Fossils
In the fifth extinction event we saw the death of dinosaurs around 65 million years ago; quite recently we might say, considering the long history of the existence of life on Earth.
Our usual view of history involves a picture of different types of dinosaurs roaming about the surface of Earth and the famed pterodactyls, the winged dinosaurs, flying in the sky in large swarms. Beyond that, our picture is blank, since we are taught through science fictions that the dinosaurs were some of the earliest life forms on the planet.
Movies have captured our imagination, giving a view of how terrifying the world was when the dinos roamed about on the surface. It is sad to say that the dinos were a recent phenomenon, but the good news being there were even more terrifying beasts before the dinos, roaming about the very surface we walk on right now. What happened to them then? Extinction, of course!
The 3 extinction events before the dinosaurs, namely the Devonian, Permian and the End-Triassic extinctions, left Earth depopulated on a large scale, with each event occurring for a short or a longer duration of time. The causes of those phenomena are still unknown, but what was important was the fact that life found its way in one way or the other to continue existing and evolving.
While the minor extinction events which occurred sporadically were confined in terms of duration and the overall impact on life forms, the major extinction events had a very wide impact on the living organisms. In each of the events, the total decrease in the species count was no less than 90 percent (!), with only a few species surviving into the successive periods.
The Animal Kingdom
After the fifth extinction event โ the K-T extinction or the Cretaceous-Tertiary extinction event โ began the Cenozoic era from 65 million years ago till today. The animal kingdom which we see today evolved during the early part of this era, the Palaeogene period (65 million years ago to 24 million years ago). Some animals that came about during this period were the elephants, deer, rhinos, horses, hedgehogs, rabbits, etc.
The Neogene period (24 to 1.8 million years ago) which followed, gave rise to sheep, cattle, whales, bears, modern birds, dogs, monkeys etc. The highlight of this period was the appearance of Australopithecus, the earliest precursor to modern man.
