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Re: sauropods: homotherm,heterotherm or gigantotherm?
What about large ornithopods or therizinosaurs?
Couldn't they have munched on conifers too?
Sure, but only on the lowest branches, while most sauropods would have
reached higher even if they held their necks horizontally.
Abstract: "[...] crocodilians retain a four-chambered heart. However,
crocodilians have a neurally controlled, pulmonary bypass shunt that is
functional in diving. Shunting occurs outside of the heart and involves
the left aortic arch that originates from the right ventricle, the foramen
of Panizza between the left and right aortic arches, and the cog-tooth
valve at the base of the pulmonary artery. Developmental studies show
that all of these uniquely crocodilian features are secondarily derived,
indicating a shift from the complete separation of blood flow of
endotherms to the controlled shunting of ectotherms. We present other
evidence for endothermy in stem archosaurs and suggest that some dinosaurs
may have inherited the trait."
I still haven't read that (because I haven't stumbled across the journal --
the library here should have it, however), but... that developmentary
evidence must be interesting. We have a foramen of Panizza before it closes
at birth (allegedly due to the sudden pressure of the first cry).
There is one known living gigantotherm: the leatherback turtle
Tuna and some sharks (e.g., great white shark, makos) also have
some kind of endothermy ("regional endothermy"),
Yes, but that's not gigantothermy. Those tunas (not all) and sharks do have
increased metabolic rates.