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answers to the bipedal ptero challenge



Scott wrote:

Dave,
     I'll try to get a better character list later (I have to be in
class in 20
minutes)

but 1) pterosaurs can't move bipedally like dinosaurs because they a)
don't
have their center of gravity in the right place for a horizontal
posture,

>> answer: IMHO the center of gravity in pterosaurs is close to the
notarial section of the dorsal series, just posterior to the glenoid.
The toes can be brought beneath this point in a balanced bipedal pose. I
can send you drawings if you still doubt. If the center of gravity were
near the hips, as in theropods, then pterosaurs probably could not
fly.<<

b)
fail to enlarge their illia anteroposteriorly like theropods do.

>> answer: IMHO, pterosaur ilia are enlarged anteroposteriorly as in
theropods, incorporating more than the diapsid minimum of two sacrals.
In Pteranodon I think the number reaches ten and in ctenochasmatids the
posterior ilium is elongated as much as the anterior portion.


2) they don't show the adaptatins to upright bipedalism seen in
hominids,
especially the double curve in the sacral series.

>> answer: IMHO this is a different sort of bipedalism. Not of the
diapsid sort and so is not a good analogy.


.