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 Cylindrophiidae Fitzinger, 1843 General information. Cylindrophiids consist a monotypic family of uropeltoids, with a single genus, Cylindrophis and more than a dozen species, distributed only in Sri Lanka, southeastern Asia, and Indonesia ( Wallach et al. 2014 ; Boundy 2021 ). The vertebral morphology of cylindrophiids is primarily characterized by an elongate centrum, depressed cotyle and condyle, depressed neural arch, absent or very shallow median notch of the neural arch, absent haemal keels in mid- and posterior trunk vertebrae, neural spine vestigial and restricted to the posterior portion of the neural arch (disappearing entirely in the posterior vertebrae), absence of any subcentral structures in the cloacal and caudal portion of the column (with the exception of a moderately developed ridge-like keel in the last cloacal and two succeeding caudal vertebrae in Cylindrophis ruffus ), and a very low number of caudal vertebrae (for more details, see Description and figures of Cylindrophis below). Previous figures of vertebrae of extant Cylindrophiidae have been so far presented by Rochebrune (1881) , Williams (1954, 1959 ), Gasc (1974) , Hoffstetter and Rage (1977) , Rieppel (1979) , Polly and Head (2004) , Ikeda (2007) , Xing et al. (2018) , Fachini et al. (2020) , Palci et al. (2020) , Head (2021) , and Alfonso-Rojas et al. (2023) . Among these, vertebrae from the cloacal and caudal series were presented by Gasc (1974) , Palci et al. (2020) , and Alfonso-Rojas et al. (2023) . Quantitative studies on the intracolumnar variability of cylindrophiid vertebrae were conducted by Gasc (1974) , Polly and Head (2004) , and Head (2021) .