Saurischian dinosaurs

Saurischians include two major groups. Sauropodomorpha are mainly large-bodied creatures with pillar-like legs, extraordinarily long tails, long necks ending in small heads, and jaws lined with simple, peg-shaped teeth, indicating a mainly herbivorous diet. These include such giants as members of the diplodocoid, brachiosauroid (Figure 31), and titanosaurian groups. Theropoda are markedly different to their sauropodomorph relatives. They are almost entirely agile, bipedal, and predominantly meat-eating dinosaurs (Figures 30, 31). A long, muscular tail counterbalances the front of the body at the hip, leaving the arms and hands free to be used to grab their prey; their heads also tend to be rather large, and their jaws lined with sharp, knife-like teeth. These types of dinosaur range from small and rather delicate creatures similar to Compsognathus, which are commonly referred to as coelurosaurs, through to such enormous creatures such as the legendary Tyrannosaurus, while other equally large and fearsome-looking theropods include Giganotosaurus, Allosaurus, Baryonyx, and Spinosaurus. Although some of these dinosaurs may be well known, M the group as a whole is proving to be extraordinarily diverse, and in | some cases quite bizarre. Newly discovered therizinosaurs, for £ example, appear to have been huge, lumbering creatures with long, scythe-like claws on their hands, enormous bellies, and ridiculously small heads whose jaws were lined with teeth that are far more reminiscent of plant-eaters than conventional meat-eaters. Yet other theropods known as ornithomimians and oviraptorians were lightly built, rather ostrich-like creatures that were entirely toothless (and therefore beaked just like living birds). However, the source of greatest interest among this entire group of dinosaurs is the subgroup known as dromaeosaurians.

Dromaeosaurians include such renowned creatures as Velociraptor and Deinonychus, and a host of similar but less famous creatures that have been discovered recently. Their particular interest lies in the fact that their skeletal anatomy is closely similar to that of living birds; indeed, the similarities are so great that they are thought to be direct bird ancestors. Dramatic new discoveries, at sites in Liaoning Province, China, that exhibit truly exceptional preservational conditions, of dromaeosaurian theropods reveal a

body covering made of either keratinous filaments (like a coarse form of hair) or in some cases genuinely bird-like feathers, which emphasizes their similarity to modern birds.

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