250 Million Years of Turtle Evolution

In a way, turtle evolution is an easy story to follow: the basic turtle body plan arose very early in the history of life (during the late Triassic period), and has persisted pretty much unchanged down to the present day, with the usual variations in size, habitat, and ornamentation. As with most other types of animals, though, the turtle evolutionary tree includes its share of missing links (some identified, some not), false starts, and short-lived episodes of gigantism. Turtles That Werent: Placodonts of the Triassic Period Before discussing the evolution of genuine turtles, its important to say a few words about convergent evolution: the tendency of creatures that inhabit roughly the same ecosystems to develop roughly the same body plans. As you probably already know, the theme of squat, stubby-legged, slow-moving animal with a big, hard shell to defend itself against predators has been repeated numerous times throughout history: witness dinosaurs like Ankylosaurus and Euoplocephalus and giant Pleistocene mammals like Glyptodon and Doedicurus. This brings us to the placodonts, an obscure family of Triassic reptiles closely related to the plesiosaurs and pliosaurs of the Mesozoic Era. The poster genus for this group, Placodus, was an unremarkable-looking creature that spent most of its time on land, but some of its marine relatives--including Henodus, Placochelys, and Psephoderma--looked uncannily like genuine turtles, with their stubby heads and legs, hard shells, and tough, sometimes toothless beaks. These marine reptiles were as close as you could get to turtles without actually being turtles; sadly, they went extinct as a group about 200 million years ago. The First Turtles Paleontologists still havent identified the exact family of prehistoric reptiles that spawned modern turtles and tortoises, but they do know one thing: it wasnt the placodonts. Lately, the bulk of the evidence points to an ancestral role for Eunotosaurus, a late Permian reptile whose wide, elongated ribs curved over its back (a striking adumbration of the hard shells of later turtles). Eunotosaurus itself seems to have been a pareiasaur, an obscure family of ancient reptiles the most notable member of which was the (completely unshelled) Scutosaurus. Until recently, fossil evidence linking the land-dwelling Eunotosaurus and the giant, marine turtles of the late Cretaceous period was sorely lacking. That all changed in 2008 with two major discoveries: first up was the late Jurassic, western European Eileanchelys, touted by researchers as the earliest marine turtle yet identified. Unfortunately, only a few weeks later, Chinese paleontologists announced the discovery of Odontochelys, which lived a whopping 50 million years earlier. Crucially, this soft-shelled marine turtle possessed a full set of teeth, which subsequent turtles gradually shed over tens of millions of years of evolution. (A new development as of June 2015: researchers have identified a late Triassic proto-turtle, Pappochelys, that was intermediate in form between Eunotosaurus and Odontochelys and thus fills an important gap in the fossil record!) Odontochelys prowled the shallow waters of eastern Asia about 220 million years ago; another important prehistoric turtle, Proganochelys, pops up in the western European fossil record about 10 million years later. This much bigger turtle had fewer teeth than Odontochelys, and the prominent spikes on its neck meant that it couldnt fully retract its head under its shell (it also possessed  an ankylosaur-like clubbed tail). Most important, the carapace of Proganochelys was fully baked: hard, snug and pretty much impervious to hungry predators. The Giant Turtles of the Mesozoic and Cenozoic Eras By the early Jurassic period, about 200 million years ago, prehistoric turtles and tortoises were pretty much locked into their modern body plans, though there was still room for innovation. The most notable turtles of the Cretaceous period were a pair of marine giants, Archelon and Protostega, both measuring about 10 feet long from head to tail and weighing about two tons. As you might expect, these giant turtles were equipped with broad, powerful front flippers, the better to propel their bulk through the water; their closest living relative is the much smaller (less than one ton) Leatherback. You have to fast-forward about 60 million years, to the Pleistocene epoch, to find prehistoric turtles that approached the size of this duo (this doesnt mean that  giant turtles werent around in the intervening years, just that we havent found much evidence). The one-ton, southern Asian Colossochelys (formerly classified as a species of Testudo) can pretty much be described as a plus-sized Galapagos tortoise, while the slightly smaller Meiolania from Australia improved on the basic turtle body plan with a spiked tail and a huge, weirdly armored head. (By the way, Meiolania received its name--Greek for little wanderer--in reference to the contemporary Megalania, a two-ton monitor lizard.) The turtles mentioned above all belong to the cryptodire family, which accounts for the vast majority of marine and terrestrial species. But no discussion about prehistoric turtles would be complete without a mention of the aptly named Stupendemys, a two-ton pleurodire turtle of Pleistocene South America (what distinguishes pleurodire from cryptodire turtles is that they pull their heads into their shells with a sideways, rather than a front-to-back, motion). Stupendemys was far and away the largest freshwater turtle that ever lived; most modern side-necks weigh about 20 pounds, max! And while were on the subject, lets not forget the comparably ginormous Carbonemys, which may have done battle with the giant prehistoric snake Titanoboa 60 million years ago in the swamps of South America.

