[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]
Re: Sauropods,monotremes, and physiology
> Date: Mon, 30 Jun 1997 02:29:13 -0400 (EDT)
> Reply-to: NJPharris@aol.com
> From: NJPharris@aol.com
> To: firstname.lastname@example.org
> Subject: Re: Sauropods and those little heads
> In a message dated 97-06-27 09:49:41 EDT, email@example.com (Michael)
> > I suspect that you and George are right. The correct term is
> > heterothermy though. Endotherms keep their body temperature in a
> > small range. Heterotherms have a much larger range.
> One more time.
> Endotherms generate heat internally.
> Ectotherms rely on heat from outside sources.
> Heterotherms are endotherms sometimes and sometimes allow their body temps to
> drop to (or near) ambient levels.
> Homeotherms keep their body temperatures relatively constant.
> Poikilotherms have body temperatures that fluctuate more widely.
> Tachymetabolic organisms have high basal metabolic rates.
> Bradymetabolic organisms have low basal metabolic rates.
> And of course there are levels in between the extremes listed here. Great
> white sharks and tuna, for instance, are partial endotherms. Monotremes and
> some lipotyphlans have much higher metabolic rates than lizards but somewhat
> lower than other mammals.
> What you are proposing here, if I understand you, is that sauropods were
> bradymetabolic (slow metabolism) endotherms (heat from inside) that were
> mildly poikilothermic (temps fluctuated somewhat).
I believe that my response was in relation to monotremes which are
hetereotherms. I choose to look at this issue as the ability of the
animal to keep its temperature within a certain range. Hetereotherms
are not capable of keeping their body temps within the range that you
or I can. Remember however than all animals have diffuculty doing
this under the wrong (or right) circumstances. A whale out of water
would have a heat stroke. Put a human in cold water and its temp
drops and it dies. I look at monotremes as intermediate between
ectotherms and endotherms. Some animals exhibit limited heterothermy
and are ectotherms and others are endotherms. When you throw in
altered states like turpor, hibernation, etc., the water gets even
muddier. Also, ectothermy implies lower BMR's.
Back to sauropods. Most likely the early dinosaurs were somewhere
metabolically and physiologically on the way to endothermy. However,
a large bodied animal in a warm climate would have more problems
getting rid of heat than obtaining it. I doubt its temp would
flucuate that much though for many reasons.