Megalodon

? Megalodon Conservation status: Fossil Scientific classification Kingdom: Animalia Phylum: Chordata Class: Chondrichthyes Subclass: Elasmobranchii Order: Lamniformes Family: Lamnidae Genus: Carcharodon Species: megalodon Binomial name Carcharodon megalodon Agassiz, 1843 Megalodon is also a tradename for a make of rebreather for scuba diving. The Megalodon or Megatooth shark (Carcharodon megalodon, from ancient Greek, megalos + don, lit. "big tooth") was a giant shark that probably lived between 20 and 1.2 million years ago (some suggest the shark might have died out more recently, or even might still be alive; see "Relict" below) The Megalodon is known only from fossil teeth and a few fossilized vertebral centra, and a very few incomplete skeletons (vertabrae columns and associated teeth). The teeth are in many ways similar to great white shark teeth and can measure over 7 inches long (maximum slant length); recent studies cited by Roesch suggest Megalodon was a "close relative" of the great white. A growing number of researchers dispute this, however, and reason the similarity of the teeth to the great white shark is simply due to convergent evolution. The best educated estimates of this creature's maximum size range from 40-50 feet (about 12-15 metres) Previous much larger reconstructions of the shark's size, up to about 100 feet (30 m), are generally considered inaccurate. Around 1995 the species was proposed to be placed in the new genus Carcharocles. To date this has not been resolved. Many paleontologists are now favouring Carcharocles and others with more of a marine biology background maintaining its link to the great white shark by placing Megalodon within the Carcharodon genus. Carcharocles proponents give Megalodons likely ancestor as Otodus obliquus from the eocene epoch, and the ancestor of the great white shark not Megalodon but Isurus hastilis, the "broad tooth mako". There is a theory that the adult Carcharodon megalodon fed largely on whales and went extinct as the polar seas became too cold for sharks, letting whales go out of reach of sharks for the summer. Relict While most mainstream experts contend that available evidence suggests that the Megalodon is extinct, the idea of a relict population seems to have seized the public imagination, though most evidence supporting such ideas is generally seen as scant and ambigous. Megalodon teeth have been discovered that some argue date as recently as 10,000 to 15,000 years ago. This claim is based on the discovery of two teeth by the HMS Challenger (these teeth were dated by estimating the amount of time it took for manganese to accumulate on them, althought it is quite possible the teeth were fossilized before being encrusted). Others have countered that such recent estimates for theses teeth are inaccurate, and "claims of post-Pliocene C. megalodon ... are erroneous" and based on outdated testing and methodology. [1] Roesch and others also note that Megalodons were probably coastal sharks, and that deep-sea survival is extremely unlikely. In addition, bones and carcasses of very large sperm whales have reportedly been found with megalodon teeth jammed into them. Such tales are most likely a form of urban legend, as such discoveries have thus far escaped the notice of shark experts, who would be immensely interested in such reports, if verified. Some relatively recent reports of large shark-like creatures have been interpreted as surviving Megalodons, but such reports are usually considered misidentification of basking sharks, whale sharks or other large creatures. One well-known exampled was reported by writer Zane Gray. It is possible, but unlikely, that some of these sightings might be due to abnormally large Great White Sharks. One famed example is this, told by Australian naturalist David Stead. Though widely circulated, this account is of generally regarded as of little value, because most of the claiments are anonymous: "In the year 1918 I recorded the sensation that had been caused among the "outside" crayfish men at Port Stephens, when, for several days, they refused to go to sea to their regular fishing grounds in the vicinity of Broughton Island. The men had been at work on the fishing grounds—which lie in deep water—when an immense shark of almost unbelievable proportions put in an appearance, lifting pot after pot containing many crayfishes, and taking, as the men said, "pots, mooring lines and all". These crayfish pots, it should be mentioned, were about 3 feet 6 inches [1.06 m] in diameter and frequently contained from two to three dozen good-sized crayfish each weighing several pounds. The men were all unanimous that this shark was something the like of which they had never dreamed of. In company with the local Fisheries Inspector I questioned many of the men very closely and they all agreed as to the gigantic stature of the beast. But the lengths they gave were, on the whole, absurd. I mention them, however, as a indication of the state of mind which this unusual giant had thrown them into. And bear in mind that these were men who were used to the sea and all sorts of weather, and all sorts of sharks as well. One of the crew said the shark was "three hundred feet [90 m] long at least"! Others said it was as long as the wharf on which we stood—about 115 feet [35 m]! They affirmed that the water "boiled" over a large space when the fish swam past. They were all familiar with whales, which they had often seen passing at sea, but this was a vast shark. They had seen its terrible head which was "at least as long as the roof on the wharf shed at Nelson's Bay." Impossible, of course! But these were prosaic and rather stolid men, not given to 'fish stories' nor even to talking about their catches. Further, they knew that the person they were talking to (myself) had heard all the fish stories years before! One of the things that impressed me was that they all agreed as to the ghostly whitish color of the vast fish. The local Fisheries Inspector of the time, Mr Paton, agreed with me that it must have been something really gigantic to put these experienced men into such a state of fear and panic." In Fiction A supposed surviving population of Megalodon sharks has been the subject of fictional novels, including several by Steve Alten, and a feature-length movie entitled Shark Attack 3: Megalodon. External links Megalodon: Shark Glossary An impressive photograph of this shark's jaw More photos Carcharodon or Carcharocles? A Critical Evaluation of the Supposed Contemporary Existence of Carcharodon megalodon by Ben S. Roesch Does Carcharodon Megalodon Still Exist? by Richard J. Ravalli, Jr. Reconstructing Megalodon Megalodon fact file from BBC, with pictures and video [2] [3] Pictures and chat area of recent museum quality examples of megaladon taken from South Georgia riversde:Megalodon Search Term: "Megalodon" Categories: Sharks | Prehistoric fish | Extinct animals

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