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Re: Pterosaur relationships



 
-----Original Message-----
From: David Marjanovic <david.marjanovic@gmx.at>
To: The Dinosaur Mailing List <dinosaur@usc.edu>
Date: Wednesday, September 27, 2000 2:58 PM
Subject: Pterosaur relationships

Maybe this topic should not be discussed on this list, but the current view of Ornithodira has become so entrenched that e. g. The Dinosauricon includes pterosaurs. My question is: What are, to date, the arguments for pterosaurs being close relatives of dinosaurs rather than Prolacertiformes?
A website providing the evidence for (Prolacertiformes + (Langobardisaurus + (Cosesaurus + (Sharovipteryx + Pterosauria)))) is http://home.stlnet.com/~azero/Pterosaur_homepage. The evidence presented there is quite compelling, but the usual hypothesis makes some sense (e. g. one origin for ?bipedalism, ??digitigrady and endothermy), so I'd like to know whether we really have to abandon it.
 
Padian gives an interesting synopsis of the features relating pterosaurs to dinosaurs, (as well as possible links to lagosuchians and scleromochlus) in his article titled:"The Origin of Pterosaurs" (1984) Third Symposium on Mesozoic Terrestrial Ecosystems" Wherin he states..."Like dinosaurs,pterosaurs have unusually large skull openings. The presacral vertebral column is regionalized into three distinct segments(cervical, cervico-thoracic, and lumbar: see Bonepart 1975). The scapular is long, straplike, and not distally flared; the coracoin is longer than wide. There are at least three sacral vertebrae, and possibly four.  The femur has a "fully off-set head"(Charig 1972)........" yada yada yada(although a short, and interesting paper, can`t copy it all here!)
 
For an even more detailed analysis of synapomorphies linking ornithodirans check out Sereno`s papers : "Dinosaurian Precursors from The Middle Triassic of Argentina:Lagerpeton Chanerensis" Sereno and Arcucci JVP 13 (4):385-399, Dec 1993
 
and "Dinosaurian Precursors from The Middle Triassic of Argentina:Marasuchus Lilloensis,Gen. Nov." Sereno and Arcucci JVP 14 (1): 53-73, Mar 1994.
 
I don`t know if any of these authors believes in one origin for "bipedalism, digitigrady, or endothermy', but personally, I favor a non-convergent view of these traits........and, for a possible alternate view (strictly my own ...it seems...8^) of phylogeny that might link prolacertiforms to pterosaurs, as well as birds and dinosaurs, check out my website at: http://www.capital.net/~larryf/