An analysis of the theories of extinction of dinosaurs

The other groups mentioned are, like dinosaurs and pterosaurs, members of Sauropsida the reptile and bird cladewith the exception of Dimetrodon which is a synapsid. Definition Triceratops skeleton, Natural History Museum of Los Angeles County Under phylogenetic nomenclaturedinosaurs are usually defined as the group consisting of the most recent common ancestor MRCA of Triceratops and Neornithesand all its descendants. In traditional taxonomy, birds were considered a separate class that had evolved from dinosaurs, a distinct superorder.

See Article History Alternative Title: Dinosauria Dinosaur, the common name given to a group of reptilesoften very large, that first appeared roughly million years ago near the beginning of the Middle Triassic Epoch and thrived worldwide for nearly million years.

Most died out by the end of the Cretaceous Periodabout 66 million years ago, but many lines of evidence now show that one lineage evolved into birds about million years ago.

An analysis of the theories of extinction of dinosaurs

The English anatomist Richard Owen proposed the formal term Dinosauria in to include three giant extinct animals MegalosaurusIguanodonand Hylaeosaurus represented by large fossilized bones that had been unearthed at several locations in southern England during the early part of the 19th century.

Owen recognized that these reptiles were far different from other known reptiles of the present and the past for three reasons: Originally applied to just a handful of incomplete specimens, the category Dinosauria now encompasses more than generic names and at least 1, species, with new names being added to the roster every year as the result of scientific explorations around the world.

Not all of these names are valid taxahowever. A great many of them have been based on fragmentary or incomplete material that may actually have come from two or more different dinosaurs.

Dinosaur - Simple English Wikipedia, the free encyclopedia

In addition, bones have sometimes been misidentified as dinosaurian when they are not from dinosaurs at all. Nevertheless, dinosaurs are well documented by abundant fossil remains recovered from every continent on Earthand the number of known dinosaurian taxa is estimated to be 10—25 percent of actual past diversity.

Courtesy of Paul C. SerenoUniversity of Chicago dinosaur; fossilLearn about the history of people discovering fossils and the coining of the term dinosaur. The extensive fossil record of genera and species is testimony that dinosaurs were diverse animals, with widely varying lifestyles and adaptations.

Their remains are found in sedimentary rock layers strata dating to the Late Triassic Epoch approximately million to The abundance of their fossilized bones is substantive proof that dinosaurs were the dominant form of terrestrial animal life during the Mesozoic Era about It is likely that the known remains represent a very small fraction probably less than 0.

Scientists excavating dinosaur fossils from a quarry wall in Dinosaur National Monument, Colorado. National Park Service fossilFossil of a dinosaur in the Lufengosaurus genus lying where it was unearthed in Yunnan province, China.

Robert Reisz The search for dinosaurs The first finds Before Richard Owen introduced the term Dinosauria inthere was no concept of anything even like a dinosaur.

Large fossilized bones quite probably had been observed long before that time, but there is little record—and no existing specimens—of such findings much before In any case, people could not have been expected to understand what dinosaurs were even if they found their remains.

The first finds

For example, some classical scholars now conclude that the Greco-Roman legends of griffins from the 7th century bce were inspired by discoveries of protoceratopsian dinosaurs in the Altai region of Mongolia.

In Robert Plot of the University of Oxford included, in a work of natural history, a drawing of what was apparently the knee-end of the thighbone of a dinosaur, which he thought might have come from an elephant taken to Britain in Roman times.Types of dinosaurs.

Dinosaurs are united by at least 21 traits in their skulls and skeletons. These common characters (called 'synapomorphies') are the reason palaeontologists are sure dinosaurs had a common origin.

However, when definite dinosaur fossils appear (early in the Upper Triassic), the group had already split into two great orders, the Saurischia, and the Ornithischia. Whipping Tail Action! Dino-Damage wound! Note: There is a doubt on this figure’s authenticity as being part of the line.

Dinosaurs are a diverse group of reptiles of the clade first appeared during the Triassic period, between and million years ago, although the exact origin and timing of the evolution of dinosaurs is the subject of active research.

An analysis of the theories of extinction of dinosaurs

They became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event million years ago; their dominance. Years of scientific debate over the extinction of ancient species in North America have yielded many theories. However, new findings reveal that a mass extinction occurred in a geological instant.

Extinction of Dinosaurs Two-hundred and thirty million years ago the first dinosaur-like creature roamed the earth. Dinosaurs were a very successful and diverse group, dominating the terrestrial environments of the earth for million years. The Extinction of Dinosaurs Essay Sample Theories about the extinction; Until today, theories are still being developed to give light to what happen to the species that died out and how.

There are many stipulations about it ranging from animal parents killing their own .

The Great Mystery: Current Arguments