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RE: turtle origins?

> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Joshua Dyal
> I have to admit to guilt in being out of the "turle loop" but when did
> they get moved into Diapsida?  I thought the turtles were considered to
> be anapsids.

The turtle origins debate is actually one where there remains no good
consensus.  Unlike the case of bird origins, there is abundant conflicting
data for the sister group of turtles.

Among the main possibilities (below, Sauria = all descendants of the most
recent common ancestor of Lepidosauria and Archosauria):
Turtles are outside Sauria, and are the sister group to procolophonids
(Reisz & Laurin).
Turtles are outside Sauria, and are highly derived parieasaurs (Lee).
Turtles are saurians, are the sister group to sauropterygians, and are
lepidosauromorphs (Rieppel).
Turtles are saurians, are the sister group to sauropterygians, and are
Turtles are saurians, and are pseudosuchian archosaurs (based on Blaire &
Hedges) molecular data.

One position previously suggested, that turtles are outside Synapsida +
Diapsida, has not held up at all under morphological studies and most (all?)
molecular studies.

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-314-7843