Despite having a set of teeth shaped like a circular saw, an extinct shark probably devoured only soft-bodied prey.
The spiral-shaped tooth arrangement (pictured) of Helicoprion davisii, an animal some 300 million years old, has puzzled palaeontologists for more than a century. Last year, a team determined that the teeth were surrounded by the shark's lower jaw.
In a follow-up study, Jason Ramsay at the University of Rhode Island in Kingston and his team used computed tomography scans of the fossils to reconstruct the jaw muscles and model the mechanics of the jaw and teeth to determine how and what the animal ate. They concluded that older teeth at the front of the jaw snagged prey whereas younger, stronger teeth deeper in finished them off.
The shark teeth were rarely worn or broken, suggesting the animals ate soft-bodied sea creatures such as cephalopods.
J. Morphol. http://dx.doi.org/10.1002/jmor.20319 (2014)