Dinosaurs

Dinosaurs were vertebrate animals that dominated terrestrial ecosystems for over 160 million years, first appearing approximately 230 million years ago. more...

Home
Birds
Cats
Dinosaurs
Dogs
Farm/ Countryside
Fish/ Marine
Insects/ Butterflies
Other Animals
Taxidermy
Wild Animals

At the end of the Cretaceous Period, 65 million years ago, dinosaurs experienced a catastrophic extinction, which ended their dominance on land. Taxonomists consider modern birds to be the direct descendants of theropod dinosaurs.

Since the first dinosaur was recognized in the 19th century, mounted, fossilized dinosaur skeletons have become major attractions at museums around the world. Dinosaurs have become a part of world culture and remain consistently popular among children and adults alike. They have been featured in best-selling books and films such as Jurassic Park, and new discoveries are regularly covered by the media.

The term dinosaur is sometimes used informally to describe other prehistoric reptiles, such as the pelycosaur Dimetrodon, the winged pterosaurs and the aquatic ichthyosaurs, plesiosaurs and mosasaurs, although technically none of these were dinosaurs.

What is a dinosaur?

Definition

The taxon Dinosauria was formally named by the English palaeontologist Richard Owen in 1842 as "a distinct tribe or suborder of Saurian reptiles". The term is derived from the Greek words δεινός (deinos meaning "terrible", "fearsome" or "formidable") and σαύρα (saura meaning "lizard" or "reptile"). Owen chose it to express his awe at the size and majesty of the extinct animals, not out of fear or trepidation at their size and often-formidable arsenal of teeth and claws.

Dinosaurs were an extremely varied group of animals; according to a 2006 study, 527 dinosaur genera have been identified with certainty so far, and 1,844 genera are believed to have existed. Some were herbivorous, others carnivorous. Some dinosaurs were bipeds, some were quadrupeds, and others, such as Ammosaurus and Iguanodon, could walk just as easily on two or four legs. Regardless of body type, nearly all known dinosaurs were well-adapted for a predominantly terrestrial, rather than aquatic or aerial, habitat.

Dinosaur synapomorphies

All dinosaurs so far discovered share certain modifications to the ancestral archosaurian skeleton. Although some later groups of dinosaurs featured further modified versions of these traits, they are considered typical across Dinosauria; the earliest dinosaurs had them and passed them on to all their descendants. Such common structures across a taxonomic group are called synapomorphies.

Dinosaur synapomorphies include: reduced fourth and fifth digits on the manus ('hand'), reduced number of digits on the pes (foot) to three main toes, a sacrum (the region of the vertebral column to which the pelvis attaches, composed of three or more fused vertebrae) and an open or perforate acetabulum (hip socket with a hole at its centre). Dinosaurs are unique among all tetrapods in having this perforate acetabulum.

Read more at Wikipedia.org