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Re: EARLY EVOLUTION OF 'BIRDS'
At 04:19 PM 11/8/98 -0000, John V Jackson wrote:
>--Original Message-- From: Stanley Friesen <firstname.lastname@example.org>Date: 08
>>It needn't be all that weird.
>>A) Most Jurassic pterosaurs are found in only two or three lagerstaetten,
>>all lakes or lagoons.
>>B) Pterosaurs can fly, basal maniraptorans most likely could not. Ergo,
>>pterosaurs are more likely to die where they can end up in a lake than are
>>the terrestrial mani's.
>Yes, but the issue is not "Where are the pterosaurs?" - I
>brought those up to show the J wasn't that bad compared to the
>K. I know some animals really don't preserve well - the *true*
>ancestors of Archae for example, but the real issue is "Where
>are those larger terrestrial/'cursorial' maniraptorans?"
Who says there *were* any? The basal maniraptorans seem to be small forms,
so it is quite likely that the entire pre-Cretaceous maniraptoran lineage
is composed of small animals. (In fact I suspect that most maniraptorans -
at ALL times - were arboreal as well, and that the known Cretaceous
maniraptorans are very atypical, even for that time, in being large and
That is why the taphonomic factors matter. Small, non-flying (or
semi-flying) arboreal/terrestrial forms are FAR less likely to be preserved
in the fossil record than similarly sized flying forms - especially if
those flying forms were aerial insectivores that regularly flew over the
water to feed. Thus the near absence of maniraptorans in the Jurassic may
be a simple, and quite normal, artifact of known and prosaic taphonomic
[Note, even if the early maniraptorans were gliders, as George suggests,
they would not be feeding "on the wing", as most of the Solnhofen
pterosaurs probably were: swifts, swallows, and ducks are more likely to be
preserved than flying squirrels, or even parrots; the Solnhofen pterosaurs
were apparently the swift and falcon equivalents of the Jurassic].
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