An updated paleontological timetree of lissamphibians, with comments on the anatomy of Jurassic crown-group salamanders (Urodela)

Abstract

We present an update of our time-calibrated supertree of extant and extinct lissamphibians (Marjanović D, Laurin M. 2007. Fossils, molecules, divergence times, and the origin of lissamphibians. Syst Biol 56(3):369–388) and of the divergence dates that can be inferred from it. The present version contains 319 extinct species or possible species of lissamphibians, compared to 223 previously. Discoveries of new fossiliferous sites, advances in phylogeny and recently obtained radiometric dates have offered opportunities to test our results, including the conclusion that the fossil record of Lissamphibia is dense enough to provide reliable calibration constraints for molecular divergence dating. By and large, the results are upheld. Some of the divergence dates we infer from the tree are up to 15 Ma younger than we previously published, some are up to 15 Ma older, some have had their range of uncertainty drastically reduced and the maximum age for the origin of Urodela (the salamander crown group) is no longer well constrained. The dermal bone plates in the gill region of the Jurassic urodeles Beiyanerpeton, Seminobatrachus and Chunerpeton and the grooves for the lateral line organ on the skull of the first require either unexpected reversals or several independent losses in other lissamphibians and indeed other urodeles.

Keywords::

• Lissamphibia
• Caudata
• Urodela
• supertree
• timetree
• calibration

Acknowledgements

Eduardo Ascarrunz, Michael Wuttke, James Gardner and Florian Witzmann kindly provided electronic reprints, Susan Evans kindly sent one on paper. Borja Sanchiz and an anonymous reviewer made helpful comments; the former additionally made us aware of literature we had overlooked and explained the current state of the Opisthocoelellus confusion to us. D.M. is benefitting from a postdoctoral grant by the Alexander von Humboldt Foundation; M.L. is financed by the CNRS and French Ministry of Research grants to UMR 7207.