more or less) distinct lateral lobes and no median lobe in dorsal view, while in anterior view, it is slender and slightly arched (e. g. NHMUK PV R 38944 [Fig. 9 A, D] and the holotype [NHMUK PV R 10795; Figs 1 A, D; 2 A, E]) to very arched (e. g. NHMUK PV R 38942 [Fig. 8 F], NHMUK PV R 38943 [Fig. 8 K]). Nevertheless, there are cases, where a median lobe is present and the lateral lobes are incipient (NHMUK PV R 10797; Figs 7 E; 8 D). Although prezygapophyseal accessory processes are absent in other specimens, tall, blade-like processes extending anterolaterally beyond the margins of the prezygapophyseal articular facets are clearly visible in NHMUK PV R 10797 (Figs 7; 8 D-E). Like in the holotype, all vertebrae possess, on each side of the neural arch, a small, pterapophysis-like, tubercle. The posterior median notch of the neural arch is either absent or (at maximum) rather shallow. Lateral foramina are present. Subcentral foramina are variably present across trunk vertebrae: usually a single one on the left side of the hypapophysis, however, there are cases that these are doubled, i. e., one across each side of the hypapophysis (NHMUK PV R 38950; Fig. 9 J). The zygantral roof is thickened in all vertebrae, giving a dome-shaped appearance. Interestingly, paracotylar ventrolateral processes (a plesiomorphy for alethinophidian snakes) are absent in all specimens of the new taxon. The paradiapophyses are prominent, much ventrally expanded, and seem not to be divided into diapophyses and parapophyses (like in Russellophis but unlike caenophidians). The prezygapophyseal buttresses are prominent in all vertebrae. Some variation is also observed in the neural spine across trunk vertebrae. This structure is strictly confined in the posteriormost portion of the neural arch in all specimens. The dorsoventral height of the neural spine slightly varies: it is mostly short and usually somehow posteriorly inclined. The most important variation though regards the shape, size, and direction of the hypapophysis, which differs across trunk vertebrae. The hypapophysis can be rather broad and prominent in some trunk vertebrae. Such broad hypapophysis (in lateral view) is observed in the holotype (NHMUK PV R 10795; Figs 1 C; 2 H, L), the paratype (NHMUK PV R 10798; Figs 3 C; 4 D, E), and the referred vertebra NHMUK PV R 38946 (Figs 5 C; 6 D, H). In contrast, vertebrae NHMUK PV R 10792, NHMUK PV R 38944 (Fig. 9 C), NHMUK PV R 38950 (Fig. 9 H), and NHMUK PV R 10792 (Fig. 9 M) have a more slender and somehow acute hypapophysis (in lateral view). In some trunk vertebrae, the hypapophysis is shorter in lateral view, with its posterior edge slightly dorsoventrally high (e. g. NHMUK PV R 10797 [Figs 7 D; 8 C]). It is difficult to assess the intracolumnar position of the available trunk vertebrae of Paradoxophidion richardoweni n. gen., n. sp. This is particularly the case for the specimens with very broad hypapophyses (NHMUK PV R 10795 [holotype; Figs 1; 2], NHMUK PV R 10798 [paratype; Figs 3; 4], and NHMUK PV R 38946 [Fig. 5]). NHMUK PV R 38942 is probably an anterior trunk vertebra, due to the fact that its neural arch is more vaulted (vaulting ratio sensu Georgalis et al. 2021 b equal to 0.54) and the hypapophysis is thinner in lateral view, seeming more posteroventrally directed (Fig. 8 F-J). Finally, NHMUK PV R 38945 seems to represent the anteriormost available vertebra, as it can be attested by its very slender, long, and posteroventrally directed hypapophysis, the vaulted neural arch, and the tiny prezygapophyseal articular facets – this specimen also has the thinnest zygantral roof. NHMUK PV R 38947 (Fig. 10 A-E) and NHMUK PV R 38948 (Fig. 10 F-J) likely represent cloacal vertebrae. These are wider and anteroposteriorly shorter than trunk vertebrae, a pattern particularly