Dinosaurs Historic Site.
Another major historic site was the Lance Creek area of northeastern Wyoming. There J.B. Hatcher discovered and collected dozens of horned Dinosaur remains for Marsh and Yale College, among them the first specimens of Triceratops and Torosaurus. Marsh was aided in his work at these and other localities by the skills and efforts of many other collaborators like Hatcher‹William Reed, Benjamin Mudge, Arthur Lakes, William Phelps, and Samuel Wendell Williston, to name a few. Marsh's specimens now form the core of the Mesozoic collections at the National Museum of Natural History of the Smithsonian Institution and the Peabody Museum of Natural History at Yale University.
Cope's Dinosaur explorations ranged as far as, or farther than, Marsh's, and his interests encompassed a wider variety of fossils. Due to a number of circumstances, however, Cope's Dinosaur discoveries were fewer and his collections far less complete than those of Marsh. Perhaps his most notable achievement was finding and proposing the names for Coelophysis and Monoclonius . Cope's Dinosaur explorations began in the eastern badlands of Montana, where he discovered Monoclonius in the Judith River Formation of the Cretaceous period. Accompanying him there was a talented young assistant, Charles H. Sternberg. Later Sternberg, with his three sons, went on to recover countless Dinosaur skeletons from the Late Cretaceous Oldman and Edmonton formations along the Red Deer River of Alberta, Canada.
Dinosaur ancestors During the early decades of Dinosaur discoveries, little thought was given to their evolutionary ancestry. Not only were few specimens known, and those specimens so unlike any living animal, but the concept of evolution itself was still a radical idea. With the growing acceptance of Charles Darwin's theory on the mutability of species during the last half of the 19th century, the question of dinosaurian origins acquired respectability and serious thought.
Early on, it was recognized that, as a group, Dinosaur appear to be most closely allied with crocodilians. Two anatomic features‹socketed teeth and a doubly fenestrated (diapsid) skull‹are present in both. The earliest crocodilians occurred nearly simultaneously with the first known dinosaurs, so neither could have given rise to the other. The most likely ancestry of Dinosaur lies within a poorly understood group of Triassic reptiles termed pseudosuchian ("false crocodile") thecodonts ("socket-toothed reptiles").
An early candidate for ancestor of the Dinosaur was an advanced thecodont of South Africa, Euparkeria , of the Early Triassic epoch. Euparkeria was a diapsid with socketed teeth, a preorbital fenestra (opening), and semierect hind limbs‹conditions all equivalent to, or approaching, those of dinosaurs. New discoveries suggest an even more dinosaur-like creature in the Middle Triassic small South American form Lagosuchus.
The earliest appearance of "true dinosaurs" is almost impossible to pinpoint. First, it can never be known with certainty that the very first (or last) specimen of any kind of organism has been found. The stratigraphic succession is discontinuous and contains many gaps in the geologic record. Similarly, the fossil record of Dinosaur and other creatures contained in the rock strata is far from complete.
Second, evolution from ancestral to descendant form is usually a gradational process; consequently, in the transformation from a theoretical thecodont ancestor to a recognizable dinosaur, it is extremely difficult to determine at exactly what point every diagnostic feature of the dinosaurian condition first appeared. A true Dinosaur possessed all of the following anatomic features: a diapsid skull, a preorbital fenestra, a mandibular fossa, a perforated hip socket, an offset femoral head, a fourth trochanter of the femur, a mesotarsal ankle joint, digitigrade feet, and at least four sacral vertebrae. The first such animal is still being sought.
Pre-Triassic and Early Triassic reptiles that had acquired some of these features, the archosaurians ("ruling lizards"), diversified along a variety of evolutionary pathways. Only a few, however‹possibly one‹passed on to the Dinosaur an improved stance and posture with a resulting improved gait, increased efficiency of food gathering and processing, apparently higher metabolic rates and cardiovascular nourishment, and, for most, an overall increase in size. All these trends, individually or in concert, probably contributed to the collective success of dinosaurs, which resulted in their dominance among the terrestrial animals of the Mesozoic.
Modern studies During the first century or more of Dinosaur awareness, workers in the field more or less concentrated on the search for new specimens and new kinds of animals. Their discoveries then required detailed description and analysis followed by comparisons with other known kinds in order to classify the new finds and develop theories about Dinosaur evolutionary relationships. All these pursuits continue, but newer methods of exploration and analysis have been adopted. Emphasis has shifted from purely descriptive procedures to quantitative analytical and multivariate statistical analysis and the application of such analysis to functional anatomic systems.
Functional anatomic studies make extensive use of living analogues that, together with both mechanical and theoretical models, make it possible to visualize certain aspects of the once living animal. For example, reconstruction of the limb musculature, combined with examination of the biomechanics of the leg and joint skeletomuscular system and analysis of trackways, can provide information about an animal's locomotion‹walking and running‹and estimates of normal walking and maximum running speeds. The same method has been applied to jaw mechanisms and tooth wear patterns for a better understanding of feeding habits and capabilities.
Original colours and patterns cannot be known, but it is possible to speculate on them with an understanding of
the ecological functions of pattern and colour in modern analogues. Are large animals mostly brightly coloured or
drab? How important is colour vision, and what kinds of organisms see colours? Dinosaur skin texture has rarely
been preserved, but there are a few examples. Most show a knobby or pebbly surface and not a scaly texture
such as might be expected in reptiles. What might that indicate about Dinosaur environments or about dinosaur
relatives? In short, modern inquiry focuses more on the biology of Dinosaur and their various modes of life than
on their immense size and strange design.
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Original Source - http://www.crystalinks.com/
Alternative Theory On Dinosaurs
Paleontology
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