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Re: flying Archie
Don Ohmes wrote:
An alternative "bottleneck" evolutionary path to the gradual terrestrial
transition scenario; abandonment of terrestrial locomotion entirely
(perhaps/probably for an aquatic environment), and then after the avian
bodystyle was well-established, re-invasion of the terrestrial environment.
Flight superiority well in wing, so to speak. No worries about
center-of-mass issues relative to the hindlimbs during "remodeling" there.
Yes, that's possibly what happened. The modern avian body plan (including
the short tail) appears to be primitive for the Ornithothoraces, and so
precedes the Enantiornithes-Euornithes split. There are many basal
euornithean birds that appear to have been adapted to an aquatic environment
(_Archaeorhynchus_, _Yanornis_, _Yixianornis_, _Gansus_, _Hongshanornis_,
_Ichthyornis_, Hesperornithiformes). Also, we know that that
confuciusornithids fed on fish (Dalsatt et al., 2006). So an aquatic
ecology might have facilitated evolution of the modern avian body plan
('remodeling', as you nicely put it) in ornithothoracean birds.
For the above to be true, the arboreal adaptations of enantiornitheans would
be derived relative to the basal ornithothoracean condition. This requires
that enantiornithean birds headed out of the water, and up into the trees
long before the euornitheans (including neornitheans) did. In support of
this, the perching adaptations of enantiornitheans (especially the
avisaurids) are very different to those of neornitheans, so arboreal
perching almost certainly evolved independently in these two lineages.