A baleen whale was lunch for a giant shark — possibly a megalodon — some 12–15 million years ago, bite marks on a fossilised flipper bone (or ‘radius’) have revealed.
Perhaps fortunately for the whale, it was most likely dead at the time and floating at the sea surface when the shark scavenged it, Calvert Marine Museum experts said.
The damage to the radius was analyzed and it appears that one shark repeatedly dug its teeth into the corpse, thrashing its head to remove each bite.
As is standard for so-called ‘trace fossils’ — evidence of animal behaviour — the bite marks were given their own species name, that of ‘Linichnus bromleyi’.
The 11-inch-long bone was found at Parkers Creek, in Maryland’s Calvert County, by local fossil collector William Douglass, and donated to the Calvert Marine Museum.
Identifying the exact shark species that left the bite marks is difficult — but suspects include a young Otodus megalodon, the largest shark ever known to have lived.
Megalodon was an extinct mackerel shark thought capable of growing up to 65 feet in length and biting through flesh and bones with a force of 182,200 newtons.
A baleen whale was lunch for a giant shark — possibly a megalodon — some 12–15 million years ago, bite marks on a fossilised flipper bone, or ‘radius’, have revealed. Artist’s impression of the shark eating on the larger whale
‘This bone is very unusual because it preserves so much evidence of head-thrashing behaviour of an extinct shark feeding on an extinct whale’, Calvert Marine Museum’s curator of palaeontology and paper author Stephen Godfrey said in a press release.
Multiple gouge marks were discovered on both sides the whale’s flipper bones, indicating that the shark had taken at least three bites from the large marine mammal.
‘The bite–shake traces consisting of shallow, thin arching gouges on the radius likely indicate scavenging rather than active predation,’ Dr Godfrey told Live Science.
The shark would have clamped down on the flipper and then shaken its head vigorously to try to cut through the bone (unsuccessfully) and to remove any flesh. After removing some, the shark would re-bite the flipper to remove any more.
Based on the radius bone’s flattened and curved shape, the researchers believe that the fossil originally belonged to a filter-feeding baleen whale — most likely Diorocetus hiatus, an extinct species known to have lived in the area.
Dr Godfrey explained to Live Science that when a whale dies, it inverts into a floating object at the surface of water because of the buildup of abdominal gases due to decomposition.
Scavenging sharks often feed at the ocean’s surface — and the whale’s flipper would have been an easy target for the hungry creature, the team explained.
The damage to the radius was analyzed (pictured, after whitening to increase the contrast). It is evident that the shark repeatedly bit into the corpse, tearing off each bite with a slash. The numbers indicate how many gouges each bite left, in the most likely order they were done.
Dr Godfrey stated that Megalodon and other sharks may have been responsible for the posthumous attack.
Unfortunately, the bite marks do not indicate clearly enough whether or not the shark had serrated teeth — which could have been used to narrow down the culprits.
Were the marks made by a shark with non-serrated teeth, Dr Godfrey told Live Science, then the ‘most likely candidate would be Carcharodon hastalis — the ancestor of the living great white shark.’
The journal Carnets Geol published all findings.
William Douglass, a local fossil collector, found the 11-inch-long bone at Parkers Creek in Maryland’s Calvert County. He donated it to the Calvert Marine Museum