New Prehistoric, Extinct Shark Group Revealed After the Discovery of Hook-like Fossil Teeth

Scientists have uncovered a new lineage of extinct sharks that didn't eat meat, but instead feasted on plankton. The sharks once lived in warm oceans during the age of the dinosaurs, nearly 100 million years ago.

The new findings are actually based on newly collected tiny fossil teeth, as well as a reinterpretation of previously reported specimens from Cretaceous rocks in the U.S. and Russia. These tiny teeth, in particular, are very similar to those of the modern-day, plankton-eating megamouth shark.

The new group of sharks is called Pseudomegachasma. The name, which means "false megamouth shark," is due to the shark's dental features which are superficially nearly identical to the modern-day megamouth shark that evolved much later in time. The new genus is currently represented by two extinct species. There's Pseudomegachasma casei from Russia and Pseudomegachasma comanchensis from the United States. Both of these species evolved from a group of extinct sandtiger sharks that likely had a fish-eating diet.

 "The study is significant because Pseudomegachasma would represent the oldest known plankton-feeding shark in the fossil record," said Kenshu Shimada, one of the researchers, in a news release. In addition, these sharks would have evolved independently from the four known lineages of modern-day planktivorous cartilaginous fishes: the megamouth sharks, the basking sharks, the whale sharks and manta rays.

The findings reveal a bit more about these ancient sharks, and show that planktivorous sharks evolved independently of one another.

The findings are published in the Journal of Vertebrate Paleontology.

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