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Turtles are parareptiles, and Eunotosaurus is their sister


Lyson, T.R., G.S. Bever, B.S. Bhullar, W.G. Joyce & J.A. Gauthier. In press.
Transitional fossils and the origin of turtles. Biol. Lett.   published
online before print June 9, 2010, doi:10.1098/rsbl.2010.0371


The origin of turtles is one of the most contentious issues in systematics
with three currently viable hypotheses: turtles as the extant sister to (i)
the crocodile-bird clade, (ii) the lizard-tuatara clade, or (iii) Diapsida
(a clade composed of (i) and (ii)). We reanalysed a recent dataset that
allied turtles with the lizard-tuatara clade and found that the inclusion of
the stem turtle Proganochelys quenstedti and the 'parareptile' Eunotosaurus
africanus results in a single overriding morphological signal, with turtles
outside Diapsida. This result reflects the importance of transitional
fossils when long branches separate crown clades, and highlights unexplored
issues such as the role of topological congruence when using fossils to
calibrate molecular clocks. 

Thomas R. Holtz, Jr.
Email: tholtz@umd.edu   Phone: 301-405-4084
Office: Centreville 1216                        
Senior Lecturer, Vertebrate Paleontology
Dept. of Geology, University of Maryland
Fax: 301-314-9661               

Faculty Director, Science & Global Change Program, College Park Scholars
Fax: 301-314-9843

Mailing Address:        Thomas R. Holtz, Jr.
                        Department of Geology
                        Building 237, Room 1117
                        University of Maryland
                        College Park, MD 20742 USA