The Jurassic Time Period

What dinosaurs ruled during this period and how long ago was it? Did T-rex live there or was is Pteranadon? Or maybe even Brontosaurus?

The Jurassic Period of dinosaurs probably brings memories of the movie Jurassic Park. And rightly so, since the dinosaurs so aptly portrayed in this movie are some of the same ones from the Jurassic Period.

The Jurassic Period is also known as the Age of the Dinosaurs and occurred 205 to 145 million years ago. This time is the second of three periods in the Mesozoic Era. The name Jurassic comes from the Jura Mountains between Switzerland and France.

In the beginning of the Jurassic Period most of the continents were joined together before the Atlantic began to form and the Americas split off from Africa. Eastern North America was primarily elevated and had a tendency to erode. Before the end of this period, the Pacific border of North America, from California to Alaska, was submerged. The end of this era in North America was marked by widespread folding along the western border of the continent with the intrusion of lava as the eastern edge of the plate that carries the Pacific Ocean was thrust underneath the westward drifting plate that carries the North American continent.

During this time lived the largest land animals to ever exist -- the Jurassic sauropods. Among these great giants were the Apatosaurus, also known as Brontosaurus, Brachiosaurus and Seismosaurus. Sauropods had four legs, long necks and fed on a variety of plants. They walked the great flood plains, eating leaves of tall conifers and drinking from the rivers as they traveled. Their history has been studied by paleontologists and it is believed they traveled at a leisurely place in a herd.

Though these Sauropods are shown standing on their hind legs to reach the tops of trees, scientists think these creatures really weren't capable of such a feat given their immense weight and size. But Brachiosaurus did have nostrils on the top of its head which enabled it to escape predators easier by going into water. What all the Sauropods had in common was their need to consume large amounts of food in order to survive. They needed to nearly eat continuously to keep up their energy and be able to escape predators.

Stegasaurs also lived during this time, including the well-known Stegosaurus. This dinosaur is famous for the row of back plates and spikes on the tail. With a very small head and large body, this dinosaur didn't move very fast and had a small brain. The plates down the back contained blood vessels, which helped the dinosaur regulate body temperature while also providing protection against predators.

The pint-sized birdlike Compsognathus lived during the late Jurassic period. This dinosaur was a carnivore with a jaw that contained many sharp teeth. The Compsognathus had hips similar to today's lizards and stood on its hind legs with the tail equipped for balancing while it chased after its prey.

Archaeopteryx existed in the Jurassic Period and was a feathered bird of sorts. Actually, this was a dinosaur with feathers as odd as that may sound. It had a long boy tail, three fingers on each hand, a long thin neck and a slight built skull with teeth in the jaw. Birds don't have either teeth or bony tails. Fossils of Archaeopteryx also indicate this dinosaur was capable of flying like birds of today.

The meat-eating dinosaur Allosaurus was prevalent during this time and had large, narrow jaws, long and well-muscled forelimbs with huge claws and large legs ending in clawed feet. They were fierce hunters able to grab prey with their clawed arms and rip it to shreds with their mighty jaws. It is even possible that the taloned hind limbs were used to take down large prey as well. The Allosaurus was a large carnivore during the late Jurassic Period. As a relative to the Tyrannosaurus of the Cretaceous period, this fearsome meat-eater grew up to 40 feet long from head to tail. Its head could be up to 3 feet long and was filled with sharp teeth that could bite giant chunks of flesh from its prey. The hands and feet had sharp claws that could be used for grasping prey while it walked on its hind legs, using its heavy tail for balance.

Dinosaurs in the water were also present during the Jurassic Period. One such creature was Ichthyosaurus. They had flexible bodies and presumedly swam by undulating like today's eels. Ichthyosaurus was not a dinosaur but within a separate group of marine vertebrates. These swimmers first appeared during the previous Triassic period and became more advanced during the Jurassic Period.

As for plant life, there were no palm trees like the dinosaurs would have liked, or even any other flowering plants. Instead, ferns, ginkgoes and true cycads thrived during the Jurassic Period. Conifers also existed, including close relatives of today's redwoods, cypresses, pines, and yews.

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