Fossil calibration dates for molecular phylogenetic analysis of snakes 1: Serpentes, Alethinophidia, Boidae, Pythonidae

Abstract

Snakes possess a dense fossil record through the Late Cretaceous and Cenozoic and are an important clade for studies of molecular phylogenetics. The use of the snake fossil record has historically been a limited and inaccurate source of temporal data in molecular studies due to taxonomic and phylogenetic ambiguities. Here I provide 10 fossil calibration dates for phylogenetic analysis of higher-order interrelationships of snakes. Calibration points include apomorphy-based systematic justifications and precise dates for hard minimum divergence timings. Calibrated nodes are for the snake total clade, Alethinophidia, and boid and pythonid taxa. Hard minimum divergence timings range from earliest late Cretaceous to middle Miocene. These dates provide precise minima for constraining the early evolutionary history of Serpentes. Comparisons of phylogenetically justified calibrations with published studies that employed form-taxon assignments suggests greatly younger divergences for justified nodes and indicates that deep-time divergence estimates that have been correlated with tectonic histories may be considerably too old and reliant on presumptions of Early Cretaceous Gondwanan vicariance as a mechanism of speciation. Jason J. Head. Department of Earth and Atmospheric Sciences and Nebraska State Museum of Natural History University of Nebraska-Lincoln, Lincoln, NE 68588-04340. Jhead2@unl.edu.