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Megalodon

  Megal皇冠体育APPlodon (Carcharocles megalodon), meaning "big tooth", is an extinct species of shark that lived 皇冠体育在线文娱直播roximately 23 to 2.6 million years ago (mya), during the Early Miocene 皇冠体育APP to the end of the Pliocene. It was formerly thought to belong to the family Lamnidae, making it closely related to the great white shark (Carcharodon carcharias). However presently there is near unanimous consensus that it belongs to the extinct family Otodontidae, which diverged from the ancestry of the great white shark during the Early Cretaceous. Its genus placement is still debated, authors placing it in either Carcharocles, Megaselachus, Otodus, or Procarcharodon.

  Scientists suggest that megalodon looked like a stockier version of the great white shark, though it may have looked similar to the basking shark (Cetorhinus maximus) or the sand tiger shark (Carcharias taurus). Regarded as one of the largest and most powerful predators to have ever lived, fossil remains of megalodon suggest that this giant shark reached a length of 18 meters (59?ft). Their large jaws could exert a bite force of up to 110,000 to 180,000 newtons (24,000 - 41,000 lbf). Their teeth were thick and robust, built for grabbing prey and breaking bone.

  Megalodon probably had a major impact on the structure of marine communities. The fossil record indicates that it had a cosmopolitan distribution. It probably targeted large prey, such as whales, seals, and sea turtles. Juveniles inhabited warm coastal waters where they would feed on fish and small whales. Unlike the great white, which attacks prey from the soft underside, megalodon probably used its strong jaws to break through the chest cavity and puncture the heart and lungs of its prey.

  The animal faced competition from whale-eating cetaceans, such as Livyatan and other raptorial sperm whales, which have been cited as a cause of the shark's extinction but actually died out before, or at the same time as, the shark. Ancestral orcas such as Orcinus citoniensis have also been cited as outcompeting the shark, but their skull and teeth are less formidable than that of mammal-eating orcas today, suggesting they were not competing heavily with megalodon. As it preferred warmer waters, it is thought that oceanic cooling associated with the onset of the ice ages, coupled with the lowering of sea levels and resulting loss of suitable nursery areas, may have also contributed to its decline. A reduction in the diversity of baleen whales and a shift in their distribution toward polar regions may have reduced megalodon's primary food source. The extinction of the shark 皇冠体育在线文娱直播eared to affect other animals; for example, the size of baleen whales increased significantly after the shark had dis皇冠体育在线文娱直播eared.

  According to Renaissance accounts, gigantic, triangular fossil teeth often found embedded in rocky formations were once believed to be the petrified tongues, or glossopetrae, of dragons and snakes. This interpretation was corrected in 1667 by Danish naturalist Nicolas Steno, who recognized them as shark teeth, and famously produced a depiction of a shark's head bearing such teeth. He described his findings in the book The Head of a Shark Dissected, which also contained an illustration of a megalodon tooth.

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