COLUBRINAE Oppel, 1811

Jacisin Iii, John J. & Lawing, A. Michelle, 2024, Fossil snakes of the Penny Creek Local Fauna from Webster County, Nebraska, USA, and the first record of snakes from the Early Clarendonian (12.5 - 12 Ma) of North America, Palaeontologia Electronica (a 2) 27 (1), pp. 1-42 : 12

Subfamily COLUBRINAE Oppel, 1811

Diagnosis. Holman (2000) outlined some general osteological characters for colubrine snakes, which were later examined and modified by Ikeda (2007). The trunk vertebrae are typically longer than wide, are often lightly built, and lack hypapophyses ( Holman, 2000; Ikeda, 2007; Ikeda et al., 2016). The neural spines are somewhat thin, tall, mostly uniform in width, and often project posteriorly over adjacent vertebrae ( Holman, 2000). The prezygapophyseal accessory processes are well-projected and prominent ( Holman, 2000; Ikeda, 2007; Ikeda et al., 2016). The hemal keels are well-projected from the centrum and may or may not be relatively thin ( Holman, 2000; Ikeda, 2007; Ikeda et al., 2016), and the subcentral ridges and grooves are distinct ( Holman, 2000, Ikeda, 2007; Ikeda et al., 2016). Epizygapophyseal spines may or may not be present ( Holman, 2000).

Remarks. While Holman’s (2000) diagnosis of colubrines appears to fit North American taxa, Ikeda (2007) noted that the lightly build vertebrae and relatively thin hemal keels are not features consistent with some non-North American taxa, as these features show various states amongst extant species. These characters may only be consistently useful for North American taxa, and should not preclude taxa from being assigned to the subfamily Colubrinae if those characters are not present as described in Holman (2000). Furthermore, Head et al. (2016) point out that while a precloacal vertebral column without hypapophyses have been traditionally used to differentiate colubrines from natricids and elapids ( Bell et al., 2004; Szyndlar, 2012), this absence also occurs in a number of dipsadid and elapid taxa as well ( Dowling and Duellman, 1978 after Pyron et al., 2013). This character therefore cannot fully diagnose colubrines to the exclusion of other clades on its own ( Head et al., 2016).