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Re: New refs
"Brian Lauret" <email@example.com> wrote:
Considering "hysilophodontids" were the ancestral Iguanodontoids it seems
rather strange they were endotherms while their
Perhaps not so strange. It helps if you avoid thinking of "endothermy" and
"ectothermy" as polar opposites, and think of them as two ends of the same
spectrum. Among modern mammals, small mammals can be regarded as "more"
endothermic than big mammals, since their high surface area to volume ratios
renders them more prone to loss of body heat. Also, some fishes (tuna, some
sharks) show a degree of endothermy.
In the course of dinosaurian evolution, individual lineages may have slid
across the endothermic-ectothermic spectrum, depending on many factors: body
size, required activity levels, diet, climate etc. The small size and
cursorial habits of hypsilophodontids may have favored a greater emphasis on
endothermy than their bulkier relatives (e.g. hadrosaurs), who could rely
more on their sheer body mass to retain heat.
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