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The Dinosaur Portal

Introduction

Stegosaurus stenops
(a stegosaur)

Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is a subject of active research. They became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201.3 mya and their dominance continued throughout the Jurassic and Cretaceous periods. The fossil record shows that birds are feathered dinosaurs, having evolved from earlier theropods during the Late Jurassic epoch, and are the only dinosaur lineage known to have survived the Cretaceous–Paleogene extinction event approximately 66 mya. Dinosaurs can therefore be divided into avian dinosaurs—birds—and the extinct non-avian dinosaurs, which are all dinosaurs other than birds.

Dinosaurs are varied from taxonomic, morphological and ecological standpoints. Birds, at over 11,000 living species, are among the most diverse groups of vertebrates. Using fossil evidence, paleontologists have identified over 900 distinct genera and more than 1,000 different species of non-avian dinosaurs. Dinosaurs are represented on every continent by both extant species (birds) and fossil remains. Through the first half of the 20th century, before birds were recognized as dinosaurs, most of the scientific community believed dinosaurs to have been sluggish and cold-blooded. Most research conducted since the 1970s, however, has indicated that dinosaurs were active animals with elevated metabolisms and numerous adaptations for social interaction. Some were herbivorous, others carnivorous. Evidence suggests that all dinosaurs were egg-laying, and that nest-building was a trait shared by many dinosaurs, both avian and non-avian. (Full article...)

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Iguanodon is a genus of ornithopod dinosaur that lived roughly halfway between the first of the swift bipedal hypsilophodontids and the ornithopods' culmination in the duck-billed dinosaurs. Many species of Iguanodon have been named, dating from the Kimmeridgian age of the Late Jurassic Period to the Cenomanian age of the Late Cretaceous Period from Asia, Europe, and North America. However, research in the first decade of the 21st century suggests that there is only one well-substantiated species named I. bernissartensis, that lived from the late Barremian to the earliest Aptian ages (Early Cretaceous) in Belgium, between about 126 and 125 million years ago. Iguanodon's most distinctive features were its large thumb spikes, which were possibly used for defence against predators, combined with long prehensile fifth fingers able to forage for food. Named in 1825 by English geologist Gideon Mantell, Iguanodon was the second dinosaur formally named, after Megalosaurus. A large, bulky herbivore, Iguanodon is a member of Iguanodontia, along with the duck-billed hadrosaurs. (see more...)

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Dinosaurs

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Scelidosaurus harrisonii restored as a bipedal ornithischian

Photo credit: User:Jack Mayer Wood

Did you know...

...that Atlascopcosaurus and Qantassaurus are two Australian dinosaurs named after businesses?
...that a specimen of Brachylophosaurus nicknamed 'Leonardo' was found fully articulated and wrapped in impressions of its skin?