Jurassic Period Key Facts
Timescale: 206 million years ago (MYA) to 144 MYA.
Environment: closely grouped continents; tropical, sub-tropical, temperate and arid climates.
Notable dinosaurs: Diplodocus, Brachiosaurus, Stegosaurus, Allosaurus.
Other animals: early mammals; flying reptiles (pterosaurs); early birds; insects; marine life.
There had been no holding back dinosaurs by the end of the Triassic Period. Then, during the Jurassic Period, they became the dominant animal life-form on the planet. Not only that, but Jurassic dinosaurs were big - very big. Giant herbivores, known as sauropods, evolved during the Jurassic. They were the largest land animals ever to walk the Earth.
An evolving world
Jurassic Earth was on the move. The Pangaea super-continent began to split into two during the mid-Triassic and this trend continued during the Jurassic Period. As early versions of today's continents moved away from each other, the oceans began to exert more influence on Earth's weather: the climate became far more varied. Vegetation was becoming more sophisticated, too. Palm-like plants and conifers flourished. Some experts also believe that the first flowering plants developed at the end of the Jurassic.
Land of the giants
The late Jurassic Period is renowned for huge dinosaur herbivores, known as sauropods. The largest grew to more than 40 metres in length and probably weighed up to 100 tonnes. You wouldn't have wanted one of these titans to step on your toe but sauropods weren't as heavy as their size might have suggested. They were actually quite lightly built creatures: much of their apparent bulk was due to internal, air-filled sacs.
Not walking in water
Palaeontologists used to believe that sauropods were amphibians. Artists' impressions of the large herbivores always depicted them grazing in lakes. It wasn't thought possible that sauropods could support their supposed vast weight without the buoyancy of water. Today's dinosaur experts are confident that sauropods had legs that were akin to a modern elephant's - easily able to support their own body weight.
Huge herder
Long-necked and long-tailed, Diplodocus ("double beam") is probably the best-known sauropod. Herds of these giant dinosaurs dominated the late Jurassic period. They were so big (25 metres and over) that they would have changed the landscape around them. To get at its food, diplodocus tore up saplings and pushed over trees, creating open plains. Everything about diplodocus was big - even its eggs were a hefty 25 centimetres across.
Tree grazer
Brachiosaurus ("arm lizard") was another well-known late Jurassic giant. Tall rather than long, brachiosaurus could grow up to 30 metres. It had a long neck that allowed it to graze among treetops and long legs that kept its body high off the ground. Its front shoulders were higher than its haunches, giving it a sloped appearance rather like a modern giraffe.
Plated-up
Stegosaurus ("roof lizard") was a medium-sized herbivore of the late Jurassic. Around 7 metres long and up to 3 tonnes in weight, Stegosaurus had a series of large, bony plates running along its spine. Experts have suggested several uses for these plates. They could have been used in courtship display or they may have served as heat-regulating devices. Perhaps they were defensive armour or maybe Stegosaurus could have made itself more terrifying in combat by pumping the plates with blood. At any rate, Stegosaurus was no pushover in the dangerous world of Jurassic Earth. It had a fearsome defensive weapon - a powerful, spiked tail that could deliver crippling blows to would-be predators.
Jurassic slasher
As large herbivores became more prevalent, bigger predators emerged, too. Allosaurus ("other lizard") was the commonest large predator of the period. Around 12 metres long, it is known to have preyed on big sauropods as well as smaller animals. Its curved teeth and huge jaws inflicted deep slashing wounds on its victims. You wouldn't last long once you were corned by an Allosaurus. Nimble prey might have outrun this predator, though, because it wasn't capable of sustained bouts of speed. Interestingly, there is some evidence that Allosaurus cared for its young, bringing back meat for its offspring, who lived in a protected den until they were old enough to fend for themselves.
Quick dino-facts
Three stars of Jurassic Park - Triceratops, Tyrannosaurus rex and Velociraptor - weren't actually around during the Jurassic Period. They didn't evolve until the late Cretaceous.
After studying fossil tracks, modern palaeontologists concluded that giant sauropods walked with their tails held aloft, not dragging along the ground.
Giant sauropods had large stones in their stomachs to help them digest tough vegetation.
An evolving world
Jurassic Earth was on the move. The Pangaea super-continent began to split into two during the mid-Triassic and this trend continued during the Jurassic Period. As early versions of today's continents moved away from each other, the oceans began to exert more influence on Earth's weather: the climate became far more varied. Vegetation was becoming more sophisticated, too. Palm-like plants and conifers flourished. Some experts also believe that the first flowering plants developed at the end of the Jurassic.
Land of the giants
The late Jurassic Period is renowned for huge dinosaur herbivores, known as sauropods. The largest grew to more than 40 metres in length and probably weighed up to 100 tonnes. You wouldn't have wanted one of these titans to step on your toe but sauropods weren't as heavy as their size might have suggested. They were actually quite lightly built creatures: much of their apparent bulk was due to internal, air-filled sacs.
Not walking in water
Palaeontologists used to believe that sauropods were amphibians. Artists' impressions of the large herbivores always depicted them grazing in lakes. It wasn't thought possible that sauropods could support their supposed vast weight without the buoyancy of water. Today's dinosaur experts are confident that sauropods had legs that were akin to a modern elephant's - easily able to support their own body weight.
Huge herder
Long-necked and long-tailed, Diplodocus ("double beam") is probably the best-known sauropod. Herds of these giant dinosaurs dominated the late Jurassic period. They were so big (25 metres and over) that they would have changed the landscape around them. To get at its food, diplodocus tore up saplings and pushed over trees, creating open plains. Everything about diplodocus was big - even its eggs were a hefty 25 centimetres across.
Tree grazer
Brachiosaurus ("arm lizard") was another well-known late Jurassic giant. Tall rather than long, brachiosaurus could grow up to 30 metres. It had a long neck that allowed it to graze among treetops and long legs that kept its body high off the ground. Its front shoulders were higher than its haunches, giving it a sloped appearance rather like a modern giraffe.
Plated-up
Stegosaurus ("roof lizard") was a medium-sized herbivore of the late Jurassic. Around 7 metres long and up to 3 tonnes in weight, Stegosaurus had a series of large, bony plates running along its spine. Experts have suggested several uses for these plates. They could have been used in courtship display or they may have served as heat-regulating devices. Perhaps they were defensive armour or maybe Stegosaurus could have made itself more terrifying in combat by pumping the plates with blood. At any rate, Stegosaurus was no pushover in the dangerous world of Jurassic Earth. It had a fearsome defensive weapon - a powerful, spiked tail that could deliver crippling blows to would-be predators.
Jurassic slasher
As large herbivores became more prevalent, bigger predators emerged, too. Allosaurus ("other lizard") was the commonest large predator of the period. Around 12 metres long, it is known to have preyed on big sauropods as well as smaller animals. Its curved teeth and huge jaws inflicted deep slashing wounds on its victims. You wouldn't last long once you were corned by an Allosaurus. Nimble prey might have outrun this predator, though, because it wasn't capable of sustained bouts of speed. Interestingly, there is some evidence that Allosaurus cared for its young, bringing back meat for its offspring, who lived in a protected den until they were old enough to fend for themselves.
Quick dino-facts
Select your bookmark
What is social bookmarking?