Loxocemidae Cope, 1861, 1827

Szyndlar, Zbigniew & Georgalis, Georgios L., 2023, An illustrated atlas of the vertebral morphology of extant non-caenophidian snakes, with special emphasis on the cloacal and caudal portions of the column, Vertebrate Zoology 73, pp. 717-886 : 717

Loxocemidae Cope, 1861

General information.

Similar to Xenopeltis , the interrelationships of the Central American species Loxocemus bicolor have been convoluted for many decades, with the taxon placed either close to booids and pythonoids or either close to “anilioids” ( Cope 1861a, 1861b, 1887; Boulenger 1893; Schmidt 1923; Stull 1935; Romer 1956; Kuhn 1961; Bogert 1968a; Smith et al. 1977; McDowell 1987; Rage 1987). Nevertheless, the advance of phylogenetics shed more light on its exact affinities, with most recent studies recovering Loxocemus as closely related to Xenopeltis and pythonids (e.g., Slowinski and Lawson 2002; Wiens et al. 2008; Pyron and Burbrink 2012; Pyron et al. 2013 Reynolds et al. 2014; Figueroa et al. 2016; Streicher and Wiens 2016; Zheng and Wiens 2016; Harrington and Reeder 2017; Burbrink et al. 2020; Onary et al. 2022) and accordingly Loxocemidae has been placed into Pythonoidea in recent taxonomic schemes ( Wallach et al. 2014; Georgalis and Smith 2020; Smith and Georgalis 2022). Fossil record attests the presence of loxocemids already since the late Eocene ( Smith 2013).

Vertebral morphology of Loxocemidae is reminiscent of other constrictors, but some important characteristic features can be indeed recognized (see Description and figures of Loxocemus below for details).

Previous figures of vertebrae of extant Loxocemidae have been so far presented only by McDowell and Bogert (1954) and Bogert (1968a). Among these, vertebrae from the cloacal and/or caudal series have never been figured so far. Besides, important descriptions and notes on loxocemid vertebrae have been made by Underwood and Kochva (1993), Szyndlar and Böhme (1996), Rage (2001), and Smith (2013).