SOLOMONS, MD – August 2021 – Years ago, the late fossil enthusiast Norm Riker (Figure 1) found a sperm whale tooth (Figure 2) in fossil-rich spoil piles in the Aurora Phosphate Mine, Aurora, North Carolina, USA. More recently, when he donated his important collection of fossils to the Calvert Marine Museum, Paleontology Collections Manager John Nance discovered that there were large shark bite marks on the sperm whale tooth. This is a first for the fossil record – that bite marks from a megatoothed shark, like megalodon, have been found on another raptorial macro-predator, a sperm whale. 

“I noticed the large sperm whale tooth while processing the thousands of fossils donated by Norm Riker,” said John Nance. “After picking up the tooth I saw the serrated scrapes on it and brought it to Stephen’s attention, realizing it was an important fossil.” A description of this remarkable find was published recently in the open-access paleontology journal Acta Palaeontologica Polonica. The tooth shows three gouges, one of which also preserves raking bite traces, made as the serrations on the giant shark tooth struck and cut into its surface (Figures 3 and 4). Calvert Marine Museum Curator of Paleontology Dr. Stephen Godfrey said that they do not know if these bite traces came about as a result of scavenging or active predation. However, because the bite traces occur on part of the skull, this suggests a live predatory interaction (Figure 5) instead of just scavenging by the giant shark. 

This tooth preserves the first evidence in the fossil record of a possible predatory/antagonistic interaction between a sperm whale and a megatoothed shark. What makes these bite traces even more interesting is that they occur on part of the root that was originally embedded in the sperm whale’s jaw. In order for the shark teeth to have marked the sperm whale tooth, they would first have had to cut/break through the whale’s jaw bone. The bite most likely also damaged the surrounding bone. This implies the ability of a powerful bite on the part of the shark. From where the tooth was found in the mine, we do not know exactly how old it is. It could have come from sediments as young as 6 million years or as old as 18 million years. 

Although we do not know for sure if these bite traces came about as a result of scavenging or active predation, we think that a stronger case can be made for active predation (Figure 5). It would seem unlikely that a large shark would target the jaws of a floating or seafloor carcass of a sperm whale. There would be little flesh in return for the effort on the part of the megatoothed shark. Rather, these bite traces suggest a live antagonistic interaction. They hint at an attack to the head of the sperm whale with the goal of the giant shark inflicting a mortal wound. This kind of attack to the skull contrasts with the strategies used by modern large sharks to attack small, echolocating toothed whales (like dolphins). Both modern and fossil dolphins and sperm whales had the ability to echolocate… that is the ability to use sound to navigate through dark or murky waters, kind of like a sound-generated radar. Modern large sharks are thought to concentrate their attacks on the posterior part of dolphin bodies, whereby avoiding detection by both the dolphin’s ability to see and their biosonar, i.e., their ability to “see” with sound. 

Apparently, in stark contrast to this strategy on echolocating dolphins, predation patterns in living great white sharks on non-echolocating seals inferred from wounded carcasses, differ in that bite marks are more evenly distributed all over the body. They have even been found with regularity on the head, suggesting that great white sharks focus on the head-end of the body when attacking these prey. Prehistoric bite traces by megatoothed sharks have now been found in all regions of whale and dolphin skeletons. However, we do not yet know if megatoothed sharks had preferred attack strategies for different kinds of prey. Other fossil finds may yet answer that question.

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