Re: Layperson question on endothermic dinosaurs

[Vivian Allen <mrvivianallen@googlemail.com>]

Theropods, yeah. You've got several lines of evidence that make that
one pretty solid. Off the top of my head:

Feathers. I know feathers have other functions (display,
water-proofing, flying eventually) but I'm going to go out on a limb
and say one of the main things feathers do is insulate the body. Why
would you need to insulate yourself if you were not warm-blooded?

Extensive, bird-like lungs.  Most theropods had very large, complex
breathing structures similar to those seen in birds. In birds, these
lung complexes are very efficient at extracting a lot of oxygen from
the air (http://en.wikipedia.org/wiki/Bird_anatomy#Respiratory_system),
and you need a lot of oxygen to power a high metabolism. So again, why
have these complex lung structures unless you need a lot of oxygen?

Relationship with birds. Less concrete, but the fact is that birds are
living theropod dinosaurs, and they are endothermic. You may argue
that this is just because they fly, but many species of birds have
become more-or-less terrestrial, and they still maintain endothermy.

Long legs. The biomechanics behind it may be a little above layperson
level (paper here if you are interested:
http://www.plosone.org/article/info:doi/10.1371/journal.pone.0007783 ,
but fairly simple put, moving around on long legs requires quite a lot
of consistent effort from quite large muscles, and to provide
consistent energy for a lot of large muscles you need a high metabolic
rate, i.e. are in the 'warm-blooded' part of the metabolic spectrum.

I'm sure other list members will be happy to add to the list (and
correct me if I am wrong), but yeah, I think there is a very good case
for endothermy in theropod dinosaurs.

In other dinosaurs (the long-necked sauropods and the very diverse
ornithischians) it is difficult to be sure - they do not have living
representatives, so it is more difficult to make inferences about
their biology. But, a lot of ornithischians have similar body
proportions to theropods, again with these long legs, which does
indicate that they were pretty active, high-metabolism creatures.

Viv

On 15 May 2013 17:34, Kelly Clowers <kelly.clowers@gmail.com> wrote:
> Hi, I am hoping that I could get sense of  what the consensus, if any,
> is on endothemry. I try to stay up to date and knowledgeable on all
> things dino-related, but I just want to be clear on this to help
> settle a discussion on the Ars Technica forums.
>
> I believe that it pretty solidly accepted for therapods, but maybe
> somewhat less so for the rest? Or am I all wrong?
>
> Thanks very much,
>
> Kelly Clowers