Caenophidia

Diagnosis. The vertebral synapomorphies of crown Caenophidia include well-developed prezygapophyseal accessory processes, synapophyses that are well-differentiated into para- and diapophyseal articular facets, the presence of pleurocentral hypapophyses throughout the precloacal vertebral column, the presence of one or more paracotylar foramina, a condyle and cotyle that are relatively small (compared to Constrictores) and circular to ovoid and elongate in cross section, and well-developed paralymphatic channels that define the lateral margins of a distinct hemel keel (Holman, 2000; Head et al., 2016).

Remarks. The vertebral morphologies of Caenophidians is markedly different from that of Booidea, including many of the most notable components of a snake vertebrae (e. g., neural spine, centrum, synapophyses, etc.). The works of Head (2015) and Head et al., (2016) to provide fossil calibration dates for snakes also summarize the morphological synapomorphies that differentiate these groups after the taxonomic restructuring of Caenophidia by Zaher et al. (2009), and Constrictores by Pyron et al. (2014), and Georgalis and Smith (2020).