 |
Business | Industries | Finance | Tax |
| Index: > A B C D E F G H I J K L M N O P Q R S T U V W X Y Z |
|
|||||
| First Prev [ 1 2 3 4 ] Next Last |
| Dinosauria
Fossil | ||||||||
|---|---|---|---|---|---|---|---|---|
T. Rex skull, picture taken at Field Museum of Natural History, Chicago | ||||||||
| Scientific classification | ||||||||
| ||||||||
| Orders | ||||||||
|
Saurischia Ornithischia
|
The dinosaurs were a diverse and long-lived superorder of prehistoric reptiles.
Dinosaurs are a superorder of reptiles that first appeared approximately 230 million years ago. A few lines of primitive dinosaurs diversified rapidly after the Triassic; the reign of dinosaurs encompassed the ensuing Jurassic and Cretaceous periods. At the end of the Cretaceous, 65 million years ago, nearly all species of dinosaur became extinctIn biology and ecology, extinction is the disappearance of a species or group of species. The moment of extinction is generally considered to be the death of the last individual of that species. In species which reproduce sexually, extinction of a species (the Cretaceous-Tertiary extinction eventThe Cretaceous-Tertiary (KT) extinction event also known as the KT boundary (from German: , was a period of extremely frequent extinction of species, about 65. 5 million years ago. It corresponds to the end of the Cretaceous period and the beginning of th), except for the line that had already led to the first birds. There is now sufficient evidence to demonstrate that the birdFor other meanings of bird see bird (disambiguation). Many see text Birds are bipedal, warm-blooded, egg-laying vertebrates characterized primarily by feathers, forelimbs modified as wings, and hollow bones. There are almost 9000 known species of birds ins are the descendants of theropod dinosaurs.
The formal name Dinosauria was first proposed by the EnglishEngland is the largest, the most populous, and the most densely populated of the four " Home Nations" which make up the United Kingdom of Great Britain and Northern Ireland (UK). Occupying the south-eastern portion of the island of Great Britain, England scientist Richard OwenSir Richard Owen ( July 20, 1804 December 18, 1892) was an English biologist, comparative anatomist and palaeontologist. Early life and career Owen was born in Lancaster. He received his early education at the grammar school of that town. In 1820 he was a in 1842Events February 21 John J. Greenough patents the sewing machine. March 5 Over 500 Mexican troops led by Rafael Vasquez invade Texas briefly occupy San Antonio and then head back to the Rio Grande. This is the first such invasion since the Texas Revolution. The term is a combination of the GreekThe Greek language ( /Elini'k{/) is an Indo-European language which has existed from around the 14th century BC in the Cretan inscriptions called Linear B. Mycenaean Greek of this period is distinguished from later Classical or Ancient Greek of the 8th ce words deinos ("terrible" or "fearfully great" or "formidable") and sauros ("lizard" or "reptile").
Dinosaurs are archosaurs, like modern crocodylians. These are set apart by having diapsid skulls, having two holes where jaw muscles attach, called temporal fenestrae. Birds and most retiles are diapsids; mammals, with only one temporal fenestra, are called; and turtles, with no temporal fenestra are anapsids). Dinosaurs also have teeth that grow from sockets, rather than as direct extensions of the jaw bones, as well as various other characteristics. Within this group, the dinosaurs are set apart most noticeably by their gait. Instead of legs that sprawl out to the side, as found in lizards and crocodylians, they have legs held directly under their body.
Many other types of reptiles lived at the same time as the dinosaurs. Some of these are commonly, but incorrectly, thought of as dinosaurs: these include plesiosaurs (which are not closely related to the dinosaurs), and Pterosaurs, which developed separately from reptile ancestors in the late Triassic.
| Politics | Business | Finance |
 |
 |
 |
|