Did the world's largest prehistoric shark need orthodontics or did it just eat a bad lunch? Researchers from North Carolina State University (NCSU) and the North Carolina Museum of natural science examined the deformed teeth of a giant toothed shark (o. MEGALODON) to determine the root cause - whether it is a developmental problem or related to eating?
It is understood that these findings can give paleontologists a deeper understanding of the development process and predation behavior related to the tooth damage of ancient sharks.
One of the controversial explanations is an abnormal phenomenon called bidentate pathology, that is, the "division" of a single tooth. There are many possible reasons behind this: during tooth development, two tooth buds can fuse into one, or one tooth bud can split into two (this process is called doubling). Fusion and doubling can be caused by disease, heredity or physical damage to tooth buds.
"We don't have a lot of data on the bidentate disease of ancient shark species," said Harrison Miller, corresponding author of the paper describing the work. "So this is an opportunity to fill these gaps - maybe we can learn more about sharks in the process."
The researchers examined three unusual teeth: a 4-inch tooth from a giant toothed shark, a top predator the size of a school bus that ruled the ocean during the Miocene and early Pleistocene (from 11 million to 3.7 million years ago); The other two are from the true bull shark (Carcharhinus leucas), a smaller species of bull shark that lived in the same period and still roams the sea today.
All three oddly shaped teeth show a pathological form of double teeth. The researchers compared the teeth with the normal teeth of the two species and also performed nano CT imaging of the deformed teeth so that they could check what was happening inside.
Although diseased teeth do have more internal pipelines than normal teeth - confirming the incomplete division or connection of two teeth during development - the researchers cannot clearly determine the cause of development.
Haviv avrahami, a doctoral student in North Carolina and co-author of the paper, said: "Part of the difficulty is to apply the working terminology of humans and other mammals to sharks. Sharks have cartilaginous bones, not bony bones, so their jaws are rarely preserved in the fossil record, and usually we only find individual isolated teeth. In addition, sharks have different tooth development mechanisms - they have continuous tooth replacement, so you can't see what's happening in the rest of the jaw Except for fusion or doubling. "
However, given the researchers' understanding of this pathology of modern shark teeth, they tend to consider feeding related injuries as a more likely cause.
"Megatoothed sharks, in particular, are currently understood to feed mainly on whales. But we know that tooth deformities in modern sharks may be caused by sharp objects piercing the conveyor belt of tooth development in the mouth. According to what we see in modern sharks, this injury is likely to be caused by biting a barbed fish or being stabbed by the barb of a stingray," avrahami said.
"We also know that megatoothed sharks have nests near Panama, where relatives of modern stingray species also inhabit," Harrison said. "And these spines can become very thick. Therefore, this type of tooth damage may indicate that megatoothed sharks are more like a universal predator - especially if this megatoothed shark has only a bad day."
Lindsay zanno, head of paleontology at the North Carolina Museum of natural sciences, associate research professor at North Carolina State University and co-author of the study, agrees. "When we think about the encounter between predators and prey, we tend to retain our sympathy for prey, but the life of predators, even giant toothed sharks, is not a piece of cake," he said
It is reported that the relevant research report has been published in peerj.