RE: mosasaur babies/no marine dinos

["Tracy L. Ford" <dino.hunter@home.com>]

-----Original Message-----
From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
John Bois
Sent: Tuesday, January 01, 2002 6:49 PM
To: dinosaur@usc.edu
Subject: mosasaur babies/no marine dinos


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Assumption: Dinosaurs were endothermic.  This is a more expensive metabolic
mode
and requires a more precise/demanding incubation regime or period than that
of ectothermic
reptiles.  Indeed, this lifestyle _requires_ parental investment-to provide
greater access to oxygen (i.e., eggs could not be buried and forgotten), and
to hold temperature closer to the optimum (e.g., by shading, maintaining a
vegetation mound, active brooding).  Slow metabolic rates of lizard babies
probably required less oxygen...and could handle the slow delivery rate in
placenta-less lizard mommy's tummy.

Hypothesis:  Dinosaurs could not be fully aquatic because their embryos
require more oxygen than is available in aqueous environment without a
delivery system (e.g., a placenta).<<

I'm not sure I understand what your saying. Are you saying NO dinosaur could
have lived an aquatic life (in rivers, etc) or are you saying no dinosaur
could live a MARINE life like a Marine iguana?
*   There is more oxygen in air than water.  Penguins demonstrate
the effectiveness of the body plan as a fishing machine.  But, the oxygen
requirement means that eggs must be placed on land.  This limits
size-inasmuch as birds designed for swimming are clumsy on land (imagine an
elephant seal incubating an egg).  So, ectotherms and placentals are the
only large size animals to rule the waves
To summarize: archosaurs are very efficient fish hunters but are
size-limited in the marine environment.  This is due to a) high oxygen
demand for developing egg/embryo; b) inability to incubate a land egg with a
fish body plan.<<
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* Penguins also live in colder waters and need to be warm blooded to do so
(though some do come into warmer waters). Penguins aren't a good analogy for
dinosaurs, they are too advanced.

A related phenomenon is the distribution of penguins.  Given their great
fishing ability, they should be competitive in all parts of the world.  But
their distribution is primarily southern.  I believe nest sites are the
limiting factor here; that is, nest sites and predator abundance--which
amounts to the same thing--nest sites without predators are much more common
in the Southern H. than the Northern.
Comments welcome.<<
I believe some sort of aquatic lifestyle was possible for some dinosaurs.
Why are there so many Hadrosaurs and ankylosaurs found in marine deposits?
Have they all been swept out too sea? Not having dinosaurs living near the
waters edge, whether it is lagoonal, estuarine, shoreline, etc is taking out
an ecological niche. The niche was there and it WAS filled.

Tracy L. Ford
P. O. Box 1171
Poway Ca  92074
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