Fossil of great white shark’s extinct 30-foot ancestor found in Mexico

Scientists have found an exceptionally preserved giant fossil of an ancestor to great white sharks, revealing how these ancient predators that lived alongside dinosaurs went extinct.

Sharks of the genus Ptychodus were first discovered in the 18th century and described based mostly on fossil teeth specimens, but their true body shape and size remained elusive.

“Specimens mostly consist of isolated teeth or more or less complete dentitions whereas cranial and post-cranial skeletal elements are very rare,” the scientists involved in the discovery said.

The newly unearthed fossils, however, include a specimen with a full body outline. The fossil is from the early Late Cretaceous period of Mexico, beginning about 100 million years ago.

The “well preserved” fossil reveals crucial information about the anatomy and systematic position of Ptychodus, the scientists said.

Analysing the 30-foot-long fossil specimen, the researchers gained insights into the shark ancestor, its shape, mobility, and hunting techniques in water.

They found that the large predator belonged to the mackerel shark group or Lamniformes – which includes great whites and salmon sharks – and had grinding teeth unlike those seen in today’s sharks.

These sharks likely fed predominantly on hard-shelled prey such as ammonites and sea turtles rather than deep sea invertebrates, the researchers said.

They suspect these ancient sharks were highly diverse with a streamlined body shape, indicating that they travelled at high speeds.

The sharks occupied a “specialised predatory niche”, representing a “dominant group” in the Cretaceous marine ecosystems.

Their extinction before the asteroid impact that took out the dinosaurs suggests these ancient sharks might have been wiped out due to competition with emerging giant marine reptiles that targeted the same prey.

“Its extinction during the Campanian, well before the end-Cretaceous crisis, might have been related to competition with emerging blunt-toothed globidensine and prognathodontine mosasaurs,” the scientists said.