Pythodon: The prehistoric shark that chewed… turtles

Complete fossilized skeletons of the prehistoric Ptychodus shark discovered in the past decade are giving scientists new insights into this creature that roamed the seas some 105 to 75 million years ago.

The latest fossils were unearthed in small quarries in Vayesijo, northeastern Mexico. Fossils of Ptychodon have been found before, but as its bones are composed of cartilage, which does not mineralize well enough to be preserved, most finds were single teeth, which were huge and folded (the shark’s name comes from the words “fold ” and “tooth”).

It was, therefore, difficult to determine exactly what Pythodon looked like and where it stood on the evolutionary family tree. “Its general appearance has remained a mystery for almost two centuries, due to the lack of more complete material,” Dr. Romain Vullo from the University of Rennes, lead author of the study published in the journal Proceedings of the Royal Society B.

“The discovery of the new specimens from Bayesillo, which reveal the body shape and anatomy of this extinct shark, solves this mystery.”

What the samples revealed

Vullo and his colleagues report how they studied six specimens of Pythodon, dating back to about 93 million years ago. Among them was a complete specimen revealing a side view of the prehistoric shark, which contained not only almost all of its skeletal elements, but also teeth, preserved muscle remains and an outline of the body with all its fins.

Another three of the specimens were nearly complete, including a juvenile Pythodon just over 56 cm long, while the remaining two specimens were incomplete or partial skeletons.

Analysis of the specimens reveals that Ptychodont belonged to the order Lamnomorpha, which includes the extinct giant Megalodon shark and the great white shark that inhabits the oceans today.

The look of the shark

The researchers add that in addition to its body shape and proportions, certain characteristics of Pythodon such as the size, shape and position of its fins, as well as its thick spine, suggest that it was a fast swimmer, while the huge and peculiar teeth suggest they fed on creatures that had shells, such as sea turtles and ammonites.

While Pythodon was probably the largest shark ever to live on such a diet, the new fossils show it had a maximum length of about 9.7 meters – longer than today’s great white shark but smaller than previous estimates of it being over 10 meters.

As for the extinction of the Pythodon, the study argues that it happened due to competition with other creatures, such as large aquatic reptiles, that fed on similar prey.