5-Million-Year-Old Saber-Toothed Cat Fossil Discovered in Florida Belongs to New Genus and Species

Scientists say that a new genus and species of extinct saber-toothed cat has been unearthed in Polk County, Fla.

The fossil, which is 5-million-years-old, is related to the carnivorous predator Smilodon fatalis from the La Brea Tar Pits of Los Angeles. This group of saber-toothed cats known as Smilodon were thought to have originated in the Old World, and later migrated to North America. However the age of the new species suggests that the group evolved in North America.

Study co-author Richard Hulbert Jr., a vertebrate paleontology collections manager at the Florida Museum of Natural history, says that Smilodon appears in the fossil record about 2.5 million years ago, however there were not many intermediate forms to indicate to scientists where it originated. He added:

"The new species shows that the most famous saber-toothed cat, Smilodon, had a New World origin, and it and its ancestors lived in the southeastern U.S. for at least 5 million years before their extinction about 11,000 years ago," Hulbert said in a statement. "Compared to what we knew about these earlier saber-toothed cats 20 or 30 years ago, we now have a much better understanding of this group."

Hulbert and his team of researchers discovered the fossils of the new cat, Rhizosmilodon fiteae, during the excavation of a phosphate mine in 1990. The new species was named for Barbara Fite of Lutz, Fla., who donated a fossil of the species from her collection, which had a very well-preserved lower jaw with all three chewing teeth. The name Rhizosmilodon means "root of Smilodon", because the scientists believe that the cat may be the direct ancestor of Smilodon, which went extinct 11,000 years ago.

To determine the cat's biological grouping, the researchers did a comparative analysis of saber-toothed cat anatomy. The animal's lower jaw and teeth were smaller than Smilodon's, about the size of a modern Florida panther.

While alive, the Rhizosmildon fitea would have lived along with tapirs, peccaries, llamas, rhinos, three-toed horses and deer in a coastal forest. It is here that scientists believe that the cat took advantage of its small size to climb trees and hide captured prey from larger meat-eaters, including packs of extinct bears that are larger than today's grizzlies and hyena-dogs.

Originally, the new cat was misindentified from a partial lower jaw fossil in the early 1980s as a member of the genus Megantereon. It's actually been found to be a sister species to Megantereon and Smilodon, but is older than both groups.

The new species was reported on March 13 in the journal PLOS ONE.