observed in NHMUK PV R 38947 (Fig. 10 E). These vertebrae are characterized by the presence of lymphapophyses instead of paradiapophyses. They both preserve the bases of the dorsal and ventral lymphapophyseal processes, which are separated by a wide and somehow concave arc. These structures are better preserved in NHMUK PV R 38947, in which, apart from the bases, there also remain portions of the left lymphapophyseal processes (Fig. 10 A, B). There are no lymphapophyseal foramina among the bases of the lymphapophyses. The neural spine in NHMUK PV R 38948 (Fig. 10 H) is dorsoventrally shorter and anteroposteriorly longer than the preceding trunk vertebrae, with its base crossing around half of the midline of the neural arch. Both cloacal vertebrae have hypapophyses. The hypapophysis extends across the whole midline of the centrum in ventral view. Nine caudal vertebrae of Paradoxophidion richardoweni n. gen., n. sp. are available in our sample. NHMUK PV R 10796 (Figs 11; 12; Appendix 2), NHMUK PV R 10799 (Fig. 13 A-E), and NHMUK PV R 10793 (Fig. 13 M-Q) are anterior caudal vertebrae. This is most probably the case also for NHMUK PV R 10791 (Fig. 13 K-L), NHMUK PV R 10800 (Fig. 13 F-J) and NHMUK PV R 38951 (Fig. 13 R-U), though we cannot exclude that they could alternatively represent instead posteriormost trunk or cloacal vertebrae. Almost all of these vertebrae are wider compared to the trunk vertebrae described above. These are characterized by the presence of a short hypapophysis / haemal keel, instead of paired haemapophyses; such hypapophysis / haemal keel is relatively sharp and thin in ventral view, while it is dorsoventrally rather short in lateral view. The pleurapophyses are incomplete in all specimens, with the exception of NHMUK PV R 10796, where the right pleurapophysis is complete, being very elongated and slender (Figs 10; 11) and, to a lesser degree, NHMUK PV R 10793, which preserves part of the left pleurapophysis (Fig. 13 M, N). Unlike trunk vertebrae, where subcentral foramina are usually small to medium-sized, in certain anterior caudal vertebrae, these are considerably large (e. g. NHMUK PV R 10791 [Fig. 13 K]; NHMUK PV R 10796 [Figs 11 E; 12 D, N]). Notably, in three specimens of the new taxon, the anterior caudal vertebra NHMUK PV R 10791 (Fig. 13 K) and, to a lesser degree also the anterior caudal vertebra NHMUK PV R 10793 (Fig. 13 Q) and the paratype trunk vertebra NHMUK PV R 10798 (Figs 3 E; 4 K, L), there is short median ventral process / tubercle in the ventral margin of the cotyle. NHMUK PV R 38941 (Fig. 14 A-E), NHMUK PV R 38949 (Fig. 14 F-J), and NHMUK PV R 38955 represent more posterior caudal vertebrae and they have a pair of haemapophyses (instead of hypapophysis) and a relatively longer centrum. These haemapophyses are rather short, not protruding much ventrally below the centrum. Like in the preceding trunk vertebrae, the neural spine is confined to the posteriormost portion of the neural arch; however, in NHMUK PV R 38949 (Fig. 14 I) and NHMUK PV R 38955 this structure is anteroposteriorly longer than remaining caudal vertebrae. The ventral surface of the centrum can bear also a pair of subcentral foramina, but these vary in size and degree of symmetry. Other features of the caudal series, which are also observed in the trunk vertebrae, include the thickening of the zygantrum, the thin zygosphene, the large neural canal, the small, pterapophysis-like, tubercle on each side of the neural arch, and the small and circular cotyle and condyle.	en	Georgalis, Georgios L., Jones, Marc E. H. (2025): A new peculiar early diverging caenophidian snake (Serpentes) from the late Eocene of Hordle Cliff, England. Comptes Rendus Palevol 24 (25): 505-530, DOI: 10.5852/cr-palevol2025v24a25, URL: https://doi.org/10.5852/cr-palevol2025v24a25
