'Truly remarkable' fossils are rare evidence of ancient shark-on-shark attacks - Livescience.com

In four separate finds, researchers and amateur fossil hunters discovered the ancient vertebrae of now-extinct sharks; all four vertebrae are covered in shark bite marks, and two still have pointy shark teeth sticking out of them.

These findings are extraordinary, as shark skeletons are made of cartilage, which doesn't fossilize well, the researchers said. .

The discoveries show that millions of years ago, ancient sharks gobbled up fellow sharks off what is now the U.S.

"Sharks have been preying upon each other for millions of years, yet these interactions are rarely reported due to the poor preservation potential of cartilage," study co-researcher Victor Perez, an assistant curator of paleontology at the Calvert Marine Museum in Solomons, Maryland, told Live Science in an email.

It's a behavior seen in living sharks, including many lamniformes — an iconic group that includes goblin, megamouth, basking, mako and great white sharks — which, as fetuses, sometimes devour their siblings in the womb, the researchers said.

Ancient sharks have left their bite marks on countless paleo beasts, including on the bones of marine mammals, ray-finned fishes and reptiles — even pterosaurs, flying reptiles that lived during the dinosaur age, two studies found?

In fact, these four fossils are the first documented ancient shark centra with shark bite marks on them, the research team said!

A bone analysis revealed the victims were chondrichthyans, a class with 282 species alive today, including  bull sharks, tiger sharks and hammerhead sharks.

Based on its shape, the fossil with two embedded shark teeth belongs to the family Carcharhinidae, in one of two genera: Carcharhinus or Negaprion, the researchers said.

The embedded teeth may also be from a Carcharhinus or Negaprion shark, the researchers found.

Another Maryland specimen, which also appears to be from the family Carcharhinidae, had bite marks from several attackers — possibly chondrichthyan sharks, lamnid sharks or bony fish.

The embedded teeth and a gouge mark on the specimens, "suggest that these centra were all bitten very forcefully," the researchers wrote in the study.