Re: [asa] AIG blurb of the week

From: David Campbell <pleuronaia@gmail.com>
Date: Thu Dec 14 2006 - 16:56:38 EST

> However, as I read this blurb one statement stood out that may suggest a less catastrophic and even more mundane reason for this ichthyosaur fossil caught "in the process of giving birth to a fully formed baby." Note the description of the fossil given by AiG ... "The baby, except for the head, appears to have emerged from the body of the mother." Now growing up on a farm and having been present at the birth of numerous calves (and other animals), it has been my observation that births go best when the baby is delivered head first ... not head last. When an unassisted animal gives birth tail first, usually the baby dies and frequently the mother does too. Now I wouldn't claim any expertise as an ichthyosaur natal specialist but if this fossil represents a tragic breach birth incident then we don't even have to assume that some catastrophic burial event caught these ichthyosaurs precisely at the second before the birth was completed. We may just as reasonably propose t!
 hat these two marine reptiles died naturally in the course of a difficult birth and were subsequently buried hours or even days afterwards by processes that may or may not have been overwhelmingly catastrophic. <

An air-breathing animal born head first underwater has trouble
breathing. Thus, modern whales, dolphins, etc. are born tail-first,
and it is presumed that ichthyosaurs normally did so, too.

However, it is perfectly possible that the birth in question had some
sort of problem (or that the mother died of unrelated causes; the
contractions, etc. might continue in a moribund individual and I think
there's a specimen or two with adjacent young, presumably born as the
mother was dying on the sea floor). Thus, the two certainly could
have died in an ordinary manner before sinking into deep anoxic water
and eventually getting buried and fossilized.

The burial was actually probably relatively slow, because the outlines
of soft tissue present in the deposit (Holzmaden shale, Jurassic)
prove to be bacterial in origin, suggesting that the organisms sat a
while slowly decaying on the anoxic, live animal-free seafloor. Also,
the fossils are somewhat compacted and the levels of organic compounds
are rather high, both of whcih suggest that the mud supply was
relatively modest (to not provide more madding for the fossils nor to
dilute out the supply of organic material).

-- 
Dr. David Campbell
425 Scientific Collections
University of Alabama
"I think of my happy condition, surrounded by acres of clams"
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Received on Thu Dec 14 16:56:56 2006

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