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Re: Rauisuchids and Thecodonts



>Is Thecodont a term that encompasses such animals as the Rauisuchids and
>Phytosaurs? Or are Thecodonts a separate group with representatives such as
>Euparkaria?

Essentially, "thecodont" means any archosauromorph which is not a dinosaur,
bird, pterosaur, or crocodile, so the answer is yes to the first question,
no to the second.  Most paleontologists today no longer use the term
"thecodont" in a phylogenetic sense, recognizing that traditional
thecodonts fall in three places in the archosaur family tree:

Crurotarsi:  crocodiles and their relatives, including most of the
traditional "thecodonts" (phytosaurs, rauisuchians, aetosaurs, etc.)

Ornithodira: Dinosaurs, pterosaurs, and their closest relatives, such as
Marasuchus (formerly Lagosuchus) and Lagerpeton

and those archosauromorphs which diverged before the Crurotarsi-Ornithodira
split, such as Euparkeria, Proterosuchidae, Erythrosuchidae

>
>Also, did Phytosaurs continue on into the late Mesozoic along with
>crocodilians, or did they succumb at the T-J boundary?

There are no post-Triassic phytosaurs (or parasuchians) described, and in
fact there is no definitive evidence that they even made it to the Tr-J
boundary.

                                
Thomas R. Holtz, Jr.                                   
tholtz@geochange.er.usgs.gov
Vertebrate Paleontologist in Exile                  Phone:      703-648-5280
U.S. Geological Survey                                FAX:      703-648-5420
Branch of Paleontology & Stratigraphy
MS 970 National Center
Reston, VA  22092
U.S.A.