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Re: climbing dromaeosaurs and friends




Chris Bennett wrote:

> I argued that the fact that pterosaurs could have their hindlimbs preserved
> both ways indicated that their hip joint was more mobile than that of
> Archaeopteryx, and furhter that this was because in pterosaurs the hindlimb
> was extended out in the plane of the wing and was involved in wing function.
> I also suggested that the hindlimbs were more often splayed out, unlike
> Archaeopteryx, because the wing membrane would tend to pull them out
> laterally.

Although I don't agree with Chris that the hindlimb of ALL pterosaurs was
necessarily involved in wing function, I do agree that it may have been, and in
cruise flight, the hindlimb was almost certainly extended out in the plane of
the wing as he suggests, at least to the knee, no matter what the trailing edge
attachment of the wing.  There appears to be some possibility that in some
pterosaurs, outboard of the knee, the tibia and pes may have angled back to some
degree, perhaps with an included angle on the loose order of about 127 degrees
which minimises total drag for most configurations. Though it is possible that
the hindlimb was involved with with the wing function in all pterosaurs.  It
would appear to have substantially reduced the soaring efficiency and potential
migration ability of the larger pterosaurs, so I'd like to see it investigated
further.  And of course, during cruise the leg would likely have been carried in
much the same position for either configuration, outboard subparallel to the
wing to at least the knee.

Chris, I hope my paraphrase of your position isn't a mistatement.  If so, I
apologise, and please correct me.  I greatly admire your work, and someday would
like to see you address possible membrane loadings and attachments between the
wing membrane and the hindlimb.  For the larger pterosaurs, I'm interested in
ways that the wing membrane might have hooked to the leg while maintaining
reasonable attachment stresses and sustainable muscle loads at the pelvis.

All the best,

JimC