The Triassic Period: The Evolution Of Dinosaurs

The Jurassic Period is a time period were new dinosaurs were being discovered and found. It was about 199.6 to 145.5 million years ago. Some of the species that were found in the Jurassic Period are the Stegosaurus, Ceratosaurus, Brachiosaurus, and Allosaurus. Each dinosaur had their own characteristics for survival.

Nobody knows for sure exactly how the dinosaurs became extinct. However scientists have speculated for decades about possible events that caused the dinosaurs to die out. Possibilities range from asteroids, to volcanoes, to climate changes. One of the more popular or well-known extinction theories involves the belief that an asteroid struck the Earth, causing devastating effects, and triggering mass extinctions around the end of the Cretaceous period.

Shifting from the end of the Permian period 250 million years ago into the next era, the Triassic period occurred between 250 and 199 million years ago and was know for further diversifying life on land. After the Permian period, the Triassic period was largely successful in adapting and evolving, as the world was going through many changes. The land mass known as Pangea began its separation, which would be completed in the Jurassic period. The climate was relatively more severe during this time, with hotter summers and colder winters, but because of the warmer atmosphere, there were no polar ice caps at this time. Towards the center of Pangea, it was mostly a dry desert climate. As for life on earth, most of the marine life had been wiped

The main dinosaurs that died off were Sauropod dinosaurs, long necked, four legged dinosaurs, and stegosauridae, class holding Stegosaurus. Other species that died include ammonites, similar to the living animals called nautilus, many marine reptiles, and bivalves, relatable to modern mollusca. Not much is known about this extinction. It is mainly linked to climate change. So far, no connection to volcanic activity or an asteroid has been made. This extinction gave way to the Cretaceous Period.

out (Bagley, 2014). This was the closer of the Permian-Triassic period. This means that the rest

The Cretaceous period is a period of time within the Mesozoic Era lasting from 146 million years ago to 65.5 million years ago. It is one of three periods in the Mesozoic Era along with the Triassic and Jurassic periods. The Cretaceous period is well known for the amount of dinosaurs it had, and the event that put an end to the dinosaurs reign, the K-T mass extinction. During the K-T mass extinction, a huge asteroid hit earth and caused tons of dust to infiltrate the air. Only a small portion of dinosaurs died on impact Instead, the dust blocked out sunlight which caused plants to die. Without plants, many dinosaurs did not have a food source, so the died out. Carnivore dinosaurs, such as the Tyrannosaurus Rex, survived a little longer

Since the 1980s the most popular theory for why dinosaurs became extinct was because of a meteor, but many people are skeptical of whether or not the meteor was the only factor in the extinction of the dinosaurs. In Stephen Brusatte’s “What Killed the Dinosaurs,” Dr. Brusatte talks about how the mystery of the extinction of the dinosaurs was a hug influence on his life and caused him to become what he is today. As a teenager Brusatte had a chance to talk to Walter Alvarez, the man who proposed the idea of a meteor being the cause for the extinction of the dinosaurs. Alvarez was able to come up with this hypothesis by examining the clay band between the Cretaceous period and the Paleogene period. The Cretaceous period was a time when the Earth had a surplus amount of dinosaurs and the Paleogene period was the time period directly after the Cretaceous period where dinosaurs had become extinct. When Alvarez studied the clay band he had discovered that the band was saturated in iridium which is an element common on meteors and asteroids. This led him to believe that a meteor may have led to the downfall of the dinosaurs.

The first dinosaurs were small, meat-eating animals that first arose over 200 million years ago. From such small beginnings evolved thousands of different species, including the largest animals ever to walk on Earth. At the Smithsonian, some of the most important dinosaurs known to science stand in our exhibit halls, from the ferocious Allosarus to eighty-foot Diplodocus. Learn more about our famous dinosaurs

Basically when the asteroid impacted earth it most likely killed the bugs, insects and small animals that walked or were in the ground at the time.

