Exceptional fossil reveals what prehistoric basking shark looked like

Vastly well-preserved fossils of a dinosaur-era shark have finally revealed what the predator looked like – and why it may have become extinct.

An international group of paleontologists has found an exceptionally complete fossil of a basking shark. The so-called Ptychodus lived at the same time as the dinosaurs – in the Cretaceous period, about 145 million to 66 million years ago. The unique find appears to solve a long-standing mystery about how this shark hunted and where it fits in the evolutionary tree. The paleontologists describe their findings in the journal Proceedings of the Royal Society B: Biological Sciences.

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Giant teeth

The first remains of it were discovered in the mid-eighteenth century Ptychodus found it. But subsequent descriptions were largely based on their gigantic teeth, which could measure nearly 20 inches long and 18 inches wide and were suitable for crushing shells. Bones were missing, making their anatomy only guesswork.

Up to now. The scientists found complete and almost complete Ptychodusfossils in a limestone quarry in northeastern Mexico. Of one of them, almost the entire skeleton, muscle remains and body outline were preserved, see image below.

The sharks were able to fossilize so well because they ended up in a quiet area without scavengers. The carcasses were then quickly buried under soft lime mud before they could completely decompose.

Competition of marine reptiles

Analyzes of the fossils show that the large predatory fish grew to almost ten meters in length and belonged to the mako sharks, a group that also includes the well-known White shark belongs.

It was already known that the teeth of Ptychodus were perfect for grinding hard things. Scientists therefore suspected that the shark was feeding on shellfish on the seabed, such as mussels. But that image now needs to be changed. The shark had a streamlined body, which indicates that it was a fast-swimming predator. According to the researchers, he looks a bit like the one that is still alive today porbeagle shark.

Where had Ptychodus are those molars necessary? The paleontologists think that the prehistoric shark hunted in open water for ammonites – extinct squids with a shell – and sea turtles.

For a while he had a kind of monopoly on these prey. But in the Late Cretaceous, the basking shark faced increasing competition, including from marine reptiles such as mesh lizards. Probably dolphin Ptychodus the worst, causing it to eventually become extinct.

Sources: Proceedings of the Royal Society B: Biological Sciences, Phys.org, LiveScience