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dinosaur endothermy??



Last month Terry Jones left the dinosaur list, and just after he did
there were some messages here about endothermy.  I forwarded a couple
to him, and got the following in response.  I should have passed it
along then, but I was wrapped up making slides for a conference, then
I was at the conference and... it didn't seem as relevant for a while.
Since we're cycling back through the topic, I'll give it to you for
your perusal.  I apologize for the fact that some of the points seem
to come from left field -- Terry was responding mainly to one previous
message (and I don't see much point in resurrecting it just for this
message; it wasn't one of John Bois' messages even though it might
seem that way in parts of the following response...). 

-- MR

Date: Wed, 13 Nov 1996 09:03:35 -0800
To: "Mickey P. Rowe" <mrowe@indiana.edu>
From: jonest@ava.bcc.orst.edu (Terry D. Jones)

There is currently NO evidence for endothermy in dinosaurs.
Unfortunately, regardless of the a large body of (obviously ignored)
evidence to the contrary, the religious fervor about warm-blooded
dinosaurs has not diminished.

I have found only one paper that deals with dinosaur growth rates
(Ruben, J.  A.  1995.  Annu. Rev. Physiol.  57:69-95).  In this paper
Troodon and American alligator growth rates are shown to be similar
(25-50 g/day).  Last time I checked, Alligators were reptiles...

There is currently no evidence that dinosaur young were altricial.  If
they were altricial would it seems highly illogical to have them out
in the open where everyone could snack on them.  Modern altricial
young are found in nests that are away from most predators (e.g., in
trees, on islands, in caves or dens).  "Open pits" are utilized in
rare cases when predators are not a (major) problem or there is no
place to "hide" a nest.

There were some inaccuracies in Horner's presentation.  Regardless, we
should wait until it comes out in print before we assume it's validity or
invalidity.  Nick Geist and I have already shown that development of the
long bones gives no evidence as to the altriciality or precociality of
hatchling birds and crocodilians (Science 272: 712-714).  However, as we
said in our paper,  the degree of ossification of the pelves indicates
maturity at hatching (this conclusion was not even addressed in Jack's
presentation).  Afterall, if an animal is capable of walking at at hatching
the locomotory muscles must have a firm attachment.  The pelves of altricial
birds are poorly ossified at hatching whereas those of precocial birds,
corocidilans and ALL known dinosaur embryos are well-ossified.

As for the feathered dinosaur, shouldn't we wait until we decide this?  As
far as I know only one person in the Western hemisphere has seen this
specimen.  From what I've seen of the pictures, feathers are not the first
conclusion I would make--in fact, the preserved soft tissues look similar to
the mid-dorsal fringe present on a number of extant reptiles (e.g.,
Basilisk, etc.).  Nonetheless, to assume they are feathers based on the
observations of a single (albeit respected) person seems premature.

As for fossil bone isotopic composition, the assumptions of Barrick and
Showers regarding physiology are flawed.  It appears that the isotopic
composition of is more reflective of the temperature of the ground
water/sediments in which an animal is preserved--therefore, bone isotopes
are altered.

Many years ago my mother gave me advice that has been very helpful, and I
pass it on to you...Believe only what you see.  Since then similar advice
has been given to me:  "believe none of what you're told, a tenth of what
you read, and half of what you see".  

TDJ
:-{)
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    Terry D. Jones                             Voice:  541/737-6120       |
    Oregon State University              Fax:      541/737-0501          
    Dept. of Zoology                         JONEST@bcc.orst.edu
    3029 Cordley Hall
    Corvallis, OR  97331-2914
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