Pleistocene
It may be hard to imagine, but about 20,000 years ago Canada was at the peak of its last glaciations and 97% of Canada was entirely covered by ice! The animals which lived on the planet at this time had to adjust so many of them had thick coats of fur.
During the most recent ice age, the Pleistocene Ice Age, which occurred 70,000 to 10,000 years ago, there were many animals living in North America that are quite different than the ones we have today.
We had mastodons and mammoths, elephant-like mammals that has tusks, long hair covering their body, and were herbivores. Although they looked very much alike, there are some ways to tell them apart:
- Tusks. The mammoth had long curved lower tusks, reaching up to 4.5 meters in length. The mastodon had shorter, straighter upper tusks, which reached only 2.5 meters.
- Teeth. Mastodons and mammoths had the same amount of teeth over their life time, but mastodons had more teeth in their jaw at one time. Mastodons and mammoths also had different food sources, which are reflected in their teeth. Mammoths grazed on grasses, similar to modern cattle, while mastodons ate softer vegetation, such as leaves and twigs.
- Size. A mastodon typically stood 2-3 meters tall. They generally had flatter heads than mammoths, and were bulkier. Mammoths typically stood at 4 meters tall.
Molar tooth of a mastodon, Highgate, Kent County, Ontario
Donated by Shirley Fenton of Waterloo.
Upper molar of mammoth, Tara Bruce County, Ontario.
Mesozoic Era
The Mesozoic Era in Canada, as with the rest of the world, was marked by the dominance of dinosaurs for 160 million years.
Dinosaurs are a group of now extinct reptiles who roamed the planet during the Mesozoic era. They first appeared approximately 251 million years ago and went extinct 65.6 million years ago. There are several hypothesises as to why these fascinating animals went extinct, but the most widely accepted one is that they died out when a large meteor hit the earth, sending a cloud of particles into the atmosphere and blocking out the sun.
Some dinosaur species that roamed Canada:
Tyrannosaurus Rex, “King of the Tyrant Lizards”
- Order: Saurischia, lizard-hipped dinosaurs
- Length: 12 to 15 metres
- Weight: 6.35 tonnes
- When did I live? Late Cretaceous period, 65 million years ago
- Where? Western North America
- What family did I belong to? Carnosaur Tyrannosaurids
- What food did I eat? I preyed on large plant eating dinosaurs such as duckbills, ankylosaurus and triceratops
- What special feature did I have? My size; I was the largest member of my family at 5 meters tall
Parasaurolophus, “Similar Crested Lizard”
- Order: Ornithischia, bird-hipped dinosaurs
- Length: 9 metres
- Weight: 3.26 tonnes
- When did I live? Early Cretaceous Period, 75 million years ago
- Where? North America
- What family did I belong to? Hadrosauridae, which means “duckbill”
- What food did I eat? Vegetarian
- What special feature did I have? My unusual long crest that curved backwards from my head helped me breathe and smell
- This specimen was discovered at Little Sandhill Creek, Alberta. The skeleton displayed here is a cast; the original is on display at the Royal Ontario Museum, Toronto
Deinonychus, “Terrible Claw”
- Order: Saurichia, lizard-hipped dinosaurs
- Length: 3-4 metres
- Weight:70 kg
- When did I live? Early Cretaceous Period, 140 million years ago
- Where? Western North America
- What family did I belong to? Theropoda, Dromaesaurids
- What food did I eat? I ate plant-eating dinosaurs such as titanosaurs and ankylosaurs
- What special feature did I have? The large curved claw on the second toe of my foot. When I ran the claw was flicked back to place the shorter toes on the ground. I balanced on one foot in order to swing the claw at the belly of another dinosaur. The foot of Deinonychus is one of the most extraordinary of any dinosaur
Albertosaurus “Alberta Lizard”
- Order: Saurichia, lizard-hipped dinosaurs
- Length: 35 feet
- Weight: more than 2 tonnes
- When did I live? Late Cretaceous, 70 million years ago
- Where? North western America
- What family did I belong to? Theropoda, Tyrannosauridae
- What food did I eat? I ate plant-eating dinosaurs. I swallowed my foot in large chunks without chewing it
- What special feature did I have? Albertosaurus skeletons have been found lying together in Canada. This suggests that this animal lived in herds.
Troodon “Wounding tooth”
- Order: Saurichia, lizard-hipped dinosaurs
- Length: 6.6 feet
- Weight: 50 kg
- When did I live? Late Cretaceous 76-70 million years ago
- Where? North America
- What family did I belong to? Troodon formosus
- What food did I eat? Small animals
- What special feature did I have? A Troodon had the largest brain in proportion to its body weight. It may have been the smartest dinosaur (as smart as a modern bird).
