Monday, May 10, 2010

Warm Blooded (Endothermic)

Research provides strong evidence that pterosaurs were actually warm blooded (endothermic).
There is no clear evidence that dinosaurs were warm blooded.
(Of course birds are warm blooded as well.)
The presence of pycnofibres (and the demands of flight) imply that pterosaurs were endothermic (warm-blooded).
ancient pterosaurs and modern birds may have shared one important feature in common: a warm-blooded metabolism. There's evidence that some pterosaurs (like Sordes) sported coats of primitive hair, a feature usually associated with warm-blooded mammals, and it's unclear if a cold-blooded reptile could have generated enough internal energy to sustain itself in flight.
The basic themes of the new theropodan dogma
are that birds are living dinosaurs, that flight originated
from the ground up, and that feathers arose
as a downy insulative covering to insulate small
endothermic dinosaurs. Yet there has never been,
nor is there now, any clear evidence that dinosaurs
were endothermic (Feduccia, 1973, 1999a).
When D'Emic doubled dinosaur growth rates and added birds into the calculations, the beasts ended up with growth rates that looked a lot like warm-blooded mammals, he said.
Moreover, the original study did not group birds with nonavian dinosaurs and Archaeopteryx (a transitional species between dinosaurs and birds) because they are substantially different.
Evidence for mesothermy in dinosaurs

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