Monday, 8 October 2007

Cephalopods, mosasaurs, and Cretaceous parenting


Typical. You go away on holiday, you come back, and it's International Cephalopod Awareness Day. And me with nothing to wear, and shoes that don't match my dress, and a handbag that's so last season... anyway, moving swiftly on, back to the cephalopods.

As any palaeontologist worth his (or her) salt knows, the ultimate cephalopods are ammonoids and nautiloids. Whilst taking my MSci I briefly studied these fantastic beasties, completing a three month research project on predation on ammonoids. During my studies, I came across this fascinating research paper (Kaufmann 2004), detailing a mosasaur attack on a Cretaceous nautiloid. In this paper Kaufmann presents a nautiloid (Argonautilus catarinae) recovered in San Diego county, California (image below).

As you can see the nautiloid has three large puncture marks (indicated AT in the figure), and five smaller ones (indicated JT). From the size and spacing of these puncture marks Kaufmann infers them to be mosasaur bite marks, most likely from Mosasaurus or Platycarpus. The smaller punctures form a separate bite, and precede the larger punctures making up the second bite. This second bite most likely killed the nautiloid and caused it to sink, penetrating the flotation and living chamber. Kaufmann argues that these bites consist of two mosasaurs of the same species, an adult and a juvenile.

Evidence from the pattern of bite marks in ammonites implies a learned mosasaur behavior pattern of blind-side attack of the prey first, followed by positioning bites using both the stabbing and pterygoid teeth, followed by one or more bites across the living chamber of the ammonite designed to rip the prey animal out of the shell to consume it. Combining these two lines of evidence, Kaufmann paints a picture of a mother mosasaur teaching the child the best way to tackle this food source. So from this specimen (and with only minor speculation!) we have inferred not only part of an ecosystem, but part of a mode of life, and maybe part of the parent-child dynamic also.

And that's what's so fascinating about palaeontology. This vignette played itself out millions of years ago - not only are its individual actors long dead, but so are their entire species. And yet from a small fragment of rock we can reconstruct so much of their lives. From that rock, just for a moment, we too can swim in the Cretaceous seas, can envisage a life far removed from our own, infer its dramas and imbibe of its wonder.

Amazing.

References:

KAUFFMAN, ERLE G. Mosasaur Predation on Upper Cretaceous Nautiloids and Ammonites from the United States Pacific Coast Palaios 2004 19: 96-100

9 comments:

Cephalopodcast said...

Great ICAD entry. Thanks for participating and representing the cephalopod ancestors.

David Marjanović said...

The picture shows a crocodile, not a mosasaur.

Platecarpus is a mosasaur, on the other hand, but it has no Y...

Ben D said...

It was such a cool picture I didn't want to leave it out though. And Kaufmann 2004 spells it Platycarpus - it's odd the peer review didn't pick that up. Maybe both spellings can be used?

Ben said...

Amazing, or in fact hand-waving bollocks? Though palaentology does rule ;)

Kevin Z said...

I love it. These are the types of paintings that enthralled me as kid and got me interested in science. I would like to frame these and put them in my 2 year old's bedroom. Of course as scientists we know its utter crap, but who cares, its a possibility, a hypothesis, just not a testable one.

Cool find.

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