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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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