Pre-Historic Sea Dogs

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Pre-Historic Sea Dogs The word shark is thought to be driven from the Mayan word xoc which can pronounced shawk or shock meaning fish. Sailors once called them seadogs because their relative resemblance of dogs and not until the late fifteen hundreds were they called sharks. Sailors saw one and began to call the sea dogs of the Caribbean Sea sharks and to eventually refer to sharks in whole as a species. Sharks are a part of group of fish that have been dated with a fossil record back four hundred fifty million years ago to the late Devonian period in which land vertebrates had not yet taken form. Most of the time only the teeth are found due to the internal skeleton made of cartilage in which easily decays. The teeth are made of material similar to bone which is easily fossilized. The oldest dated shark was from about three hundred seventy million years ago and is known as cladoselache. It was very primitive in that it had stiff triangular fins and unlike today’s moderns sharks did not have many rows of replaceable teeth. Although sharks did not appear on earth until about one hundred million years ago and were thought to be of decent of the mackerel shark modern day Great White Sharks teeth have been dated back sixty five million years ago to times when dinosaurs were still alive. Early in shark evolution two main families were created. One of the lineages in which most modern day sharks are decent of were equipped with coarsely serrated teeth. The other lineage were equipped with finely serrated teeth but could reach over 50 feet long and have been discovered to eaten large marine creatures such as whales. There are over four three hundred and seventy species of sharks ranging in size from the smallest shark the pygmy shark which doesn’t normally grow larger than six inches , to the whale shark which can attain sizes of thirty five to forty feet. They are

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