Late Triassic Mass Extinctions and the Rise of the Dinosaurs
Introduction
Presently, dinosaurs are symbols of failure, largely due to their failure of the lineage to survive. The present absence of the dinosaurs negatively portrays these creatures, which retell successful stories behind their existence (Gould, 23). The study discusses the period the Late Triassic and the rise of the dinosaurs.
The Triassic Period
The Late Triassic is final of the three epochs of the Triassic period within the geological timescale (Ghose, Para 2). It is within this period when the Triassic-Jurassic extinction period began among the major mass extinction events of the earth. The Late Triassic is divided further into the Canadian, Norian, and the Rhaetian periods. The first dinosaurs, which evolved in the late Triassic, are the Plateosaurus, the Coelophysis, and the Eoraptor. During this period, more than 76% of terrestrial and marine life species disappeared. Although the period was not as distractive as the Permian period, more than 70% land species became lost.
In the Mesozoic period, there was a rapid diversification of life and giant reptiles, and dinosaurs on the earth. This period is, approximated as 252-66 million years ago, commonly referred to as the age of the dinosaurs. The first geologist to create the global geological timescale was an English referred to as John Philips. He correlated sediments around the world to defined times (Butler, Para 5). The Permian-Triassic boundary at the beginning of the Mesozoic is mainly known as the period when eel-like creatures, the conodont, initially appeared (University of Museum of Paleontology, Para 1). The final boundary of the Mesozoic period, the Cretaceous-Paleogene, contains well-preserved fossils of the iridium among other elements from the effect of the asteroid. These elements are assumed to have wiped out dinosaurs.
Evolution of Dinosaurs
Dinosaurs as the dominant large vertebrates reigned more than 135 million years ago. They were twice the length of the average mammal that ever dominated after their extinction. Research is still being conducted on the presence and extinction of these unique species from the face of the world. Therefore, in the developing research, no single study can wholly determine and categorize the exact date of their origin, their existence, exact reasons for their origin, and reasons behind their extinctions.
In their existence, dinosaurs diversified to reign in more than 1,000 ecologically and morphologically diverse species. Dinosaurs survived in all the continents including the Antarctica and varied in size from the pigeon-sized that weighed less than one kg to 70 tons’ herbivorous creatures that reigned as the largest in the animal kingdom. Even though dinosaurs presently are absent, it is of great essence to note of how and why they became so successful. With the discovery of the origins of the dinosaurs, high rates of fossils and species are continuously increasing. According to Stanley (15), every 1.5 weeks, a new dinosaur species is being named, apart from the 11 new species named since 2005.
Another study affirms that the first dinosaur appeared in the fossil record more than 240 million years ago within the Middle Triassic. With developing proofs, the extinction of dinosaur are approximated to be in the long-term recovery of ecosystems from the Perm-Triassic (PT) mass extinction. This extinction is asserted as the most severe in history and was assumedly caused by intense volcanic eruptions and related rapid climatic variations (Fortey, 56). These extinctions not only cleared the creature but it also decimated majority of the reptiles and amphibians species. The result was a huge environmental space for other species of dinosaurs to evolve as well as other creatures to arise.
Even after 40 years of evolution, dinosaurs remained a minority group in the reptile world. Another research combined the evolution of trees with data such as body size to test quantitatively and explicitly the hypotheses over timing, rate and radiation processes of the dinosaur (The University of Museum of Paleontology, 8). At the end of the Triassic period, a majority of the reptile category died out due to increased massive volcanic activities and climatic variations. Dinosaurs survived and increased rapidly in the diversity while undergoing dramatic size increment, which marked the onset of the age of these creatures. It is still unclear why dinosaurs survived the extinction that was marked in this period while other reptiles did not. Paleontologists, however, assert that the unique features in these creatures such as the high growth rates and efficient bird-like lungs enabled them to prosper in unfavorable conditions (Fortey1, Para 43). The evolution of the dinosaurs is therefore driven by three huge extinctions that were assumedly caused by rapid, traumatic, and huge environmental variations. Firstly, the end of the Permian led to the creation of environmental space for the creatures to evolve. Secondly, the end of the Triassic facilitated dinosaurs to dominate and evolve to unfeasible sizes. Thirdly, the end of the Cretaceous resulted to the end of the dinosaurs. Finally, during the end of mass extinction as driven by human beings, the fossil record includes that of dinosaurs. These records offer insights on the role of mass extinctions in defining and modifying the course of evolutionary background.
