Scientists at the University of Alaska,Fairbanks and Florida State University have found that almost all types of Arctic dinosaurs, from avian dinosaurs to giant tyrannosaurs, breed in the area and may be there all year round. Their findings are detailed in a new paper published in the journal Contemporary Biology.
The paper's lead author, Pat Druckenmiller, director of the Northern Museum at the University of Alaska, said that not long ago, people were shocked to find that dinosaurs lived in the Arctic 70 million years ago. We now have clear evidence that they also nest there. This is the first time that dinosaurs have been shown to be able to breed at these high latitudes. These findings contradict previous assumptions that these animals migrated to lower latitudes for the winter and laid their eggs in those warmer regions. This is also convincing evidence that they are warm-blooded animals.
For more than a decade, Druckenmiller and Gregory Erickson, a professor of biological sciences at Florida State University, have conducted fieldwork in the Prince Creek formation in northern Alaska. They excavated many dinosaur species on the cliffs above the Colville River, most of them new. Their latest discovery is seven species of tiny teeth and bones of perinatal dinosaurs, a term that describes baby dinosaurs that have just hatched or just hatched.
One of the biggest mysteries about Arctic dinosaurs is whether they migrated seasonally to the north or lived year-round, and researchers unexpectedly found the remains of nearly every dinosaur in the formation, which resembled a prehistoric delivery room. Recycling these bones and teeth, some no larger than a needle, requires perseverance and keen eye. At the site, the scientists dragged buckets of sediment from the surface of the cliffs to the river, where they washed the material with smaller and smaller sieves to remove large rocks and soil. Once back in their lab, Druckenmiller, Erickson, and co-author Jaelyn Eberle from the University of Colorado boulder further sifted through the material. The team, which included graduate and undergraduate students, then examined the remaining grains of sand under a microscope to find bones and teeth.
Next, the scientists teamed up with Caleb Brown and Don Brinkman of the Royal Thiel Paleontology Museum in Alberta, Canada, to compare the fossils to those from other locations in the lower latitudes. These comparisons helped them conclude that these bones and teeth were from perinatal dinosaurs. Once they learned that these dinosaurs nested in the Arctic, they realized that these animals had lived in the area for a lifetime.
Erikson's previous research has shown that these types of dinosaurs hatched for three to six months. Because summers in the Arctic are short, even if dinosaurs laid their eggs in the spring, their offspring would be too small to migrate in the fall. In the Cretaceous Period, global temperatures were much higher, but Arctic winters still consisted of four months of darkness, bringing icy temperatures, snowfall, and little fresh vegetation for food. Although winter is dark and bleak, there are 24 hours of sunshine in the summer, which is good conditions for dinosaurs if they can grow quickly before winter comes.
The researchers say they solved several long-standing dinosaur mysteries, but also opened up a new puzzle, namely how did they survive the Arctic winter?