As birds, like mammals, are warm-blooded, they too are able to sustain their own body heat throughout the year. If dinosaurs were able to, as well, that would compose even more evidence in favor of dinosaurs sharing more traits in common with birds than with reptiles, as their given name, “terrible lizard”, would wrongly infer. Consequently, it seems that this discovery brings out a whole new set of questions as to how the dinosaurs truly ended up dying off at the end of the Mesozoic era, whether it be that their food supply dwindled or a combination of catastrophes that

According to a live science, an article written by Mary Bagley, "The Cretaceous Period was the last and longest segment of the Mesozoic Era. It lasted approximately 79 million years, from the minor extinction event that closed the Jurassic Period about 145.5 million years ago to the Cretaceous-Paleogene extinction event dated at 65.5 million years ago"(Mary Bagley, LS). In the cretaceous period, the continent of Pangea was still breaking away from itself, forming what we now know as the seven world continents. In the many eras of dinosaurs, the cretaceous era was responsible for evolving some, but not all the dinosaurs from full land dinosaurs to some who were able to live both on land and in water, semi-aquatic carnivorous dinosaurs. This era had produced some of the dinosaurs that maybe us non- paleontologist are more familiar with like the all mighty tyrannosaurus rex or the long neck. Well let me tell you, there were a lot more dinosaurs than just those two. Although the tyrannosaurs rex was an enormous dinosaur, a bigger dinosaur was discovered in 1912, the Spinosaurus. This discovery would change peoples, kids, and paleontologists view on which dinosaur was bigger than the other. This semi-aquatic dinosaur, Spinosaurus, was much larger than the T-rex due to its sail like backbones that stuck out of its back. Furthermore, spinosaurus had a huge advantage that the tyrannosaurus-rex did not.

The dinosaurs appeared after the greatest mass extinction event occurred. This is known as the Permian-Triassic extinction. It has been estimated to have occurred around two hundred and fifty million years ago. (6) It is also known as the Great Dying with over ninety percent of species dying off, leaving the Earth essentially a wasteland. It led to the extinction of “57% of all families, 83% of all genera and 90% to 96% of all species. 53% of marine families, 84% of marine genera, about 96% of all marine species and an estimated 70% of land species, including insects.”(7) By the late-Permian, global temperatures were very hot, with them being the highest ever on the planet.

According to the research made by Alvarez (1980), it was due to an asteroid impact that single-handedly destroyed dinosaurs to extinction. Advocacy of this mechanism has been aided by the availability and tangibility of supporting evidence in the form of impact craters- the Chicxulub crater in the Yucatan Peninsula's date and timing of impact (dating produced an almost exact date of 65 million years ago), location, enormous size-170 km (Hildebrand et al.1991) and its high iridium content ( a metal not commonly found at the Earth's surface) make it seem that with a theoretical asteroid 10 km big caused the crater great damage at the end of the Cretaceous (Alvarez et al. 1980).

Jurassic is a period of time with Dinosaurs, rodents and birds. There were also island seas consisting of sharks, sea monsters and blood-red planktons. The existing plants in that period were cycads, ferns and conifers. The Mesozoic era was about 245 million years ago to 65 years ago, so it almost lasted about 180 years in total. The Mesozoic era is divided into three periods of Triassic, Jurassic and Cretaceous. Mesozoic era means middle animals and it is the era, which the word’s fauna has changed from what is in the Paleozoic era and the most famous organisms of this era are dinosaurs. In the Mesozoic era, the extinction of more than 90 percent of species in the earth was observed and the reason behind it was mostly volcanic eruptions and climate changes. On the other hand, this era had massive changes that represented ecological niches and rise to new creatures such as rodent-size mammals and first dinosaurs. In Triassic, which was the first period of Mesozoic, the mammals and first dinosaurs existed. Later than that, the second period was Jurassic, which giant shaped dinosaurs and other kinds of dinosaurs were developed. Besides that the first flowering plants and primitive birds, with long teeth appeared in that era as well.

These techniques led to the discovery of the boundary between the two eras. A single thin layer of clay found within predominantly limestone rocks established this. By comparing the marine life found in, above, and below the clay, the marine life, like the dinosaurs, had been terribly affected by the extinction event. The percentage of life in the upper layers was dramatically lower than that in the lower. This was far more compelling than what was suggested by dinosaur’s fossils.