Wednesday, 9 October 2013

Pleistocene Megafauna

In the past, we've been focusing on very old fossils, mainly from the Mesozoic. This week, we're going to talk about some fossils that are a bit younger, specifically, from the Ice Age. These animals are commonly referred to as the Pleistocene Megafauna, where the Pleistocene is the time period (epoch) that the most recent ice age occurred and these animals lived in (2.5 million to 11 700 years ago), and megafauna refers to the large size of these animals compared to what we see today. 

A number of these fossils are very well known, like mammoths, and sabre-toothed cats, but other ones are less well known. Although Albertan palaeontology tends to mainly be dinosaurs and similarly aged animals, there are actually a number of the Pleistocene megafauna fossils that can be found in Alberta. Relatives of modern animals like horses (from the genus Equus, the same genus as modern horses) and Bison are often found in Alberta, as well as mammoth fossils. Mammoth fossils can be found near Medicine Hat, as well as several places in western and northern Canada. Mammoths are extinct relatives of elephants that lived in colder habitats during the Ice Age. They are well known for often having long, curved tusks, which are found commonly in Canada. As mammoths lived in glacial environments, they can often are found mummified, so we know a lot about their biology.
Mammoth skeleton. Photo by WolfmanSF
Another example of a Pleistocene megafauna that lived in Alberta during the Ice Age was Jefferson's ground sloth, Megalonyx jeffersoni. This giant ground sloth measured 3 m long, and as much as 1 ton in weight. Shockingly, this is only medium sized among the giant ground sloths, but it's still significantly bigger than any sloths alive today. Its fossils are more rare than mammoths, but they can be found in Alberta, Saskatchewan, the Yukon, and NWT. Its peg-like teeth and plantigrade (flat) feet allowed the animal to reach up on its hindlimbs and pull leaves down from trees and break down the tough plant material. They also had long claws on the forelimbs probably used for stripping branches. 
Megalonyx skeleton. Photo by Daderot
Finally, who knew there were camels in Alberta? One species of camel, known as Yesterday's Camel, has also been found in Alberta.  It was over 2 m tall at the shoulders, and weighed 800 kg, and is thought to have been an opportunistic herbivore, meaning it would eat whatever plants it could find. The camelids, horses, and mastodons all went extinct in North America at approximately the same time as Clovis tools (early human tools) became common. This has lead to the belief that increased human activity in North America actually drove these animals to extinction as we started to hunt. This is also possibly the case for the disappearance of the Pleistocene megafauna from around the world.

There are many other megafauna found in Alberta, and around the world, but here was a brief overview and some examples from Alberta and western Canada. I hope you found this brief report interesting!

Jass, C.N., et al. 2011. Description of fossil muskoxen and relative abundance of Pleistocene megafauna in central Alberta. Canadian Journal of Earth Science 48: 793-800.