- Despite previous Permian period’s widespread devastation, life recovered and new species, such as dinosaurs, arose
- Check out our graphic to learn about the anatomy of a Plesiosaurus, a marine reptile that was a top predator in the ocean
Plesiosaurs appeared about 203 million years ago and ruled the oceans unchallenged for millions of years. Photo: ShutterstockThe words “palaeontology” and “Triassic” typically conjure images of ferocious dinosaurs roaming the Earth. But what was the Triassic period and how did dinosaurs come to thrive?
It started on the supercontinent
Earth’s continents are constantly shifting. About 252 to 199 million years ago, all the continents were actually one huge “supercontinent” surrounded by one enormous ocean. Slowly, this giant continent, called Pangaea, broke apart and spread to form the continents we know today.
The Triassic period was a unique episode in Earth’s ecological history, and it began on Pangaea. During this time, the climate ranged from arid with searing heat in the centre of the continent to monsoons along the coastal regions, but it did not have ice caps and flowering plants.
Life in the Triassic period had a rough start. In the Permian period before, the largest mass extinction event in Earth’s history had just taken place.
Despite the widespread devastation, life recovered during the Triassic period as new species arose and diversified quickly. This also marked the first time the earliest dinosaurs appeared. The Permian period’s mass extinction had wiped out the mammals that could have been competitors for these reptiles on land and in water. One example of these mammals would be the Dimetrodon, which had a large, sail-like structure on its back.
Reptiles take to the land, sea and sky
Some of the reptiles living on land evolved to become dinosaurs during the mid-Triassic period (between 247 and 237 million years ago). At first, these creatures were much smaller, but they eventually outgrew other animals such as the Lystrosaurus, a dog-sized animal that looked like a cross between a pig and a lizard.
These evolved land reptiles thrived during the periods after the Triassic – Jurassic and Cretaceous – and ruled Earth’s landscape for 165 million years. Some, like the Tyrannosaurus rex, emerged as top predators that dominated the food chain on land.
Dinosaur embryo found curled up and ready to hatch like a bird
In the Triassic ocean, marine reptiles such as the plesiosaurs were kings. Plesiosaurus, an early plesiosaur, was about 4.5 metres long with a broad, flat body and a short tail (see graphic).
Plesiosaurs appeared in the late Triassic period about 203 million years ago and ruled the oceans unchallenged for millions of years. One of these marine reptiles, Elasmosaurus, evolved to be about 13 metres long.
The Triassic period also saw reptiles take to the skies. Pterosaurs were the first vertebrates that evolved to fly.
The end erupts
Most scientists believe the Triassic period ended when Pangaea started to break apart. This resulted in huge and widespread volcanic eruptions, leading to the demise of many of these magnificent animals.
A new palaeontology gallery is opening at the Hong Kong Science Museum this year. Visit to find out more about these mighty ancient creatures!
Young Post is pleased to partner with Hong Kong Science Museum and Hong Kong Space Museum on our STEM Lab series. Our aim is to encourage you in your pursuit of science. Every month, the two museums will answer your burning questions about the fantastic world around us, the cosmos, and beyond.