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Re: Trialestes, dino? croc? or proud parent to both?



Thanks, Jamie,

I understand what you are saying. But all you have to do is plug enough taxa 
into a cladogram and you'll find Turfanosuchus and Trialestes fall outside of 
the croc/dino split: Pre-Pseudhesperosuchus/Scleromochlus/Gracilisuchus, etc. I 
don't know of any more primitive crocs than those. Be glad to know them though, 
if they are reasonably intact.

The exception might be that the new data, if valid and referrable, pushes 
Trialestes into the Croc clade. We'll see. And if so, that's okay. That's why 
it's good to leave some question about it currently.

The dino/ptero split occurred somewhere around Casineria, 100 million years 
earlier. So, not a factor. 

Perhaps Clark et al. would have been more enthusiastic with their referrals if 
they had had a decent cladogram to start with. So many taxa are enigmas with 
the current trees. That can be fixed with more work. 

David Peters
St. Louis

 



-----Original Message-----
>From: "Jaime A. Headden" <qilongia@yahoo.com>
>Sent: Sep 4, 2007 11:22 AM
>To: dinosaur@usc.edu
>Cc: david peters <davidrpeters@earthlink.net>
>Subject: Re: Trialestes, dino? croc? or proud parent to both?
>
>Dave Peters (davidrpeters@earthlink.net) wrote:
>
><That's what I like to see. Corroborating evidence. Would love to see some pix.
>Thanks for the reference Tim!>
>
>  I don't have access to this at the moment, but I would contend against the
>post's subject line, since it is assuming the nature of the features without
>understanding the fossil or its application. Then again, I've read most, if not
>all, of the papers in Clark et al.s bibliography on the subject, and the group
>to which *Trialestes* is referred or suggested in referral to is dear to me.
>
>  In this case, you get a particularly elongated forelimb with elongated
>carpals, a perforated acetabulum, and the vertically arranged hindlimb. These
>are not at odds with a crocodylian, especially one associated with a
>particularly fascinating group such as the "Sphenosuchia." Note that there are
>grades of this group, which may be cladistically defined, or simply left as is
>until more material is found. Crocs like *Dibrothosuchus*, *Hesperosuchus*,
>*Psuedhesperosuchus*, and *Terrestrisuchus* are all particularly gangly-limbed,
>terrestrial, "running" crocs, and all of them show pelvic, femoral, scapular,
>and forelimb adaptations for cursoriality, a topic I may eventually become able
>to address in detail. These crocs are also well-nested within Crurotarsi, and
>in fact Crocodylomorpha as well, and the likelihood they are ancestral to
>anything pterosaurian and/or dinosaurian is remote to unlikely, and dare I say,
>even improbable.
>
>  Clark et al. are understandably cautious in their referrals, though they do
>not approach the topic of speculating heavily, with good reason, the
>crocodilian nature of all three fossils and they're belonging to the same
>taxon. They may well all belong to different crocs, and maybe there's a
>"silesaurid" or some such in there. Yet they may belong to a similar group of
>taxa, but may bear distinct names. Hopefully time and more interesting recovery
>periods in the fossil horizons will provide new and interesting -- and
>hopefully, clarifying! -- data.
>
>  Cheers,
>
>Jaime A. Headden
>http://bitestuff.blogspot.com/
>
>"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)
>
>
>       
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