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Isotopic evidence on ~1 m long juvenile hypacrosaurs (upcoming in Paleobiology)
and on small adults (Protoceratopsid, Orodromeus) and larger adult
Hypacrosaurus (in review) as well as T. rex (Science) all indicate that they
were pretty good homeotherms.  The small size of some of these individuals
indicates the necessity of endothermy in order to maintain homeothermy (though
not necessarily mammalian or avian metabolic rates).
For those of you stressed about diagenesis we found a nice cold-blooded signal
from a varanid (in review) from the same formation as several of the dinos.
Are all dinosaurs metabolically equal. No. I've also found evidence of a
heterothermic nodosaur (in prep).  The only large sauropods were homeotherms.
Were they mass homeotherms or endotherms is hard to say from adult specimens.
The really large ones (30-80 tonnes) would have had small mass specific 
metabolic rates though a high metabolism for the individual.  The more 
interesting question is did they grow up as endotherms or ectotherms?
Reese Barrick