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Translation: Outside Heat
An ectotherm (EK-toe-therm) is a cold-blooded animal whose body heat comes from exposure to the sun or some other source of heat in its environment. Ectotherms regulate their body temperature by moving in and out of shaded areas. Today's snakes and alligators, as well as lizards, are ectotherms. See Endotherm and Homoiotherm.

The condition of a cold-blooded animal raising or lowering its internal temperature by exposure to the Sun or another heat source. See Ectotherm.

Most, if not all, dinosaurs laid eggs, and many fossilized eggs, egg shells, and even embryos have been found in dinosaur nests. Some complete eggs have been found, but most are in bits and pieces. The largest egg found to date is 10 inches (25 cm long). Eggs were generally laid in sandy nests. Some nests have been found to contain only one egg, while others contained more eggs than was possible for a dinosaur to lay, suggesting that perhaps more than one dinosaur shared the same nest or that the nest was used year after year. The first dinosaur eggs to be found were of Protoceratops, but some of the most important eggs found were of Maiasaura, since the nests in which they were found revealed clues to nurturing behavior in dinosaurs. It is possible, however, that some dinosaurs gave live birth to their offspring.

Elmisauridae (Elmisaurids)
Translation: Foot Lizards
Elmisauridae (el-mi-SAW-ri-day) is a rare subfamily of the Maniraptora theropods. This subfamily had small, lightly-built bodies bearing slim hands and large feet.

Translation: Inner Heat
An Endotherm (EN-doe-therm) is a warm-blooded animal. Its internal temperature does not change with the temperature of its environment; it maintains a constant internal temperature. An endotherm regulates its temperature by perspiring, panting, and shivering. It is speculated that at least some dinosaurs may have been endothermic. Some may have been covered with feathers or even fur, although except in the case of Archaeopteryx, there is no proof of feathers, much less fur. Why do we believe that dinosaurs were warm-blooded? Walking upright is one indication. Also being bipedal indicates speed, high activity and agility. Birds are warm-blooded, and there is evidence that birds are descended from the dinosaurs. For more information, see "Warm-Blooded vs. Cold-Blooded" in Theories and Controversies. See Ectotherm

The condition of being warm-blooded or producing heat internally. See Endotherm.

Eosuchians (Eosuchia)
Translation: Early Crocodiles
Eosuchians (ee-o-SOOK-ee-anz) an order of diapsid reptiles that looked like crocodiles and could be the ancestors of snakes and lizards. These carnivores preyed on insects and smaller dinosaurs. They could grow up to 8 feet (2.4 meters) long.

Euhelopodidae (Euhelopodids)
Translation: Good Marsh Foot
The Euhelopodidae (you-HEL-oh-POE-dih-day) is a newly established family of sauropods possessing unique features, such as a greater number of vertebrae in front of the pelvis than any other dinosaur; and a more delicate sauropod skull. Euhelopodids were similar to the Camarasaurinae, having short skulls and front legs as long as their hind legs. Members of this group of quadrupedal herbivores lived during the Late Jurassic Period, and have been found in China.

Evolve means to change slowly. Change is marked in gradual stages and takes many centuries. Generally, species evolve to meet the conditions of its environment. When a species ceases to evolve or cannot meet the challenge of its environment, it becomes extinct.

The extinction of dinosaurs 66 million years ago has been the subject of discussion since their fossils were first discovered. Dinosaurs were the dominant species for over a hundred million years, yet suddenly (in geologic terms) they disappeared. For more information, see "Extinction of the Dinosaurs" under Theories and Controversies.

Eustreptospondylidae (Eustreptospondylids)
Translation: Well-Curved Vertabrae Lizards
The Eustreptospondylidae (you-STREP-tuh-spon-DIH-lee-day) is a carnosaur family, characterized by long heads and short snouts. Currently, Eustreptospondylus is the only member of this family, although Piatnitzkysaurus has been proposed to be a relative. Debate continues on whether Eustreptospondylidae is actually a genus of Megalosauridae.

Species generally develop the equipment they need to be successful. Good eyesight is not always necessary, as is demonstrated by the rather limited vision of the modern rhinoceros, which is near-sighted. Often, good hearing substitutes for good eyesight. Dinosaurs probably had eyesight as modern species have eyesight; that is, some species probably had good eyesight, while others depended on other senses. Herbivores such as the ornithopods probably had good eyesight. Lacking defenses other than speed, their eyesight would have allowed them to see trouble approaching early enough to sound the alarm and escape. As predators, theropods probably had excellent hunting eyes, quick to detect movement at great distances. Dinosaurs may have had seen in color. There are several arguments supporting this idea: dinosaurs appear to have been most active in the daytime, and daytime animals are generally color-sighted; surviving reptiles that are related to dinosaurs, such as crocodiles and alligators, are color-sighted; and the only descendents of dinosaurs, birds, are color-sighted.

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