‘Evolutionary Dead End’: Extinct ‘Stilt’ Horse Named for Canadian
A newly-discovered branch of the horse family has been named after the Canadian who first studied its remains in the Yukon, where it lived until the end of the last ice age.
Close study of the North American stilt-legged horse has revealed that the ice age-era mammal was an “evolutionary dead end” in the horse family, which developed through the Equus genus to spawn modern-day horses, asses and zebras. The taller, thinner stilt-legged horse lived up until approximately 17,000 years ago and died out entirely after the last ice age, according to the new study published in the journal eLife.
The study authors have officially classified the stilt-legged horse as a separate genus from the Equus, based on differences observed at the DNA level. The stilt-legged horse was first described in the 1970s by Canadian paleontologist Richard Harington, but was thought at the time to be related to the Asiatic wild ass or onager.
The new genus has been dubbed Haringtonhippus francisci, after Harington. Harington did not work on the new study, but the study’s authors say they named the new genus after him as a tribute to his groundbreaking work on the ancient animal.
“I am delighted to have this new genus named after me,” Harington, emeritus curator of quaternary paleontology at the Canadian Museum of Nature, said in a news release from the study authors.
Co-author Grant Zazula said the discovery would not have been possible without Harington’s “life-long dedication” to studying the stilt-legged horse in Canada’s North.
“There is no other scientist who has had greater impact in the field of ice age paleontology in Canada than Dick,” Zazula, a paleontologist with the Yukon government, said in the news release.
A connection that goes way, way back
The discovery is expected to shake up long-held theories that horse evolution was fairly straightforward, by demonstrating that a divergent branch of the family tree emerged some 4-6 million years ago before dying out.
“The horse family, thanks to its rich and deep fossil record, has been a model system for understanding and teaching evolution,” first study author Peter Heintzman, of UC Santa Cruz, said in the news release. “Now, ancient DNA has rewritten the evolutionary history of this iconic group.”
The study authors say the Equus and Haringtonhippus genuses thrived alongside one another in North America, although they did not interbreed. They co-existed with such large ice-age mammals as the woolly mammoth and the sabre-toothed cat, which also died out when the glaciers receded. The North American Equus and Haringtonhippus died out around the same time, but the Equus survived though a number of ancient horses that remained in Eurasia.
The stilt-legged horse discovery was made based on DNA taken from fossils in the Yukon’s Klondike gold fields, as well as from Natural Trap Cave in Wyoming and Gypsum Cave in Nevada.