Are Dinosaurs Real? A Definition and Explanation - Essay Sample

Introduction

If I may ask, how many of you have watched the movie Jurassic Park or have had the opportunity to visit the Universal Studios in Florida to ride the Jurassic park ride? If you have experienced the both or not, then let me tell you what you have missed out. When the average person thinks of the term dinosaur, a lot comes to his mind, but there are specific characteristics and categories you must fall under to be considered a dinosaur. This paper will define a dinosaur and briefly explain the classifications of dinosaurs, the different timelines when these creatures ruled the world and finally take a closer look at the dinosaurs of the Jurassic period.

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So what is a dinosaur? This might seem like an easy question but describing what makes a dinosaur is a question which has been debated for a very long time. The likely definition of a dinosaur is "a reptile of bird-like animal with an upright posture that spent most of its life on land." Why emphasize the term upright? This is because it highlights the fact that the animal walks and stands with its legs right beneath its body. This definition means that animals like a pterodactyl and Ichthyosaurus (referred as dolphins now) fall under another category and not dinosaur though some lived with dinosaur.

Dinosaurs came in different shapes and sizes, some were carnivorous, and others were herbivorous, and a few were omnivorous. The best way of distinguishing dinosaurs was by placing them in classifications based on their similarities. Dinosaurs are classified into two categories due to hip morphology, Saurichians or Ornithischians. Classification based on hip morphology focuses mainly on the arrangement of their pelvic bones. They are further divided into subgroups, clades, and other classifications. (Sereno, 1997)

Saurischian

Saurischian dinosaurs have their pelvis bones arranged in a pattern similar to that of a modern lizard and crocodile, in which the pubis pointed forward and downwards and almost straight up. Based on this Saurichians are also called the Lizard-hipped dinosaurs.Saurischians were diverse with some being meat eaters while others being vegetarians. They were as well diverse in their sizes with some weighing over 20000 pounds while others being about the chicken size. Despite these differences, Saurischians shared a couple of similarities. One of their similar traits was their partially opposable thumbs. This made them extra flexible hence helping them in grasping food for both carnivorous and herbivorous. A long neck was also a notable similarity among the Saurischians. The herbivores used the long neck in reaching the tall trees which the other dinosaurs could not. On the other hand the carnivorous used the advantage of the long neck in killing their prey through picking and shaking them with their strong neck until they exhaust their energy.

Saurischian can be classified into two main groups. The first is the Sauropods which were herbivorous and walked on all four limbs. Being herbivores they needed little thoughts for munching vegetables thus smaller brains compared to other carnivorous dinosaurs. They possessed a long tail as well as a large complex digestive system helpful in processing their food. They are among the largest animals to ever exist on the earth, for instance the Argentinosaurus which measured 130 feet long. The smallest Sauropod, Ohmdenosaurus measured 13 feet long (Bybee et al., 2006). Richard Owen, a 19th-century Biologist, identified the first known Sauropod as the giant aquatic crocodiles and named them plesiosaurs or the whale lizards.This is because they were large and they were found in aquatic sediments. The other category of Saurichians dinosaurs is Theropods. Theropods are some of the most recognizable and fearsome dinosaurs. They were carnivorous, and they walked on two legs. Debates have been run on whether these large creatures actively hunted their prey or they scavenged cadavers. The scientist has pointed that these animals worked together as opportunistic hunters during which they brought down a prey.It is also evident that they also ate lying carcasses. Fossil hunter has also found that theropods engaged in cannibalism because of the bite marks on their bones. Currently it appears that these animals did not hunt their own, but they scavenged their own (Wedel, 2009).

Ornithischians

What differentiates Ornithischains from Saurischia? The answer is that the Ornithischia have pelvis similar to birds in which their pubis pointed backward. Ornithischians are further divided into other kinds of dinosaurs dating back to the Jurassic era. Ornithopoda included the Hadrosaurs also referred as the "duck-billed dinosaurs," the heterodontosaurs, iguanodontids, and the hypsilophodontids among other dinosaurs. Ceratopsia is also classified in this category, and it includes the horned dinosaurs, the stegosaurs, the Ankylosauria, the Thyreophora (armored dinosaurs) the Pachycephalosauria and the exceedingly thick-skulled pachycephalosaurus. These are group of small and rather large armored herbivorous dinosaurs. The first armored dinosaur was Scutellosaurus. This slender-tailed beast is known to have existed in the earlier Jurassic period in western North America. It is known to have grown to about 2 meters long and possessed an armored plate in the skin of its back. The other Thyreophoran is Scelidosaurus, which existed over 180 years ago and lived in Western Europe. This dinosaur grew about a meter tall had a length of about four meters. Just like the later armored dinos, these dinosaurs had hoof-like claws, and its back had spikes. Its spikes were used as a defensive weapon in case of an attack by a predator. They also used the spikes while hunting their prey.

