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 Author Jacisin Iii, John J. Author Lawing, A. Michelle text Palaeontologia Electronica 2024 a 2 27 1 1 42 http://dx.doi.org/10.26879/1220 journal article 10.26879/1220 1094-8074 10962250 Genus PANTHEROPHIS Fitzinger, 1843 Diagnosis. The vertebrae of North American Pantherophis are relatively short, but robustly built compared to most of their contemporary colubrids. The vertebrae have wide, high neural spines and broad hemal keels, but lack epizygapophyseal spines ( Holman, 2000 ; Parmley and Hunter, 2010 ). The parapophyseal process is poorly developed on either side, and the interzygapophyseal ridge is straight in lateral view ( Ikeda, 2007 ). Remarks. The vertebrae of North American Pantherophis are similar to some species of other large-bodied colubrine genera. In North America, the vertebrae of Pantherophis differ from those of New World Masticophis and Coluber in that they are relatively shorter and more robustly built, have higher and wider neural spines, have wider hemal keels, and lack epizygapophyseal spines ( Holman, 2000 ). Pantherophis generally differs from Lampropeltis in possessing a higher, more vaulted neural arch, a higher neural spine (compared to at least some species of Lampropeltis ), straight and less defined subcentral ridges, and less robust vertebrae ( Holman, 2000 ; Parmley and Hunter, 2010 ). Pantherophis differs from Pituophis in having a lower neural spine and a zygosphene that is rarely or never concave ( Auffenberg, 1963 ). Pantherophis differs from Drymarchon in possessing a zygosphene that is rarely or never concave, greater posterolateral curvature of the neural arch, less posterior curvature of the neural spine, and a deeper concavity on the posteromedial portion of the neural arch ( Jasinski and Moscato, 2017 ). There has been no work to definitively separate the vertebral morphology of Pantherophis and Elaphe , in part because their reclassification as separate genera has not been morphologically defined since their separation in Utiger et al. (2002) .