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What is a Sauropod?
Sauropods were plant-eating dinosaurs which lived from 200 to 65 million years ago, from the late Triassic period to the end of the Cretaceous period. This group of dinosaurs includes the largest land animals ever to inhabit the earth. Sauropods had massive legs built for walking. Fossilized trackways indicate that these animals traveled in herds. That sauropod fossils have been found on every continent suggests they were able to adapt to diverse environments.
Prosauropods roamed the earth from 210 to 190 million years ago, during the late Triassic and early Jurassic periods. The fossil record indicates that members of this group were the first dinosaurs to rely on plants for food. As their numbers declined, prosauropods were replaced by larger plant-eating sauropods.
There are two kinds of dinosaur hips. Paleontologists use the difference to divide dinosaurs into two large groups. In one group, the two bones called the pubis and the ischium are positioned as seen in the sauropod pelvis in the movie. Called Saurischia, this group includes plant-eating sauropods, as well as all meat-eating dinosaurs. The name Saurischia is from the Greek words meaning "lizard-hip". This phrase was chosen because this hip structure resembles that of present-day reptiles, though these two groups are not closely related. The other group of dinosaurs is called Ornithischia.
Pterosaurs were flying reptilian cousins of the dinosaurs. Many of the pterosaurs' skeletal modifications paralleled those of birds. There was fusion of skull bones, a reduced number of vertebrae, hollow bones, a strong and large sternum. Later forms were toothless. The pterodactyl group, with very long skulls and short tails, range from sparrow size in the Jurassic (144 to 213 million years ago) to toothless giants with 27 foot wingspread in the Cretaceous (65 to 144 million years ago).
Therapsids were mammal-like reptiles derived from Pelycosaurs in Permian Time (248 to 286 million years ago). Some were herbivorous (plant-eaters) and some were carnivorous (meat-eaters). The herbivorous therapsida, or anomodontia, were variable in size, form, and dentition (teeth). Important in their time, they represented an evolutionary blind alley.
The carnivorous therapsids gave origin to the mammals in the Triassic Time (213 to 248 million years ago). The carnivorous therapsida, or theriodontia, developed mammalian characteristics. The complete transition to mammals depended upon methods of reproduction, the ability to nurse the young, development of hair and warm-bloodedness, and other features of which skeletal remains give no evidence. The last of the therapsids died out in the Jurassic (144 to 213 million years ago).