Dinosaurs of the Jurassic Period, Research Paper Example

Abstract

This paper examines the Dinosaurs of the Jurassic Period.  The paper considers the holistic view of the Jurassic period in addition to the Dinosaurs that roamed the Earth during this period.  In this sense it considers the environment and climatic conditions that supported them.  Finally, historical consideration evidence leading to the demise or disappearance of the dinosaurs. Analysis is based upon research conducted from 10 academic reference sites.  The paper provides an understanding of the different species that lived during the Jurassic period and the environmental and climatic conditions that supported them. Why did the dinosaurs flourish during the Jurassic period ? How did the environment and climatic conditions impact the evolution of the species ?  What ultimately resulted in the extinction of the species ?

Dinosaurs of the Jurassic Period

The Jurassic period, also known as the age of reptiles, and is marked from the end of the Triassic period to the beginning of the cretaceous period.  There are three main extinction events in the life of the dinosaurs but none  took place during the Jurassic period.  The term Jurassic was linked to the Jura mountains of Switzerland , a small range north of the Swiss Alps dividing the Rhone and Rhine rivers.  (Rieboldt.S, 2002)  Time periods are normally broken down into Early, Middle and Late Jurassic.  In the Jurassic period the main vertebrates living in the Oceans were fish and marine reptiles.  These included that of marine crocodiles, ichthyosaur, plesiosaurs and metriothynchidae.  The Jurassic period saw the introduction of several new groups during this period. These includes types of bivalves and belemnites.  Also about 4 or 5 planktonic organisms appeared for the first time; in accordance with fossil records from that period. Were the dinosaurs of the jurassic period influenced by climatic and environmental changes ?

On the land reptiles remained dominant and this was considered to be the golden age of the large herbivorous dinosaurs known as the sauropods.  These in turn were preyed upon by large theropods i.e. ceratosaurus, megalosaurus, toryosaurus and allosaurus.

Figure 1 Stegosaurs

One of the premier places for fossils of this period is that of the Morrison Foundation, a distinct sequence of late Jurassic rock found in the Western United States.  The upper jurassic Morrison formation is considered is considered to be one of the most opulent sites of dinosaur faunas in the world and provides information about the geographical and climatical terrain of that time.  Fossils provide an indication of the species that made up the dinosaur community during this period including, Camarasaurus, Allosaurus, Stegosaurus and Diplodocus.  The Morrison dinosaur bones were initially discovered in Cimarron County, Oklahoma close to the Oklahoma- New Mexico State line.  The discovery in 1931 revealed initially 5 different types of dinosaur bones ” more than 3,500 individual bones, most from a single genus brontosaurus, have been collected”  (Stovall, 1938).

One of the remarkable things about the discoveries in the Morrison Foundation is the excellent quality of the exhibits discovered.  Many jaws of the Antrodemus species are so well preserved that full sets of teeth were found to be in place.  This yielded a tremendous amount of dental information including that of tooth growth, tooth replacement. “Antrodemus , was theoretically never left with a gap of more than one tooth’s space on each maxillary or dental bone at any one time..”  (Stokes, 1945).

In the Lloyd quarry there was an absence of gastroliths found with other dinosaur remains. Many other dinosaur species were represented so this proposed a bit of a mystery.  200 feet higher in the rock face there were many gastrolths evident but very few bones. The evidence suggested that the highly polished stones in the Morrison have no real relation or reference to the digestive habits of the dinosaurs.

Another interesting discovery in the Morrison related to the footprints of a gigantic sauropod dinosaur identified as that of a brontosaurus.  The American Museum is installing these book prints has a mounted exhibit.  The quality of the exhibits discovered near Glen Rose in Texas has been a very high quality.  Glen Rose is considered to be the middle formation of the Trinity group and is considered the tape earlier than the Neocomian times in Europe.  Edward Berry of the Johns Hopkins University, expressed concerns relative to the actual dating of the Morrison site.  Hence, if a ” drastic dinosaur, of the vertebrate chronology, creates footprints at a horizon near the middle of the Marine bought the cretaceous, invertebrate chronology, which we go from here?” (Berry, 1941).

