Re: where do proterochampsids belong?

[David Marjanovic <david.marjanovic@gmx.at>]

----- 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.