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Saurischia (Saurischians)
Translation: Lizard Hipped
Saurischia (sawr-RIS-kee-ah) is one of the two orders of animals called dinosaurs. (The other is Ornithischia.) Saurischians had lizard-like pelvises and clawed feet. Some were bipedal, while others were quadrupedal. Some were meat eaters; others were plant eaters. Saurischia is divided into two suborders: 1: Sauropodomorpha -- Basically quadrupedal and herbivorous. Members of sauropodomorpha include the largest creatures ever to exist on Earth, such as Seismosaurus. 2: Theropoda -- Bipedal and carnivorous. Theropoda includes such famous predators as Tyrannosaurus and Velociraptor.

Sauropoda (Sauropods)
Translation: Lizard-footed
Sauropoda (sawr-oh-POH-dah) is the infraorder of giant, quadrupedal, herbivorous saurischian dinosaurs. This group included the largest known animals to live on the Earth. Sauropods had huge bodies, long necks, whip-like tails, and elephant-like legs. In comparison to their usually enormous body size, sauropods had quite small brains. Sauropods lived on dry land or in swampy areas. They traveled in herds, and there is some evidence that they may have positioned their young in the center of the herd, surrounding them with adults, for protection against marauding predators. Sauropod eggs were about twice the size of ostrich eggs. See also Brachiosauridae and Titanosauridae Families

Sauropodomorpha (Sauropodomorphs)
Translation: Lizard-footed Forms
Sauropodomorpha (sawr-oh-POH-dah-more-fah) is one of two suborders of Saurischian dinosaurs. This group includes both the sauropods, the largest of dinosaurs, and the prosauropods (which predated the sauropods). Most were four-legged, and all ate plants; although some of the earlier prosauropods could also walk on two legs and may have eaten meat as well. They all had small heads, long necks, and long tails. They lived from the Middle Triassic through the Cretaceous Periods.

Scelidosauridae (Scelidosaurid)
Translation: Ribbed Lizards
Scelidosauridae (skel-ih-do-SAWR-ih-day) is a family of thyreophoran ornithischians. Scelidosaurids were once considered to be ancestors of the stegosaurs and ankylosaurs. They grew to 12 feet (3.7 meters) and lived in England during the Early Jurassic Period. Scelidosaurus

Segisauridae (Segisaurids)
Translation: Segi Canyon Lizards
The Segisauridae (see-gih-SAW-ri-day) is a family of small ceratosaurian theropods characterized by relatively long necks and slim bodies. Procompsognathus has been recently moved to this family.

Segnosauria (Segnosaurs)
Translation: Slow Lizards
Segnosauria (seg-noh-SAW-rih-uh) has been recently classified as an infraorder of Theropoda, although this may change as more is learned about this branch. These Late Cretaceous dinosaurs, recently found in Mongolia, represent a unique line of evolution, appearing to split between Saurischia and Ornithischia. They were meat-eaters, although there is some evidence that they may also have eaten plants.

Segnosauridae (Segnosaurids)
Translation: Slow Lizards
Segnosauridae (seg-noh-SAWR-ih-day) is a new family of Late Cretaceous dinosaurs recently found in Mongolia. These dinosaurs represent a unique line of evolution, one between Saurischia and Ornithischia. They may have been meat-eaters, although there is some evidence that they also ate plants. Segnosaurids are currently classified as an infraorder of Theropoda. {bml see_bios.bmp} Segnosaurus and Erlikosaurus

Sensory Perception
The structure of dinosaur bones suggests that most dinosaurs had keen senses. For example, the eye sockets of Saurornithoides and Dromaeosaurus were large and spaced far apart, which would indicate that they were probably able to judge distances with great accuracy. The bones of hadrosaurs indicate good hearing; and the large nasal cavities of lambeosaurine hadrosaurs indicate a keen sense of smell.

Dinosaurs varied greatly in size, some taller than a building of several stories and others the size of a chicken. There is no generally accepted explanation for their great size. They had large pituitary (growth) glands, but that fact leaves unanswered the question of how these glands themselves became large. The greater solar radiation present during the age of dinosaurs may have in some way contributed to growth, and large size may have been a good genetic survival strategy in that large animals cool more slowly than smaller ones. But these two explanations do not account for the simultaneous presence of the smaller animals. The largest known dinosaur is a recently-discovered sauropod called Argentinasaurus, probably 160 feet (49 meters) long, 70 feet (21 meters) tall, and weighing 120,000 lbs (54,432 kg). The smallest known adult dinosaurs are among the coelurosaurs. Compsognathus and Saltopus were about the size of chickens.

