DALLAS – After years of searching the Arctic Alaska, scientists at the Southern Methodist University in Dallas discovered the fragment of a baby dinosaur’s small jaw, providing what they believe is a significant clue to the behavior of certain dinosaurs. .
The theory: Some carnivorous dinosaurs, called dromaeosaurs, lived year-round in the Arctic.
Decades ago, scientists realized that birds could share a common ancestor with dromaeosaurs. So they thought that some dinosaurs migrated south with the changing seasons in search of food like the birds of today.
Today, most researchers assume that polar dromaeosaurs made the Arctic their home year-round, because their relatively small sizes would make migration difficult.
Dr. Anthony Fiorillo and his team recently published their findings on PLOS One. The presence of this baby dinosaur also suggests that during the Cretaceous Period, the Arctic was rich in prey to support the families of these carnivorous dinosaurs.
There would have been enough food available in the harsh Arctic environment to support a population of carnivorous dinosaurs, Fiorillo said. “For me, this specimen suggests that dromaeosaurs were thriving in an environment because their prey, herbivorous dinosaurs, had also successfully adapted to an extreme environment,” he said.
Artist rendering of a juvenile dromaeosaurus 70 million years ago in the Prince Creek Formation in northern Alaska. (Andrey Atuchin / Southern Methodist University)
More information about the life of different polar dinosaurs can help scientists better understand how they adapted to live year-round in these cooler, darker regions.
The discovery of this juvenile jaw could also help understand the diversity of animals that lived in the ancient Arctic, said Dr. Patrick Druckenmiller, a paleontologist at the University of Alaska Museum of the North in Fairbanks.
During the Cretaceous Period, which occurred between 66 and 145 million years ago, the Prince Creek Formation of northern Alaska was an open forest filled with conifers and flowering plants. The ancient Arctic was probably a little warmer than it is today, but there would have been mountains, with peaks high and cold enough to be covered with fields of snow.
The area was once part of “Beringia”, the land bridge that stretched between present-day Asia and North America, allowing dinosaurs to move freely between the two continents. Dinosaurs likely passed through parts of modern northern Alaska on their round trips. For a time, this land was considered a “dinosaur highway”.
In the 1970s and 1980s, paleontologists found similar species of large dinosaurs in both northern Alaska and southern Alberta. Since the dinosaur fossils were found thousands of kilometers away, some scientists thought that the dinosaurs might have migrated south from the Arctic in search of food when the weather turned colder.
“People thought that big dinosaurs used to migrate when we saw dinosaurs again not as heavy lizards but as dynamic ancestors of birds,” said Druckenmiller.
But the dinosaurs would have had to travel 1,000 miles to migrate from northern Alaska to Alberta or Montana, both south of the Arctic Circle. That would be a longer distance than any living vertebrate, or an animal with a backbone, can migrate on land. The current record of land vertebrate migration is in the hands of caribou, which flock about 400 miles each year.
For these reasons, other scientists believed that large dinosaurs could have lived in the Arctic throughout the year. But experts say they never thought that smaller dinosaurs, like dromaeosaurs, migrated south from the Arctic. Adult dromeosaurs are only 6 to 8 feet long, and it would be difficult for their small bodies to walk thousands of miles without running out of energy.
Dr. Anthony Fiorillo in his field in northern Alaska. (Southern Methodist University)
For 22 years, Fiorillo has traveled from his SMU office to Alaska, including his field site in Alaska’s Prince Creek Formation.
Fiorillo was looking for fossils to support the theory that dromaeosaurs lived north of the Arctic Circle. He and his team of scientists would assemble inflatable boats and travel up and down the windy Colville River examining the cliffs for fossils.
The researchers thought they found evidence of fossils from the Cretaceous period on an almost vertical cliff. As the sun rose during the day, the researchers worked to collect rocks from the frozen ground and routinely had to dodge rocks that fell from the melted ice.
While searching the cliff in 2007, Fiorillo’s team found the 14-millimeter dinosaur jaw with pointed teeth. It most likely is from a young dromaeosaur the size of a small cub, Fiorillo said.
Experts agree that the bone suggests that some small carnivorous dinosaurs lived north of the Arctic Circle.
“Having such a young person from this group of dinosaurs means that they likely lived somewhere close, even, if not exactly, in the fossil locality,” said Jack Tseng, paleontologist at the University of California, Berkeley.
But Druckenmiller is skeptical about whether the jaw fragment is from a dromeosaur. “Those teeth look quite different from the dromaeosaur teeth I’ve seen, and I’m not sure of their identity,” he said.
Druckenmiller, along with Dr. Jaelyn Eberle, a paleontologist at the University of Colorado, Boulder, argues that the jaw fragment reveals nothing new about Beringia’s role as a home for dromeosaurs.
At the 2019 Annual Meeting for the Vertebrate Paleontology Society, the Druckenmiller team reported in a conference summary that they found even smaller dinosaur teeth near the Prince Creek Formation.
Fiorillo says the fragment of the baby’s jaw that his team found is the first physical evidence that actually indicates that the dinosaurs used the Arctic as a place to live. “When I make that claim,” he said, “I follow what is in the published literature, and conference abstracts are generally not considered part of the published literature because they are opinion pieces that have not been peer-reviewed.”
Gina Mantica reports on science for The Dallas Morning News as part of a scholarship with the American Association for the Advancement of Science.
