[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: Brachiosaurid metabolism?
There are several problems with this discussion. First of all, just
because someone published a mass estimate does not make it plausible.
There is no way you can get more than 40 tons onto a normal African B.
brancai. And the largest specimens of B. altithorax probably don't
exceed 50t, unless it differes even more from the African species than
Second of all, as David has asked, where on Earth is the growth-rate
estimate coming from for a 5t Hypselosaurus to take 8-11 decades to
grow up? The only in-depth osteological study I'm aware of for
sauropod growth is Currie-Roger's work on Apatosaurus. This (much
larger) sauropod was growing up in a time frame on teh order of 2
decades, not 8. If Hypselosaurus took more than 8-10 years to grow up,
it was really dawdling by sauropod standards.
As for metabolism in sauropods; it's clear that the kind of growth that
has been empirically determined for them requires a metabolic rate
higher than in extant lizards and crocs, although how much higher
cannot be precisely determined. The airsac respiratory system of
sauropods is consistent with elevated aerobic capacity (i.e. they were
probably physicall active), but that needn't imply a body temperature
as high or as stable as most placental mammals, let alone most birds.
Wyoming Dinosaur Center
110 Carter Ranch Rd.
Thermopolis, WY 82443
(800) 455-3466 ext. 230
Cell: (307) 921-8333
Sent: Wed, 22 Nov 2006 7:41 AM
Subject: Re: Brachiosaurid metabolism?
If you take e.g. a smaller european sauropod _Hypselosaurus_ with
a mass of some 5300 kg when it was adult, compare it to the hatchling
weight of the same genus (2,4 kg) and use the calculated grow rate,
Wait, wait, wait.
Firstly, *H.* is a quite fragmentary affair. Remember that mass
*Brachiosaurus*, for which the complete skeleton can be reconstructed
from a few
individuals, range from 15 to 75 t (ignoring even higher outliers for
moment), and then have another look at *H.*...
Secondly, there's no evidence that any of the many oospecies from the
and Maastrichtian of southern France belongs to *H.*. For a long time
the only named sauropod from that general time and place, but now
Thirdly, where does the estimate of hatchling mass come from?
And lastly, what growth speed estimate are you using?
And because much larger sauropods such as _Brachiosaurus_ weighed
seven or more times as much as _Hypselosaurus_,
or three or less...
So then there's a theory I kind of like wherein sauropods were
endothermic upon hatching and then their metabolisms gradually
slowed as they got bigger. But, it's hard to tell and
noone seem to favour it anymore.
One reason for this is that ecto- and endotherms differ in the
their cell membranes (those of endotherms are more permeable for sodium
Another is that it's difficult to imagine how an ectothermic animal of
could have functioned.
Der GMX SmartSurfer hilft bis zu 70% Ihrer Onlinekosten zu sparen!
Ideal fÃr Modem und ISDN: http://www.gmx.net/de/go/smartsurfer
Check out the new AOL. Most comprehensive set of free safety and
security tools, free access to millions of high-quality videos from
across the web, free AOL Mail and more.