University of Vienna researchers have determined that parts of vertebral column found in northern Spain belonged to a long-extinct species of mega shark, the Ptychodontidae.
The fossils, which were first unearthed in 1996, were found encased in limestone that dated back to Cretaceous period around 85 million years ago. Ptychodontidae were a widespread species across the region that mysteriously vanished well before the infamous end-Cretaceous extinction event. They are are mainly known from their flattened teeth, which allowed them to crush hard-shelled prey like bivalves or ammonites, similar to some of today’s ray species.
Because of their cartilaginous skeleton, examples of ancient shark vertebrae are extremely rare. They can be extremely valuable when determining more about extinct species, which typically only left behind their teeth for researchers to study.
“Based on the model, we calculated a size of 4-7 meters and an age of 30 years for the examined shark. It’s astonishing that this shark was not yet mature when it died despite its rather old age,” Patrick L. Jambura, lead author of the study, said.
Jambura estimates that the shark that the vertebral column belonged to still had a lot of growing to do. His findings were published in the latest issue of PLOS One.
“This shark doesn’t show any signs of flattenings or inflections in the growth profile, meaning that it was not mature—a teenager, if you want,” he said. “This suggests that these sharks even grew much larger and older.”
The slow growth and massive size may have been a factor in the shark species’ sudden demise.
Many living sharks, like the whale shark or the great white shark, show very similar life history traits, a combination of low recruitment and late maturation, which makes them vulnerable to anthropogenic threats, like overfishing and pollution.
“It might be the case that similar to today’s sharks, ptychodontid sharks faced changes in their environment to which they could not adapt quickly enough, and ultimately led to their demise, even before dinosaurs went extinct. However, unlike in the Cretaceous period, it is up to us now to prevent this from happening to modern sharks again and to save the last survivors of this ancient and charismatic group of fishes.”