An illustrated atlas of the vertebral morphology of extant non-caenophidian snakes, with special emphasis on the cloacal and caudal portions of the column

Abstract

Abstract We here present a thorough documentation of the vertebral morphology and intracolumnar variation across non-caenophidian snakes. Our studied sample of multiple individuals covers a large number of genera (67) and species (120), pertaining to almost all extant non-caenophidian families. Detailed figuring of multiple vertebrae across the trunk, cloacal, and caudal series for many different individuals / taxa documents the intracolumnar, intraspecific, and interspecific variation. An emphasis is given in the trunk-to-caudal transition and the pattern of the subcentral structures in that region of the column. Extant non-caenophidian snakes show an astonishing diversity of vertebral morphologies. Diagnostic vertebral features for extant families and many genera are given, though admittedly vertebral distinction among genera in certain groups remains a difficult task. A massive compilation of vertebral counts for 270 species, pertaining to 78 different genera (i.e., almost all known valid genera) and encompassing all extant non-caenophidian families, is provided based on our observations as well as an extensive literature overview. More particularly, for many taxa, detailed vertebral counts are explicitly given for the trunk, cloacal, and caudal portions of the column. Extant non-caenophidian snakes witness an extremely wide range of counts of vertebrae, ranging from 115 up to 546. A discussion on the diagnostic taxonomic utility and potential phylogenetic value of certain vertebral structures is provided. Comparisons of the subcentral structures of the cloacal and caudal vertebral series are also made with caenophidian lineages. We anticipate that this illustrative guide will set the stage for more vertebral descriptions in herpetological works but will also be of significant aid for taxonomic identifications in ophidian palaeontology and archaeozoology.