Climatic features are a very important consideration in Jurassic times.  It is considered somewhat similar to modern day times.  For example: they experienced strong seasonal contrasts within large continental areas, they had polar ice and monsoons were dominant on the continents.  Scientists noted a considerable spread of heredity in southern Eurasia during the late Jurassic period, and attributed this to orographic effects.  Scientists reach consensus that the climates of the Jurassic were very similar to that of the cretaceous period.  More recently, however.  Scientists have challenged the traditional view, stating that in reality, the Jurassic.  Was more likely to have experienced a considerable seasonal range of temperatures.

Research into the flora distributions join the Jurassic period, showing a wide distribution of ferns.  These type of ferns, not being frost tolerant.  Scientists have mapped the northern flora’s so in the lower Jurassic.  This has embraced such countries as Greenland, northern and central Europe, Siberia and Japan.  They then mapped the southern zone, which extended from Mexico to the Middle East and southern China.  Hence the zones reflected a wide variation of the latitudinal differentiation.  This giving evidence to the degree of contrast between the seasons.  The climate of the northern zone was considered to be humid and moderately warm whilst that of the southern zone compared to the present humid tropical zone.  Conifer pollens have been used as an indicator to detect the amount of aridity during this period.  The pollens will note, the most abundant upper Jurassic sediments, and as such indicated a time of maximum aridity during that period.  Scientists also served strong differentiation between the conifer species observed in the northern hemisphere and that of the southern hemisphere.  This is considered not a reflection of climate change, but more of shifting continents as pollen, cannot cross oceans.

Studies of coral reefs and their subsequent movements support the theory of tectonic activity and shifting continents during this period.  The corals enable the tropical belt, to be clearly identified, and they clearly show displaced terrains where movement has occurred.  The richest foreigners are seen to occur in the upper Jurassic of the United States Western Interior and Tanzania in Africa, however  scattered occurrences spread across a much larger distance ranging from United States, Europe and China to that of Patagonia and Australia.  The most important sedimentary rocks applicable to the Jurassic are that of ” limestone’s, tillites, evaporites and coals”  (A Hallam, 1993).

Figure 2 The Jurassic Landscape

The upper Jurassic Morrison formation produced one of the richest fauna deposits in the world, with sediments, distributed over more than 1,000,000 km² across the United States.  Essentially this is a vast alluvial plane that was nourished by the debris from ancient rocks from the Rocky Mountains.  Dinosaurs were seen not to be contained within any specific area but they spread across the complete distribution ” Morrison’s sediments were laid down as a comparatively thin sheet of continental sandstones, mudstones and lacustrine limestones over a vast area of the  Western United States”  (P.Dodson A.K. Behrensmeyer R.T. Bakker, 1980).

There have been many mass extinctions in the history of the evolution on Earth.  Probably none as dramatic as that of the dinosaurs disappeared some 65 million years ago.  Most of the research on the extinction of the dinosaurs focused on the late Triassic period.  During that time.  It was estimated that some 20% or more families of animals died out, and thereby eliminating some 50% of species.

At the borders of the Triassic-Jurassic period, there is  evidence that points to an extinction of ammonoids and bivalves.  It was not until the end of the Triassic period that a mass extinction on a large scale occurred.  There have been a number of speculations as to what was the precise cause of this.  Some point to the possibilities of climatic change, whilst others consider possible impacts from a comet or meteor.  There is a major impact site located in the Manicougan site of Quebec.  However, the most significant site is believed to be the large impact crater site in the Gulf of Mexico.  The site of the crater impact in the Gulf of Mexico is of a significant size and proportion that you would associate with the possibility of a mass extinction event.  It has been documented that there were at least three major extinction event that occurred.  Sure in the late Triassic period.  The fact that the dinosaurs remained a dominant species on the planet.  For some hundred and 60 million years makes the extinction events even more puzzling.  There is a strong body of opinion that supports the concept of nature extra terrestrial impacts on the planet.  Such impacts having occurred at regular intervals in time.  Nevertheless, this hypothesis has yet to be substantiated with any firm evidence.  There are certain inconsistencies with this concept that do not fit with the extinction events that took place in the in the Triassic period.   Scientists have carried out simulated studies of what a large impact from a meteor or comet would have on the planet.  Studies in particular, looking at the Gulf of Mexico site in terms of size and mass of a potential body hitting the plant with an explosive force equivalent of hundreds of thermonuclear weapons exploding simultaneously.  Such a blast would undoubtedly create unprecedented, tidal waves if the asteroid landed in the ocean.  This would’ve created flooding on an unprecedented scale over land areas and subsequently drowning most of the large animals.  The explosion would also have sent a vast amount of rock debris and dust into the upper atmosphere and creating the potential effect of a nuclear winter.  This means that the vast cloud of dust, which circumnavigated the planet would have brought out any sunlight, and therefore destroyed all life as we know it on the planet.  Those animals that initially survived would not have lived long without any food, as the vegetation would have quickly died due to lack of sunlight. (Padian, 1988)