Fossilized impressions of dinosaur skin, or skin casts, indicate that most of them had tough, leathery skin. However, a few advanced dinosaurs, such as Saurornithoides, may have had fur or feathers. The leathery skin was of different textures. Hadrosaurus skin was similar to the pebbled surface of a football; Edmontosaurus skin was similar to that of a modern Gila Monster; and Corythosaurus skin was composed of polygonal bumps, with oval bumps on the belly and pelvic area. Sauropods had coarse, granular scales like some lizards of today, while Ankylosaurs and others had heavy bony plates embedded in their skin. Hadrosaurus, Anatosaurus, Corythosaurus, and Ankylosaurus.

Although some dinosaurs were slow, like the larger sauropods, which moved probably no faster than 4 miles per hour (6.5 km/h), many were swift indeed. Acrocanthosaurus may have been able run at up to 25 mph (40 km/h). The ornithomimids might have reached speeds of 40 mph (64 km/h). Dromiceiomimus may have been the fastest dinosaur. Scientists estimate the speed of dinosaurs from the length of their strides, as revealed in trackways, and by anatomical comparisons with animals whose speed is known. Acrocanthosaurus

Several prehistoric animals had long spines along their backbones, and scientists assume that they supported a skin fold or fin. These fins may have been used to regulate temperature; the large skin surface they would have provided could have collected heat from direct sunlight or could have dissipated excess heat (if the dinosaur were standing in the shade). Scientists do not think that the fins were raised or lowered; they were virtually immovable. Three dinosaurs we know of had fins on their backs: Ouranosaurus, Altispinax, and Spinosaurus. Of the three, Spinosaurus had the largest spines, at 6 feet (1.8 meters) long. Dimetrodon, which is popularly assumed to be a fin-backed dinosaur, is not a dinosaur at all, but a pelycosaur that was extinct before the dawn of the Mesozoic Era (the Age of Dinosaurs). This fact has not stopped its inclusion in sets of dinosaur models intended for children, a heedless error that is at least partly responsible for its false status as a dinosaur. Spinosaurus, Ouranosaurus, and Altispinax.

Spinosauridae (Spinosaurids)
Translation: Spiny Lizards
Spinosauridae (spy-nuh-SAWR-ih-day) is a family of carnosaurs characterized by long spines along the backbone. The only positively known member of this group is Spinosaurus, which was equipped with a spiny fin about 6 feet (1.8 meters) high, and which lived in North Africa. Some scientists include Altispinax in this group. Spinosaurus

Staurikosauridae (Staurikosaurids)
Translation: (Southern) Cross Lizards
Staurikosauridae (sto-rik-uh-SAWR-ih-day) comprise the most primitive family of theropods. Staurikosaurids were a family of ceratosaurian theropods that lived during Middle Triassic Period. Staurikosaurus

Stegosauria (Stegosaurs)
Translation: Plated Lizards
Stegosauria (steg-oh-SAWR-ee-uh) is an infraorder of the Thyreophora branch of ornithischian dinosaurs which bore rows of plates along their backs and spikes on their tails. No one knows exactly what the plates and spikes were for. They could have attracted mates; they could have protected them from carnosaurs; or, since they had many blood vessels running through them, they could have been temperature control devices. Members of this suborder are famous for having a tiny brain in their heads and what seems to be a yet-smaller brain in their tails. Stegosaurus, Dacentrurus, Dravidosaurus, Kentrosaurus, and Lexovisaurus.

Stegosauridae (Stegosaurids)
Translation: Roof Lizards
The Stegosauridae (steg-uh-SAW-rih-day) family was composed of medium-to large-size forms of Stegosauria, having only three toes on the feet. Their armor plates were configured in rows paired in two's, or in an alternating arrangement.

Synapsida (Synapsid)
Translation: Fused Arch
Synapsida (sih-NAPS-ih-dah) is a class of animals with only one opening low on each side of their skull behind the eye sockets. The mammal-like reptiles of the late Paleozoic and early Mesozoic Eras were synapsids, as are present-day mammals. Dimetrodon was a synapsid. Reptiles are diapsids.

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