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Pterosaurian Pedal Clinching (Batman! :) )



Andrea Kirk wrote:

<...For example, were pterosaurs arboreal? Could their
feet lock on a perch like a bird's? Or did they evolve
from a known arboreal animal?>

  Given either of the two theories regarding pterosaur
evolution, one being the archosaur derivative, and the
other lepidosauriform derived, both have ancestors
that could be and probably were, scansorial or
arboreal.

  1) Archosaurian [Ornithodiran, to be exact
(Gauthier, 1986) == Pterosauria + Dinosauria } ] where
the closest common ancestor of either group would be
*Scleromochlus* (Benton, 1999). All three demonstrate
a fundamentally similar pelvic and hindlimb
proportions basally, but these features are also seen
in basal crocodiles and basal archosauromorphs, so
pish, this is plesiomorphic. *Scleromochlus* has
remarkably short forelimbs, and magnificently long
legs, more so than in *Marasuchus*, and definitely
moreso than in *Eoraptor* or Herrerasauridae or any
dinosaur or theropod since, with the possible
exception of certain predaceous gruiforms or
struthioniform paleognathans, and definitely
tyrannosauroids.

  2) Lepidosauriform (see work by Peters, both
published and on-line), where the ancestor is
lizardlike and steadily elongated the forelimbs rather
than the hindlimbs, as in archosaurs, with the
exception of some certain maniraptorans (i.e.,
*Sinornithosaurus*).

  Both groups have fundamentally similar feet with
large ankles and uncompressed metatarsals having a
divergent fifth toe. The digits are long and unreduced
except in select lineages (being some crocodiles, lots
o' dinos, snakes [of course], and a few other limbless
things). Now, harkening back to a couple of posts
earlier this year, pterosaurs can most probably climb,
having large manual claws in the "rhamphorhyncoid"
lineages, and being relatively small with the largest
members having only a 5ft or so wingspan (see
Welnhoffer, 1991) they had a small enough mass to take
to the branches without being in danger of breaking
them. Given the local Solnhofen flora as being perhaps
fern- and/or cycad-based, "elephant-ears" could
possibly support the weight of smaller pterosaurs
(like those I mention) but not the larger ones.
Incidentally, the largest *Rhamphorhynchus* specimens
are bigger than the largest *Pterodactylus* specimens
(see Welnhofer, again) so don't get cladistic on me
when it comes to find the "arboreal clades" (pun
intended).


=====
Jaime "James" A. Headden

"Come the path that leads us to our fortune."

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