Lambeosaurus “Lambe’s Lizard” (Named for Lawrence Lambe, a Canadian palaeontologist)
- Order: Ornithopoda, bird-hipped dinosaurs
- Length: 50 feet
- Weight: 6000 kg
- When did I live? Late Cretaceous, 70 million years ago
- Where? Alberta, Mexico, North America
- What family did I belong to? hadrosauridae, Lambeosaurinae
- What food did I eat? I ate plants
- What special feature did I have? Lambeosaurus had a high, domed head with a large hatchet-shaped crest containing hollow nasal air passages. There is also ample evidence that some hadrosaurus were social animals; they may have travelled in large herds. Hatchlings lacked crests, but developed them as the skull grew until it reached its adult form.
Carboniferous
Pennsylvanian Coal Swamps
During the Pennsylvanian period (286-320 million years ago), extensive forests grew in swamps on river deltas. The coal swamps of eastern North America occupied a basin bordered on the south and east by the Appalachian Highlands and on the north by the low swell of the Canadian Shield. Trees over 30 metres high grew on a mush of organic material. In death they made their own contribution to the peaty layer.
Bacterial decay was limited by a lack of oxygen, allowing delicate fossil leaves to be preserved. As the area cycled from swamp to a shallow marine environment, the organic material was covered by layers of sediment. Sand formed sandstone, mud formed shale and siltstone, marine creatures with calcium carbonate skeletons formed limestone. The swamp deposit sank deep under the weight and the water was squeezed out. Ten meters of wet, porous material was converted to one meter of coal.
Amphibians
Amphibians dominated swamps that covered much of coastal North America and Europe in Late Carboniferous (Pennsylvanian) and early Permian times. Amphibians were the first backboned animals with limbs designated for use on land. They evolved from Rhipdistian fishes about 350 million years ago. Like their descendants, frogs and newts, early amphibians had to lay their shell-less eggs in water to prevent them from drying up. The eggs hatched into tadpoles which breathed through gills that later usually shrank. Some adults grew as big as a crocodile. Early amphibians lived mainly in or near fresh water, hunting fishes, insects, or reptiles. Early species of amphibians gave rise to reptiles and so, indirectly to all other backboned land animals.
Cambrian
When the geologic time scale was originally designed, the beginning Cambrian period was considered to be the first appearance of life on earth. Scientists named this period the Cambrian, meaning life, for this reason. Only recently have we discovered that early forms of life did exist before the Cambrian, and we now have the Ediacaran period thanks to discoveries of life dating back to the Precambrian, such as the Mistaken Point fossil assemblage.
A significant breakthrough in our understanding of the complexity of life during the Cambrian came thanks to the discovery in 1910 of the Burgess Shale. The single locality, high on a mountainside in Yoho National Park, was found accidentally in 1910 by Charles D. Walcott, who later became head of the U.S. Geological Survey. His horse apparently overturned a fossiliferous slab of shale and further examination revealed the locality. He returned for several years following, quarrying the locality and carrying material down to the base camp. Even today the location of the camp is pinpointed by the piles of shale that were sorted and split in the search for these fossils.
The Burgess shale locality represents a window allowing us to see the full array of soft-bodied organisms that were living 550 million years ago (the middle of the Cambrian Period) as well as those organisms with hard exoskeletons.
The fossils represent the primitive ancestors of nearly every class of arthropods together with many other groups (sponges, worms, algae, and a host of extinct forms of uncertain biological affinities). The fossils thus have enormous importance in geology and biology in the understanding of early metazoan evolution, particularly for the arthropods - the largest phylum existing today.
A model of Olenoides serratus, a species of arthropod found in the Burgess Shale.
A model of Canadaspis perfecta, a species of arthropod found in the Burgess Shale.
Precambrian
The most prominent fossil from the Precambrian Period of 4,570 - 542 million years ago are stromatolites. Stromatolites still exist today, but they were much more abundant about 1.2 billion years ago, during the Precambrian, after which there was a decline in their numbers and diversity.
The creatures which form stromatolites have lived on the Earth for billions of years. Stromatolites are fossil algal mats, also called microbial mats, formed by sediment trapped by biofilms, or slime. They are some of the earliest evidence of life in the geological record, possibly going as far back as 3.5 billion years.
The earliest stromatolite organisms, the blue-green algae, are thought to have helped prepare the Earth for future life by increasing the oxygen content of the planet’s atmosphere through photosynthesis.
One reason for the stromatolites being most prolific during the Precambrian could be the rise of more complex grazing life forms, which ate the stromatolite organisms, or a change in ocean chemistry. Modern stromatolites are usually found in saltine lakes and marine lagoons where high salinity inhibits grazing animals which would normally eat the stromatolites. One locality where they are being formed today is Shark Bay, Western Australia.