Dinosaur of the Jurassic Period

The Jurassic period is the geological period which occurred about 208 to 144 million years ago. During this era, the vegetation was greener and dinosaurs, rodents, birds and other reptiles ruled the land. Though we doing bear concrete evidence about the climate during this period, we do know that the forests were greener and the dinosaurs grew larger and larger. Research on the flora distribution shows how a wide array of ferns, conifers, cycads, ginkgoes, and many others existed. During this period the supercontinent Pangaea spilled apart forming the oceans and the continents. This rifting and warmer global temperatures allowed the divergence and dominance of dinosaurs. This period was dominant of the reptiles because they had overcome the evolutionary sprints which amphibians could not. Dinosaurs among other reptiles had strong skeleton and advanced muscular body which aided in locomotion. Despite existence of different strange creatures, dinosaurs were notable and foremost among those creatures. There were different classes of dinosaurs during this amazing period. (Baron et al., 2017)

Brachiosaurus

During this period one of the first things you could not miss would be various Sauropods which were the largest terrestrial dinosaurs to have ever existed. Brachiosaurus is one of these dinosaurs because of its front legs (arms) which were longer than the hind legs. It is estimated to have been about 40 feet tall and 82 feet long. They are also believed to have approximately weighed about 60 tons. Scientists in recent studies have revealed that upon total submergence in the water a large creature like Brachiosaurus could not have inhaled and inflated its lungs. This reveals the idea that these creatures might have been forest inhabitants.

Stegosaurus

This is another Jurassic Dinosaur which is well known for its huge bony plates and not its size as the Brachiosaurus. It is characterized by the huge bony plate along its entire back and the large spikes on its tail. It is estimated to have been about 30 feet long. The spikes on its tail were most likely used for self-defense against the predators or trespassers. The large plates on its back are believed to have also been used for defensive reasons. Similarly, the large plates are believed to been thermo regulators in which they had lots of blood vessels and also provided enough surface area in which the body heat escaped into cooler surroundings.

Thyreophoran (Armored Dinosaurs)

These are a group of small and rather large armored herbivorous dinosaurs. The first Armored dinosaur was Scutellosaurus. This slender-tailed beast is known to have existed in the earlier Jurassic period in western North America. It is known to have grown to about 2 meters long and possessed an armored plate in the skin of its back. The other Thyreophoran is Scelidosaurus, which existed over 180 years ago and lived in Western Europe. This dinosaur grew about a meter tall had a length of about four meters. Just like the later armored dinos, these dinosaurs had hoof-like claws and back with spikes. The spikes are believed to have been used as defensive mechanism. In the late Jurassic period, these creatures became more diverse although Dravidosaurus lived only in India before its extinction and the Stegosaurids lived in most parts of the globe. The other group of this category is the Ankylosaurus which had like the whole patches of external bones attached to plates. They were characterized by their extensive heads and spikes on the back of their skulls and a tail which was club-like. The club is believed to have been a defensive mechanism against predators.

Carnosaur

These are one of the meat-eating dinosaurs. They are distinctively characterized by their large eyes, a long narrow skull, and their long legs. These species appeared in the middle Jurassic period that is around 177million years ago. Canausaurus has been primarily used to describe a large number of theropods. However, analysis in the 1990s has shown how the group was polyphyletic because of its few distinguishing characteristics (Rauhut et al., 2005).

Paleoecology

Paleoecology is defined as the study of the factors which controlled the abundance and distribution of fossil organisms. Paleoecologists examines the life habits of a certain species, also known as autecology. Paleoecology involves the assemblage of organisms which existed at the same community ecology and same time. Paleoecology is described by the following terms namely Fauna, Paleofauna, Biogeography and paleobiogeography. Fauna is the grouping of organisms occupying a certain region. Paleofauna is the assemblage of fossil animals which occupied a particular region at a particular geological period. Biogeography involves studying of organisms' distribution by a region and the factors controlling the distribution. Paleobiogeography is the study of fossil organisms' distribution by region over time and the factors influencing the distribution (Oliver et al., 2003). Migration in Camarasaurus is a good example of Autecology. A geochemist Henry Fricke and his colleagues conducted a study based on the idea that isotopic water composition differs from a spot to spot due to the difference in evaporation, temperature, and other factors. They compared the composition of clay minerals and the teeth of Camarasaurus from different spots in the Morrison Formation.

The study showed the clay minerals with only isotopic compositions from the lowland environment since that's where the teeth were found while the Camarasaurus teeth showed an expansive range of values inclusive of upland marks. Upon looking on individual teeth, some succession of layers showed lowland values then switched to highland values. This has interpreted to the migration of species between the highlands and the lowlands. Another example of Autecology is the infection in Tyrannosaurs. A lot of Tyrannosaurus specimens show cuts in the lower jaw. First these lesions were assumed to be bite marks from other bully dinosaurs, but after a closer analysis the marks were found to be r...