Earlier I wrote about dinosaurs of Jurrasic period. This time around, trying to cover the whole kingdom for the children (of Sneh Sadan) who showed curiosity about dinosaurs.
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| "Image courtesy of Anusorn P nachol / FreeDigitalPhotos.net". |
During the Mesozoic era(165 million yrs ago), the evolution of gigantic beasts happened on this planet which gave rise to the era of dinosaurs. In fact, dinosaurs can be defined as large reptiles of the per-historic period. Actually speaking, nobody knows for sure, how dinosaurs looked like, but by their fossils one can figure out how they must have looked like.
Some people may think that dinosaurs were imaginary creatures like dragons, hydras, leviathans etc. But they were not. In fact, they were real and gigantic creatures. Well, not all, some of them were as small as that of size of a small cat too - e.g. Gallimimus.
Not all the dinosaurs were terrestrial. Many were marine inhabitants like Plesiosaurus, Ichthyosaurus etc. And many others were the masters of the skies known as Pterosaurs.
Dinosaurs are classified into two types according to the type of their hips, and are further classified again into various sub- types which makes the entire kingdom of dinosaurs very vast.
Dinosaurs are classified as Saurischians and Ornithischians. Saurischians are dinosaurs that had lizard like hips, while Ornithischian dinosaurs had bird like hips and many other characteristics that resembled to that of birds like duck –billed mouth, crests on the top of their heads, e.g. Zuniceratops .
Saurischians are divided into following two groups:
Theropods- They were ferocious meat eaters and were the apex predators of the food chain. They possessed hands and strong long legs with sharp claws used for gripping their prey, e.g.- Tyrannosaurus, Allosaurus etc. It also consisted of the smaller meat eaters too.
Sauropods- They were long necked herbivores and this feature has enabled them to browse on leaves of taller trees. Also , many of them had longer tails to defend from predators, e.g.- Apatosaurus, Saltasaurus, Brachiosaurus etc.
The number of dinosaurs falling in Ornithischians group is very huge and almost infinite and they are divided into the following types-
Ceratopsians
Ceratopsians are those dinosaurs which are characterized by horns which emerged from their skull and a frill on the top of their head. They were pure vegetarians and used their horns for fighting and while defending predators, e.g.- Triceratops, Styracosaurus group, Torosaurus etc.
Duck- billed dinosaurs
These dinosaurs had strange characteristic features like a bird’s mouth, a crest like a bird, bird like hips etc. Many of these dinosaurs lived in North America and other parts during the Cretaceous period. All of them were herbivores and many of these dinosaurs often travelled in groups. Many of these dinosaurs made trumpet like sounds, e.g. Parasaurolophus, Corythosaurus, Hadrosaurus etc.
Ankylosaurs
These dinosaurs had scales all over their body which is obviously a characteristic feature of any reptile. This might have served as a protection from predators. Also, they had clubs at the back of their tails to whip the predators off. E.g.- Ankylosaurus, Euplocephalus etc.Also, these dinosaurs were pure herbivores and slow moving.
Stegosaurs
The most obvious feature of these dinosaurs were that their bodies were always covered with plates from neck, covering the whole back and finally ending at the tail. They were herbivores and most of these species were found during the Jurassic period in much of North America. E.g.- Stegosaurus , Kentrosaurus, Tuojiangosaurus etc. Their powerful tails also had spines to fight with or defend predators. Another weird fact about them is that their brains were about the size of a peanut.
Pachycephalosaurs
These dinosaurs were again herbivores and inhabited during the Cretaceous period. They were herbivores and lived in herds. Another remarkable fact about these dinosaurs is that their heads were so strong and bony that during the mating season their males often butt their heads with each other. Thus, these dinosaurs are also known as head- butting dinosaurs. E.g.- Pachycephalosaurus, Stegoceras fighting etc.
It was during the Cretaceous period only that all sorts of dinosaurs vanished from the surface of the earth. Nobody knows why but there could be many reasons. Scientists have many theories about why and how these prehistoric beasts vanished from this planet. The most agreed upon theory among them was due to the meteors which struck the earth (65 million yrs ago), but not with 100% confidence though.
After the great doom of the dinosaurs only, the evolution of modern animals( mammals, reptiles, amphibians, birds) started. For instance mammoths evolved to modern elephant, Homo Erectus to Modern human being(Homo sapiens), Quaggas to modern zebras etc. To say that the current number of species of animals today is around crores from the giant blue whale to the smallest micro organism.
Also, there are many reptiles which have dinosaurs as their ancestors like the crocodilians( crocodiles, alligators, caimans etc.).
Any Lesson for us?
As we humans today are ruling the planet, we all of us know that dinosaurs are extinct. They are gone forever. We only see their photographs in any source(books, newspapers, internet etc.),their statues in various parks, their cartoons and animated characters in movies and serials, their fossils etc. But the thing is that the extinction of dinosaurs can also provide humans a valuable lesson in the conservation of current endangered species.
As we progressed on and on, we have mercilessly poached many wild animals for their (skins, body parts), we have encroached in their habitats etc. This has drastically reduced their numbers and many are on the verge of extinction. Tigers, many primate species, blue whales, rhinos etc. to name a few. These species need to protected carefully as they maintain the ecological balance. But, if nothing is done to save these species, we all will see them like dinosaurs i.e. only their photographs, statues, skeletons etc.
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