The giant, extinct megalodon shark ruled the seas millions of years ago, but even this fearsome ocean-eater wasn’t immune to dental problems.
Recent analysis by a megalodon (Otodus megalodon) tooth with a rare anomaly – a groove down the middle – suggests the tooth deformity may be tracing its roots to an injury to the basking shark’s jaw, possibly caused by prey fighting back. In an illustration depicting a possible encounter, a fish pierces the jaws of the pursuing predator with its sharp beak, which may have set the stage for the megalodon to grow a cloven tooth.
Another possibility is that the great shark was speared by a stingray, scientists wrote in a new study.
In humans and other mammals, genetic factors, disease, or injury can sometimes affect tooth buds, causing a tooth abnormality known as “double tooth pathology,” in which a single tooth grows with a gap running lengthwise down the center, the authors wrote the study. Such teeth may represent two tooth buds uniting into one tooth, a process known as fusion, or a single tooth bud dividing, known as gemination. However, little is known about this pathology in sharks.
For the study, the researchers analyzed a 4-inch (10 centimeter) long split megalodon tooth along with split fossil teeth from other sharks to determine what might have caused the deformities. The scientists concluded that traumatic injury was the most likely cause of the prehistoric split teeth, and the encounter that damaged the megalodon tooth may have influenced the shark’s hunting and feeding habits.
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Megalodon was one of the largest predators that ever lived, measuring at least 15 meters long and at least 50 feet (15 meters). as much as 65 feet (20 m) long by some estimates, Live Science previously reported. To put that in perspective, modern great white sharks (Carcharodon carcharias) usually do not exceed 6 m in length.
Although the megalodon thriller “The mega(Warner Bros Pictures, 2018) suggested that individual megalodons may still be lurking in the ocean depths, most megalodon fossils date to around 15 million years ago and all evidence of the basking sharks disappeared from the fossil record after they went extinct about 2.6 million years ago.
Sharks have skeletons made of cartilage, which isn’t as strong as bone and doesn’t usually fossilize well, so most megalodon fossils that survive to this day are teeth. Like modern sharks, megalodon was constantly losing teeth and growing new ones, with a constantly regenerating supply stored in its jaws. Thanks to this so-called dental conveyor belt, some sharks can lose and replace tens of thousands of teeth over their lifetime, studies co-author Haviv Avrahami, a graduate student in North Carolina State University’s Department of Biological Sciences at Raleigh, told Live Science in an email.
“It would be like losing about 20 baby teeth every month,” Avrahami said.
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To find out what the root of the split megalodon tooth might be, the researchers combed through hundreds of fossil shark teeth in the collection of the North Carolina Museum of Natural Sciences in Raleigh. They found just two other examples of the unusual split-tooth deformity: two bull shark teeth Carcharhinus leucas, a species that lived alongside Megalodon millions of years ago (but was much smaller, reaching a maximum body length of about 12 feet, or 3.7 m) and that still exists today.
They measured the deformed teeth alongside normal teeth of the two shark species and then made calculations roentgen tomography or CT scansto map the pulp cavities in bull shark teeth and the vascular networks inside the megalodon tooth and see how they might have evolved.
Their analysis suggested that gemination was more likely than fusion to have produced the double teeth based on where the pulp cavities and networks split “and the absence of major root abnormalities” in all double teeth, according to the study. The split teeth are also very symmetrical, which would not be the case if they had formed from the fusion of two tooth buds at different stages of development, the scientists reported.
The root of the matter
What may have caused the pathology, traumatic damage to the tooth bud from a puncture wound is a more likely cause than disease or infection, which sharks usually shrug off, Avrahami explained. “Sharks are odd in that they seem particularly resistant to infection,” he said. Because of this, “it is believed that other tooth deformities in sharks are more likely to result from trauma,” he added. Modern bull sharks are known to feed on spiny prey capable of causing such injuries, including sawfish, rays and sea urchins, and while megalodon is believed to have primarily hunted marine mammals – and perhaps fish and turtles – its diet may have been more diverse than expected, including sea creatures with pointed defensive weapons.
With around 300 teeth in its mouth, the megalodon probably wasn’t too bothered by a single split tooth. But if its tooth bud had been injured by a barb or spine, which then became lodged in the great shark’s jaws, “it would likely have caused the animal great pain and possibly made it difficult to hunt,” Avrahami noted.
The study’s closer look at megalodon teeth not only offers new insights into tooth misalignments in sharks; It also raises questions about how common double tooth pathologies might have been in other animal lines that also had continuous dentures, such as: dinosaur (including toothed birds) and crocodiles, Avrahami said.
“I’ve seen many hadrosaur teeth in my life, which are dinosaurs that also have extensive tooth battery conveyor belts, and not a single one had a double-tooth appearance. Why?” he asked. “So I really hope future researchers explore this more.”
The results were published in the journal on May 11 peerJ (opens in new tab).
Originally published on Live Science.
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