It’s only taken eight or nine million years to surface, but scientists have evidence now that a long-extinct member of the rhinoceros family once rumbled through the Canadian Yukon.
Grist for the conclusive proof of that surprising finding has actually been in human hands for nearly 50 years. But it is only recently that researchers were able to link the beast to an environment far from where its contemporary descendants can still be found.
Jaelyn Eberle, a curator of fossil vertebrates at the University of Colorado Boulder’s Museum of Natural History, is lead author on a recently published study that used cutting-edge modern technology to shed light on the origins of fossil tooth fragments which have been sitting for years like an unanswered question for the ages in the Yukon Government fossil collections in Whitehorse.
The tooth fragments were discovered by a Saskatchewan school teacher named Joan Hodgins, while hiking in the Wolf Creek area south of Whitehorse, Canada, in 1973. Eberle, herself, is a native Saskatchewan.
“It’s kind of strange, they were discovered by somebody from Saskatchewan, and studied by somebody from Saskatchewan, who didn’t know each other. Kind of unusual,” Eberle said earlier this month.
Her opportunity to connect with the decades-old mystery, she said, came at a recent conference.
“A colleague and I were both at a paleontology meeting together, and he said, ‘You know there are some fossils from the Yukon. I have looked at them, but I don’t know what they are.’”
That was Ross MacPhee, who would become a co-author on Eberle’s study, published recently in American Museum Novitates, a peer-reviewed academic journal published by the American Museum of Natural History.
“Most of my work the last 10 years or so has been in the higher Arctic, and this is from the Yukon. I just told them, ‘Send them to me — the stuff that nobody else wants to deal with,’” Eberle said with a laugh.
It so happened that she was headed at the start of this year to Bonn, Germany, to work during a sabbatical with Wighart Von Koenigswald, an emeritus professor of paleontology, a pioneer in the study of enamel microstructure.
“Whereas most of us, we look at the teeth themselves, the bumps, the cusps, the ridges and valleys that’s how we regard (fossil) teeth. He is different, he’s a pioneer in the study of enamel microstructure, looking at the inside of the enamel instead of what most of us do, which is looking at the outside.”
Eberle arrived with the Yukon fragments just after the first of the year. But even before she made the trip, she had a “gut feeling,” she said, from looking at them under a regular light microscope, that they might come from a rhino.
“They had these stripes or banding that I could see on the chewing surface of one fragment and when you see that banding, it suggests to prisms (within the enamel) are vertical,” as opposed to horizontal, as would the case with most large mammals.
But when she got the samples to Von Koenigswald’s lab in Bonn, and put them under his scanning electron microscope, the structure of tooth enamel was revealed in incredible detail, and their origins were clear.
“I remember I emailed Grant (co-author Grant Zazula), and said, “Grant, you got a rhino in the Yukon.’ And he was just so excited, saying ‘Oh my gosh, this is big Jaelyn, this is really big.’”
“In the Yukon, we have truckloads of fossils from ice age mammals like woolly mammoths, ancient horses and ferocious lions,” Zazula, a Yukon Government paleontologist, said in a statement. “But this is the first time we have any evidence for ancient mammals, like rhinos, that predate the ice age.”
Hodgins, who now is retired, is excited to see what became of the fossils she and her students discovered more than 40 years ago: It’s “just so wonderful to learn what has developed with them from long ago,” she said.
The find, dating to the Miocene Epoch, fits into paleontologists’ understanding of the Earth during the Tertiary Period — a broad span of time that began after the dinosaurs went extinct and ended about 2.6 million years ago — when a land bridge called Beringia linked what are today Russia and Alaska.
“We know, or we think at least people would hypothesize, the rhinocerotids came from Asia and tromped across Beringia into North America, and they were probably going back and forth across Beringia. We’ve been hypothesizing this for a long time, that Berengia was the likely source for rhinos and a lot of big animals coming into North America. But we have not had a lot of direct evidence.”
Rhinocerotid is the family to which the Yukon samples have been assigned, but as for genus or species, those for now remain a mystery.
“At the level of tooth enamel structure, a rhino is a rhino is a rhino,” Eberle said. “We could estimate that we’re dealing with a large rhino,” one that most likely browsed on leaves, as opposed to one that grazed on grasses.
And, unlike the rhinos with which we’re familiar in this day and age, it most likely would not have had a horn.
Eberle said Zazula has expressed an interest in taking her to the Wolf Creek site where Hodgins made her lucky find, to see what else they might discover.
Also previously found alongside the rhino’s tooth chips had been fossil fragments linked to two species of turtle, an ancient deer relative and a pike fish, suggesting the Yukon had a wetter and warmer climate than it does today.
“We’ve got people saying, now that we know the Yukon has this, we better start looking,” Eberle said.