Dinosaurs poles apart
UNEXPECTED: AT LEAST SEVEN SPECIES CAPABLE OF NESTING IN ARCTIC
Fossils found in regions once thought to be too hostile for reptilian life.
Dinosaur species, large and small, made the Arctic their yearround home and probably developed wintering strategies like hibernation or growing insulating feathers, according to a new study.
The paper in the journal Current Biology is the result of more than a decade’s worth of painstaking fossil excavations, and puts to rest the notion that the ancient reptiles lived only in hotter climes.
“A couple of these new sites we found in the last few years turned up something unexpected, and that is they’re producing baby bones and teeth,” lead author Patrick Druckenmiller of the University of Alaska Museum of the North said.
“That’s amazing because it demonstrates these dinosaurs weren’t just living in the Arctic, they were actually able to reproduce in the Arctic.”
Researchers first discovered dinosaur remains at the frigid polar latitudes in the 1950s, regions once thought to be too hostile for reptilian life.
This led to two competing hypotheses: either the dinosaurs were permanent polar residents, or they migrated to the Arctic and Antarctic to take advantage of seasonally abundant resources and possibly to reproduce.
The new study is the first to show unequivocal evidence that at least seven dinosaur species were capable of nesting at extremely high latitudes – in this case the Upper Cretaceous Prince Creek Formation which lies at 8085 degrees North.
The species uncovered include duck-billed dinosaurs called hadrosaurs, horned dinosaurs such as ceratopsians and carnivores like tyrannosaurus.
The team is confident the tiny teeth and bones they found, some of which are only a few millimetres in diameter, belong to dinosaurs that were either newly hatched or died just prior to hatching, because of their distinct markings.
“They have a very specific and peculiar kind of surface texture – it’s highly vascularised and the bones are growing quickly, they have a lot of blood vessels flowing into them,” explained Druckenmiller.
Unlike some mammals such as caribou that give birth to young that can walk long distances almost immediately, even the largest of dinosaurs had tiny hatchlings that would have been incapable of making migratory treks of thousands of kilometers.
What’s more, given what is known about how some species incubated their eggs well into the summer, the dinosaur young would not have had time to mature before winter arrived, the team argues.
The Arctic was warmer in the Late Cretaceous period than today, but conditions were still very challenging.
The average annual temperature was about six degrees Celsius but there would have been around four months of winter darkness with freezing temperatures and occasional snowfall.
“We now understand that probably most of the meat eating dinosaur groups we find up there were probably feathered,” said Druckenmiller. “You can think of it as their own down parka, to help them survive the winter.”
Dinosaurs’ ability to survive the Arctic winter is the “most compelling evidence yet” that they can be added to the list of species capable of thermoregulation, concluded co-author Gregory Erickson of Florida State University.