Images of dinosaurs as cold-blooded creatures needing tropical temperatures could be a relic of the past.
University of Alaska Fairbanks and Florida State University scientists have found that nearly all types of Arctic dinosaurs, from small bird-like animals to giant tyrannosaurs, reproduced in the region and likely remained there year-round.
Their findings are detailed in a new paper published in the journal Current Biology.
“It wasn’t long ago that people were pretty shocked to find out that dinosaurs lived up in the Arctic 70 million years ago,” said Pat Druckenmiller, the paper’s lead author and director of the University of Alaska Museum of the North. “We now have unequivocal evidence they were nesting up there as well. This is the first time that anyone has ever demonstrated that dinosaurs could reproduce at these high latitudes.”
The findings counter previous hypotheses that the animals migrated to lower latitudes for the winter and laid their eggs in those warmer regions. It’s also compelling evidence that they were warm-blooded.
For more than a decade, Druckenmiller and Gregory Erickson, a Florida State University professor of biological science, have conducted fieldwork in the Prince Creek Formation in northern Alaska. They have unearthed many dinosaur species, most of them new to science, from the bluffs above the Colville River.
Their latest discoveries are tiny teeth and bones from seven species of perinatal dinosaurs, a term that describes baby dinosaurs that are either just about to hatch or have just hatched.
“One of the biggest mysteries about Arctic dinosaurs was whether they seasonally migrated up to the North or were year-round denizens,” said Erickson, a co-author of the paper. “We unexpectedly found remains of perinates representing almost every kind of dinosaur in the formation. It was like a prehistoric maternity ward.”
Recovering the bones and teeth, some no larger than the head of a pin, requires perseverance and a sharp eye. In the field, the scientists hauled buckets of sediment from the face of the bluffs down to the river’s edge, where they washed the material through smaller and smaller screens to remove large rocks and soil.
Once back at their labs, Druckenmiller, Erickson and co-author Jaelyn Eberle from the University of Colorado, Boulder, screened the material further. Then, teaspoon by teaspoon, the team, which included graduate and undergraduate students, examined the remaining sandy particles under microscopes to find the bones and teeth.
“Recovering these tiny fossils is like panning for gold,” Druckenmiller said. “It requires a great amount of time and effort to sort through tons of sediment grain-by-grain under a microscope. The fossils we found are rare but are scientifically rich in information.”
Next, the scientists worked with Caleb Brown and Don Brinkman from the Royal Tyrrell Museum of Palaeontology in Alberta, Canada, to compare the fossils to those from other sites at lower latitudes. Those comparisons helped them conclude that the bones and teeth were from perinatal dinosaurs.
Once they knew the dinosaurs were nesting in the Arctic, they realized the animals lived their entire lives in the region.
Erickson’s previous research revealed that the incubation period for these types of dinosaurs ranges from three to six months. Because Arctic summers are short, even if the dinosaurs laid their eggs in the spring, their offspring would be too young to migrate in the fall.
Global temperatures were much warmer during the Cretaceous, but the Arctic winters still would have included four months of darkness, freezing temperatures, snow and little fresh vegetation for food.
“As dark and bleak as the winters would have been, the summers would have had 24-hour sunlight, great conditions for a growing dinosaur if it could grow quickly enough before winter set in,” said Brown, a paleontologist at the Royal Tyrrell Museum.
Year-round Arctic residency provides a natural test of the animals’ physiology, Erickson added.
“We solved several long-standing mysteries about the dinosaur reign, but opened up a new can of worms,” he said. “How did they survive Arctic winters?”
“Perhaps the smaller ones hibernated through the winter,” Druckenmiller said. “Perhaps others lived off poor-quality forage, much like today’s moose, until the spring.”
Scientists have found warm-blooded animal fossils in the region, but no snakes, frogs or turtles, which were common at lower latitudes. That suggests the cold-blooded animals were poorly suited for survival in the cold temperatures of the region.
“This study goes to the heart of one of the longest-standing questions among paleontologists: Were dinosaurs warm-blooded?” Druckenmiller said. “We think that endothermy was probably an important part of their survival.”
Reference: “Nesting at Extreme Polar Latitudes by Non-Avian Dinosaurs” by Patrick S. Druckenmiller, Gregory M. Erickson, Donald Brinkman, Caleb M. Brown and Jaelyn J. Eberle, 24 June 2021, Current Biology.
This research was supported by the National Science Foundation.
“Scientists have found warm-blooded animal fossils in the region, but no snakes, frogs or turtles, which were common at lower latitudes.”
That is strange, because those animals hibernate at lower latitudes. What would prevent them from hibernating at high latitudes as well?
