Dinosaur Fossils and Reptile Fossils

Dinosaur Fossils and Reptile Fossils for Sale

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About Dinosaur and Reptile Fossils

While they occupy a tiny part of the monophyletic Class Reptilia, the extinct non-avian dinosaurs capture the imagination of many people of all ages. A relatively recent scientific revelation is that dinosaurs are in fact not extinct, since birds are now considered to be descendants of non-avian dinosaurs. Dinosaurs appeared and thrived during the Mesozoic Age between 231 and 65 million years ago. All dinosaurs were terrestrial, though their close relatives were aquatic or marine. They are differentiated from other reptiles by skulls with two extra openings behind the orbits, a perforate acetabulum (hip socket) that more directly supported the weight of the articulation with the legs than in the usual reptilian morphology, and three or more vertebrae comprising the sacrum. Dinosaurs evolved to amazing diversity, occupying an amazing array of ecological niches. Some dinosaurs were huge and some were bird-size. Some walked on four legs and some on two legs. Some were fierce meat-eaters and some were docile plant eaters. Dinosaur fossils have been found on every continent on earth and dominated earth during the Jurassic, with many new groups appearing. The Cretaceous period saw the peak of dinosaur evolution when huge carnivores like Tyrannosaurus rex and Giganotosaurus appeared, as did Triceratops and numerous others.

So why are bird fossils included here? Because the phylogeny of vertebrates, particularly over the past decade, has supported the hypothesis that birds, the avians, are dinosaurs. More semantically correct is calling birds avian dinosaurs with other dinosaurs classed as non-avian dinosaurs. Thus, as dinosaurs are reptiles, so are birds. More recent research provided strong evidence that the avians are members of the theropod dinosaurs with whom they likely share the closest commen ancestor.

Dinosaurs are but a small part of Class Reptilia, the reptiles, that includes the ectothermic snakes, lizards, crocodiles, turtles, and the endothermic birds. Repeating, even birds can be considered reptiles because they descended from dinosaurs. Class Reptilia is represented by six Orders: 1) Crocodylia – Crocodilians; 2) Rhynchocephalia – Tuataras; 3) Squamata (that includes Suborder Sauria – Lizards and Suborder Serpentes – Snakes; 4) Testudines – Turtles, and 6) the Superorder Dinosauria containing Order Saurischia (lizard-hipped) and Order Ornithischia (bird-hipped).