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extinctions



Recent postings to this and other related lists regarding dinosaur
extinctions have focussed on environmental changes, egg predation,
climactic events, or impacts.  Reasonable arguments may be proposed
against all of these based on the very successful exploitation of many
ecological niches by dinosaur groups, and how unlikely it would be for
a given environmental change to eliminate all dinosaur groups.  Much
of the adaptive success of dinosaurs has also related to their
reproductive strategy.  The laying of large clutches of eggs allows
rapid re-population of dinosaur groups (an r-strategy) whereas the
large adult size fits the K-strategy.

Much of the thinking about extinction events or scenarios seems to
center on the elimination of adult animals.  Perhaps we should focus
more on some common structural or functional feature of all dinosaur
groups that might represent their Achilles heel.  The secret to their
extinction may actually lie in the key to their success.  Questions
that occur to me whenever I consider dinosaur extinction are these: Is
the short-term physiological adaptability of adult dinosaurs
constrained in some way by structural limitations imposed by their
method of reproduction?  Did a relatively sudden extinction event act
on the adult animals (the K-strategy) with all their different
phenotypes, geographical ranges, diets, sizes, habitats, etc., or did
it act on their eggs (the r-strategy), arguably the most vulnerable
point in their life cycle and the one point at which all dinosaurs
would be most alike?

I would appreciate any and all feedback relative to these questions,
and the logic of looking "inward" into dinosaur reproduction for the
answer, rather than "outward" to external environmental changes acting
on adult animals.

James

James M. Norton, Ph.D.
University of New England
11 Hill's Beach Road
Biddeford, ME  04005
phone: [207]283-0171 x2270
fax: [207]283-3249
email: jnorton@mailbox.une.edu