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Re: To climb or not to climb



>-----Original Message-----
>From: Jaime A. Headden <qilongia@yahoo.com>
>To: dinosaur@usc.edu <dinosaur@usc.edu>
>Cc: larryf@capital.net <larryf@capital.net>
>Date: Friday, December 18, 1998 3:23 AM
>Subject: Re: To climb or not to climb


>>Larry Febo wrote:
>>
>><This may also have been a reason for the apparent decline of smaller
>>pterosaur species in the Cretaceous, a loss of habitat. I can see
>>pterosaurs landing on long springy Cycad type leaves, but not upon
>>angiosperm branches (I think they lacked that precise
>>maneuverability). They may have been confined to relatively tropical
>>areas that sported cycads, until outcompeted even on their own turf by
>>the evolving avian form.>
>>
>>  How would apparently more ungainly pterosaurs manage on springy,
>>flexible, bend under its weight, cycad fronds more lilkely than firmer
>>angiosperm branches? And what about gymnosperms (conifers et al.)?
>>While agreeably the only comparative habitat of bird/pterosaur we have
>>is the Solhofen, with low-laying plants and possibly short trees, does
>>that neccesarily preclude incapability of landing in trees (real
>>trees, not cycads)?



I see pterosaurs as being not only not nearly as maneuverable as modern type
(perching birds), but as being somewhat top-heavy as well, causing landing
on their forepaws as well as hind (due to forward momentum and large
crania). The feet (of some of the Rhynchoidea) seem adapted to climbing the
spines of the compound leaves in a ladderlike fashion.

What about the Gymnosperms? As Tom Holtz pointed out, I should have used the
more concise  term Conifer (maybe I`ll get flak here too as I`m certainly no
botanist!). Gymnosperms also include the earlier "tree ferns" which the
pterosaurs could have negotiated as well. As such, the more "prickley"
conifer types began evolving into larger tree forms in the early Triassic
(so I`ve read) and by the end of the Jurassic were taking preceedence over
the Cycads in geographic range. If you see "Aves" as starting with
Archaeopteryx, then you can say the conifer enviornment was already well
established, If you see Avian origens as beginning back in the Triassic (as
I do), there might have been smaller areas of such conifers where birds
could develope in isolation from (pterosaurs and out of direct
competition)...again, ...just my speculation.

As far as the Solnhofen enviorn, I`m not so sure Archae was that great a
flier. Could have secondarily lost some abilities. I think it might have
flown short distances to the tree tops, as a pheseant might have flown up to
roost. (Probably more maneuverable than pterosaurs though).