Rhinoceroses Lived in Yukon Territory 8-9 Million Years Ago
The fossil tooth fragments from extinct rhinoceroses that lived 8-9 million years ago have been found in Canada’s Yukon Territory.
The fossils were originally discovered by schoolteacher Joan Hodgins and her students in 1973.
“In the Yukon, we have truckloads of fossils from ice age mammals like woolly mammoths, ancient horses and ferocious lions,” said Dr. Grant Zazula, a paleontologist with Yukon Government.
“But this is the first time we have any evidence for ancient mammals, like rhinos, that pre-date the Ice Age.”
During the Tertiary period, a span of time that began after the dinosaurs went extinct and ended about 2.6 million years ago, a land bridge called Beringia connected what are today Siberia and Alaska.
Paleontologists believe that animals of all sorts, including mammoths and rhinos, poured over that bridge.
The geology and environment of the Yukon, which sat at the center of that mass migration route, isn’t conducive to preserving fossils from land animals.
“We know that a land bridge must have been in operation throughout much of the last 66 million years,” said Dr. Jaelyn Eberle, a curator of fossil vertebrates at the University of Colorado Boulder’s Museum of Natural History.
“The catch is finding fossils in the right place at the right time.”
The team used a scanning electron microscope to analyze the structure of enamel in the fossil tooth fragments.
“Mammal teeth aren’t all built alike,” Dr. Eberle explained.
“The crystals that make up enamel can grow following different patterns in different types of animals, a bit like a dental fingerprint.”
“The Yukon tooth enamel carried the tell-tale signs of coming from a rhinoceros relative.”
The method isn’t detailed enough to determine the precise species of rhino.
“But, if this animal was anything like its contemporaries to the south, it may have been about the same size or smaller than today’s black rhinos and browsed on leaves for sustenance,” Dr. Eberle said.
“It also probably didn’t have a horn on its snout.”
The paleontologists also looked at a collection of fossils found alongside the rhino’s tooth chips.
They belonged to two species of turtle, an ancient deer relative and a pike fish.
The discovery of the turtles, in particular, indicated that the Yukon had a warmer and wetter climate than it does today.
Hodgins, now-retired, is excited to see what became of the fossils she and her students discovered 46 years ago: “It’s just so wonderful to learn what has developed with them from long ago.”
The team’s paper was published in the journal American Museum Novitates.
Jaelyn Eberle et al. 2019. The First Tertiary Fossils of Mammals, Turtles, and Fish from Canada’s Yukon. American Museum Novitates 3943: 1-28; doi: 10.1206/3943.1