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Re: Testing competitive exclusion in birds, bats and pterosaurs
Birds developed the specializations for marine soaring flight within 5
million years of the demise of pterosaurs (different requirements from
terrestrial soaring). I think a speculative case could be made that
pterosaurs may have been excluding birds from this niche.
It does seem quite suggestive, especially given that pelagic birds
apparently existed throughout much of the Cretaceous, but no lineages
(that we know of) generated large-bodied soarers until after the K/T.
Note also that there is still no consensus that all or any pterosaurs
had a wing-hindlimb connection.
Good point. I think morphospace analyses of pterosaurs (like the one
referenced at the start of this thread) sometimes confuse the results
of quadrapedal terrestrial gaits (and their subsequent constraints on
limb proportions) with evidence for a wing-hindlimb connection.
A universal wing-hindlimb connection in all species implies that
pterosaurs were specialized for terrestrial soaring. Unusual in
animals that seem to have been mostly fish eaters.
In addition, the planforms proposed for wings connected to the hindlimb
in pterosaurs tend to be poor even for a terrestrial soaring form, with
both the estimated loadings and aspect ratios often falling well below
those seen in living dedicated thermal soarers. Living raptors and
storks do not have wings nearly as short and broad (nor masses as low)
as some individuals seem to expect. After all, living inland soaring
birds use a number of sources of lift other than thermals, many of
which are better extracted with greater spans and/or higher loadings.
Such species also have to travel between lifting sources at a
reasonable rate. Not to mention that the largest pterodactyloids would
be seriously pushing the limit with regards to being able to stay
within a narrow thermal ring, simply by virtue of total span. Cloud
streets would be much more useful to an animal that size, and I expect
that extracting energy from cloud streets would usually select for a
narrow chord planform.