An international team of researchers reported the discovery of a fossil of a megatooth shark in the deep sea. The fossil—a single, well-preserved tooth—was found during a survey of the ocean floor near Cornwallis Island, a remote atoll in the North Pacific Ocean, located about 750 nautical miles (1,390 kilometers) southwest of the island of Hawaiʻi.
Fossil shark teeth are common in the fossil record, but so far, they were found buried in marine sediments or washed ashore after a storm reworked older deposits. Finding a shark tooth in situ on the ocean floor, where it was likely deposited shortly after its former owner lost it, is only possible if specific environmental conditions are met. The researchers suggest the tooth was able to remain in its original position due to its location, a part of the sea floor where the currents prevent the buildup of sediment but are not strong enough to move or destroy the fossil. The site where the sample was collected was a relatively flat area on a ridge crest of an unnamed seamount at a depth of 3,090 meters. The fossil was found sticking out from a field of manganese-oxide nodules. Such nodules form in areas of the ocean floor with low sediment input and where chemical precipitation prevails.
After documenting the fossil, the researchers recovered it thanks to a remotely controlled underwater robot and identified it as an Otodus megalodon tooth.
The megatooth shark Otodus megalodon roamed the world’s oceans approximately 23 to 3.6 million years ago.
Despite its fame in pop culture, surprisingly little is known about this species. Scientists have long debated, based on fragmentary remains and fossil teeth, on life-appearance and size. Often depicted as a super-sized white shark, an anatomical study published in 2020 concluded that O. megalodon was more closely related to the modern mako shark Isurus oxyrinchus, and the living animal’s length is thought nowadays to be about 20 meters—the maximum size sharks can get.
The fossil from the Pacific Ocean likely came from a small to medium-sized animal based on the average size of the tooth. The recovered specimen is relatively small, measuring 6.8 centimeters, with O. megalodon teeth easily growing over 15 centimeters in length.
The study “First in situ documentation of a fossil tooth of the megatooth shark Otodus (Megaselachus) megalodon from the deep sea in the Pacific Ocean” was published in the journal Historical Biology (2023).