We know from our observations of both the moon and nearby planets like Mars, a large impacts do occur on a frequent basis over time.  We are surrounded by an asteroid belt that periodically releases launched volumes of rock into space.  So it is not out of the question, that in the more turbulent years of our planets evolution, it would’ve been hit by one or more asteroids.  Each of these would have undoubtedly impacted life on the earth at a time.  (Benton, 1993)

Nobody knows for certain what the cause of the late Triassic extinction was.  As previously stated, it might’ve been the result of global cooling, or an asteroid impact.  The crater that surrounds Manicouagan Reservoir in Quebec Canada was offered as a possible candidate as it fits the bill up being about 210 million years old.  It was that extinction event that gave rise to the dinosaurs, expanding into those niches that were unoccupied.

It was the Jurassic period that we observed the breakup  of the pangaen supercontinent into two large pieces.  These were defined as Laurasia in the North and Gondwana in the South.  The breakup led to the formation of huge intra-continental lakes and rivers with a hot and humid climate, producing a steady rainfall considered ideal conditions for rapid growth of lush green plants.  In the first instance, giving rise to many plant eating or vegetarian, small quadrupedal dinosaurs that subsequently involved in the gigantic sauropods.  The.  Also gave rise to the rise of medium-size carnivores, i.e. Allosaurus and make Megalosaurus resulting in the evolution of armoured herbivores.  As the dinosaurs continued to grow bigger on land.  A similar devolution, very scale was being adopted in the Jurassic seas.  The seas at this time were full of fish that provided an ample source of food for the large number of marine reptiles.  The Jurassic period also witnessed devolution in the skies with such creatures as pterodactyls and pterosaurs. ” At up to 148 feet in length, Seismosaurus, meaning “Earthquake Lizard,” outgrew even Apatosaurus. Its head was so small and its body so big that more than 200 gastroliths, or stomach stones, were needed to help pulverize the constantly incoming food. Stegosaurs formed another common Jurassic herbivorous group.”  (Viegas, 2010).

So in essence the Jurassic period was a time of abundance in terms of  vegetation growth and the evolutionary growth of the dinosaurs.. ” The dinosaurs of the Jurassic were much more different from each other than in other periods: there was a greater variety. Because of the different climate, the forests grew, and the herbivores became huge in order to feed on the tall trees. The carnivores then had to become larger and more fierce to deal with such huge prey.”  (Anon, 2010).

In addition to the devolution of the development on the land.  A similar spectacle was taking place in the oceans at this time.  This in particular with the newly formed shallow interior seas.  The breaking up of the supercontinent created a new environment, which teemed with marine life.  Right at the top of the food chain was a wreck to the creature with a long neck and paddle fins called a plesiosaurs.  In addition to this.  There were giant marine crocodiles shocks and rays.  The abundant amount of squid and octopus provided food for the larger creatures.  Stop in the warmer waters caught Rory’s flourish, producing spongers snails and mollusks.  It is considered that the plankton at the time was so abundant in the ocean may have turned parts of the ocean red.

During the Jurassic period.  It was a time of the largest  land animals ever to exist on our planet.  i.e., the Jurassic sauropods.  These included the Apatosaurus, also known as the Brontosaurus and Seismosaurus.  These animals had four legs  and a long neck and were  vegetarian feeding on a variety of plants.  These animals walked the great floodplains eating the leaves of tall conifers and taking water from the rivers as they traveled.  They are believed to be in herd animals that traveled at a very leisurely pace.  These animals consumed, a vast amount of food in order to survive.  They needed to eat continuously in order to store up large surpluses of energy for the ability to escape predators.

Another animal was the stegosaurs including the famed stegosaurus.  This animal featured in many movies about prehistoric times.  Famous for the row of back plates and spikes on the tail.  It has a small head and large body.  The stegosaurus had a small brain.  He did not move very fast, but was a fierce adversary because of its armour and a tail which could lash out with a fierce spike attached.

