U. FLORIDA (US) — A new genus and species of saber-toothed cat may be a missing link to and direct ancestor of Smilodon, a cat that went extinct about 11,000 years ago.
The 5-million-year-old fossils from Polk County, Florida, belong to the same lineage as Smilodon fatalis from the La Brea Tar Pits in Los Angeles, a large, carnivorous apex predator with elongated upper canine teeth.
Previous research suggested the group of saber-toothed cats known as Smilodontini originated in the Old World and then migrated to North America, but the age of the new species indicates the group likely originated in North America.
Richard Hulbert Jr. measures fossil teeth of a newly named species of saber-toothed cat recovered from a phosphate mine in Central Florida. In the foreground, the lower jaw of the 5-million-year-old new species is pictured between a modern Florida panther, left, and the famous Smilodon fatalis from about 15,000 years ago. (Credit: Jeff Gage)
“Smilodon first shows up on the fossil record around 2.5 million years ago, but there haven’t been a lot of good intermediate forms for understanding where it came from,” says study co-author Richard Hulbert Jr., vertebrate paleontology collections manager at the Florida Museum of Natural History at the University of Florida.
“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 US for at least 5 million years before their extinction about 11,000 years ago. 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 helped uncover fossils of the new genus and species, Rhizosmilodon fiteae, from a phosphate mine during excavations in 1990. The species was named after Barbara Fite of Lutz, Florida, who in 2011 donated one of the critical specimens used for the new description and allowed scientists to make casts of two other partial jaws in her collection.
Scientists say the donation was a major contribution because the remarkably well-preserved lower jaw contains almost pristine examples of all three chewing teeth. The genus name Rhizosmilodon, means “root of Smilodon.”
The study’s lead author, Steven Wallace, an associate professor in the department of geosciences and member of the Don Sundquist Center of Excellence in Paleontology at East Tennessee State University, used comparative analysis of saber-toothed cat anatomy to help determine the animal’s taxonomy.
Published in the journal PLOS ONE, the analysis was primarily based on structure of the animal’s lower jaw and teeth, smaller than the Smilodon and about the size of a modern Florida panther.
“The taxonomy of this animal was controversial because when it was first published 20 years ago, they only had one partial, somewhat-decent lower jaw, and it was missing some of the critical features,” Hulbert says. “We now have more complete specimens showing it has a mixture of primitive and advanced characters, and does not match any previously named saber-toothed cat genus or species.”
Originally misidentified as a member of the genus Megantereon in the early 1980s, Rhizosmilodon is instead the sister taxon to Megantereon and Smilodon, and the oldest of the group. These three cats are in the same tribe—meaning they are more closely related than a family or subfamily—and are often called as saber-toothed cats because of their long canine teeth.
“When people think of saber-toothed cats, they think of it as just one thing, as if the famous tar pit saber-toothed cat was the only species, when in fact, it was an almost worldwide radiation of cats that lasted over 10 million years and probably had a total of about 20 valid species,” Hulbert says. “Counting the newly described animal, there are now six different species of saber-toothed cats known just from Florida.”
The study helps settle the debate about whether the tribe arose from the Eurasia before coming to North America, says Julie Meachen, an instructor at Marshall University School of Medicine in Huntington, West Virginia.
“The fact that it’s one of the oldest lineages is really interesting because that means that this exciting group of saber-toothed cats really is a North American tribe—it evolved and persisted in North America.”
Source: University of Florida