SOLOMONS, MD – Sept. 8, 2022 – Living great white sharks don’t always succeed at killing their intended prey, and so it would seem with the extinct megatooth shark megalodon.
Two associated (i.e., from the same individual) Miocene-epoch fossil whale vertebrae found along Calvert Cliffs were so traumatically damaged in life that the most plausible cause was a predatory encounter between the small whale and the giant shark megalodon. Yet, the whale survived…for a time.
This is the conclusion to which researchers at the Calvert Marine Museum (CMM), Maryland, and the New York Institute of Technology (NYIT), College of Osteopathic Medicine have come to after a detailed study of these 15-million-year-old fossils.
One of these two whale vertebrae, from an individual that would have been about 13 feet long, preserves evidence of a major shear-compression fracture (Figures 1 and 2). For this kind of injury to happen, the whale’s backbones had to have been bent very forcefully into such a tight curve that pressure from the adjacent forward vertebra smashed the one shown in Figures 1 and 2. This would have been an excruciatingly painful injury for the whale.
These unusual fossils were found by long-time Calvert Marine Museum volunteer and fossil collector Mike Ellwood. CT scans of this pathological whale vertebra by Calvert Memorial Hospital show how it was broken (Figure 2). The lower front end of the vertebra was broken off and telescoped into that part of the bottom of the vertebra that was not broken. Following the traumatic injury, this broken piece of bone was fixed in place by new bone growth (bottom of Figure 2).
In addition to the two whale vertebrae, Dr. Stephen Godfrey, CMM, and Dr. Brian Beatty, NYIT, describe a single megatoothed shark tooth from Otodus megalodon found with the whale vertebrae (Figure 3). It was not embedded in either of the vertebrae, nor did they see megalodon bite marks on the vertebrae.
There are several seemingly equally likely explanations for the association of this lone megalodon tooth with these vertebrae.
- This tooth may have become associated simply by chance, unrelated in any way to the originating trauma or even the final death, and presumed to scavenge off the cetacean.
- The tooth became embedded in the whale’s body, resulting from a bite associated with the originating trauma. Then the tooth remained embedded in the whale’s body until it died, and both the vertebrae and tooth were subsequently preserved in very close proximity (i.e., touching).
- The tooth was shed by the shark that killed the whale. Or finally,
- A shark shed the tooth as it scavenged the whale’s carcass.
The fractures are severe and unlikely to have come about due to convulsions, seizures, or spasms, but these causes, other than the megalodon attack, can’t be completely ruled out. Seizures can cause vertebral fractures in humans, though these are most common in elderly adults with poor bone health.
Bone-crushing seizures have not been observed in whales and dolphins, though domoic acid poisoning from harmful algal blooms is known to cause seizures in whales and is implicated in the deaths of newborn baleen whales. It is unlikely but possible that a large whale would be affected by domoic acid poisoning to the point of a spinal fracture-causing seizure.
Similarly, protozoal infections are known to cause seizures in toothed and baleen whales, though a physical diagnosis of this is impossible in a fossil. Bone skull fractures from possible collisions with the seafloor have been reported, but a spinal fracture this far back in the spinal column seems unlikely to result from a seafloor collision.
Even though the cause of the shear-compression fracture and resulting pathological bone growth is unknown, we think that the most plausible cause was a crushing ambush delivered by a megatoothed shark, Otodus megalodon (Figures 4 and 5). From other fossil finds along Calvert Cliffs, we know that the megalodon was successfully preying upon both whales and dolphins.
However, the circumstantial evidence pointing towards megalodon as the likely predator, other albeit smaller macropredators are known from fossils along the cliffs, including the sharks Parotodus benedenii and one of the ancestors of the living great white shark, Carcharodon carcharias. Additionally, the researchers can’t rule out the possibility that the injury was caused by an attack from a Miocene macroraptorial sperm whale.
The severity of this traumatic injury ranks up there with those seen in modern whales that have suffered from anthropogenically-induced trauma, like boat-strike blunt force injuries to their skull and vertebrae, blubber, and muscle bruises forming large blood clots. Even with this variety of humanly induced traumas, shear-compression fractures like the one seen in the fossil whale have not yet been reported in living whales or dolphins.
Despite the whale’s gruesome encounter with the megalodon, it survived for a period of about two months before it died of unknown causes. The paper describing these amazing fossils was just published in the open-access online journal Palaeontologia Electronica.