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Re: questions about the Odontochelys study
Tim Williams wrote:
With the disclaimer that I don't know all that much about turtles...
I do know that the snapping turtle and mata mata are ambush
predators, so protecting the underside may not be so important. Or
at least, belly armor (plastron) is not as important as it is to
aquatic turtles that spend more of their time swimming in the water
column. In other words, if such aquatic ambush predators spend much
of their time motionless, with their bellies close to the sediments
underneath, then their bellies are not as vulnerable to attacks from
below - hence the secondarily reduced plastron.
I think you're more or less right on the money. In fact, mata-matas
and alligator snappers both rarely swim in the water column even while
moving about; they move along largely by punting, and so they are
almost always near the substrate. The reduced plastron is therefore
of limited cost, while it provides substantial benefits in allowing a
transiently higher "walking" gait for punting along the bottom -
improved mobility for marginal cost. Common snappers free swim more
often, but still spend large amounts of time bottom resting, and have
the added advantage of intense offensive weaponry.
Michael Habib, M.S.
Center for Functional Anatomy and Evolution
Johns Hopkins School of Medicine
1830 E. Monument Street
Baltimore, MD 21205