Fossils reveal shark that made great white look like small fry
Fossil experts have gained unprecedented insights into an enormous prehistoric shark, after finding complete skeletons of the creature.
The specimens, found in northeastern Mexico, belong to Ptychodus – a creature that roamed the seas from around 105m to 75m years ago.
Ptychodus fossils have turned up before but with its bones made of cartilage, which does not mineralise well, many just consisted of teeth. As a result, exactly what Ptychodus looked like, and where it sat on the evolutionary family tree, was somewhat difficult to pin down.
“Its general appearance has remained a mystery up to now,” said Dr Romain Vullo, first author of the research from the University of Rennes. “The discovery of the new specimens from Vallecillo, revealing the body shape and anatomy of this extinct shark, solves this enigma.”
Prof Michael I Coates of the University of Chicago, who was not involved
in the work, said the new fossils were superb. “Ptychodus has long been a classic example of teeth in search of a body,” he said. “And here we have it, with thorough analyses of where it sits in the shark family tree and a good stab at its ecomorphology – how it fits into marine ecosystems of the late Cretaceous.”
Writing in the journal Proceedings of the Royal Society B, Vullo and colleagues report how they studied six Ptychodus specimens, dating from around 93m years ago.
Among them is a complete specimen revealing a side view of Ptychodus, containing not only almost all its skeletal elements but also teeth, preserved muscle remains and an outline complete with fins. Estimates of its size based on the new fossils suggest it had a maximum length of about 9.7 metres
Analysis reveals Ptychodus was a kind of mackerel shark – a group that includes the extinct gigantic shark Megalodon and the great white shark – which can grow to six metres and inhabits oceans today.
The researchers believe it was fastswimming and hunted prey in open water, with its meals probably comprised of sea turtles and ammonites rather than creatures such as clams that dwelled on the sea floor, as had been thought.