Essay on Wartime Changes the Transformation of Jimmy Cross

War Time Changes: The Transformation of Jimmy Cross Many authors tend to use character transformations to further an idea in a story. Tim O’Brien’s story â€Å"The Things They Carried† has an open ending, which he uses to signal a new beginning with the transformation of Jimmy Cross. The transformation greatly ties in with one of the major themes of the story, that war changes people. Tim OBrien provides his audience with a very descriptive image of both the physical and mental things the characters in the story carried. He gives the reader insight as to how the characters are physically and mentally dealing with the turmoil of the war. However, in the end of the story - Jimmy Cross - a round character, reacts to the death of Ted†¦show more content†¦Jimmys transformation begins when he decides to burn the pictures and letters of his girlfriend, Martha. To be a leader in war was meaningless to Jimmy Cross compared to the love he had for Martha. Cross subsequent burning of Marthas letters suggests that hes determined to put such romantic ideas behind him. He repeatedly convinces himself that there will be no more fantasies about Martha. The burning of Martha’s things is symbolically used by O’Brien to signify a turning point in Cross’ development. Cross realizes that Marthas feelings for him were not those of love, for she is an Englis h major, a girl who lives in the world of words. Cross was rationalizing his un-requiting love for Martha to create a â€Å"home world† inside his mind so that he could mentally escape from the war when he needed to. Aside from abandoning the letters and pictures, Jimmy Cross also abandons his innocence. He wants to concentrate on the responsibilities of leading his men, for he was now determined to perform his duties firmly and without negligence. The new lieutenant Cross would dispose of the good luck pebble, issue new SOPs, and would confiscate the remainder of Lavenders dope. Overall, Lieutenant Jimmy Cross would accept the blame for what had happened to TedShow MoreRelatedThe Things They Carried By Tim O Brien846 Words   |  4 Pagesanxious or even confused. Vietnam War was â€Å"a personal failure on a national scale† (Hochgesang). There are many videos, documents and movies about the Vietnam War that show different angles of the Vietnam veterans’ exper ience and how the war really changes their life. In â€Å"The Things They Carried† written by Tim O’Brien, he argues about how the Vietnam War affect the soldiers in many ways, not only physically, but more important is the psychological effects before, during and after the war. DuringRead MoreStephen P. Robbins Timothy A. Judge (2011) Organizational Behaviour 15th Edition New Jersey: Prentice Hall393164 Words   |  1573 PagesPower and Politics 411 Conflict and Negotiation 445 Foundations of Organization Structure 479 v vi BRIEF CONTENTS 4 The Organization System 16 Organizational Culture 511 17 Human Resource Policies and Practices 543 18 Organizational Change and Stress Management 577 Appendix A Research in Organizational Behavior Comprehensive Cases Indexes Glindex 637 663 616 623 Contents Preface xxii 1 1 Introduction What Is Organizational Behavior? 3 The Importance

International Law Legislative Power

Question: Discuss about the International Lawfor Legislative Power. Answer: The general power of the government to exercise authority over the entity and person within its territory is referred to as the jurisdiction. There are different forms of jurisdiction the most prominent is given to perspective jurisdiction and the enforcement jurisdiction. The right of the legislature is to create, amend and repeal the legislation is referred to as the perspective jurisdiction or the legislative power. On the other hand, the enforcement jurisdiction is the right of the government to enforce the legislation through policing and prosecuting. Therefore, from the above discussion it can be seen that the main difference between the perspective and enforcement jurisdiction is that the perspective jurisdiction is the legislative power of the government whereas the enforcement jurisdiction is the executive power of the government. In the case of SS Lotus (France v Turkey)(1927) PCIJ Ser A, No 10 there are two principles of lotus case. The first principle provides that a stat e cannot exercise its power in any form in the territory of another state without the permission of the international law or treaty (Ryngaert, 2015). The second lotus principle is that even if an international law does not permit a state can exercise its power in its territory in any form. For example, a country can ban certain products by exercising its perspective jurisdiction but it cannot enforce the ban on another state outside its territory that is absent of enforcement jurisdiction. In this case, citizen A of country B has committed a crime against country A. The country A can with the help of country can bring citizen to justice. The Model Law of extradition 2004 and Model law Mutual assistance 2007 provides that if an appropriate request is received for cooperation then it is the responsibility of the state receiving the request to cooperate as per international laws and treaties (Shihata, 2013). Reference Ryngaert, C. (2015).Jurisdiction in international law. OUP Oxford. Shihata, I. F. (2013).The Power of the International Court to Determine Its Own Jurisdiction: Comptence de la Comptence. Springer.