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Re: Pterorhynchus dewlap
Ebel's work aside (it's been discussed before on the list, as far as
I recall), I wonder if any pterosaurs could submerge (partially or
completely) for brief periods?
Interesting. I'm sure birds don't have a patent out on water repellent
coverings of wings. Not knowing more about the nature of the
integument of pterosaur wings (could velvet or waxy coating be ruled
out?), I would guess that any lineage of flying animals that have to
deal with the aquatic environment over such a long period of
geological time could have perfected this, as birds have, which I
suspect is a major reason they can dive and then escape the water to
launch back into the air.
I suspect that pterosaurs did not have much ability to swim underwater,
but not because of waterproofing issues. The hindlimbs of pterosaurs
are not well constructed for subaqueous foot-propelled paddling (there
is some possibility of surface swimming, though even that seems
dubious). Mostly, the hindlimbs are simply not as robust as would be
expected for extended paddling.
That leaves the forelimb, and I sincerely doubt that pterosaurs could
have managed amphibious flight given their wing structure. First off,
the wings are far too lengthy (long moment arm), and much to fragile at
the distal end. Additionally, the bone stiffness is rather low in the
distal wing bones (despite maintaining high strength), especially in
pterodactyloids. I'm also not certain if pterosaurs could manage a
power upstroke (I don't just mean an active upstroke, but a fully
powered one). In fact, pterosaurs probably used passive upstrokes (as
part of a continuous vortex gait) most of the time, given their size
Of course, shearwaters (soaring birds related to albatrosses, but much
smaller) manage amphibious flight with long wings. However, they have
thickened bone cortices (compared to non-diving procellariiforms),
flattened humeri, and they flex the handwing back almost 90 degrees
(ie. at the wrist) during swimming. Shearwaters are also not
particularly large (around 1 kg).
Bats are also not good divers, even those that hunt aquatic prey
(though some can take off from the surface, albeit with difficulty).
This is not to draw an serious parallels between pterosaurs and bats
(which have practically polar opposite flight modes), but to point out
that for 2/3 groups of flying vertebrates, despite dealing with the
aquatic environment in some way, subaqueous diving simply never shows