Dinosaurs - Origin and Facts

The Giants Who Roamed the Earth: Origin and Facts About Dinosaurs

The origin of dinosaurs has many interesting facts and myths attached to it. The term 'dinosaur' evolved from a scientific term, 'Dinosauria', which referred to a varied group of animals with widely different modes of living.
Dinosaurs lived on the Earth for about 165 million years during the Mesozoic Era―the age of reptiles―and mysteriously went extinct 65 million years ago, leaving back their gigantic bones as the evidence of their existence. People studying dinosaurs believe that they live even today as birds; a conclusion which is based on the study of feathers on their skeletons. Dinosaurs comprised a specific subgroup of the archosaurs―a group that includes crocodiles and birds. The dinosaurs of the Mesozoic Era left behind many clues about what they looked like and how they lived. Their fossils give us clues about their lifestyle. Some of the dinosaurs had thick, bumpy skin, and some even had primitive feathers.
It was a highly diverse group of reptiles. Most of the dinosaurs hatched from eggs. Most of them could neither fly, nor live in water. They were fast and energetic though. The largest dinosaur was 100-feet long, while the smallest was the size of a chicken. Even after extensive research and observations, researchers say that it is very difficult to figure out their behavior, mating, and color. It is difficult to determine whether a dinosaur is a male or female from its fossil. Dinosaur fossils had been known for centuries as 'dragon bones' or 'the remains of giants'. Different types of dinosaurs lived at different times. Some walked on two legs (bipedal), while some on four legs (quadrupedal).
Their diet can be determined from their tooth structure (dentition) and the contents of their stomach. Well-preserved dinosaur skeletons have traces of apparent food items preserved in their abdominal cavity at times. Their stomachs had well-rounded stones called gastroliths, which were probably used to grind food in a muscular crop or gizzard like some birds and crocodilians do. Most of them were plant eaters (herbivores), while some were meat eaters (carnivores).
Based on the sequence of their footprints (trackway), the fact that crocodiles are dinosaurs' closest living relatives, and birds are their living descendants, the following conclusions can be drawn ...
1) Parental care was involved in their lifestyle.
2) They are extensive nest builders.
3) Some non-avian dinosaurs traveled in large groups.
4) Non-avian dinosaurs moved with their feet held underneath their body, like birds and mammals do.
5) Some non-avian dinosaurs moved rather quickly, but some plodded along at a leisure pace.
6) Some say that dinosaurs were complete endotherms just like birds, while others say that they had an intermediate type of physiology between endothermy and ecothermy. However, it is believed that they were mostly inertial homeotherms; they were ectothermic, but maintained a constant body temperature by growing large.
7) From the preserved footprints, it is possible to determine how fast that particular creature was traveling at that moment. This method uses simple equations based on the distance between footfalls and the size of the feet. The fastest speed evident from dinosaur tracks―a medium-sized theropod in this case―is of 12 meters per second (27 mph).
Dinosaurs are vertebrates and stood erect, like birds and most mammals; they did not keep their legs sprawling out to the side of their body like most lizards and salamanders do. Also, from the trackways of dinosaurs, we know that they rarely dragged their tail on the ground. So, mammals and birds are probably better models for understanding dinosaur locomotion than lizards are. However, it's safe to assume that all are useful to some degree and all are limited in their usefulness.
Although dinosaur remains had been found earlier elsewhere, it was their discovery in North America in the second half of 1800s that provided the first real glimpses of what these animals were like. It gave paleontologists some clues about the diversity of life on the Earth in the past. The late 1800s were the 'golden age' of dinosaur paleontology, when many animals that you might be familiar with were discovered and named. Today we seem to be in another 'dinosaur renaissance'.
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