Sunday, July 01, 2007

Dinosaurs on the Jurassic Coast

About 225 million years ago, the first dinosaur appeared in the forests of what is now South America. It was a small two-legged animal about the size of a chicken. It was quick and agile on its two strong legs, and probably a very effective hunter. Within about 30 million years its dinosaur relatives had become the dominant creatures on the planet; they were to reign for about 165 million years

Most people know the dinosaur is a reptile, but many erroneously think the term applies to all giant reptiles. In fact dinosaurs came in all shapes and sizes; but certainly some of the larger ones were the biggest, fastest and most ferocious animals that have ever walked the Earth. The main distinguishing feature of a dinosaur is that it is a reptile that developed an upright gait. This gave it an immediate advantage over other reptiles with thier awkward sideways gait

At the beginning of the Triassic period there was a mass extinction of many species. These events have happened a number of times during geological history and have continued to puzzle geologists. Certainly much competion to the emerging dinosaurs was removed by this global catasrophe. The dinosaurs diversified rapidly during the Triassic and, with little competition, got bigger and bigger. Other reptiles also evolved, some taking to the air

During the Jurassic dinosaurs diversified further and became truly dominant. Huge plant eating varieties evolved along with ferocious predators. Other forms of life also flourished and, in the sea, other reptiles grew to immense size. The shallow, tropical seas in which Dorset's rocks were deposited must have been home to a fantastic array of life

The Cretatious period saw dinosaurs continue to dominate. Some of the most well known dinosaurs like Tyrannosaurus lived in this period and the shallow lagoons where the Purbeck rock was formed have helped preserve thier bones for us to study. At Durlston Bay and Worbarrow Bay it is possible to sea the footprints of these massive creatures. The most likely example you will find is the three pronged footprint of the Iguanadon (pictured above), a plant eater that was up to 10 metres long and 5 metres high. At the end of the Cretatious period (about 65 million years ago) the dinosaurs died out.

Whether or not it was the impact of a huge meteorite as has been suggested is still open to debate. The evidence is strong, but it should be remembered that mass extinctions have taken place at other times


Text: Fossils and Rocks of the Jurrasic Coast by Robert Westwood
Graphic: Wikipaedia

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