Dinosaurs: General name for two extinct orders of reptiles from the Mesozoic era: Saurischia and Ornithischia.Fossils: Remains, impressions, or traces of animals or plants of past geological times which have been preserved in the earth's crust.Paleontology: The study of early forms of life through fossil remains.Alligators and Crocodiles: Large, long-tailed reptiles, including caimans, of the order Loricata.Reptiles: Cold-blooded, air-breathing VERTEBRATES belonging to the class Reptilia, usually covered with external scales or bony plates.Skeleton: The rigid framework of connected bones that gives form to the body, protects and supports its soft organs and tissues, and provides attachments for MUSCLES.Anatomy, Comparative: The comparative study of animal structure with regard to homologous organs or parts. (Stedman, 25th ed)Extinction, Biological: The ceasing of existence of a species or taxonomic groups of organisms.Biological Evolution: The process of cumulative change over successive generations through which organisms acquire their distinguishing morphological and physiological characteristics.Geological Processes: Events and activities of the Earth and its structures.Skull: The SKELETON of the HEAD including the FACIAL BONES and the bones enclosing the BRAIN.Body Size: The physical measurements of a body.Birds: Warm-blooded VERTEBRATES possessing FEATHERS and belonging to the class Aves.Struthioniformes: An order of flightless birds comprising the ostriches, which naturally inhabit open, low rainfall areas of Africa.Carnivory: The consumption of animal flesh.MontanaEgg Shell: A hard or leathery calciferous exterior covering of an egg.Feathers: Flat keratinous structures found on the skin surface of birds. Feathers are made partly of a hollow shaft fringed with barbs. They constitute the plumage.Tooth: One of a set of bone-like structures in the mouth used for biting and chewing.Geological Phenomena: The inanimate matter of Earth, the structures and properties of this matter, and the processes that affect it.Geology: The science of the earth and other celestial bodies and their history as recorded in the rocks. It includes the study of geologic processes of an area such as rock formations, weathering and erosion, and sedimentation. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 6th ed)Phylogeny: The relationships of groups of organisms as reflected by their genetic makeup.Bone and Bones: A specialized CONNECTIVE TISSUE that is the main constituent of the SKELETON. The principle cellular component of bone is comprised of OSTEOBLASTS; OSTEOCYTES; and OSTEOCLASTS, while FIBRILLAR COLLAGENS and hydroxyapatite crystals form the BONE MATRIX.Paleodontology: The study of the teeth of early forms of life through fossil remains.Humerus: Bone in humans and primates extending from the SHOULDER JOINT to the ELBOW JOINT.Horns