[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
MRs OF SLOTHS etc
Some quick responses to David's recent terramegathermy opus (though
I regret that I don't have time to read through the whole thing)...
> ...Migrators must be tachymetabolic.
As a generalisation this is nonsense, seeing as gecarcinid crabs, some
rattlesnakes, monarch butterflies and a million other bradymetabolic
> while populations of megamammals are
> small and unstable and can't easily be refilled by reproduction.
Unfortunately I don't have the literature with me, but some historical
elephant populations have been huge. 'Can't easily be refilled by
reproduction'? - you MUST read Clive Spinage's _Elephants_ (Poyser
Natural History) for detailed discussion on this. Even megamammals
can breed fast and young and produce populations that cannot then be
supported by their environment (hence the proposed 'boom and bust'
model for elephant populations).
> Desert elephants never overheat, so HiMR sauropods shouldn't have
> either. Therizinosaurs, and maybe early dinosaurs with small ilia,
> probably had InMRs like giant sloths.
I wasn't aware David Oren and colleagues had finally captured a live
mapinguary - have they published? Sarcasm aside, how do you know
anything about the MR of ground sloths? Extrapolation from extant
sloths might be reasonable but is obviously speculative. And BTW
therizinosaurs hardly have 'small ilia' (nor, sensu Colbert, are they
Don't get me wrong, I have no opinion on dinosaur metabolism either
way. It's just that we're on very dodgy ground if extrapolations on the
MRs of fossil animals are based on equally dodgy assertions or
extrapolations about living ones.
PALAEOBIOLOGY RESEARCH GROUP
School of Earth & Environmental Sciences
UNIVERSITY OF PORTSMOUTH
Burnaby Road email: email@example.com
Portsmouth UK tel (mobile): 0776 1372651
P01 3QL tel (office): 023 92842244