RE: Gansus Bird-Dino Connection - Penn Press Release

[Tim Williams <twilliams_alpha@hotmail.com>]

> "The enantiornitheans had the best adaptations for perching, so they were 
> able to dominate the ecological niche that we would associate with 
> songbirds, cuckoos, woodpeckers or birds of prey," Harris said.  "Gansus 
> appears to have had adaptations for a lifestyle centered around water, 
> based on things like the proportions of the leg and foot bones."
> While the enantiornitheans are now long gone, their perching lifestyle has 
> now been taken over by the descendents of birds like Gansus.

I don't think this point gets emphasized enough.  There is precious little 
evidence for perching in the vast majority of Mesozoic birds - the perching 
enantiornitheans are the exception.  The feet of certain enantiornitheans 
(avisaurids) show perching specializations, though the retroverted hallux 
was achieved in a very different manner to that of modern perching birds.  
Confuciusornithids (maybe) show some adaptations for perching.  But the rest 
(including _Archaeopteryx_, other enantiornitheans, basal ornithuromorphs, 
basal ornithurans) show no perching adaptations at all.

For ornithuromorphs, a perching pes does not appear until quite late in 
their evolution, well into the crown-group Neornithes.  The most basal 
neornithean group to exhibit perching might be certain galloanserine birds 
that roost in trees - like modern tree-ducks, or guans.  Either perching 
ornithuromorphs were around in the Mesozoic, and the fossil record is doing 
a really good job keeping them secret; or this is a relatively recent 
innovation for this group, and ornithurans (as neognaths) did not venture 
into the trees until the Cenozoic.

Cheers

Tim