Dinosaur World

The Classification Of Dinosaurs; Before The Dinosaurs And The First Dinosaur.

The classification of dinosaurs began as there was life on earth for about 3,250 million years before the first dinosaurs appeared. The story of early life can be broken down into stages, each on marking a crucial along the path towards the emergence of the first dinosaurs, some about 250 million years and maybe more. Thus the evolution of the early life can be traced to the point at which dinosaurs came to the scene.

classification of dinosaurs

  • Pre- Cambrian period (3,500- 570 million years ago): for the first 3,000 million years of life on earth, all was microscopic- it would be small to see with the naked eye. Today, you can only see the remains of these tiny ancient creatures, preserved as microfossils, with the help of a microscope. All life was in the oceans- there was no life on land.
  • Cambrian Period (570- 510 million years ago): the first creatures big enough to be seen with the naked eye appeared. These were creatures without any sign of backbones, the invertebrates such as mollusks, sponges, worms, jellyfish and starfish. All life was in the oceans.
  • Ordovician Period (510- 440 million years ago): creatures with backbones, the vertebrates appeared. The oceans were home to corals, trilobites, sponges, jellyfish and graptolites which lived in colonies and floated through the water. All life was in the oceans.
  • Silurian Period (440- 410 million years ago): the first dish with jaws evolved. Coral reefs flourished in the oceans. The first plants grew on land. Scorpions and millipedes came out of the water and adapted to living on land.
  • Devonian Period (410- 360 million years ago): this was ‘the age of fish’. Fish dominated life in the seas. The first insects appeared. The first amphibians evolved- created that can live in water and on land. Primitive plants formed the first forest on land. Horse- tails and club mosses appeared.
  • Carboniferous Period (360- 290 million years ago): snails, centipedes, millipedes, cockroaches and giant dragonflies thrived in the warm, damp climate. The first small insect- eating reptiles, which evolved from amphibians, appeared. Giant tree ferns, hose- tails and conifers formed forest.
  • Permian Period (290- 250 million years ago): new species of larger reptiles evolved and took over from amphibians. Ferns, horse- tails and conifers were widespread on land.

Classification Of Dinosaurs: The First Mass Extinction

The first great extinction of animals happened of the end of the Permian Period, 250 million years ago, when about three quarters of all amphibians and reptiles species died out on land and half of all species in the oceans. This event is the catastrophic loss of life ever knows on earth- greater even than the extinction of the dinosaurs. The reason why so many animal species disappeared at this time are unclear, although most scientist think that it was because of massive changes that happened on a global scale such as alterations in the climate and the drying up of the oceans.

Classification of dinosaurs and Harry Seeley.

In 1887, British geologist, Harry Seeley came up with a way of dividing into two basic groups or orders. Over many years he had made a careful study of dinosaur skeletons in museums collections, noting their similarities and differences. He noticed that dinosaur hip bones were either shaped like those of lizards or birds. This important observation led him to propose a new idea- that dinosaurs should be divided into order Saurischia (lizard- hipped dinosaurs) and the order Ornithischia (bird- hipped dinosaurs).

The classification of dinosaur

The classification of dinosaurs begins with the dinosaurs themselves.

Dinosaurs: all dinosaurs were descended from reptiles called thecodonts, which first appeared on earth during the Triassic period. Thus, these dinosaurs classified into:

  1. Saurischia: these dinosaurs otherwise known as the lizard- hipped dinosaurs were dinosaurs whose hip were shaped like those of lizards fall into two types: the agile, meat- eating theropods and the sower- moving, plant- eating sauropods.
  • Theropods: the name of this dinosaur means beast foot. They are dinosaurs which walked on three- toed bird- like feet with sharp claws for friction and meat snaking. They had powerful legs, small arms, a short compact chest, a long muscular tail, a curved and flexible neck, and large eyes with dagger like teeth. Some examples of these are, Allosaurs, Baryonyx, Deinonychus, Oviraptor and Tyrannosaurs. They are carnivores- meat eating dinosaurs.
  • Sauropods: name means lizard foot. They have large massive- sized dinosaurs which walked on all four feet. They had small heads, long necks, bulky bodies and long tails. They were herbivores- plant- eating dinosaurs. Examples are: Apatosaurs, Brachiosaurs, Diplodus and Seismosaurs.
  1. Ornithischia: this dinosaur like wisely called bird- hipped dinosaurs whose hip bones were shaped like those of living birds were far more varied than the lizard- hipped dinosaurs. These dinosaurs are divided into five types: ankylosaurs, ceratopsians, ornithopods, pachycephalosaurs and stegosaurs.
  • Ankylosaurs: this name means fused together reptiles. They are small to medium- sized dinosaurs. They had low, squat bodies with massive limbs. Their bodies were covered in flexible, bony armor of slabs, plates and spikes and they had small teeth and weak jaws. They were herbivores- plant- eating dinosaurs. Examples are, Ankylosaurs and Euoplocephalus.
  • Ceratopsians; name means horned faces. This dinosaur have small to large dinosaurs that moved on two or four legs. Some had horned and frilled heads and some had narrow parrot- like beak. They probably lived in large herds and were also herbivores- plant eating dinosaurs. Same examples like Psittacosaurs and Triceratops.
  • Ornithopods: name means bird feet. They are small to very large dinosaurs that walked and ran on their two back feet. Some lived in large herds. Some had crest on their heads and around their neck. They were herbivores- plant eaters. Examples; Lesothosaurs, Iguanodon and Parasaurolophus.
  • Pachycephalasaurs: name means bone heads. These dinosaurs are small to medium sized dinosaurs. They were slow moving, had thick skulls and moved about on two back legs. They lived in herds and were herbivores i.e. plants eating dinosaurs. Some examples are, Pachycepholosaurs and Stegoceras.
  • Stegosaurus: name means roofed reptile. Stegosaurus are more of a medium- sized dinosaurs and as such Stegosaurus move about all fours and were slow moving, their skins were covered in bony plated or spiked and they had short, weak teeth. They were herbivores- plant eaters. Some examples are, Kentrosaurus and Stegosaurus’.

classification of dinosaur


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