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thoughts on Pterasaur feet
I've never been happy with long-5th-toed pterasaur feet reconstruction.
Couple of weeks ago I asked Kevin Padian for some references for them.
I was asking him why he's restored them as rear-pointing toes with his
bipedal models of pterasaur locomotion (something I don't like since
there's no strength in the articulation of the foot in this position.
He said there was lots of play in the articulartion of this toe. He
mentioned that Dave Peters doesn't restore them this way, that he thinks
they were used like the reinforciing bone-spur on the
tail-to-foot-membrane of a bat.
I've been thinking about this. I've dragged out my copy of THE
ILLUSTRATED ENCYCLOPEDIA OF PTERASAURS, Wellnhofer, 1991 edition.
I've been looking at toe bones in the specimen photograghs, and have
noticed that, as Wellnhofer mentions, the undisturbed specimens with the
long toe have the toe pointing towards the tail. In addition, in the
case of these specimens, the long toe is always in similar orientation
to the wing, INCLUDING FOLDS OR BENDS OF THE WING.
The wing is folded in the specimen of Dorygnathus (photo pg 15) which
was shoen also in x-ray in the book. The left wing is folded at the
wrist, and further down the long finger of the wing probably at the
second phalange from the wrist (not in either photo) there is another
fold-probably not natural to the animal. The long-toe on the left foot
is in nearly-identical orientation and is also folded in nearly the same
position as the wing with similar angles to each bend, forming a very
tidy triangle. The right foot's long toe is the exact mirror image.
The specimen of Peteinosaurus zambelli (the one with no skull-photo pg
66) has a broken (left?) wing in that the long finger has folded back
over the wrist the wrong way, but if it was oriented in it's natural
position to the way the body lies in the slab, the left long-toe again
would have a similar orientation and fold pattern.
The left and right wings are also flipped over from their normal
position over the back of the wrist on the specimen of Rhamphorhynchus
longicaudus (photo pg 82) and again, if placed in it's proper
orientation to the body the long-toes are in similar orientation again.
The juvenile Scaphognathus (photo pg 91) has a very non-typical position
of the wings in death, perhaps flattened-out while in the animal was in
a quadrapedal position with the elbows up behind the back, but the
long-toe of the left foot >seems< to be lying along the plane of the
foot with a curve similar to the left wing in flight.
Anurognathus ammoni (photo pg 93) was very split-legged in pose compared
to the mostly-folded position of the wings, but again the long-toes of
each foot are in a similar position and orientation to the wings.
Sordes pilosus (photo pg 101) has the long-toe of the right foot folded
into a triangle again with similar orientation to the wing.
The Rhamphorhynchus specimen (photo pg 149) has a badly-folded body with
strangely undisturbed wings and again the curve and position of the
long-toe (of which ever foot is preserved sticking above the wings) echo
the position of the wings.
If these particular examples are of well-preserved, undisturbed bodies,
isn't it a rather important piece of information that this toe orients
WITH the WING, NOT the FOOT, and that this should lead somebody to the
conclusion that this toes' primary function was NOT as an aid to
digigrade or plantigrade locomotion??
I'm not saying there was any big, fancy membrane attach it to the wing.
There's no evidence of one where fossilization HAS preserved webs
between the other toes. I think the long-toe was similar to how
Professor Manfred Reichel had restored them (illustration pg 169) but
with more reduced membranes than even he shows here. I don't know what
it's function was, or what benefit it would be to the animal, but to
restore the toe as a functional digigrade reversed toe is just plain out
wrong. The way Reichel had restored it simply fits in with the evidence
of the toe itself.
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