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Re: Theropod herbivory - parallel evolution or one clade?
Scott Hartman wrote:
Jeholornis was certainly a seed eater, and I wouldn't be shocked if
Jinfengopteryx was (although I would be suprised if "Jinfengopteryx" is
actually different enough to be separated from Sinovenator). But niether
is a climber, and Jeholornis was not landing in trees.
I suspect they were all ungainly climbers, but climbed nonetheless. You
have to start somewhere, after all.
These feathered maniraptorans (including _Archaeopteryx_ and other basal
birds; microraptorans; maybe _Protarchaeopteryx_; maybe basal troodontids)
strike me as animals that were heading up into the vegetation, but didn't
want to relinquish their ancestral theropod 'bauplan'. So they could put up
with being poor climbers and/or poor fliers, as long as they were
comfortable running on the ground. Hence the retention of long legs, long
tail, and hand-claws.
I don't see these ancestral theropod features as "baggage". Instead, these
feathered maniraptorans wanted to hang onto their theropod roots rather than
commit themselves to the 'new-fangled' advanced avian (ornithoracean)
bauplan, with its forward-shifted center of mass and the complete
re-modeling of the pelvic limb that it required. It's all a trade-off.
It's all a Just-So Story, I know. But avian evolution has traditionally
been viewed as a headlong rush to abandon all 'reptilian' characters in
favor of birdy characters. To me, this doesn't do justice to the success of
the ancestral theropod bodyplan. The presence of long-bony-tailed birds in
the Early Cretaceous, and even close to the end of the Cretaceous
(_Rahonavis_), tells me they were doing something right.
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