Portal:Dinosaurs

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The Dinosaur Portal

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Introduction

Mounted skeletons at the AMNH.

Dinosaurs are vertebrate animals that dominated terrestrial environments for over 160 million years, first appearing approximately 230 million years ago. At the end of the Cretaceous Period, approximately 65 million years ago, a catastrophic extinction event ended the dinosaurs' dominance on land, making them extinct. However, taxonomists consider modern birds to be direct descendants of theropod dinosaurs, making them the only "dinosaurs" alive today. 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.

Before their extinction, dinosaurs were the dominant group of lifeforms on the planet. They were extremely varied, abundant and found in most areas of the earth. 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.

Since the first dinosaur fossils were recognized in the nineteenth century, mounted dinosaur skeletons have become major attractions at museums around the world and have amassed a large fan base 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.
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Styracosaurus (meaning 'spiked lizard') was a genus of herbivorous ceratopsian dinosaur from the Cretaceous Period (Campanian stage), about 74 to 72 million years ago. It had four to six long horns extending from its neck frill, a smaller horn on each of its cheeks and a single horn protruding from its nose, which was around 60 centimeters (2 ft) long and 15 centimeters (6 in) wide. The function or functions of the horns and frills have been the subject of debate for many years.

Styracosaurus was a large dinosaur, reaching lengths of 5.5 meters (18 ft) and weighing nearly 3 tons. It stood about 1.8 meters (6 ft) tall. Styracosaurus possessed four short legs and a bulky body. Its tail was rather short. It also had a beak and flat cheek teeth, indicating that its diet was herbivorous. Like other ceratopsians, this dinosaur may have been a herd animal, traveling in large groups, as suggested by bonebeds. Named by Lawrence Lambe in 1913, Styracosaurus is a member of the Centrosaurinae. Three species, S. albertensis, S. ovatus, and S. parksi are currently assigned to Styracosaurus, though the last species may be synonymous with S. albertensis. Other species assigned to the genus have since been reassigned elsewhere. (see more...)

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