A fragment of whale rib found in a North Carolina strip mine is offering scientists a rare glimpse of the interactions between prehistoric sharks and whales some 3- to 4-million years ago during the Pliocene epoch.
Three tooth marks on the rib indicate the whale was once bitten severely by a strong-jawed animal. Judging by the two-inch (six-centimeter) spacing between tooth marks, scientists believe the attacker was the mega-toothed shark Carcharocles megalodon, or perhaps another species of large shark existing at that time. The whale appears to have been an ancestor of a great blue or humpback.
The Smithsonian Science website featured a story about the discovery, November 9, 2011. A paper about the finding was published online in the International Journal of Osteoarchaeology, on August 27, 2010.
Stephen Godfrey, who discovered the fossil, is a paleontologist at the Calvert Marine Museum in Solomons, Maryland. He said:
One certainly doesn’t expect to find evidence of animal behavior preserved in the fossil record, but this fossil shows just that — a failed predation. The shark may have gone away with a mouthful, but it didn’t kill the whale.
Don Ortner, an anthropologist at the Smithsonian’s National Museum of Natural History, said scientists know the whale survived because …
… most of the fossil fragment is covered with a type of bone known as woven bone, which forms rapidly in response to localized infection. Biomechanically, woven bone is not very strong. The body eventually remodels it into compact bone, but it takes time.
CT scans revealed evidence of inflammation in the bone marrow consistent with infection.
The presence of the woven bone indicates the healing was incomplete and the whale died, the scientists estimate, between two and six weeks after the attack. The whale’s death may have been unrelated to its infection and injury, Ortner said:
We don’t know why it died.
Based on the curvature of the shark’s jaw, as indicated by the arc of the impressions of its teeth, the scientists believe the shark was relatively small, between 13 and 26 feet (four and eight meters) long.
Only a handful of fossils show these kinds of interactions. There are lots of bite marks on fossils showing where the animal died and [showing that] its carcass was scavenged. This fossil is one of a very few examples that shows a trauma clearly attributed to another animal, yet also shows the victim survived the event.
Bottom line: Scientists from the Smithsonian’s National Museum of Natural History and the Calvert Marine Museum in Solomons, Maryland, have studied a fossil whale rib — found in a North Carolina strip mine — showing teeth marks attributed to a large shark of that time, possibly Carcharocles megalodon. Their paper first appeared August 27, 2010, in the International Journal of Osteoarchaeology and was featured November 9, 2011, on the Smithsonian Science website.