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Re: where do proterochampsids belong?



----- Original Message ----- From: "david peters" <davidrpeters@earthlink.net>
Sent: Thursday, July 07, 2005 7:46 PM


Here's what the literature says:
(if I missed any let me know).

Gauthier 1986
Proterochampsidae derived from Erythrosuchidae, outside of Parasuchia +
Suchia

I assume you don't mean "derived from" literally, but that instead you mean that Erythrosuchidae is the sistergroup of (Proterochampsidae + (Parasuchia + Suchia)) (or that Proterochampsidae is "more derived than" Erythrosuchidae... though this common wording isn't automatically correct). Let's illustrate that more graphically...

--+--Erythrosuchidae
 `--+--Proterochampsidae
    `--+--Ornithodira, right???
       `--Crurotarsi... sorry, Crocodylotarsi
            |--Parasuchia
            `--Suchia

Benton and Clark 1988, Benton 1990, Bennett 1996
Proterochampsidae derived from Erythrosuchidae, outside of Euparkeria

I guess this means...

--+--Erythrosuchidae
 `--+--Proterochampsidae
    `--+--*Euparkeria*
       `--+--Ornithodira
          `--Crurotarsi

...which is identical to the findings of Gauthier, except for the positions
of *Euparkeria* and Ornithosuchidae (not shown).

Sereno 1991
Proterochampsidae derived from Euparkeria, outside of Ornithodira +
Parasuchia

--+--Erythrosuchidae `--+--*Euparkeria* `--+--Proterochampsidae `--+--Ornithodira `--Crurotarsi

Differs from Benton & Clark, Benton and Bennett in one feature -- *E.* and
Proterochampsidae have switched places.

Parrish 1993,
Proterochampsidae derived from Euparkeria, outside of Ornithodira

Identical to the above, no? Or did he find Proterochampsidae inside Crurotarsi (an arrangement I've never heard of)?

Benton 1999
Proterochampsidae and Euparkeria are basal to all other traditional
archosauriformes (proterosuchids and erythrosuchids not listed).

P. and *E.* in this order? If so, then this is identical to Benton's earlier analyses. If it's the other way around, it's identical to Sereno's.

Question is: which is correct?

So we have here two almost identical phylogenetic hypotheses. Two decide, I'd look for an analysis that includes animals like *Turfanosuchus* and *Yonghesuchus*. Therefore, for the time being, I'd go with what I wrote about the *Yonghesuchus* paper, with the caveat that that paper mentions only a few characters and doesn't include an analysis.