Fossil calibration dates for molecular phylogenetic analysis of snakes 2: Caenophidia, Colubroidea, Elapoidea, Colubridae

Caenophidia, the snake clade that includes the highest species richness, morphological diversity, and ecological breadth within Serpentes, has been extensively studied with respect to molecular phylogenetic systematics. The majority of the caenophidian fossil record, though dense, has been taxonomically defined on the basis of general anatomical similarity or shared geographic provenance with extant reference taxa. As a result, historical patterns of diversification within the clade are poorly constrained due to a paucity of reliable fossil calibration dates. Here we provide 10 fossil calibration dates for phylogenetic analysis of caenophidian relationships. Calibration points include apomorphy-based systematic justifications based on cranial and precloacal vertebral elements and precise dates for hard minimum divergence timings. Calibrated nodes are for Caenophidia, Acrochordus, Elapoidea, Colubridae, and constituent sub-clades. Hard minimum divergence timings range from late Cretaceous to Miocene. The spatial and temporal distribution of reliable first occurrence of colubroid taxa suggests late Paleogene intercontinental dispersals between Asia, North America, and Africa, followed by rapid diversification and subsequent dispersals into all non-Polar continents by the early Neogene.