CHARINAIDAE Gray, 1849

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 : 8

Family CHARINAIDAE Gray, 1849 (sensu Pyron et al., 2014)

Diagnosis. The following vertebral osteological characters are modified from Brattstrom (1958), Kluge (1993), Bell and Mead (1996), Holman (2000), and Head (2015) to reflect the current nomenclature for Constrictores and Booidea ( Reynolds et al., 2014; Zaher et al., 2019; Burbrink et al., 2020; Georgalis and Smith, 2020). The vertebrae possess a flattened neural arch. The neural spines are low, and in the caudal vertebrae are expanded, exhibiting a somewhat distended or distally lobate appearance relative to pre-caudal neural spines ( Head, 2015). Prezygapophyseal accessory processes are reduced ( Holman, 2000). Paracotylar foramina are absent ( Kluge, 1993). Caudal vertebrae are very short, with a variety of processes giving them a complex appearance (with the exception of the genus Lichanura ; Holman, 2000).

Remarks. Snakes of the Charinaidae are typically small to medium in size, robust in body form, with short tails and small eyes, all of which assist them in a semifossorial lifestyle ( Holman, 2000). Many North American fossil booids, including extant genera Charina and Lichanura , were previously assigned to the Erycinae, which are generally similar in body form, vertebral morphology, and lifestyle ( Holman, 2000; see Pyron et al., 2014 and ICZN, 2020 for additional details regarding taxonomic nomenclature). Under the most recent taxonomy, North American subfamilies Charinainae Gray, 1849 ( Charina and Lichanura ) and Ungaliophiinae McDowell, 1987 ( Exiliboa and Ungaliophis ) are now grouped within the Charinaidae ( Pyron et al. 2014; Head, 2015; ICZN, 2020). This further complicates the fossil record of older North American snakes not found in Penny Creek, in that genera such as Calamagras , Ogmophis , Geringophis , Pterygoboa , and others are left with a somewhat uncertain taxonomic status, although some research has suggested that the fossil species Ogmophis compactus and Calamagras weigeli may represent loxocemid and ungaliophiine snakes, respectively ( Smith, 2013). An extensive apomorphy-based redescription and reorganization of the older fossil taxa may be necessary to determine if it is possible to morphologically differentiate them at the species or genus level given the newer taxonomy of extant booids ( Bell et al. 2010; Pyron et al., 2014; Head, 2015). The absence of paracotylar foramina in Charinaidae vertebrae differentiates the group from Boidae (sensu Pyron et al., 2014). This variable character is shared with pythonids and most non-boid booids, and as such does not differentiate Charinaidae from those groups ( Kluge, 1993; Rage, 2001; Szyndlar and Rage, 2003; Georgalis, 2019; Georgalis and Smith, 2020).