Dinosaurs :: essays research papers

DinosaursDinosaur is the name of large extinct reptiles of the Mesozoic Era,during which they were the dominant land animals on Earth. The term wasproposed as a formal zoologic name in 1842 by the British anatomist Sir RichardOwen, in reference to large fossil mug up unearthed in southern England. Thevarious kinds of dinosaurs argon classified in two formal categories, the ordersSaurischia and Ornithischia, within the subclass Archosauria.The first recorded dinosaur remains found consisted of a few teeth andbones. They were discovered in 1882 in Sussex, England, by an English doctor,Gideon Mantell, who named them iguanodon. About the same time, other fossilteeth and bones were found near Oxford, England, by Rev. William Buckland.These were named Megalosaurus. Thousands of specimens look at since beendiscovered nearly worldwide. diverse types of dinosaurs varied greatly in form and size, and theywere adapted for diverse habitats. Their means of survival can only beidentified from their fossil remains, and some identifications are in dispute.They ranged in weight from 4 to 6 lb., in the case of the compsognathus, and upto 160,000 lb., in the case of the brachiosaurus. Most dinosaurs were large,weighing more than 1,100 lb., and few weighed slight than 100 lb. Most wereherbivores, entirely some saurischians were carnivorous. The majority were four-footed but some ornithischians and all carnivores walked on their hind legs.Always classified as reptiles, dinosaurs have traditionally been assumedto have been reptilian in their physiology, cold-blooded, and ectothermic. Inrecent years several different lines of evidence have been interpreted asindicating that dinosaurs whitethorn have had warm blood and high rates of metabolism,comparable to birds and mammals. Evidence supporting this view includes uprightposture and carriage mammallike microscopical structure of bones skeletalfeatures suggestive of high activity and specialized food-processing dentitionsand low ratios of dinosaurian predators to prey animals, both suggesting highfood requirements. The evidence is not conclusive--all the facts can bealternatively explained--but some dinosaurs may have been endothermic.The reproductive means of most dinosaurs is as yet unknown. Fossil eggs,attributed to one of the horned dinosaurs and a sauropod, have been discoveredin Mongolia and France. Fragments that are presumed to be of dinosaur eggs havealso been found in Brazil, Portugal, Tanzania, and in the United States,Colorado, Montana, and Utah. In Montana, Utah, and Alberta, Canada, fossils ofunhatched dinosaur eggs have been discovered. This evidence indicates egg- lay reproduction in dinosaurs, like most modern reptiles. A few scientistsbelieve that some dinosaurs may have given birth to living young, but no