Mariah Ross Period 8 Adaption of teeth among sharks Shark teeth often change size and shape based on its position in the shark’s mouth, whether it’s from the upper or lower jaw, and the age, sex, and species of the shark it came from. Shark teeth are produced and shed serially moving forward as though they are on a conveyor belt. With this replacement system, one shark can produce, use, and shed as many as 6,000 teeth each year. If a shark tooth is well preserved it offers the scientist a number of points that can be used to identify the species and the basic taxonomic group of shark it came from. However a great number of shark tooth fossils aren’t well preserved and are often times worn down to the point being smooth and featureless, making them all but useless in the identification process. Early Fossil Shark Teeth and consequent evolution The earliest known fossil shark teeth are those of Leonodus (left) dating back some 400 million years. Their overall crown shape vaguely resembles that of fossilized Xenacanthus (right) teeth, possibly indicating that these early sharks were related. Their roots, however, are quite different, suggesting that Leonodus and Xenacanthus may have evolved similar crowns as an adaptation to feeding on similar prey rather than due to shared ancestry. No one is sure which group of sharks evolved in to their modern counterparts, but until recently many scientists believed that it was the Hybodonts. However, paleoichthyologist John G. Maisey’s extensive studies of fossil and modern sharks, causes some belief that the hybodonts were a side-branch of shark evolution that did not give rise to any group of modern shark. Maisey has proposed that a genus known as Synechodus may be more closely related to ... ... middle of paper ... ...ark can eat 1% to 10% of its overall body weight per week. Many shark species swallow their food whole without any form of chewing. While some sharks are probably not very selective feeders, certain sharks eat some foods more than others. For example, hammerhead sharks are known to eat stingrays; bull sharks eat other sharks; and smooth dogfish eat crabs and lobsters. Tiger sharks feed opportunistically on both live food and carrion. Their prey includes bony fishes, other sharks, marine mammals, seabirds, and invertebrates. How Sharks Work by Tom Harris, http://animals.howstuffworks.com/fish/sharks/shark4.htm Martin, R. Aidan. 2003. Copyright and Usage Policy. World Wide Web Publication, www.elasmo-research.org/copyright.htm http://seaworld.org/en/animal-info/animal-infobooks/sharks-and-rays/diet-and-eating-habits/ NO AUTHOR LISTED, DIET AND EATING HABITS
The Great Shark debate – to cull or not to cull, has been at the forefront of the minds of conservationists, as well as the general population for many decades now. The opinions of everyone are divided, according to their personal experiences, and views on what is right and wrong for the environment.
The relationship of the three species and their ancestors can be summarized by looking at the fossils above. It is evident that all of these three species possess fangs and other types of sharp, prominent teeth. These analogous features indicate that there is some similarity in ancestry, since they all form part of the same family group, although they come from different genus. However, there is some difference in the shape of the head. The coyote possesses a straighter jaw and more angular head. The wolf, on the other side, has a wider denture similar to the fox. These three species also share Homologous structures, such as fangs, are present in these species. Another homologous structure is the legs and ribs, since they all have a similar
Incisivosaurus Gauthier was what is believed to be a primitive Oviraptorosaurian that was recently discovered in China. The Theropod and its highly specialized skull is described as a bizarre creature that lived 128 million years ago (Gee). The characteristic that “sticks out” the most are it’s rodent-like teeth. Harry Gee has described the dinosaur as “a [cross between] Roadrunner [and] Bugs Bunny” (Ibid.) and Hillary Mayell calls it a “’Weird’ Bucktoothed Dino.” (Mayell)
The name ‘Liopleurodon’ is derived from Greek. It means “smooth-sided teeth”. The name was given by Henri Emile Sauvage. Sauvage gave this name because in 1873, he found the fossils of three teeth which were just 7 centimeter in length. The two species of Liopleurodon are L. ferox and L. pachydeirus Out of the two species, L. forex is quite known and famous. The fossils of both the species are found in the countries of England and France. L. pachydeirus is a very rare species as its fossils are not discovered in very good numbers. On the other hand, the fossils of L. ferox species are found in comparatively good number. The scientists have more knowledge about L. ferox because of the availability of the skeletons; some of which are more complete or less.
