Friday, June 17, 2011

Helicoprion



Helicoprion ("Spiral Saw") was a long-lived genus of shark-like cartilaginous fish that first arose in the oceans of the late Carboniferous 80 million years ago, survived the Permian-Triassic Extinction Event, and eventually went extinct during the early Triassic some 25 million years ago.
The exact location of the tooth-whorl in the lower jaw is unknown. Most current reconstructions place the whorl in the front of the lower jaw; however this would create drag, making the shark a less efficient swimmer, and turbulence, alerting prey of its approach. An alternate reconstruction, created by Mary Parrish under the direction of Robert Purdy, Victor Springer and Matt Carrano for the Smithsonian, places the whorl deeper into the throat. This arrangement would be best suited for soft bodied prey.

The individual teeth are serrated, and it is implied that
Helicoprion was carnivorous. As there has yet to be an actual skull found, exactly how it captured or fed on its prey are subjected to a great deal of speculation. One hypothesis that it preyed on ammonites and that the teeth were specialized for the job of breaking into the ammonites' shells. Another idea was that the shark would swim into a school of fish and fling out the jaw, snagging prey on its many teeth. Notable specimens of Helicoprion have been found in eastern Idaho, northern Utah, and the far central western part of Wyoming.

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