Charinaidae Gray, 1849 (sensu Burbrink et al. 2020), 1803

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

Charinaidae Gray, 1849 (sensu Burbrink et al. 2020)

General information.

Charinaidae currently comprise two genera, Charina and Lichanura , with four species, distributed in North and northern Central America ( Boundy 2021). It is recovered as the sister group of Ungaliophiidae in most recent phylogenetic analyses (e.g., Pyron et al. 2013; Reynolds et al. 2014; Zheng and Wiens 2016; Burbrink et al. 2020; Zaher et al. 2023). This close, sister group relationship between charinaids and ungaliophiids inferred by molecular data has prompted their treatment in many recent phylogenies and taxonomic schemes as “subfamilies” ( Charinainae and Ungaliophiinae respectively) of an expanded concept of Charinaidae (e.g., Pyron et al. 2013, 2014; Reynolds and Henderson 2018; Georgalis and Smith 2020; Boundy 2021), yet other works treat them both at the family level (e.g., Wilcox et al. 2002; Wallach et al. 2014; Burbrink et al. 2020; Zaher et al. 2023). We here follow the latter opinion and treat Charinaidae and Ungaliophiidae at the family level, taking into consideration the above mentioned fact that certain morphology-based or molecular+morphology combined phylogenies recover Erycidae and Charinaidae together as a clade (e.g., Kluge 1993b; Gauthier et al. 2012; Scanferla et al. 2016; Smith and Scanferla 2021), and most importantly the shared complex caudal vertebral morphology of charinaids and erycids, which is a key anatomical feature (e.g., Szyndlar 1994; Szyndlar and Schleich 1994; Smith 2013; Smith and Scanferla 2021).

The fossil record attests a higher diversity of charinaids in the past, including also extinct species of the extant genera (see Holman 2000; Wallach et al. 2014; Boundy 2021), as well as a significantly wider distribution, encompassing also the Eocene of Europe, where the genus Rageryx was confidently referred to that lineage ( Smith and Scanferla 2021).

Note that the original name of the family, Charinidae , recently had its spelling emended to Charinaidae by a formal decision of ICZN (2020), in order to avoid homonymy with its junior synonym of the arachnid family Charinidae Quintero, 1986, which had, however, a widespread usage in arthropod literature. An alternative name, Lichanuridae , has also been applied to this family in the 19th century ( Cope 1868b).

Vertebral morphology of Charinaidae is closely similar to that of Erycidae , with the two groups sharing also the characteristic complex caudal vertebrae, though still differences occur (for more details see Description and Figures of Charina and Lichanura below). Parham et al. (2012) proposed that the presence of a laterally swollen, trilobate neural spine combined with incipient pterapophyses on the dorsolateral margin of the posterior neural arch in caudal vertebrae is unique in Charina and Lichanura among extant snakes and can be used as the primary diagnostic feature of Charinaidae .

Previous figures of vertebrae of extant Charinaidae have been so far presented by Holman (1967), Bogert (1968a), Hoffstetter and Rage (1972), Ruben (1977), Szyndlar (1987, 1994), Gauthier et al. (2012), Smith and Scanferla (2021), and Frýdlová et al. (2023). Among these, vertebrae from the cloacal and/or caudal series have been presented by Holman (1967), Bogert (1968a), Hoffstetter and Rage (1972), Szyndlar (1987, 1994), Gauthier et al. (2012), Smith and Scanferla (2021), and Frýdlová et al. (2023). Quantitative study on intracolumnar variation of charinaid vertebrae was conducted by Head (2021). Besides, an extensive analysis of the mode of articulation between neighbouring caudal vertebrae of charinaids was provided by Szyndlar (1994). In addition, Hoffstetter and Rage (1972) and Kluge (1991) noted the occurrence of paracotylar foramina in Lichanura (but absent in Charina ).