Megalodon still roams the seas

Thanks for the topic Dagolas. According to the ReefQuest Centre for Shark Research, the Megalodon "extinction [occurred] in the Plio-Pleistocene (1.6 million years ago)." [1] The ReefQuest Centre explains that we know Megalodon is extinct because we find fossilized remains of its teeth throughout the entire world, suddenly ending 1.6 million years ago. The ReefQuest Centre answers many of the main arguments claiming that Megalodon is still alive. 1) Only 5% of the deep sea has been explored Reefquest Centre says, "Megalodon seems to have been limited to warm, shallow seas near coastlines and there is no evidence it had any specializations that would have enabled it to survive the intense cold of the deep-sea." [2] The fact that no one has seen a giant shark (large enough to swallow a rhinoceros whole) swimming in shallow waters is pretty good evidence of its extinction. 2) The rest are just different appeals to ignorance. What caused Megalodon's extinction? Answer: the closing of the Central American Seaway (through the land formation of the Isthmus of Panama), which did 3 things. 1. Ocean cooling The Isthmus of Panama altered ocean currents by cutting off the formerly open Central American Seaway, which resulted in a significant cooling in ocean temperatures during the Pliocene Era and the formation of ice sheets at the poles. [3] The colder temperatures significantly reduced the number of waters that such a large cold blooded animal could survive in and reduced suitable nursery sites for breeding. Fossil evidence confirms a SIGNIFICANT thinning out of the Megalodon population during the Pliocene. [4] 2. Food supply dwindled During the Miocene, there were 20 species of large cetaceans for the Megalodon to prey upon. However, during the Pliocene, most went extinct or moved elsewhere. Fossil records show that whale migration patterns changed during this period to more arctic regions, eliminating these large animals as a potential food source to the Megalodon. [5] A large predator needs large prey, but since small prey were either dying or moving to more arctic regions, large prey were also either dying or moving to waters where the Megalodon could not follow. 3. New competition During the Pliocene, a large species of killer whale evolved to compete for the Megalodon's dwindling food supply. [6] Killer whales were faster than the sharks, in addition to being able to sustain colder climates, so the killer whales could hunt the Megalodon's food but the Megalodon could not hunt all of the killer whales' food, meaning the ultra large orcas were better predators. Faced with an already dwindling food supply and an inability to breed, the Megalodon ultimately succumbed to these better predators. It's pretty simple; a body with a large size has a number of tradeoffs - that large size requires more resources, is more inefficient, and is more difficult to heat. Without large prey animals, the large size did not have any benefits over predators with smaller sizes, ultimately leading to extinction in a battle for the survival of the fittest. [1] http://www.elasmo-research.org... [2] http://www.elasmo-research.org... [3] http://www.whoi.edu... [4] http://www.elsevier.com... [5] http://www.sdnhm.org... [6] http://www.science.smith.edu...