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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: email@example.com Phone: 301-405-4084
Office: Centreville 1216
Senior Lecturer, Vertebrate Paleontology
Dept. of Geology, University of Maryland
Faculty Director, Science & Global Change Program, College Park Scholars
Mailing Address: Thomas R. Holtz, Jr.
Department of Geology
Building 237, Room 1117
University of Maryland
College Park, MD 20742 USA