William Douglass, a fossil collector in the state of Maryland, discovered evidence of a giant shark attack on a whale 15 million years ago. Douglass, or Douggie, donated the whale fin fossil to the Calvert Marine Museum, rather than selling it - as with most other fossils discovered by the collector.

From there, the museum's paleontology expert, Stephen Godfrey, conducted a study with his team to identify the whale and how it ended up in the Calvert Cliffs area of Maryland, where Douggie discovered it.

However, the team identified teeth marks on the radius (mammalian forelimb bone) that likely belonged to a giant shark. Since the fossil dates to the Miocene, between 23 and 5 million years ago, the biting fish may well have been a young Megalodon, the authors report.

Although a shark bite isn't exactly a pleasant thing, the whale probably didn't mind too much. That's because she was actually dead long before the shark came in to grab some pieces.

"When a whale dies, it inverts and floats on the water surface due to increased abdominal gases from decomposition," Godfrey tells Live Science. That would have made the fins an easy target for sharks, according to the research.

As is the case today, after the whale's death, several species of opportunistic sharks could feed on the carcass. The animals remove pieces of prey near the water surface, often putting their heads out to sea.

Image: Stephen Godfrey/CMM

Possible candidates for this giant shark

In addition to the obvious marks of a shark's teeth, the researchers were also able to identify some movements of the beast tearing its prey. This is because the fossil shows marks of teeth penetrating the bone, as well as signs that the shark swung its head from side to side trying to tear off the flesh.

Unfortunately, the fossils do not clearly show whether the shark had serrated teeth or not. According to the authors, this could help identify the possible giant shark responsible for the bites.

Still, the team has some more likely candidates: Alopias grandis , Allopias palatasi the genus Carcharhinus , Carcharodon hastalis , Galeocerdo aduncus , Hemipristis serra , Otodus megalodon , Physogaleus contortus e Sphyrna laevissima .

Not only among these species, but among all known species, the O. megalodon is the largest, with its estimated size approaching 20 meters in length. The animal that left its mark on this fossil, however, if it was of the species, would still be quite young. Otherwise it would have gobbled up the entire fin.

If the researchers had found non-serrated teeth marks, the most likely candidate would be the Carcharodon hastalis Despite this, their modern descendants - the white sharks - have saw-like teeth.

Image: MLbay / Pixabay

The research is available in the journal Carnets Geol. and will be presented at the Society of Vertebrate Paleontology annual conference on Nov. 5.