The Morrison formation
One of the most famous Jurassic age dinosaur bearing rock formations is the Morrison Formation in North America. The formation dates to around 155 - 147 million years and has outcrops in many states, but is mostly centered around Wyoming and Colorado. Its age is similar to to that of the Lourinhã Formation in Portugal and the Tendaguru beds in Tanzania. All were closely situated in the Late Jurassic and share some of the same fauna; it's believed dinosaurs may have migrated between the three areas.
The majority of the sediments found in the Morrison Formation were deposited by rivers, lakes, swamps and mudflats. These sediments contain abundant fossils, mostly notably those include many different types of dinosaur. Dinosaur National Monument in Utah is the site of a quarry where numerous dinosaurs were found in the early 1900s, including 23 mountable skeletons. The base of the quarry which contains a large jumble of dinosaur bones remains in place and forms one wall of the monument's Dinosaur Quarry building. Many of the dinosaur fossils at the monument were found as jumbled accumulations of bones, likely the result of the carcasses being transported along rivers and streams before their burial.
DINOSAURS OF THE MORRISON FORMATION
Allosaurus
One of the most famous carnivores of the Morrison Formation, Allosaurus was a large bipedal (walked on two legs) predator which likely reached over 39ft in length and had a sizeable skull equipped with dozens of razor sharp teeth. With its powerful hindlimbs and a heavily muscled tail, Allosaurus likely preyed upon large herbivors that shared its environment, such as Stegosaurus, ankylosaurs and sauropods.
Ceratosaurus
Ceratosaurus is another dinosaur found in the Morrison Formation. It was a medium sized bipedal carnivore, likely reaching lengths of up to 23ft. It lived alongside larger carnivores such as a Allosaurus and Torvosaurus, and had a skull with long blade-like teeth, and horns on its nose and above its eyes (which were most likely for display rather than combat). Ceratosaurus probably avoided competition with larger predators by preferring different types of prey or deploying different feeding strategies.
Stegosaurus
Stegosaurus was a large, herbivorous quadruped (walked on four legs) with broad upright plates lining its back and a spiked tail. Large individuals could grow up to 30ft in length. Today it is mostly agreed that the plates were used for display and to regulate heat, while the spiked tail was used to defend against predators. Among its predators were Allosaurus and Ceratosaurus. The first Stegosaurus was discovered in 1877 by Othniel Marsh and to date over 80 individual animals have been found. Stegosaurus is one of many herbivorous dinosaurs found in the Morrison Formation.
Diplodocus
Diplodocus, another famous dinosaur from the Morrison Formation, was a very large, long-necked quadruped dinosaur with a small head and a whip-like tail. Diplodocus is one of the longest known dinosaurs, with some estimated to reach over 100ft. Their necks were so long that it has been suggested these animals would have either required a huge heart (around 1/10 of their overall weight) or auxiliary "hearts" in their neck to help pump the blood. Others argue the animals almost horizontal posture would have helped supply blood to the brain.
earth during the jurassic
Earth 170 million years ago during the mid-Jurassic. Dinosaurs thrived as the first mammals and birds evolved. Ocean life diversified and the Earth was very warm.