Another creature during this period was the small birdlike compsognathus, associated with the late Jurassic period.  This was a carnivorous dinosaur and have a sure that contained a lot of sharp teeth.  By comparison.  It resembles many  of today’s large lizards and stood on its hind legs and tail or balancing white chased after its prey.

One of the most formidable carnivorous dinosaurs of  this time was the Allosaurus.  This was a fierce and terrifying creature that had long narrow  jaws filled with teeth that could rip its prey to shreds.  It was extremely well muscled, with four limbs containing huge teeth, only to be complemented by a further set of huge claws in the  feet off  it’s large legs.  This animal was the relative to the famed Tyrannosaurus of the Cretaceous period.  The creature was 40 feet long from head to tail with a head up to 3 feet long, containing teeth  that could literally bite chunks of flesh from its prey.

It is important to note the distinction between reptiles and dinosaurs.  Reptiles dominated the land and sea during the Mesozoic era.  When Pangaea was still a huge supercontinent.  The reptiles were more adaptable to these hot dry lands.  Cold-blooded reptiles seemed to thrive much better in desert like environments.  In these flourish to join the Triassic period.  This is the time when the first dinosaurs were evolving.  The distinction between the dinosaurs and reptiles is twofold.  First, dinosaurs, all warm-blooded creatures me the temperature of their blood was kept constant inside the body as opposed to changing with the outside temperature.  Secondly, bone structure was different in hips, legs and hands.  Dinosaurs lived after the Triassic period , and subsequently dominated the Jurassic and Cretaceous periods.

There was no polar ice caps during the Jurassic period and the sea levels were a lot higher than today.  Equally, the climate was a lot warmer and more humid. In the middle of the Jurassic period when Pangaea began to break up, vast flooded areas were introduced.. Towards the end of the period the seasons also changed, being less seasonality owing to the large water mass. The middle to the end of the Jurassic period witnessed a large amount of tectonic plate movement and this in turn created a lot of volcanic activity along the lines of the moving plates.

Figure 3   Ichthyosaur Fossil

Cyclads grew in abundance during this time, these being seed plants with large palm like fronds. These provided a staple diet for many of the herbaceous animals.

Conclusion

The Jurassic period was considered the age of the dinosaurs. It started after the Triassic period some 260 million years ago and ended some 144 million years ago, thus spanning a gap of some 60 million years in the middle of the Mesozoic period.  The climate was warm, humid, moist and stable giving rise to many new plant and fauna species. It was an ideal condition for them to live and adapt.  This abundance of plant food enabled the Herbavores to develop and become huge plain dwelling animals.  As these became bigger, evolution similarly adapted the carnivours to become larger and more ferocious to deal with the size of its prey.  As the land animals developed, equally the climatic conditions favoured the development of marine life; this creating an abundance of fish to support the development of an increasing population of predatory reptiles.

Works Cited

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Anon. (2010, 1 25). The Age of the Dinosaurs. Retrieved 2 17, 2010, from http://www.kidcyber.com.au/topics/dino_jurassic.htm

Benton, M. T. (1993). Triassic extinctions and the origin of the dinasaurs. American Association for the Advancement of Science , 769-770.

Berry, E. W. (1941). The age of Jurassic dinosaurs. American Association for the Advancement of Science , 374.

P.Dodson A.K. Behrensmeyer R.T. Bakker, J. M. (1980). Taphonomy and Paleoecology of the Dinasaur beds of the Jurassic Morrison formation. Paleobiology , 208-232.

Padian, K. (1988). Triasic Jurassic Extinctions. Science , 1358-1359.

Rieboldt.S, P. A. (2002). The Jurassic Period: 206 to 144 million years ago. Retrieved 1 17, 2010, from ucmp berkeley: http://www.ucmp.berkeley.edu/mesozoic/jurassic/jurassintro.html

Stokes, W. L. (1945). A new quarry for jurrasic dinosaurs. American Association for Advancement of Science , 115-117.

Stovall, T. (1938). The Morrison of Oklahoma and its dinosaurs. The journal of Geology , 583-600.

Viegas, J. (2010, 1 1). Jurassic Period: Dinosaur Domination . Retrieved 2 19, 2010, from Discovery Channel: http://dsc.discovery.com/dinosaurs/jurassic-period.html