Dinosaur
| Dinosaur | |
|---|---|
| |
| Scientific classification | |
| Kingdom Information | |
| Kingdom | Animalia |
| Phylum Information | |
| Phylum | Chordata |
| Class Information | |
| Class | Sauropsida |
| Sub-class | Diapsida |
| Infra-class | Archosauromorpha |
| Order Information | |
| Superorder | Dinosauria |
| Order | Ornithischia; Saurischia |
| Population statistics | |
Dinosaurs are extinct animals usually believed to be ranging in size from a few ounces to some of the largest land animals ever to exist. The word dinosaur was coined in 1841 by Richard Owen[1], from the Greek words for "terrible lizard", and reflected the creatures' large size and fearsome appearance to the early paleontologists.
Contents
Highlights of the history of dinosaur paleontology
In the United States during the 1900s, the public imagination was caught by the discoveries of Henry Fairfield Osborn (1857-1935) and the great competitive dinosaur hunters, Edward Drinker Cope (1847-1897) and Othniel Charles Marsh (1831-1899). Exploring in Wyoming, Colorado, and New Mexico, they found numerous fossil dinosaurs. Their museums worked out the techniques for mounting and displaying them.
Dinosaur Species
Dinosaurs were immensely varied, and included both herbivores and carnivores. Although many have been found in the fossil record, paleontologists expect that they have barely scratched the surface of the vast superorder that the dinosaurs encompassed.[2]
History
Dinosaurs existed on earth from 230 million years ago to 65 million years ago. The entire population of dinosaurs were wiped out by a mass extinction event (usually thought to be a meteorite) about 65 million years ago.
Extinction
Close to 65 million years ago, at the end of the Cretaceous period, and the beginning of what is called the Tertiary period, an event occurred which has come to be known as the K-T Event. This event obliterated most life on Earth, plunging the world into perennial winter, through which few extant species could survive. Although the nature of the K-T Event is still the subject of some dispute on detail (selecting among any number of catastrophes that could have caused the significant global cooling that resulted), most scientist believe that the K-T Event was caused by the collision of a massive asteroid with the Earth, the dust and debris from which would have shrouded the sky for thousands of years, cooling Earth considerably.[3] According to this view, the dinosaurs did not survive this cataclysm.[4] A layer of rock containing high concentrations of Iridium, a metal that is extremely rare on earth but common in asteroids, is attributed to the vaporization and then fall of dust from the meteorite's impact, and its compression within the subsequent geological record.[5]The evidence of a large impact crater can be found in rocks of the Yucatán Peninsula of the supposed age of this layer.[6] [7]
An Explosion of new species
The mass extinction of life, like the Permian and other extinctions before it, removed a major food competitor, and predator, of smaller animals. As a result of a new "vacancy" in the food chain, following the K-T Event, vast speciation occurred, as the evolutionary pressure of a new cold age propelled animal species to adapt or die out. Mammals were some of the main beneficiaries of this explosion: their fur allowed them to adapt to the cold, and their small size allowed them to conserve energy relative to the huge dinosaurs of the previous age.[8]
Dinosaurs and Birds
As a number of feathered dinosaur fossils have been discovered, numerous homologies between between birds and dinosaurs show that modern birds are a descendants of dinosaurs.[9]
Description
Saurischia
Herbivorous species were almost all quadrupedal. They carried peg-like teeth which cut, rather than chewed, plant material; grinding of food was aided by gastroliths. Carnivorous species were exclusively bipedal.
- Sauropoda
- Species of this infraorder are characterized by long necks and tails, barrel-shaped bodies, and column-like legs. In three families (notably Diplodocidae, Brachiosauridae, and Titanosauroidea) there are species which are of extreme size, in excess of 125 feet in length and 100 tons, making them the largest animals to have walked the earth.
- Theropoda
- Exclusively bipedal; forearms meant for grasping or holding. Fossil evidence for several species indicate pack hunting.
Ornithischia
Species of this group were all herbivorous; most were quadrupedal. Front teeth were lacking, while a predentary bone was present in the front of the lower jaw. Several species (mainly within Ceratopsia) had a distinctive parrot-like beak.
- Ceratopsia
- Species of this infraorder carried one or more horns on their heads, as well as a shield-like frill to protect the neck.
- Stegosauria
- Large dinosaurs with a row of bony plates on top of their backs, and several spikes used as a defensive weapon at the end of their tails.
- Ankylosauria
- Heavily-armored dinosaurs, some with a row of spikes along each side, and possessing a bony tail club.
- Ornithopods
- Large, herd-dwelling dinosaurs that could run bipedaly. Several species had a "boss" of bone on their heads (Pachycephalosaurs) which may have been used for head-butting similar to bighorn sheep; others a crest of bone (hadrosaurs) which may have been sound resonators.
In Popular Culture
Dinosaurs have been a fixture of popular culture since their discovery. It is theorized that some of the myths of fantastical creatures stem from the accidental discovery of dinosaur fossils. More recently, dinosaurs have featured in popular stories including books, movies, television, video games, even music.
See also
- Evolution
- Theory of Evolution and Cases of Fraud, Hoaxes and Speculation
- Irreligion and superstition
- Young earth creationism
References
- ↑ Grigg, Russell, Dinosaurs and dragons: stamping on the legends, Creation 14(3):10–14, June 1992
- ↑ Vast Majority of Dinosaurs Still to Be Found, Scientists Say, National Geographic
- ↑ Kevin O Pope, "Meteorite impact and the mass extinction of species at the Cretaceous/Tertiary boundary," Proceedings of the National Academy of Science, available at [1]
- ↑ Prehistoric Asteroid "Killed Everything", National Geographic
- ↑ Ibid
- ↑ "Dinosaur-Killer" Asteroid Crater Imaged for First Time, National Geographic
- ↑ http://www.ucmp.berkeley.edu/education/events/cowen1b.html
- ↑ Bennet, Shostak, Jakotsky, "Life in the Universe," viewable at [2]
- ↑ New Dinosaur Discovered: T. Rex Cousin Had Feathers, National Geographic
