Dinosaurs Stegosaurous.
The evidence and a general consensus argue in favour of the traditional idea that the plates projected upward and were set in two parallel rows in a staggered, or alternating, arrangement rather than side by side. Others, however, suggest that they did not project above the back at all, but lay flat to form flank armour. A few others maintain that the plates were set in a single midline row along the length of the back, beginning with small ones just behind the head, increasing in size to the hips, and then diminishing along the tail. The end of the tail bore at least two pairs of long bony spikes, indicating some sort of defensive role for the tail but not necessarily for the back plates.
The discovery in 1976 that the bony plates of Stegosaurus were highly vascularized, fed by large, hose-size blood vessels, led to the notion that these fins were large ³radiators,² or cooling vanes, to dissipate excess body heat in much the same manner as does the large surface area of an elephant's ears. The staggered arrangement in parallel rows might have maximized the area of cooling surface by minimizing any leeward breeze ³shadow² that would have resulted from a paired configuration. Asymmetry is a bizarre anatomic condition, and‹right or wrong‹this certainly is an imaginative explanation of its presence in this animal. No other stegosaur, however, had such a peculiar feature. Rather, all other taxa had a variety of paired body spikes that seem best explained as passive defense or display adaptations rather than cooling mechanisms.
Another variety of Dinosaur may be mentioned here, although its correct systematic assignment is still under review, and it is known from very few specimens. The animal has been named Scutellosaurus after one of its most distinctive features, an armour of small bony scutes. The specimens were recovered from very late Triassic or the earliest Jurassic strata of the American Southwest. In general body form, limb proportions, and tooth form, Scutellosaurus resembled the early ornithopods and was at least preferentially bipedal. Its body armour, however, was unlike anything known in other ornithopods. An array of small to moderate-size, separated bony scutes, set in multiple rows, covered the back and flanks. These attachments apparently corresponded in location with the ribs and with the vertebrae along the entire length of the backbone.
Ornithischia
Thyreophora
Ankylosauria The ankylosaurs lived during the Cretaceous Period and, like the stegosaurs, were a relatively brief dinosaurian experiment. They are called armoured Dinosaur after their most distinctive feature, an extensive mosaic of small and large interlocking bony plates that completely encased the back and flanks. Most varieties, like Euoplocephalus , Nodosaurus , and Palaeoscincus were relatively low and broad in body form and built close to the ground, with short, stocky legs and a quadrupedal stance. Again, the hind legs were longer than the front legs but not so extremely disproportionate as those of Stegosaurus. Like the stegosaurs, however, their limbs were stout and columnar, the thighbone and upper arm were longer than the shin and forearm, and the metapodials were stubby. These features point to a slow, graviportal mode of locomotion. The feet were semiplantigrade and possibly supported from beneath by pads of cartilage. The terminal phalanges of both fore and hind feet were broad and hooflike elements rather than claws.
The ankylosaur skull was a low, broad, boxlike affair with dermal scutes, or osteoderms, that often fused with the underlying skull bones. In one form, Euoplocephalus, even the eyelid seems to have developed a protective bony covering. The jaws were weak, with a very small predentary and no significant coronoid process for jaw muscle attachment. The small jaw muscle chamber was largely covered over by dermal bones rather than fenestrated. The teeth were small, loosely spaced leaf-shaped structures reminiscent of the earliest primitive ornithischian teeth. All taxa had very few teeth in either jaw, a marked contrast to the highly specialized, numerous teeth of other ornithischians. These features of the jaws and teeth lead to the impression that the animals must have fed on some sort of soft, pulpy plant food.
Not a particularly diverse or abundant group, the ankylosaurs are known only from North America, Europe, and
Asia. They are divided into two families, the primitive Nodosauridae and the advanced Ankylosauridae. The most
conspicuous difference between the two families is the presence of a massive bony club at the end of the tail in
the advanced ankylosaurs; no such tail structure is present in the nodosaurs.
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Original Source - http://www.crystalinks.com/
Alternative Theory On Dinosaurs
Paleontology
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