Cretaceous crocs crunch critters

by Greg Mayer

Earlier this year my friend Chris Noto and his colleagues Derek Main and Stephanie Drumheller published a paper describing injuries to turtle and dinosaur bones from the Cretaceous that show evidence that they were preyed upon by crocodiles.  Besides the irresistible alliteration, their paper serves to show that we can sometimes learn much more about extinct animals than merely their skeletal morphology, and, with the right sorts of evidence, can learn about their behavior, ecology, and physiology as well.

Cretaceous crocodile crunching critter (by Jude Swales)

The fossils were recovered at a site in Texas known as the Arlington Archosaur Site. Modern crocodilians feed on turtles, and also on dinosaurs, if you think of birds as dinosaurs (which, in a sense, they are).  They will seize turtles side to side (as shown in the reconstruction) or top to bottom. American alligators are particularly fond of turtles, and, compared to some other crocodilians, their rear teeth are especially blunt and peg-like (sort of like molar teeth). This helps to crush the shells of turtles they are eating (which, I have been told, break with a popping sound). E.A. McIlhenny, the great naturalist of hot sauce fame, wrote:

I have seen alligators catch large terrapins and turtles of considerable size and crush their hard shells as if they were made of paper, swallowing them whole.

Tooth scars on a turtle shell (above) and a dinosaur leg bone (below).

Noto et al’s study is a nice example that shows we can learn about more than just the morphology of extinct creatures, but can also learn about thier biology and the paleocommunities they lived in, including (in other studies) ecology, behavior, and even color (see, for example, Matthew’s recent post here, and earlier posts by Jerry here and here).

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McIlhenny, E.A. 1935. The Alligator’s Life History. Christopher Publishing House, Boston. (Reissued in a facsimile edition in 1976 by the Society for the Study of Amphibians and Reptiles, with a foreword by the great herpetologist and conservationist, Archie Carr.)

Noto, Christopher R., Derek J. Main, and Stephanie K. Drumheller. 2012. Feeding traces and paleobiology of a Cretaceous (Cenomanian) Crocodyliform: Example from the Woodbine Formation of Texas. Palaios 27:105-115. (abstract)

10 Comments

  1. eric
    Posted August 17, 2012 at 11:26 am | Permalink

    Just when you thought it was safe to go back in the cretaceous water.

    Its a good reminder that movies like Jurassic Park like to paint dinosaurs in an unrealisticaly favorable light. I.e., if any of our modern species were to meet them, the dinosaurs would kick ass. In reality, the sharks and crocs and other predators that lived in both eras probably kicked dinosaur ass as much as they kick mammal ass today.

    • bacopa
      Posted August 17, 2012 at 10:47 pm | Permalink

      I live an an area where gators are somewhat common. All the normal mammalian wildlife gets by just fine. Alligators are not unstoppable death machines.

      I would even bet that we could transport some mammalian predators back to the Cretaceous and some of them might find a way to live. I’d put my money on coyotes and cougars, because they are smart and adaptable.

  2. emmageraln
    Posted August 17, 2012 at 12:10 pm | Permalink

    Reblogged this on emmageraln.

  3. jeffery
    Posted August 17, 2012 at 9:19 pm | Permalink

    Back in the 70s, I was touring the Everglades with my girlfriend, who was an avid bird watcher. It was almost dark as we walked back on one of the boardwalks spanning a slough when I heard a commotion and then a loud, “crunch!” I looked back and saw an alligator with a soft-shelled turtle in its jaws, chomping away.

    • bacopa
      Posted August 17, 2012 at 10:53 pm | Permalink

      Lots of soft shell turtles in the local bayou, but gators are rare as the noise of the city drives them off. I wonder if the soft shell turtle is an adaptation to gator predation, or whether the soft shells have been around for tens of millions of years.

      Seems if the local predator can crush your shell it might be better to give up the shell for better speed.

      • gravelinspector
        Posted August 18, 2012 at 3:08 am | Permalink

        What is the calcium availability like in the habitats of soft-shell turtles (compared to hard-shell turtles). We don’t have any turtles, and precious few reptiles in general, so I simply don’t know what their habitats are.
        I’m assuming that hard-shell turtles have much more mineralisation in their shells compared to soft-shells, but that is a flat-out no-basis assumption ; similarly, I don’t know if the putative mineralisation is calcium based. Both are fair guesses, I hope.
        That’s just one potential compounding factor to consider in evaluating your hypothesis.

        • John Scanlon, FCD
          Posted August 25, 2012 at 7:35 am | Permalink

          Soft-shell turtles don’t lack for calcium, they actually have quite massive bones in the carapace (ribs fused to overlying dermal bone); what’s missing is cornified epidermal scales over those bones, so they’re leathery and slippery and very fast swimmers.
          They’ve been around since the Cretaceous too, at least. Every generation of aquatic turtles has been croc food since the Jurassic, so both teams are quite good at the game by now.

  4. gravelinspector
    Posted August 18, 2012 at 3:15 am | Permalink

    One of the bits of “bite behaviour” that I wish I had time and resources to actually follow up more is the asymmetry of bite marks on trilobite tests. It seems (L. E. Babcock (1993) “Trilobite malformations and the fossil record of behavioral asymmetry.” Journal of Paleontology, 3, 217–229. And other occasional references.) that a considerable majority of the trilobite specimens which are found with bite marks, have those bite marks on the (IIRC) right lobe.
    That speaks volumes for there being something decidely “handed” about the behaviour of some previous taxa. As a left-hander, my ears pricked up (approximately symmetrically) when I heard about that one.

  5. Dominic
    Posted August 19, 2012 at 4:41 pm | Permalink

    I was trying not to think of the post meal bowel movement so I hope it does dissolve that shell with its digestive juices!


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