An illustrated atlas of the vertebral morphology of extant non-caenophidian snakes, with special emphasis on the cloacal and caudal portions of the column Author Szyndlar, Zbigniew Institute of Systematics and Evolution of Animals, Polish Academy of Sciences, Slawkowska 17, 31 - 016 Krakow, Poland Author Georgalis, Georgios L. https://orcid.org/0000-0001-7759-6146 Institute of Systematics and Evolution of Animals, Polish Academy of Sciences, Slawkowska 17, 31 - 016 Krakow, Poland dimetrodon82@gmail.com text Vertebrate Zoology 2023 2023-09-27 73 717 886 http://dx.doi.org/10.3897/vz.73.e101372 journal article http://dx.doi.org/10.3897/vz.73.e101372 2625-8498-73-717 8F3D5EDA2F184E5CA53E2F7741FF1339 318B657A15AB5708B3C35FC1A82B4945 Tropidophis Bibron in Ramon de la Sagra, 1838-1843 Material examined. Tropidophis canus (Cope, 1868) ( AMNH R73066 ; UF Herp [Morphosource.org: Media 000445131, ark:/87602/m4/445131]; Tropidophis feicki Schwartz, 1957 (AMNH R81127 ); Tropidophis greenwayi Barbour & Shreve , 1936 ( UF Herp 42392 [Morphosource.org: Media 000445141, ark:/87602/m4/445141]); Tropidophis haetianus ( UF Herp 59679 [Morphosource.org: Media 000372277, ark:/87602/m4/372277); Tropidophis jamaicensis Stull, 1928 (NHMUK 1964.1239); Tropidophis melanurus (Schlegel, 1837) (AMNH R46690 ); Tropidophis semicinctus ( Gundlach & Peters in Peters , 1864) (AMNH R7386); Tropidophis taczanowskyi ( Steindachner , 1880) (NHMUK 44.2.27.8) . Description (Figs 31-35). Trunk vertebrae . The description is primarily based on the complete skeleton of Tropidophis jamaicensis (NHMUK 1964.1239). Centrum as long as wide; cotyle and condyle orbicular; neural arch moderately vaulted; posterior median notch of the neural arch shallow to moderately deep; neural spine as high as long; prezygapophyseal accessory processes vestigial; hypapophyses plate-like and with a distinct anteroventral corner, present throughout the trunk portion of the column; paracotylar foramina present. Note that a vertebra from the same specimen of T. jamaicensis was previously figured by Szyndlar and Rage (2003 : fig. 2O) as Tropidophis haetianus , as the former species was back then considered a subspecies of the latter. Figure 31. Tropidophiidae : Tropidophis jamaicensis (NHMUK 1964.1239), trunk vertebrae. Figure 32. Tropidophiidae : Tropidophis jamaicensis (NHMUK 1964.1239), posteriormost trunk, cloacal, and caudal vertebrae. Figure 33. Tropidophiidae : Tropidophis jamaicensis (NHMUK 1964.1239), caudal vertebrae. Figure 34. Tropidophiidae : Tropidophis jamaicensis (NHMUK 1964.1239), caudal vertebrae. Figure 35. Tropidophiidae : Tropidophis taczanowskyi (NHMUK 44.2.27.8), trunk vertebrae. Mid-trunk vertebrae of Tropidophis taczanowskyi (four vertebrae studied) morphologically closely resemble those of T. jamaicensis ; the main difference is that their hypapophyses are shorter, though still these possess the typical anteroventral corner. A similar situation with T. jamaicensis is also observed in the skeleton of Tropidophis greenwayi : here the hypapophysis of the mid-trunk vertebrae is also plate-like with a distinct anteroventral corner. As for other species of the genus, published figures of trunk vertebrae of Tropidophis canus ( Bogert 1968b : fig. 7B), Tropidophis haetianus ( Head 2021 : fig. 4B), and Tropidophis melanurus ( Syromyatnikova et al. 2021 : fig. 2C), demonstrate that these three species are also provided with a plate-like hypapophysis, possessing a distinct right-angled anteroventral corner produced anteriorly. Also for Tropidophis cacuangoae Ortega-Andrade et al., 2022 , the sole published X-ray image of the holotype ( Ortega-Andrade et al. 2022 : fig. 8), depicts the body almost continuously in lateral view and thus the prominent hypapophyses with right-angled anteroventral corner appear to be prominent especially in the mid- and posterior trunk portion of the column. Note though that for Tropidophis melanurus , other published figures ( Bogert 1968a : fig. 9A; Dowling and Duellman 1978 : fig. 104.2; Lee and Scanlon 2002 : fig. 10G) do show a different degree of inclination of the anteroventral corner (possessing a distinct "spur" in the anteroventral corner), and therefore in this species, the distinct right-angled anteroventral corner of the hypapophysis is evident only in part of the trunk region. Tropidophis feicki ( Bogert 1968a : fig. 8C) has a short hypapophysis similar to that of T. taczanowskyi ; for Tropidophis semicinctus , Bogert (1968a) stated that it is even less strongly developed. Bogert (1968a) regarded the structures in T. feicki and T. semicinctus to represent a haemal keel instead, but of course, the "terminology boundaries" between these elements are somehow a philosophical question (see also Discussion below). We consider the structure of T. feicki (and apparently also of T. semicinctus ) as a short hypapophysis, as was also previously suggested by Smith and Georgalis (2022) for that species, and in any case, we highlight that this taxon also possesses the characteristic right-angled anteroventral corner in mid-trunk vertebrae. As for other vertebral features, it is worth noting that except for Tropidophis jamaicensis and T. melanurus the remaining species of the genus (at least the studied or the already published ones) do not possess paracotylar foramina. Trunk / caudal transition . The description is again mainly based on Tropidophis jamaicensis . The hypapophysis of the last trunk vertebra is slightly longer than in mid-trunk vertebrae; in the following cloacal and anterior caudal vertebrae it becomes gradually shorter, inclined posteriorly, and pointed distally. A shallow groove appears on the tip of the hypapophysis of the 7th caudal vertebra (i.e., V 183) of T. jamaicensis (but in T. greenwayi , the slightly grooved hypapophysis already appears from the 3d caudal vertebra); in more posterior caudal vertebrae the subcentral structures are distally forked (grooved) hypapophyses rather than true paired haemapophyses, with this pattern continuing up to the very end of the tail. Posteriormost caudal vertebrae are fused. Number of vertebrae . Tropidophis canus (UF Herp 20220): 193 (162+3+28, including a final fusion); Tropidophis greenwayi (UF Herp 42392): 193 (156+3+34, including a final fusion); Tropidophis haetianus (UF Herp 59679): 216 (176+3+37, including a final fusion); Tropidophis jamaicensis (NHMUK 1964.1239): 207 (173+3+31, including a final fusion). Data from the literature and unpublished data from personal communications: Tropidophis cacuangoae : 157-160 trunk vertebrae plus 30-39 cloacal and caudal vertebrae, including a final fusion ( Ortega-Andrade et al. 2022 ); Tropidophis haetianus : 192 trunk vertebrae plus 4 cloacal vertebrae plus 38 caudal vertebrae (NHMUK 1897.12.31.6; Jason Head, unpublished data, personal communication to GLG); Tropidophis melanurus : ~196-198 trunk and cloacal vertebrae plus 41 caudal vertebrae ( Alexander and Gans 1966 ); Tropidophis semicinctus : 211 trunk and cloacal vertebrae plus 37+ caudal vertebrae ( Alexander and Gans 1966 ).