David Marjanovic wrote:
Firstly there is evidence that many sauropods ate tree leaves. Including (well... mainly) conifer needles. This plentiful food resource is today exploited only by insects (and the occasional sloth, specialized monkey or weird bird), and the sauropods hardly seem to have had competition in that.
And fourthly, make sure you don't overestimate the body masses of sauropods. Their vertebral columns usually contained more air than bone...
Do naked mole rats and ,possibly,crocodiles count as heterotherms descended from homotherms?
Naked mole rats are about half homoiothermic. :-) Quite little research has been done on Jurassic and Triassic crocodyl...omorphs...
There is one known living gigantotherm: the leatherback turtle (*Dermochelys coriacea*).