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Re: pterosaur test - I mean debate



Here are my views on those questions I understand well enough to have an
opinion on. ;-)

>1.  Are pterosaurs dinosaurs, ornithodires or derived eosuchians close to
>protorosaurs?

I don't beleive they were dinosaurs (unless you redefine the meaning of
"dinosaur". The earliest known pterosaurs are fully developed, so there are
obviously a lot of missing links. I suspect that they evolved from 
tree-dwellers - the archosaur equivilent of flying squirrels.

>2.  Were pterosaurs bipedal or quadrupedal or both?

I would have to say largely quadrupedal. Rhamphorhynchoids could probably
have ran on their hind legs for short distances. Since pterodactyloids did
not have a tail as a counterbalance, the only way I could see them walking
bipedally is by opening their wings and facing into the wind (such as during
take-off).

>4.  Are Pteraichnus tracks pterosaur tracks?

I doubt it. The three-fingered prints, supposidely of the forelimbs, imply
that the pterosaur is walking on its fingers. I don't think this is likely
if they were supporing the weight of a wing.

>6.  What was the function of the 5th toe of rhamphorhynchoids?

If they developed from tree-dwelers, lots of toes would be an advantage for
clinging to branches.

>7.  Did rhamphorhynchoids have a uropatagium between the hind legs?

If a uropatagium is an extension of the flight membrane then I would say
that the early members had, but as they evolved it gradually receded as the
wings became sufficient on their own.
If not then I dunno. ;-)

>8.  What was the exact shape of the pterosaur wing membrane and how was it
>tensioned?

Shame I can't draw it! With rhamphorhynchoids I think it extended down below
the knees. In pterodactyloids I don't think it would have been as wide and
would probably have stopped close to the hips. Pterodactyloids had
relatively longer wings and therefore could maintain flight with a narrower
wing. A longer, narrower wing can provide more upwards force for the same
energy input, but has to undergo greater stress.

>9. Why did the 5th toe and tail become reduced in pterodactyloids?

Simply because they weren't needed any more. Many of the rhamphorhynchoids
could have been tree-dwelling, where both toes and a tail are an advantage.
The large pterodactyloids obviously weren't (I'm not sure about smaller
ones). The tail would obviously have given a considerable amount of
stability in flight, but at the cost of additional drag. A pterosaur which
can maintain stable flight without a long tail would have an obvious
competitive advantage over one which can't.

>10.  Are there any flightless pterosaurs?

None that are obvious from the fossil record. Pterosaurs would appear to
have been very ungainly on the ground. Floghtless pterosaurs would have been
very susceptable to predators (and there were plenty of those in the
Mesozoic). For a flightless pterosaur to evolve, it would have to have been
trapped on an island where there were no predators.

Oh, I only missed one. Maybe I'll get enough right to scrape a pass! ;-)

James Shields