41: Dinosaurs of the Antarctic and Arctic

65 million years ago dinosaurs went extinct, but for many million years before this they were roaming all over the planet. There were many different species in many different places, but we most commonly associate them with old dense forests filled with ferns, or with grasslands and forests. However, they did live in quite northern and southern parts of the globe too. Of course, the climate and even the geographical location of land masses at the time were different from today, but dinosaurs did exist in what are now our Arctic and Antarctic.

This week we will be looking at the dinosaurs in the Arctic and Antarctic regions of the planet, why cold is such an issue for them, and what the world really looked like in the Age of the Dinosaurs!

A very different climate in the south

Imagine dense dark temperate rainforests with swampland, an environment likened to New Zealand’s South Island today. This is what the Antarctic continent looked like 90 million years ago. Due to far higher levels of carbon dioxide in the atmosphere at the time, the world was a lot warmer, meaning this continent wasn’t coated in a large ice sheet. Evidence for the plant life there have been found in fossilised roots and pollen held up to 30 meters deep in the sediments, under what is now sea.

Most hunts for animal fossils on this continent today have focused on sea life like sharks, but in the 1980s two geologists stumbled across the bones of an ankylosaur. These are the heavily armoured herbivores with club tails found in many parts of the globe, with this Antarctic sub-species dating somewhere between 83-72 million years ago. Named Antarctopelta oliveroi , it was 6 meters long and roamed the area at the same time as the 1.5 meter beaked herbivore Trinisaura santamartaensis.

Going back even further in time 190 million years ago, Antarctica was connected to South America, India, Australia, Africa and Arabia, forming the continent of Gondwana. At this point the Antarctica section of the continent was nearer the equator with cool coastal temperatures that didn’t drop below zero, though they may have done so further inland. It was in this world that Glacialisaurus hammeri lived. This dinosaur was a sort of precursor to the sauropods, the long necked dinosaurs which later included the largest land animals that we know to have existed. Sauropods walked on four legs, but Glacialisaurus could actually walk on two. The excavation of this creature’s fossils from the rocks of Antarctica was an incredible job in itself, involving giant rock saws, jack hammers and two whole field seasons of excavating.

Artist’s impressions of the Antarctic herbivore Antarctopelta oliveroi. Whilst we know their bone and spike structure, we know little about their soft tissue so their colours are speculative. They may have been bright pink and covered in feathers, who knows!

The Carnivores

During this same period there also roamed the Antarctic the carnivore Cryolophosaurus ellioti. It may have actually been the largest carnivore on land at the time at 6.5 meters long, running on 2 legs like a t-rex, and it could be a really important link to help us learn about how predatory behaviour in dinosaurs started and spread. Cryolophosaurus also had an unusual head crest, looking a little bit like pompadour hairdo. Whilst head crests can be found in dinosaurs, this particular shape is unusual. Its function isn’t fully known but it’s thought mostly to be a way for the animal to recognise members of its own species, and perhaps as something used in mating displays.

These dinosaurs, and many others, lived on the land mass that is now Antarctica, but that realistically had a very different climate at the time than the ice covered continent we know today. However, that wasn’t necessarily the same case in the north.

An artist’s impression of the 6.5m long, one tonne heavy Antarctic carnivore Cryolophosaurus ellioti

Arctic examples

Nowadays the north of Alaska is rocky and often ice covered. 70 million years ago it was a little different, covered in a more diverse set of plants like horsetails, confers and ferns. It was a temperate forest somewhat like the south of Alaska today. The mean temperature throughout the year was around 5oC (42F), around 21oC (70F) in summer and dropping to below freezing with snow and ice in winter. It also used to be a little closer to the North Pole, nearer by around 15o latitude. So whilst this area was a little different, it still had Arctic-ish features in climate.

