Dinosaurs Reptilian.

What, then, about the dinosaurs? From the time of the earliest discoveries in the 19th century, experts like Owen, Leidy, Marsh, and Cope classified all then-known Dinosaur remains as reptilian because they exhibited a set of anatomic features that were typical of living reptiles like turtles, crocodiles, and lizards. Dinosaur all had lower jaws constructed of several bones, featured a reptilian jaw joint, and possessed a number of other nonmammalian characteristics. Consequently, it was assumed that living Dinosaur were like living reptiles scaly, cold-blooded ectotherms and not furry, warm-blooded creatures that gave live birth. A chauvinistic attitude seems to prevail that the warm-bloodedness of mammals is better than the cold-blooded reptilian state. Turtles, snakes, and other reptiles, however, do very well by regulating their body temperature in a different way.

Dinosaurs traditionally have been placed in the reptilian subclass Diapsida, reptiles with two pairs of temporal openings in the skull. As diapsids, Dinosaur are grouped with the crocodilians, thecodonts, and pterosaurs, all of which have socketed teeth and a number of other features in common. These are the so-called archosaurian reptiles. In recent years it has been suggested that Dinosaur be ranked as a class of their own, comparable to the classes Mammalia and Aves. That idea has not been universally accepted as yet. At the present time, the term Dinosauria is not used as a taxonomic category to include all dinosaurs. Instead, they are classified in their two orders, as either Saurischia or Ornithischia.

Order Saurischia

The reptile-hipped dinosaurs.

Suborder Sauropodomorpha

All the reptile-hipped herbivorous dinosaurs. Late Triassic to Late Cretaceous.

Infraorder Prosauropoda

Facultative bipeds; primitive forerunners of sauropods. Late Triassic to Early Jurassic.

Family Anchisauridae

Primitive prosauropods including Anchisaurus and Plateosaurus . Late Triassic to Early Jurassic.

Family Melanorosauridae

Advanced prosauropods such as Melanorosaurus and Riojasaurus; probably includes the sauropod ancestry. Late Triassic to Early Jurassic

Infraorder Sauropoda

Large to gigantic obligatory quadrupeds; all herbivorous. Early Jurassic to Late Cretaceous.

Family Cetiosauridae

Primitive and poorly studied sauropods such as Cetiosaurus ; specimens mostly from the Old World; vertebrae well-excavated to lighten bone weight. Early to Late Jurassic.

Family Diplodocidae

More advanced and better-known large sauropods; highly excavated vertebrae. Diplodocus and Apatosaurus (Brontosaurus) are the best known. Late Jurassic to Late Cretaceous.

Family Brachiosauridae

Largest of all the sauropods; greatly elongated necks and highly excavated vertebrae; front legs longer than back legs. Brachiosaurus is the most famous. Middle Jurassic to Late Cretaceous.

Family Titanosauridae

Advanced sauropods, primarily from the southern continents. Examples are Titanosaurus and Alamosaurus.

Early to Late Cretaceous.

Family Camarasauridae

Moderate-size sauropods; relatively short necks and tails for this infraorder; teeth spatulate or spoon-shaped. Camarasaurus and Morosaurus are typical. Late Jurassic to Late Cretaceous.

Suborder Staurikosauria?

Primitive carnivorous Dinosaur resembling theropods; known only from South America. Classification is uncertain(?). Name bearer is Staurikosaurus. Middle to Late Triassic.

Suborder Theropoda

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Paleontology


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