Re: Prosauropod cladistics

[Tom Holtz <tholtz@geochange.er.usgs.gov>]

>Anyone like to take a stab at prosauropod phylogeny??
>The prosauropods have always been a confusing group of dinosaurs.
>Some researchers place them as direct ancestors to sauropods, and some
>as a sister group to the sauropods (with a common ancestor representing
>the Phytodinosauria).  Would love to hear anyones theories or how they
>work out the cladistics for these unique creatures.

Prosauropod cladistics: I don't know of anyone's whose broached that
subject since Galton's chapter in Weishampel et al.'s _The Dinosauria_.  He
has several monogeneric "families" and some "families" for which monophyly
is questioned (taxonomic practices which I try to avoid), the structure
seems reasonable enought to me.  It is certainly an interesting subject,
and maybe there's a graduate student out there working on it.

Phytodinosauria:  Actually, phytodinosaurs are not just sauropods and
prosauropods.  Sauropods and "prosauropods" (whether a monophyletic
Prosauropoda or a series of outgroups to Sauropoda) are grouped into the
Sauropodomorpha.

Phytodinosauria is a group named by Bakker in 1986, suggested by Bakker and
Galton in the '70s, Sereno in 1984, and Paul in 1988 (I don't know of any
more recent support).  The "Phytodinosauria Hypothesis" stands in contrast
to the "Saurischia Hypothesis".  In the first, Sauropodomorpha and
Ornithischia share a more recent common ancestor than either does with
Theropoda.  The sauropodomorph-ornithischian clade is "Phytodinosauria".
In the second hypothesis (the one favored by most dinosaur
paleontologists), Theropoda and Sauropodomorpha share a more recent common
ancestor with each other than with Ornithischia.  The theropod-sauropod
clade is "Saurischia".

[To my knowledge, no one has suggested a theropod-ornithischian clade.]

                                
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.