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Re: Pterosaurian Pedal Clinching (Batman! :) )



-----Original Message-----
From: Danvarner@aol.com <Danvarner@aol.com>
To: dinosaur@usc.edu <dinosaur@usc.edu>
Date: Wednesday, October 06, 1999 2:24 PM
Subject: Re: Pterosaurian Pedal Clinching (Batman! :) )


>In a message dated 10/6/99 9:54:44 AM Pacific Daylight Time,
>larryf@capital.net writes:
>
><< As Padian proposed it, these forms were considered to be "cursorial",
and
>that the evolution of pterosaurs was from the "ground-up" as also proposed
>(by some) for birds. >>
>
>  Question: Can anyone cite the reference for Jim Clark's recent pub about
>the Dimorphodont pes from Mexico that precludes cursorial habitus? All I've
>seen is a brief note in Discover Magazine. DV.
>

Walk this way
Henry Gee
Pterosaurs were flying reptiles that became extinct 65 million years ago,
along with non-flying dinosaurs and many other animals. Their ability to fly
is not in doubt (flying pterosaurs are known that range in size from
sparrows to small aircraft) but how did they move when they were on the
ground? Were they fleet-footed runners, sprinting along on their toes? Or
were they waddling, four-footed sprawlers, like bats?

This has been the source of heated debate among palaeontologists for
decades. In the 19 February 1998 Nature, James Clark of George Washington
University and his colleagues present new evidence in favour of the
four-footed sprawling theory. A new specimen of the crow-sized primitive
pterosaur Dimorphodon, discovered by Clark and colleagues in Mexico, shows
that it was probably flat-footed. If it had even tried to walk on its toes,
it would have dislocated its ankles and every joint in the foot.

The trouble with pterosaurs is that their bones were very lightly built,
often no more than hollow, thin- walled tubes. This means that they
fossilize poorly. If found at all, the bones are usually squashed flat. This
makes it very difficult to reconstruct their limbs and learn how they could
have moved in real life.
                   (lots more snipped)

Here ya go Dan! (8^S) Had to find it again on the internet, caused I
F-disked and erased everything (including recent email). What you seek is
probably the Nature article within. Thanks for "cluing me in" to Clark`s
arguement.

By the way, both Padian and Peters think that the digits of the pes DO flex
enough to permit a bipedal stance....(contra Clark)!