It is debatable on the cause of end-Triassic extinction (Dalling, 79). Some of the scientists contend that the event was a result of climate variation and increasing sea levels, which resulted in a sudden release of the huge amounts of the carbon dioxide. The release of the carbon dioxide from increased volcanic activity related with the rifting of the supercontinent Pangaea. In this region, the eastern North America met with the northwestern Africa that strengthened the global greenhouse effect. Recent research on the flood basalts resulted by the rifting showed that the rocks created within the 620,000 years’ interval volcanic activity occurred at the end of the Triassic. Other modern studies reveal that the relatively modest heating consequent by increasing concentrations of carbon dioxide in the atmosphere that have liberated increased amounts of methane trapped in the permafrost and undersea ice. Methane a more effective greenhouse gas than carbon dioxide resulted in the atmosphere warming significantly (Stanley, 2). Other studies, on the contrary, affirm that mass extinction was a result of the effect of the extraterrestrial bodies such as the comets or the asteroids, and were not, however, the product of the single major event but a prolonged this turnover of species over some time.
Life and Climate
The Mesozoic era is characterized roughly by rebounding of life, which eventually gave way to flourishing variety of animals, including the monstrous dinosaurs. The Triassic period saw the upsurge of the first dinosaurs (HHMI, Para 5), while the Jurassic period saw the rising of the birds and the mammals, some of which included the Triceratops and Pteranodon. There was also a high increase of the Coniferous plants, which bore cone-bearing seeds. The lush plant life in the period offered plenty of food that allowed the hugest of the dinosaurs like the Argentinosaurus, grow to 80 tons (Fortey2, 96). During that period, the earth was much warmer than it is today and there were no polar ice caps. In this period, the Pangaea consisted of one massive supercontinent, which in the absence of coastline to regulate interior temperature had major temperature instability and large swaths of desert. Nevertheless, the region was largely covered with tropical rainforest around the equator (HHMI, Para 4).
Extinctions
The period experienced two great extinctions, with a smaller extinction at the end of the Triassic era (University of Museum of Paleontology, Para 9). At the end of the Permian extinction, most of the life was wiped out of the earth for more than 60,000 years (Ghose, Para 4). By the end of the Triassic period, which is approximately 201 million years ago, a majority of the amphibians and crocodile creatures within the tropics were wiped out. More than 65 million years ago, there was a huge asteroid, which blasted into the earth and generated the huge crater at the Chicxulub , Yucatan Peninsula. It is, however, difficult to approximate the causes and rapidity of extinctions since fossil records is still incomplete. Moreover, some of the species of catastrophic periods are still missing in the record since the sediments have disappeared for more than tens of millions of years.
At the end of the Permian, the Siberian traps went through huge volcanic eruptions that are believed to have resulted in massive extinction. The eruptions resulted in the spike of carbon dioxide in the atmosphere and increased sea surface temperatures. Other effects of these eruptions include ocean acidification, which choked sea life (Butler, Para 12). The eruptions are perceived additionally to have resulted to huge troves of nickel that increased feeding microbes, which are said to have belched out some amounts of methane that superheated the planet. The majority of the scientists agree that asteroid wiped out dinosaurs during the Cretaceous period. The result is perceived to have kicked up much dust that blocked the sun, stopped photosynthesis, and disrupted food chain that resulted from too much death. Along the Indian region, massive spewing of the lava before and after the asteroid impact directly caused the dinosaurs to clear.
Volcanism is to be blamed at the end of the period as it led to global warming. From the initial volcanic eruption, there were huge amounts of sulfur, which spew into the air and resulted in brief periods of global cooling. These cooling cycles occurred hundreds of times further resulting in huge crops failures in the history, such as in Iceland in the 1700s (Fortey3, Para 6). Consequently, animals within the constant balmy temperatures within the tropics were wiped out while those insulted with the proto-feathers like the pterosaurs adapted to the already huge temperature variations. In Volcanic winters, temperatures were known to drop to lower than the freezing points in the tropics, a fact that was so devastating.
Conclusion
The Late Triassic is marked by three epochs within the geological timescale. It is the period when major extinction began as major events on earth. Dinosaurs as the overriding large vertebrates reigned more than 135 million years ago. Presently, dinosaurs are perceived as weak due to their extinction despite their successful stories of existence in tough periods. Scientists are still debating on the cause of the Triassic extinction. Some of the scientists contend that the Triassic extinction was an outcome of climate variation and increased sea levels due to a sudden release of the huge amounts of the carbon dioxide. Climate variation came as an effect of methane, which is a more effective greenhouse gas than carbon dioxide. Other scientists, on the contrary, affirm that mass extinction was a result of the effect of the extraterrestrial bodies such as the comets or the asteroids.
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