There are lot of theories on why dinosaurs went extinct. I once heard that the dinosaurs went extinct because they could not survive cold temperatures after the asteroid hit. In particular, one of my favorite teachers noted, “After the asteroid hit the earth 65 MYA, the dinosaurs died out because they all lived around the equator where the dust from the collision blocked the sun, with mammals surviving because they could live in cold temperatures and northern latitudes where dinosaurs could not”. Scientific research has however shown that this may not be accurate. In this article, I will explore whether dinosaurs could survive the cold, including adaptations that may have facilitated their survival in sub-zero temperatures such as those on the polar circles.
A Different Time, A Different Climate
In order to understand the dinosaurs’ ability to survive the cold, we must first understand the world they lived in. During the Mesozoic era, the world was much different than the one we are accustomed to. The overall temperature was far warmer, the amount of carbon dioxide in the atmosphere was likely double what it was today and most crucial for our article, there were no ice caps at the poles. Without glaciers or ice sheets in the arctic and Antarctic, one might assume that it was all peaches and cream living in those regions during the Mesozoic. This is not the case however, as the polar regions of the Mesozoic were still relatively cold due to the tilt of the earths’ axis. Since places like prehistoric Alaska and Antarctica were located at very high latitudes within the polar circle, they would still experience months without any sunlight as they do today. During these black outs, the areas affected would experience frigid winters, with temperatures dropping severely.
The Fossil Evidence Tells The Story
With Mesozoic climate in mind, was it possible that dinosaurs lived in these polar areas? To answer this, we must first understand what parts of the world lay within the polar circle. In addition to the previously mentioned Antarctica and Alaska, northern Canada, Australia and Siberia would have lay within the polar circle as well. Moreover, we know that many dinosaurs were found in the far north of these areas.
In Alaska, multiple dinosaur species are represented by both fossils and footprints. In Siberia, dinosaurs are known from both the Cretaceous and Jurassic, with fossils of everything from stegosaurids to tyrannosaurids present in the region. Rather surprisingly, Antarctic dinosaurs have been discovered, including the very primitive theropod Cryolophosaurus and the Ankylosaurid Antarctopelta. The time range for the Antarctic dinosaurs is also quite surprising, as the earliest Antarctic dinosaurs known lived some 200 million years ago with the latest living 65 million years ago, a massive period for these polar species. Last but certainly not least are the Australian dinosaurs, which are known from multiple species that are all unique to the polar forests of ancient Australia. With the sheer amount of fossil material found in Polar Regions across the globe, it is clear that dinosaurs could thrive in cold temperatures.
Now that we have established that dinosaurs could survive in the extreme colds, one question remains: How?
Theory One: Mass Migrations
Like modern animals, dinosaurs may have migrated to greener pastures during the cold polar winters, thus avoiding the large temperature drop. However, this remains a theory, as there is no evidence of migration amongst dinosaurs. Additionally, this theory is flawed in that most species of polar dinosaur are small in size, thus making them too weak to undertake large scale migrations (for example, Ankylosaurids are short with heavy bodies and armour, making long voyages difficult).
What about larger dinosaur species? Did they migrate? While the large Alaskan Hadrosaurid Ugrunaaluk (possibly a junior synonym of Edmontosaurus) was fully capable of migrating large distances, its fossil material tells a different story. Most individuals of Ugrunaaluk are juveniles, indicating an inability for these young animals to survive in the Cretaceous of Alaska. Since so many fossil remains are from juveniles, it is likely that these dinosaurs died in the cold Alaskan winter, unable to survive the harsh temperatures of a polar winter. If these animals did in fact die in the winters, it would indicate that large dinosaurs did not migrate, and thus must have lived year-round in polar climates. The fact that dinosaurs were able to survive polar climates may indicate that they were warm blooded, but that is the subject for a different article.
Theory Two: The Deep Sleep
The next theory for how dinosaurs were able to survive involves hibernation. Paleontologists have used the growth rings within their bones to determine if dinosaurs hibernated or not. If the growth rings were more frequent in the bones of polar dinosaurs it would have indicated hibernation amongst these dinosaurs. Studies of Australian dinosaur bones indicated no such frequency, clearly showing that the polar dinosaurs stayed active year-round (Woodward). Thus, hibernation did not help them survive the cold.
Theory Three: Adapt to Survive
Since polar dinosaurs spent their entire lives in polar climates, and remained active during the winters, they must have had some special adaptations to survive the cold. Some species, such as the Australian ornithischian Leaellynasaura, had enlarged eye sockets which indicated that they had developed a keen sense of vision. Having enhanced eyesight would have been important in helping these dinosaurs thrive during the dark polar winters. In addition to better eyesight, there is another adaptation that most polar dinosaurs may have possessed that would have helped them survive: feathers. Some species, such as the Alaskan raptor Dromaeosaurus and Tyrannosaurid Nanuqsaurus, have close ancestors that possessed feathers and thus would have exhibited them as well. The previously mentioned Leaellynasaura also may have possessed feathers, as some other ornithischians have been discovered with feathers (see my article on “From Russia with Feathers: Kulindadromeus”). For species who have no direct ancestors that possessed feathers, it is possible that these dinosaurs developed feathers separately from their ancestors, evolving this trait on their own.
The adaptations of these polar dinosaurs must have been successful, as dinosaurs survived in polar areas for the majority of their existence. All across the world their remains are discovered in high quantities, indicating just how prosperous these ‘dinosaurs on ice’ were.
If the fossil evidence isn’t enough, one type of dinosaur still calls Antarctica home: the penguin.
I do not take credit for any images found in this article.
Cryolophosaurus pair illustrated by Hannah Böving, found Here
A scene from Cretaceous Alaska illustrated by Julio Lacerda, found Here
Fluffy Leaellynasaura illustrated by Julio Lacerda, found Here
Fluffy Pachyrhinosaurus illustrated by Mark Witton, found Here
Modern polar dinosaurs found Here
Geggel, Laura (2015). “Brrr! Duck-Billed Dinosaur Lived Through Alaska’s Snowy Winters.” LiveScience, 22 Sept. 2015, www.livescience.com/52263-duck-billed-dinosaur-alaska.html.
Culture, Victoria. “Leaellynasaura Amicagraphica – Collections and Climate Change.”, www.cv.vic.gov.au/stories/land-and-ecology/collections-and-climate-change/fossils-rocks-and-minerals/the-past-is-the-key-to-the-future/leaellynasaura-amicagraphica/
Lucas, Spencer G (2016). Dinosaurs: The Textbook. 6th ed., Columbia University Press
Moskvitch, Katia (2014). “Dinosaur Era Had 5 Times Today’s CO2.” LiveScience, 24 Mar. 2014, www.livescience.com/44330-jurassic-dinosaur-carbon-dioxide.html
Bell, Phil R. Bell & Snively, Eric (2008). Polar Dinosaurs on Parade: A Review of Dinosaur Migration, Alcheringa: An Australasian Journal of Palaeontology, 32:3, 271-284, https://www.tandfonline.com/doi/full/10.1080/03115510802096101
Woodward HN, Rich TH, Chinsamy A, Vickers-Rich P (2011). Growth Dynamics of Australia’s Polar Dinosaurs. PLoS ONE, 6(8): e23339. https://doi.org/10.1371/journal.pone.0023339