Neonatrix, Holman, 1973

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 : 20-21

Genus NEONATRIX Holman, 1973 †

Diagnosis. Neonatrix trunk vertebrae are most easily characterized by very short hypapophyses that strongly project posteriorly, are ventrally beveled in most North American species (except Neonatrix elongata ) but are weakly developed, terminally rounded, and do not extend beyond the end of the condyle. Furthermore, they are relatively small and distinctly longer than wide. The neural spines of Neonatrix are much longer (up to 4x) than wide ( Holman, 1973, 2000; Parmley and Hunter, 2010), with reduced or absent hooked projections at each terminal end. The zygosphene is convex, but less so in caudal vertebrae ( Jasinski and Moscato, 2017).

Remarks. The hypapophyses of North American species of Neonatrix are less well-developed than the reported species from Europe ( Holman, 1973, 1982, 1996; Rage and Holman, 1984) and shorter than in any other natricid genus ( Holman, 1973, 2000). Neonatrix also differs from Thamnophis and Nerodia in possessing an anteriorly taller neural spine that lacks hooked projections and a less prominant subcentral ridge ( Jasinski and Moscato, 2017). The neural spine of Neonatrix is also taller than in Storeria , Tropidoclonion , Virginia , and Micronatrix , but shorter than in Seminatrix ( Parmley and Hunter, 2010; Jasinski and Moscato, 2017)