Alligator fossil are found in Canada artic island. two species modern crocodilian live in cave today they have no problem growing in the dark this is well known in alligator farm most modern crocodilian hunt at night and the sun of the day that why they have cat eyes that glow .modern crocodilian hunt not the warmest part of the day that very strange for a reptile because it’s a dinosaur the most advance dinosaur ever.one of dwarf caiman live in the mountain were snow run off water they hunt In that 4o degree water it actruly hate warm water .feral gator live many years in the penn state before it was shot with its extreme cold winters .this is the reason why modern crocodilian are so dangerous this is one animal should not be dumb down on they are last living dinosaur the last living spinosauridae the mesoeucrocodylia dinosaur.likely the gator is warm blooded fast growth warm blooded bones a kidney that is more advance than the mammal they solve the acid thing better than the mammal they are very active animal that why very land base one dwarf caiman have a fuse nasal like spinosaurus t.rex to kill animal with legs it’s to protect the skull from prey animal kicking the skull fuse nasal are very rare in mesoeucrocodylia because it is land feature most modern crocodilian are semi aquatic so they have the same feature as there ancestor baryonyx .baryonyx do not have fuse nasal because it’s early mesoeucrocodylia that probaly live more on land but have simular livestyle as the gator Nile crocodile .spinosaurus is more advance than baryonyx that why it has fuse nasal and live more on land but the same livestyle as baryonyx and have strange feature like the fuse nasal they were not like gator or Nile crocodile or dwarf caiman. fuse nasal only appear in modern crocodilian almost complete different animal the the dwarf caiman there hearing is like a land mammal the gator hearing is like a whale dwarf caiman temporal fenestra is like most dinosaur. dwarf caiman lacks Webb toe allso one of them have tetanuran bipedal tail they are poor swimmer This tail only use for bipedal for balancing all modern crocodilian is bipedal dwarf caiman is just better at it like early land mesoeucrocodylia they had better feature than the gator even dwarf caiman .modern crocodilian do have open hip socket some early mesoeucrocodylia have big hip socket like dinosaur and this won was extremely aquatic .macelognathus a early land mesoeucrocodylia the tibia is bigger than the femur like a horse and birds compsognathus a very fast animal feature. bird have to be fast to fly by jump from trees that were flight come from .compsognathus dinosaur was a very fast animal like there descendants the gator dinosaur allways was a fast animal they do not have the giant ankle like birds and horses .gator like the horse have a advance spleen because they are very fast animal .I would not dive with the Nile crocodile in the winter like on tv that too dangerous reason they do not attack they probaly evolve from warm places since it’s a dinosaur like the dwarf caiman it can attack in cold water just like the weak skull gharial it has weak skull still can do the death roll the most dangerous feature in the animal kingdom this feature make them the king of dinosaur .the advance dinosaur thing is a joke they are no way as advance as modern crocodilian they can not smell or hear like the gator .t.rex great smell is not as good as the gator.and the gator can not smell like the early land gator type mesoeucrocodylia .there is nothing primitive about modern crocodilian .the ancestor can not be more advance than there descendants that is against evolution.the cliam dinosaur is more advance than the gator all media hype not scientific facts it’s on winnable .
@Clyde Probably the same thing that prevents all but a handful of reptiles living near the Arctic today. Those that do are fairly specialised including bearing live young in some cases. Remember birds (and bird-dinos) warm their eggs – very few reptiles do, besides burying them which would not work in frozen ground.
Dinosaur time in artic Alaska was subtropical not like the extreme winter in the penn state. American alligator are found in cold subtropical of North Carolina were snow all the time American crocodile is found in very warm subtropical Miami were they die all the time from the cold .the feral common caiman today who live there today are not doing good.American gator can survive frozen pond this is on YouTube .the Chinese gator came from America they live in Alaska and Canada island .Chinese gator came from American gator they both have fuse nose caiman do not have fuse nose caiman are closer to Nile crocodile . Lack of fuse nose is a advance feature seen in mammal to get more oxygen fast animal need a lot of oxygen for the muscle .but it has its weakness the skull is weak fuse nose found in spinosauridae all dinosaur early gator type mesoeucrocodylia .the gator type mesoeucrocodylia no fuse nose are close to the Nile crocodile the oldest modern crocodilian Nile crocodile is the ancestor all modern crocodilian.dwarf crocodile nose is fuse .American gator Chinese gator support the land bridge from Alaska to Russia alligator salt glands does not work .some time they are found on beach expert say they can survive salt water but swim all way to China they will have problem .gator heart is like mammal and bird a warm blooded heart but more advance than mammal and birds extra valve thing the cliam that this feature is a aquatic feature I doubt that mammal was advance before they go into the water .all modern crocodilian heart are not the same allso all modern crocodilian egg are not the same gator egg more advance than the crocodile Philippine crocodile egg same as the gator.Chinese gator live in cold places allso climb cold mountain Chinese gator link with USA gator with the cold thing support the land bridge.gator esophagus is simular to humans they are use them the science for human breathing deseaise