The two sharks, dubbed Mennerotodus mackayi and Mennerotodus parmleyi, both belong to the same genus, or group of species, and are relatives of modern sand tiger sharks, according to a study published in the journal Fossil Record.
The fossils of the sharks date from between 65 million years ago to 35 million years ago, the researchers said.
The authors of the study were able to identify the sharks as new species based on examination of hundreds of isolated teeth, which were discovered in southern Alabama and central Georgia for Mennerotodus mackayi and Mennerotodus parmleyi respectively.
Fossils of sharks from the genus Mennerotodus—whose members are now all extinct, including the two newly identified species—have only previously been found in Europe and Asia, according to the scientists.
Mennerotodus mackayi appeared around 65 million years ago just after the mass extinction event caused by a giant asteroid impact that wiped out the dinosaurs, the researchers said.
“Based on the number of teeth we recovered, it was likely one of the more common species in the ancient Gulf of Mexico 65 million years ago,” Jun Ebersole, Director of Collections at the McWane Science Center in Birmingham, Alabama, and an author of the latest study, said in a statement.
Mennerotodus parmleyi, meanwhile, lived around 35 million years ago and was identified from hundreds of teeth collected from a defunct kaolinite mine in central Georgia that scientists initially thought belonged to two or three different species.
“Our reanalysis of the teeth showed they instead belonged to an entirely new species,” David Cicimurri, Curator of Natural History at the South Carolina State Museum in Columbia, and another author of the study, said in a statement.
Analysis of teeth from both of the sharks and comparisons to modern shark species revealed that Mennerotodus mackayi and Mennerotodus parmleyi are closely related to modern sand tiger sharks, which are found in warm or temperate waters across the world—apart from the eastern Pacific—and can grow to over 10 feet in length.
“Like in modern sand tiger Sharks, the front teeth in the mouths of the fossil species are very tall and fang-like” Ebersole said. “These teeth often project out of the mouth, giving the shark a snaggle-toothed appearance, and were perfect for feeding on fishes, crabs, squids, and even other sharks.”
In the study, the researchers concluded that the genus is likely more widely distributed than is currently known, but their teeth can often be mistaken for sharks of other groups.
“These teeth are significant because they represent the first occurrence of Mennerotodus in North America,” Ebersole said. “And because the Mennerotodus mackayi teeth in Alabama are older than those from other parts of the world, it strongly suggests that this group of sharks originated right here in the ancient Gulf of Mexico.”
