CHARINIDAE Node Calibrated. Divergence between the total clades Ungaliophiinae (Ungaliophis + Exiliboa) sensu Pyron et al. (2014) and total clade Charininae (Charina + Lichanura) sensu Pyron et al. (2014). Fossil Taxon. Calamagras weigeli. Specimen. PTRM 19607, caudal vertebra. Additional Materials. 19609, 19681, caudal vertebrae. Phylogenetic Justification. Caudal vertebrae lacking paired haemapophyses, haemal keels present. This morphology is only present in Ungaliophis and Exiliboa among extant taxa (Smith, 2013). Minimum Age. 35.2 Ma. Soft Maximum Age. Indeterminate. Age Justification. Minimum age is based on faunal correlation of Medicine Pole Hills fossil localities (Bowman County, North Dakota) with Flagstaff Rim localities (Natrona County, Wyoming), which are overlain by an ash layer (Ash B) that is 40 Ar/ 39 Ar dated at 35.41 ± 0.14 Ma (Obradovich et al., 1995). Smith (2011) recalculated the minimum estimate for the Medicine Pole Hills local fauna at 35.2 Ma. Discussion. Numerous fossil taxa have been described as ungaliophiines, either explicitly as related to (Ungaliophis + Exiliboa) (e.g., Rage, 2008), or as part of a “ Tropidophiidae ” (Szyndlar et al., 2008) that is not supported by either morphological (Zaher, 1994) or molecular data (e.g., Wilcox et al., 2002). As noted by Smith (2013), the only fossil record that is united with (Ungaliophis + Exiliboa) on the basis of discrete apomorphies consists of isolated cloacal vertebrae assigned to Calamagras. Generic assignment of isolated vertebrae to Calamagras is problematic in that the generic and specific diagnoses for the taxon are do not include unique apomorphies or character combinations relative to other coeval, fossils, and are redundant with each other as described (Holman, 2000). Referral to Calamagras is tentatively followed here, but until the taxonomy and systematics of the genus can be unambiguously resolved, the record described in Smith (2013) must be used as the minimum divergence timing for the total clade, and stratigraphically older records of the genus (e.g., Hecht, 1959; Rage, 1977; Danilov and Averianov, 1999) should not be cited. Usage of Charinidae follows Pyron et al. (2014).

Published as part of Head, JJ, 2015, Fossil calibration dates for molecular phylogenetic analysis of snakes 1: Serpentes, Alethinophidia, Boidae, Pythonidae, pp. 1-17 in Palaeontologia Electronica 18 on page 8, DOI: 10.26879/487, http://zenodo.org/record/13311383