Re: Theropod herbivory - parallel evolution or one clade?

[Tim Williams <twilliams_alpha@hotmail.com>]

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.

Cheers

Tim

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