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Re: DOWNY STEGOSAURS (WAS: Re: Feathers on Bloody Everything)



>>>My question was, if feathers are associated only with birds and birds
have an
extremely fast metabolism, isn't it possible that the small carnosaurs had
a
different metabolism, and so would not have required feathers?  If so, the
possible adaptations could be anything from skin (and panting?) to some
modification of scales.  This is particularly possible if the climate was
not
extreme.      <<<

First of all; the climate WAS extreme.  In the tropics today, animals face
the same range (= the difference between the highest and lowest
temperatures) as those in temperate climates.  Remember also, the Mesozoic
wasn't "warm," it was hot.  Heat is a big problem for endothermic animals
(try running around naked in Southern Florida in the summer time).  And
during monsoons, the evaporative cooling can chill an endotherm very
quickly.  So if you are illustrating endothermic dinosaurs, you need to
insulate them to be biologically accurate (size counts as insulation,
above ~400 kg).  Of course, it's hardly been proven that dinosaurs were
all endotherms.  But with large insulated theropods known (the sitting
dilophosaurine, and the Chinese therizinosauroid) known, it's starting to
look pretty good for the endothermic theropods camp.  Also, very good
papers done on sauropod growth rates placed maturity at around 11 years of
age (used three different techniques to come to that conclusion), and that
of hadrosaurs around 6 years.  Your cannot duplicate those rates without
endothermy in extant animals (and endothermic elephants don't even grow
that fast, although whales grow faster).  So there's some explaining
that's going to have to be done by the "dinosaurs are all ectotherms" camp
if the idea is to continue to be taken seriously. (see my response to
"haversian systems in lizards" for more on that topic).

Mind you I'm NOT saying that it's proven that dinosaurs were endotherms,
or that one has to assume that feathers (or "sinostructures) were on all
small dinos.  But there are some patterns in the way the evidence is
heading.  

Scott hartman