Life of the Past – Mesozoic Era
Mesozoic means “The Middle Life” which began about 225 million years ago and lasted some 160 million years. The Mesozoic era is subdivided into three periods: Triassic, Jurassic, and Cretaceous period.
The Mesozoic era is also known as the “Age of Dinosaurs”. It ended with the great meteorite impact and caused mass extinction wiping out all dinosaurs.
Triassic Period: 252 to 201 million years ago
Plant life:
During this period, most of the continental areas were above water. Climate was dry and warmer. The pteridophytes and seed ferns declined in number and gymnosperms increased very much. The cycads appeared and flourished along with conifers forming large forests.
Animal life:
New types of sponges and protozoans appeared in this period. Modern echinoids and crinoids first appeared in Triassic. Trilobites became completely extinct. Fossil remains of crocodile-like reptiles have been found in this period.
The dinosaurs of this period varied in size ranging from sheep to horse.
Jurassic Period: 201 to 145 million years ago
Plant life:
The Jurassic plant life was more luxuriant than in the Triassic period. Cycads increased in numbers. They were the dominant species during the Jurassic period and this is even known as the “Age of Cycads”. Conifers continued and were diverse large trees.
Animal life:
More than a thousand species of insects are known from this period. These were mostly modern orders like termites, grasshoppers, cockroaches, bees, wasps, ants, caddisflies, beetles, etc. There was a great increase in echinoids, crinoids, gastropods, and pelecypods.
Among the fishes, selachians and ganoids were common. Modern bony fishes, teleost appeared during this period.
Dinosaurs in Jurassic:
There were three main dinosaur groups in Jurassic: the sauropods, the stegosaurs, and the therapods.
Sauropods
These were long-necked, long-tailed four-legged monsters. The representative species was Diplodocus.
Stegosaurs
These were armored reptiles that weighed about ten tons.
Therapods
These were the carnivorous creatures that walked on their hind legs. These included Allosaurus.
Flying and aquatic reptiles were also present. This period saw the beginning of two groups i.e., birds and mammals that were later to establish their dominance. The fossils of primitive birds Archaeopteryx and Archaeornis have been discovered.
Cretaceous Period: 145 to 66 million years ago
The cretaceous period lasted some 70 million years. It was one of the most important of all geological periods, marked by a major advance of the sea in many parts of the world and by the great thickness of both marine and continental sediments.
Towards the close of this period earth movement produced mountains in Antarctica and North-Eastern Asia (Himalayas) as well as mountain ranges which are now Andes and Rockies.
This period is marked by two important events, the sudden rise of flowering plants and the widespread extinction of dinosaurs towards its end.
Summary
On the whole, the most outstanding feature of the Mesozoic era was the origin, development, and differentiation of a great variety of reptiles. Hence this era is the “Golden Age of Reptiles”. This era witnessed the large and bizarre-shaped animals ever lived on Earth.
These reptiles attained their maximum development during the Mesozoic era. They ruled the earth over 100 million years – a hundred times more as long as man has dominated it. Towards the end of the Cretaceous period, many groups of these great reptiles became extinct.