Yes, you read that correctly. Dinosaurs in the snow.
There were dinosaurs in the Arctic and in the Antarctic. There have been fossil finds in the north, across Siberia and most recently in Alaska, which have changed the conventional notions about where dinosaurs might have lived. If you’ve seen some of those National Geographic or David Attenborough shows about life on earth, you know that today, life exists everywhere–deepest ocean, darkest and coldest parts of land. Dinosaurs were spread across the globe 90 million years ago, so why wouldn’t they also have adapted to the deepest, darkest, coldest?
Where in the World is the World?
To be fair, the Arctic and Antarctic today were not that way 150 million years ago. First of all, the continents were not the same at all. When the dinosaurs first emerged and adapted to range far and wide, most of the land mass was still connected together, vestiges of a super-mass called Pangaea, which gradually started to drift apart.
Things continued to change, though, and as the continents in the south especially began to separate the water ways grew. In other words, at one point, everything was mainly the Pacific Ocean (and another called Tethys, which became the much-smaller Indian Ocean). As the Atlantic came into being, there was a waterway right through most of the center of what is now North America. Kansas was underwater. Eventually, the water receded and continental uplift occurred to create the Rockies.
There are a couple of things to take away from this little mini-paleogeology lesson. First, dinosaurs started one place, but those places drifted. And it’s not like dinosaurs had boats to leave. (…or did they? I’m sure there’s someone on the Internet who might suggest otherwise…) Certainly, it explains why very similar dinosaurs are found now in places far and away from each other, like Argentina and Mongolia; they were once close land masses. Second, what is very Arctic and impossible to live in now was relatively warmer then. There was land at the north pole, but it was not a frozen mass. At the same time, there was still a lot less light near the poles, because the earth was still round (ok ovate) and tilted on its axis.
As scientists started thinking about dinosaur survival conditions at the extremes, they needed to think about food sources, predator-prey strategies, body adaptations, and reproduction. Some of these are things that a few bones might not convey. But the paleobiologists might know that the air temperature was not swampy at the time. In fact, it was quite cool at the poles, even if not frozen. Air temperatures at these cool climates were 36-55 F in the north and 28-40 F in the south. How could they know? Leaves of plants have different shapes in cold vs. hot weather. By looking at the fossils of leaves, they could determine the temperatures 150 million years ago.
Lots of the dinos were likely feathered; dinosaurs did not adapt to grow fur, but plenty grew feathers. The Troodon was a small carnivore rare in lower latitudes but far more common in the north. Small carnivore–small game. Perhaps baby hadrosaurs.
Migrating? or Living?
For the century and a half between the discovery of dinosaurs and some of the most recent innovations of paleontology, it was believed that dinosaurs were cold-blooded. I’ve mentioned this before, but don’t want to dwell on it, because that idea has been discounted by so much other evidence. But because that idea held sway, other ideas followed in its wake. Paleontologists had found some few fossils in the north but, believing that dinosaurs were cold-blooded, they also thought they probably migrated as many animals do.
Canadian geese migrate; whales migrate. So why not dinosaurs? Go north in the summer to get new plants, maybe lay eggs and give birth, then return south for warmer climates to spend the winter near Disneyland. However, the most recent finds in Alaska and elsewhere suggested something much broader–that dinosaurs did live in these climates during the winter.
The write-up in Current Biology by Patrick Druckenmiller explains the role of tiny fossils. Dozens of itty-bitty fossils–smaller than a penny–have been harvested ever since scientists saw bones sticking out of the soil near an Alaskan river. Three decades of culling and collecting these fossils have tried to address the essential question: Were these small dinosaurs who hunkered down in the winter? Or were these baby dinos who hatched up north to their big hadrosaur mommies, then migrated south?
Druckenmiller argued that based on the size and the number of specimens found, they had to be living up north. Again, by comparing to Living Animals (see letter L), they could draw inferences. Caribou, for instance, migrate south, but only after the babies reach a size big enough to survive the journey. What these teeth and remains suggested is that the babies wouldn’t be big enough to make a long arduous trek. The migration itself would be more harmful than adapting to the cold.
As the sites from Alaska unearth more and more and fossils, the paleontologists found a whole range of dinosaurs in sizes and habitats. Even the Ceratopsidae at the extreme north could have adapted enough, between skin thickness, fur, or other physical changes, to handle the weather and light changes that would ensure. Polar dinosaurs.
The Ruthless Environment for Dinosaurs…and Paleontologists
No doubt about it, though. The dinosaurs had to get real busy when there was a spring thaw. They had that same range from spring to fall that we do, far south of Alaska, but the extremes of light would have been far more dramatic. Those hadrosaurs and cryolophasauruses (omg that’s hard to spell) had to put on the Barry White records pretty quickly as soon as the temperature turned a bit in February. Those eggs had to be laid and incubated so that they’d hatch and grow big enough before the weather changed again in late September. T is for Tail!
Finding all this information wasn’t the easiest. In Alaska, doing anything means working with the extremes. The paleontologists themselves had only a few months to do all this work. I once visited Denali Park in July, and they explained that winter would start again around September 1st. The mosquitoes and bugs in the few months of summer were giant. The ground was still partly frozen. Just digging the fossils out would take perhaps three times as long as it might in Wyoming due to more difficult climate. And Wyoming isn’t exactly tropical, but the dirt isn’t permafrost.
But as with other new ideas, these conceptions of polar dinosaurs change what we can imagine about them. Troodons, for instance, are believed to have much larger eyes to adapt to the dimmer light.
Some of Druckenmiller’s findings are only a few years old. What’s worth thinking about is how climate change may eventually affect this work. If other kinds of permafrost start to melt, there may be many more discoveries yet to be seen.
This little guy is named Nanuquosaurus, which means polar bear lizard, derived from the Inuit language. They’ve also discovered issi saaneq in Greenland, and given it the Intuit name which means cold bone.
The Inuit have a lot more other words that might need to be used before we’re done. They have, allegedly, a dozen words for snow. We may yet need them all to define the snow dinosaurs.
