Some dinosaurs had primitive feathers while others had thick bumpy skin. (Weishampel et al. , 2004 pp 376-398) Since dinosaurs were reptiles, they were hatched from eggs. However the dinosaurs could neither fly nor live in water. The species is one of the worlds known large and energetic animal. The dinosaurs were tall and long some measuring about 100 feet long although there were small dinosaurs as small as the size of a chicken. Most of the dinosaurs were medium sized. History of origin Dinosaurs emerge in the Triassic. In the Permian period, several vertebrates had developed among the mammalian group and some lizard like reptiles.
During this period, the climate became extremely hot and dry which led to desertification of vast parts of the earth. Several species were extinct and only a few survived at the beginning of Triassic. The survivors included diapside reptiles which sought shelter under rocks and looked for food at dawn and during sunset when the temperatures were favorable. When the temperatures became endurable, the modern snakes and lizards evolved from those reptiles. In early Triassic when the climate became more endurable, and plants began to spread, another group of the reptiles evolved into plant-eating rhynchosaurs.
Several species of the rynchosaurs emerged with characteristic tall clumsy bodies. The different rynausers later evolved into dinosaurs. There were different types of dinosaurs which lived at different times. Some dinosaurs walked on two hind limbs called bipedal while others moved on four limbs called quardrupedal. Dinosaurs food can be determined by the structure of their teeth. From the fossils found, dinosaurs fed on crops such as trees. Classification of Dinosaurs Dinosaurs are a clade of archosaurs and lies within the phylum Chordata. There are several classifications of dinosaurs but the most commonly used is Benton classification.
According to Benton, all dinosaurs fall under the series Amniota, Class Sauropsida, a sub class Diapsida , Division Archosauria. Benton divided dinosaurs into two major orders Saurinchia and Orinthischia. The classification of dinosaurs is complex and wide. (Benton, 2004 pp 223-345) Extinction of dinosaurs Dinosaurs originated some 165 years ago and they became extinct about 65 million years ago. The extinction of dinosaurs is a mystery. Some scientists argue that dinosaurs became extinct naturally through the natural process of death from hunger.
Since they were fed on tall trees and due to their tall and fast bodies, they cleared forests and led to desertification. They could not thrive well in a warm and dry place so they died. However this theory is highly criticized because extinction is as a result of lesser birth not death. The plants could also stand their green leaves bitten off and developed new foliage faster and grew on. According to Weishampel et al. 2004, this led to development large areas of forests thus reducing space for dinosaurs. This led to imbalance of the ecosystem with the number of plant eaters decreasing significantly.
The entire ecosystem collapsed by the end of Cretaceous. Discovery of fossils The first dinosaur fossils remains of the modern times were discovered in 1819 in England by a British fossil finder William Buckland. However the earlier discoveries on Dinosaur fossils were made by Reverend Plot in 1676 and he found a huge femur bone which was thought to belong to a giant. The first complete dinosaur fossil remains were found by William Parker Foulke in New Jersey, USA. Since the discovery of Bucklands fossil of dinosaurs in 1819, there have been over 330 various dinosaur genera discovered mostly in the USA.
The origin of dinosaurs got into the geological records as early as 1824 when the fossils were named and identified to be dinosaurs after Bucklands discovery of 1876. Fossils of dinosaur in the US were found in the following places: Alaska, Alberta Canada, Alabama, California, Florida, Georgia, El Salvador, Kansas, Illinois, Indiana, Maine, Louisiana, Missouri, Minnesota, Mississippi, Montana Nevada, Nebraska, New Jersey, New York, North Carolina, North Dakota, Nova Scotia, Ohio, Oklahoma, Pennsylvania, Oregon among other states.
Dinosaur fossils were also found in Africa, Europe Asia as well as in Australia. (James, 1999 pp 176-211) Dinosaurs fossils were thought to be of millions of years. The age was mainly based on thee geologic column which dates fossils depending on the rocks they are found in and also dates rocks by the fossils contained in them. Identifying features of dinosaurs Dinosaurs are complicated to classify and they exhibit various differing features. Just like their origin is complicated, the identifying features differ through their evolution.
Dinosaurs are vertebrates, just like birds and mammals, they stood erect and they did not keep their legs sprawling out to the side of their body as most reptiles such as lizards and salamanders do. From the track ways of dinosaurs, it is clear that they rarely dragged their tail on the ground like other reptiles. Therefore birds and mammals are probably good models for understanding dinosaurs locomotion. Dinosaurs had a unique lifestyle of higher mammals. They provided parental care to their young ones. They also built their nest which makes them to be associated with birds.
Some small sized dinosaurs could fly. The non avian dinosaurs could move faster while some walked at a more leisurely pace. The dinosaurs were said to be endothermic just as birds whiles others argue that they had an intermediate physiology between ecothermy and endothermy. Lizards are also important in identifying features of a dinosaur. It is believed however that dinosaurs were inertial hymotherms. (Benton, 2004 pp 246-402) The creatures were ectothermic in nature and maintained they body temperatures by growing larger and larger. From the preserved foot prints the speed of the dinosaurs could be determined.
They were very fast moving animals. The fastest speed that is evident to dinosaurs is approximately twelve meters per second. This is about twenty seven miles per hour. Environment inhabited by dinosaurs According to the history of origin, dinosaurs lived in most parts of the earth as long as the conditions were favorable. From their development, they must have thrived well in areas with plenty of food, i. e. plants and in favorable climatic conditions. Dinosaurs were favored by cool and wet climate which in turn supported the growth of vegetation. Dinosaurs fossils in rock dating
Fossils of dinosaurs are used in dating rocks. This is usually done on sedimentary rocks which are formed from layers called strata which are formed from sediments mixed with animal remains. Dinosaur fossils in America were widely used to date rocks and the rocks on the other hand are also used to date the fossils age. Dinosaurs fossils are found in sedimentary rocks almost in every region in the world. However the dating of rocks using fossils and fossils dating rocks has been disputed commonly known as circular reasoning. Geologic column assumes uniformity.
Uniformity has been disapproved due to possibility of misplaced fossils, poly strata fossils, missing layers. For example some ancient layers may be found on top of the young rock layers. (James, 1999 pp 176-211) In some occasions human fossil has been discovered together with the fossils of dinosaurs which suggest that man was hunting dinosaurs to extinction. The widespread fossils of dinosaurs are important in rock dating. Considering that they are virtually in every part of the United States, it becomes easier in determining the age of the sedimentary rocks as well as the use of these rocks to compare the ages of the fossils.