Nov. 28 (UPI) -- A new analysis of ancient horse fossils suggests the New World stilt-legged horse warrants a new genus.
The thin-limbed horse roamed North America during the last ice age, but is now extinct. Until now, scientists thought the horse species was a member of the genus Equus -- possible a close relative of the Asiatic wild ass, also known as an onager, Equus hemionus.
Remains of the enigmatic species have been discovered in Wyoming's Natural Trap Cave, Nevada's Gypsum Cave and among the Klondike goldfields of Canada's Yukon Territory.
Genomic analysis of stilt-legged horse remains suggest the species, now named Haringtonhippus francisci, isn't closely related to any living equine population. The genus Haringtonhippus likely diverged from the main branch of the horse family tree some 4 to 6 million years ago.
"The horse family, thanks to its rich and deep fossil record, has been a model system for understanding and teaching evolution," Peter Heintzman, a postdoctoral researcher at the University of California, Santa Cruz, said in a news release. "Now ancient DNA has rewritten the evolutionary history of this iconic group."
Researchers detailed their analysis of the New World stilt-legged horse's genome in a new paper published this week in the journal eLife.
Scientists named the new genus for Richard Harington, the paleontologist who first described the unique horse species in the 1970s.
"Our research on fossils such as these horses would not be possible without Dick's life-long dedication to working closely with the Klondike gold miners and local First Nations communities in Canada's North," said Grant Zazula, a Government of Yukon paleontologist.
The range of Haringtonhippus francisci extended across much of North America. The horse lived alongside populations of various Equus species, but didn't interbreed. Like the wooly mammoth and saber-toothed tiger, the stilt-legged horse went extinct at the end of the last ice age.