Dinosaur classification is frequently varying, as new matter is exposed and old matter is reexamined and reevaluated. New insights are often being found, and paleontologists again and again oppose on the consequence of one or a different piece of information.Dinosaurs were terrestrial reptiles that walk by an upright position. Their distinctive hip arrangement caused their legs to attach out below their bodies, and not sprawl away from the region (as with other reptiles). When dinosaurs first grow from more prehistoric archosaurs, they were bipedal (they walked on two legs). Much soon, various dinosaur groups returned to a four-legged position, most having back legs much better than their front legs. There were many special types of dinosaurs, conflicting in size and weight, locomotion (two- or four- legged walk, fast or slow speed), diet (meat or plants), and just about every other physiological and anatomical quantify.
Dinosaurs were reptiles from the Mesozoic
Era. They are classified as follows:
•
Kingdom Animalia (animals)
• Phylum Chordata
(having a hollow nerve chord ending in a brain)
• Class Archosauria (diapsids with socket-set
teeth, etc.)
• Subclass Ornithodira (dinosaurs
and pterosaurs)
• Superorder Dinosauria
(dinosaurs)
• Order Saurischia and Ornithischia
(based on hip structure)
The dinosaurs are classified on the order or size
of their hip(Pelvic) structure.They are:
• the "Lizard-Hipped" or Saurischian
dinosaurs
• The "Bird-Hipped" or Ornithischian
dinosaurs.
LIZARD-HIPPED DINOSAURS:
These types of Dinosaurs had
a hip structure similar to that of lizards. Oddly
enough, these "Lizard-Hipped" dinosaurs
were the ancestors of the birds.
Other anatomical features that characterize saurischians
include an opening below the nostrils (called
the subnarial foramen), an elongation on some
neck vertebrae (resulting in long necks), a big
thumb, an extra, wedge-shaped ankle bone (the
astragalus), and many other distinctive features.The
oldest known dinosaurs are Saurischians from the
mid-Triassic period, about 230 million years ago.Saurischians
included both meat and plant eaters.
Examples:
Theropods
- bipedal carnivores like T. rex, Velociraptor,
Compsognathus, and Deinonychus
Sauropodomorphas
- quadrupedal herbivores like Apatosaurus, Brachiosaurus,
and Diplodocus.
BIRD-HIPPED DINOSAURS:
These type of Dinosaurs had a
hip structure that is similar to that of birds
(but did not lead to the birds).They also had
beak-like bone in the lower jaw in front of the
teeth, called a predentary. Other anatomical differences
include a narrow palebral (the bone that crosses
the outside of the eye socket), and bony (ossified)
tendons above the sacral area of the vertebrae.
The Ornithischian dinosaurs were vegetarians and
included plated, armored, and horned dinosaurs.
Examples:
Ornithopods - Hadrosaurs
, Hypsilophodontids, Iguanodontids, Fabrosauria
.
Marginocephalia - Ceratopsians
, Pachycephalosauria.
Thyreophora - Stegosaurids,
Ankylosaurids.