Journal of Paleontology, 87(4), 2013, p. 612–634 Copyright Ó 2013, The Paleontological Society 0022-3360/13/0087-612$03.00 DOI: 10.1666/12-149 A DIVERGENCE DATING ANALYSIS OF TURTLES USING FOSSIL CALIBRATIONS: AN EXAMPLE OF BEST PRACTICES WALTER G. JOYCE,1,2 JAMES F. PARHAM,3 TYLER R. LYSON,2,4,5 RACHEL C. M. WARNOCK,6,7 7 AND PHILIP C. J. DONOGHUE 1Institut fu¨r Geowissenschaften, University of Tu¨bingen, 72076 Tu¨bingen, Germany, ,
[email protected].; 2Yale Peabody Museum of Natural History, New Haven, CT 06511, USA; 3John D. Cooper Archaeological and Paleontological Center, Department of Geological Sciences, California State University at Fullerton, Fullerton, CA 92834, USA; 4Department of Vertebrate Zoology, Smithsonian Institution, Washington DC 20013, USA; 5Marmarth Research Foundation, Marmarth, ND 58643, USA; 6National Evolutionary Synthesis Center, Durham, NC 27705, USA; and 7Department of Earth Sciences, University of Bristol, Bristol, UK ABSTRACT—Turtles have served as a model system for molecular divergence dating studies using fossil calibrations. However, because some parts of the fossil record of turtles are very well known, divergence age estimates from molecular phylogenies often do not differ greatly from those observed directly from the fossil record alone. Also, the phylogenetic position and age of turtle fossil calibrations used in previous studies have not been adequately justified. We provide the first explicitly justified minimum and soft maximum age constraints on 22 clades of turtles following best practice protocols. Using these data we undertook a Bayesian relaxed molecular clock analysis establishing a timescale for the evolution of crown Testudines that we exploit in attempting to address evolutionary questions that cannot be resolved with fossils alone.