Majungatholus atopus roamed the plains of northwestern Madagascar about 70 million years ago during the Late Cretaceous (Perkins, 2003; Rogers et al, 2003). The discovery of 21 tooth-marked elements originating from two Majungatholus atopus individuals suggests evidence that the dinosaur supplemented its diet by feeding on its own dead or hunting them (Rogers et al, 2003). It cannot be confirmed whether they were purely scavengers, hunters, or both. Scientists are certain that the marks are not the doing of any other predator because the teeth marks are not consistent with any other known species that lived in the area. Only one other theropod that inhabited the area during the time Majungatholus atopus did, Masiakasaurus knopfleri, had teeth and bite marks too small to have caused these markings. Two large crocodile species also shared the same ecosystem but their teeth were “too blunt and too irregularly spaced to have produced the narrow grooves found on the Majungatholus bones”(Perkins, 2003). The tooth marks on at least nine Majungatholus elements attest to intertooth spacing in the perpetrators jaw and denticle drag patterns consistent enough to make a compelling case for Majungatholus feeding on other Majungatholus (Rogers et al, 2003).
Rogers says the evidence for the theory of cannibalism comes from twenty-one tooth marked elements which were a part of two different Majungatholus individuals found in two isolated locations on the island of Madagascar.4[4] On these bones are distinct sets of tooth marks that point only to being from the jaws of a Majungatholus dinosaur; the marks not only match the size and spacing of the teeth found in the jaws of the Majungatholus, but they also have the same smaller grooves that match the sharp irregularities of this particular dinosaur. According to Rogers, “measurements taken from the modified bones and the Majungatholus teeth are comparable.”5[5] The set of parallel tooth marks found on one of the bones matched up with the same approximate inter-tooth spacing as the jaw of the Majungatholus. This particular dinosaur also can display an even pattern of tooth eruption that is evident in several of the bones in the sample.
In 2000, Dr. Philip D. Gingerich, a paleontologist from the University of Michigan, and his associates discovered two primitive whale fossils in the Balochistan Province of Pakistan. By dating the limestone located in the Habib Rahi Formation of the Balochistan Province, Gingerich estimated these fossils to be about 47 million years old. According to author David Braun of National Geographic News, “The researchers have classified one, Rodhocetus balochistanensis, as a new species of an existing genus, and the other, Artiocetus clavis, as a new species and new genus” (Braun, 5). The discovery of these two fossils suggests that the closest living relative of these primitive whales could possibly be the modern day hippopotamus. This suggested relationship is based on similarities in the bone structure between the two animals.
Mojetta wrote about prehistoric sharks, and the history of these creatures. According to Angelo Mojetta, author of Sharks, Cladoselache genus, one of the first prehistoric sharks, was buried in sediment that kept it preserved. Unlike other sharks, Cladoselache genus had a circle of tiny plates around it’s eyes for protection against it’s victim’s attempts to fight back. These sharks lived over 400 million years ago. Sharks of the past could mostly be identified by their teeth, because shark’s bodies are made of cartilage. Another shark that was focused on was called, Stethacanthus. This shark had a very unique look. Stethacanthus had a brush like decoration on the top of it’s head, and an extra fin like part that had the same bristle like decorations on it. These characteristics were thought to be used as suction cups, to hitch rides from larger fish. One of the most famous sharks that looks like an over...
Sallan, Lauren Cole, and Michael I. Coates. "End-Devonian Extinction and a Bottleneck in the Early Evolution of Modern Jawed Vertebrates." Diss. Cambridge University, 2010. 17 May 2010. Web. 25 Apr. 2012. http://www.pnas.org
Thesis: Sharks should be conserved because they are an important part of the ocean, attacks are often incidental, and human behavior influences the behavior of sharks.
Most people think that sharks are large, fast-swimmers, and savage predators. This is true of some species and groups should be interested of the appealing aspects of biology found within it: all sharks have an excellent sense of smell; some can detect electrical discharges; some sharks give birth to one of the
Sharks: Man-eating, stealthy, carnivorous creatures that roam the ocean. What could possibly come in the way of such beasts? Certainly puny humans could not interfere with these brutes. Or could we? It is estimated that over one hundred million sharks are killed each year (Why Are Sharks Endangered). All one hundred million deaths are due to mankind.
Forensic dentists have played a major role in the identification of remains in mass disasters, in crime investigations, in ethnic studies, and in the identification of decomposed and disfigured bodies in situations such as fire and car accidents (1). Teeth are considered to be a great form for identification as teeth are mostly composed of enamel. Enamel is the hardest tissue in the body and can withstand extremely harsh conditions (1). Two forms of dental identification of humans exist. These two forms are comparative and when no ante-mortem (before death) dental records are available. The comparative form of identification compares the ante-mortem and post-mortem (after death) dental records (1). Dental records con...
Studying the evolutionary history and adaption for this species is difficult and an ongoing struggle for scientists. It is classified in the order of Chondrichthyes suborder Elasmobranchii and family of Rhincodontidea. The difficulty in tracing this species evolutionary history stems from the fact that its ancestry dates back 245 million year ago to the Jurassic and Cretaceous