Fossil find adds to evidence of dinosaurs living in Arctic year-round
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[June 30, 2021]
By Yereth Rosen
ANCHORAGE, Alaska (Reuters) - Fossils from
tiny baby dinosaurs discovered in northernmost Alaska offer strong
evidence that the prehistoric creatures lived year-round in the Arctic
and were likely warm-blooded, according to a study published on Thursday
in the journal Current Biology.
The fossils are from at least seven types of dinosaurs just hatched or
still in their eggs about 70 million years ago. Researchers have never
found evidence of dinosaur nests so far north, said lead author Pat
Druckenmiller, director of the University of Alaska Museum of the North.
The find helps upend past assumptions of dinosaurs as giant cold-blooded
reptiles.
"If they reproduced, then they over-wintered there. If they overwintered
there, they had to deal with conditions that we don't usually associate
with dinosaurs, like freezing conditions and snow," Druckenmiller said.
To survive dark Arctic winters, those dinosaurs could not have basked in
the sun to warm their bodies, as lizards do, he said.
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"At least these groups had endothermy," he said, using the term for the
ability of animals to warm their bodies through internal functions.
"They had a degree of warm-bloodedness."
The discovery site is a steep bluff on the Colville River on Alaska's
North Slope, at latitude 70 and about 250 miles (400 km) north of the
Arctic Circle. In the Cretaceous period, when North America was
positioned differently, it was even farther north, at latitude 80 or 85,
Druckenmiller said.
The region was much warmer then than Alaska's North Slope is now but
hardly tropical. From remnants of ancient plants, scientists calculate
the average annual temperature at about 6 degrees Celsius (42.8
Fahrenheit) – similar to Juneau, Alaska – meaning below-freezing winters
with snow, Druckenmiller said.
While Alaska's North Slope endures two months of total winter darkness
now, during the Cretaceous period it was in total darkness for up to
four months a year, he said.
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Finding the tiny bones and teeth, some the size of a
pinhead, was laborious, Druckenmiller said. They were identified
through microscopic examination after being sifted out multiple
times from sediments collected in expeditions stretching back
decades, he said.
"I liken it to gold panning. It's a very slow process," he said.
The discovery site, called the Prince Creek Formation, has proved
crucial to modern understanding of the ancient creatures.
The first dinosaur discovery was made there in the 1960s by a
petroleum geologist. Subsequent expeditions found previously unknown
dinosaur species. Over time, evidence of year-round Arctic
occupation has mounted.
At the same formation, other scientists found a jawbone from a baby
dromaeosaurid, detailed in a study published last year in the
journal PLOS ONE. That meat-eating dinosaur would have been the size
of a small puppy and incapable of long-distance migration, said
co-author Tony Fiorillo, a Southern Methodist University
paleontologist.
The new study about nesting dinosaurs strengthens the growing
realization that dinosaurs lived full-time in the Arctic and thus
could not be cold-blooded, Fiorillo said.
"This new study broadens the conversation about year-round dinosaurs
in the Arctic. It didn't invent the conversation," he said.
(Reporting By Yereth Rosen in Anchorage; editing by Richard Pullin)
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