What types of dinosaurs lived in this world? One example is Ugrunaaluk kuukpikensis, a 9 meter long dinosaur dug up recently in the Liscomb Bonebed. They belong to a family of dinosaurs called hadrosaurs (duck-billed dinosaurs), and there are multiple hadrosaur species in this area. These dinosaurs were grazers, could walk on two or four legs, and had loads of small teeth, probably around 1,400 that grew on top of one another almost like bricks in a wall. Ugrunaaluk kuukpikensis‘ skin was covered in scales and it had plates along its back which were probably used in some form of display.

Another dinosaur around at the time was the carnivorous Troodon formosus which was found across North America but had especially large individuals in northern Alaska at 4 meters long and two meters tall, about twice the size as specimens found in Montana. Pachyrhinosaurus, who look a little like triceratops, are another herbivore species found in North Alaska, and were perhaps hunted by Troodons. Otherwise life in the area included many insects living along the shoreline as well as many plant species like ginkos, horsetails and ferns.

An artist’s impression of the predatory Troodon. Remember, the colours and in this case fur is all just speculation.

Why it’s so amazing- cold weather adaptations

It might not seem super special, but that fact that dinosaurs have been found in areas that used to have an Arctic-like climate is actually pretty ground-breaking. The modern ancestors of dinosaurs include reptiles such as crocodiles and lizards. These animals are ectothermic (cold-blooded), meaning that they don’t produce their own heat (well, they produce so little it barely matters). This means they usually live in warm places where they can get their heat from the sun, which is why lizards are often found basking in the sunshine. They’re essentially charging their batteries.

It has often been assumed that dinosaurs were the same, but if we know that some species of dinosaurs lived in areas that not only experienced temperature below zero each season, but that also experienced up to 4 months of darkness in the depths of winter, they couldn’t have survived by being cold blooded. In addition to that, no crocodile fossils have been found in the area. Crocodiles did exist in a similar form at the time and we know them to be ectothermic, so it adds evidence that cold-blooded creatures didn’t like to live in this environment. That means that the dinosaurs in what is now Alaska must have been either partially or completely warm blooded (endothermic). That is not impossible, another ancestor of the dinosaurs are modern birds, who are endothermic. However, it is unexpected as we often think of dinosaurs as more lizard-like.

There may have been other adaptations to the climate too. Many dinosaurs may have migrated south to warmer climates in winter, much like reindeer and caribou today. Others we know definitely stayed in the area year round, as analysis of the bone structure of some young hadrosaurs from the time show that they wouldn’t have been physically able to make what would have been a 5,000 mile journey in their first year of life.

Adaptation has been seen in the physical structure of some of the dinosaurs too. Troodons have very large eyes compared to their body size, and a notably large part of the brain which processes light. This would help the predator to be able to hunt in the four months of darkness each winter, especially as herbivores, with little food, would be slow and weak at this time of year anyways.

Many modern day reptiles are ectothermic and have to spend time basking in the sun to warm up before being active. (Picture: Daniel Schwen/Wikimedia Commons/ CC BY-SA 4.0)

Though often associated with the tropical parts of the world, dinosaurs have also been found at both our poles. For the South Pole, this is partly because of the movement of the earths landmasses through time, meaning that their climate and location many millions of years back was not as inhospitable as the ice covered southern continent today. However, even with some differences in climate today, parts of the Arctic such as Alaska were still pretty chilly during the ages of the dinosaurs, and the fact that they managed to survive there anyways shows that these creature were as diverse and adaptable as many creatures today, with there being thought to be at least 13 different species in northern Alaska alone. Many were just a lot more giant than the species we have today…

For more info:

A BBC News article about the study into the former climate in Antarctica when the dinosaurs roamed: https://www.bbc.co.uk/news/science-environment-52125369

There’s a NOVA documentary called “Arctic Dinosaurs” which gives a nice overview of the discovery of some dinosaurs in Northern Alaska

Music: kongano.com and “Jurassic Park Theme” by John Williams

Cover image: Julio Lacerda

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