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Fwd: More on Argentavis

I came across this article on ostriches as being neotonous
"neotony and the thyroid in ratites"
It leaves me wondering what kind of terrifying creature would fledge out of an ostrich if we gave it thyroid...

On Jul 4, 2007, at 5:53 PM, Tim Williams wrote:

Ratites are almost always recovered as a monophyletic group, and the most parsimonious explanation is that flightlessness is primitive for the clade. Given the flight abilities of the tinamou, it may be that overall poor flight ability is primitive for palaeognath birds. I agree that loss of volancy almost certainly occurred prior to an increase to ostrich size.

The basal part of the neornithean tree seems especially prone to both loss of flight and impressive increases in body size; as well as ratites, we also have dromornithids and gastornithids (both regarded as galloanseraeans, or at least basal neognaths). It could be some ecomorphological pre-disposition to loss of flight + increase in body size; or it could just be opportunistic (i.e., lots of available ecological niches at around the same time); or just coincidence.



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