There are more then 350 know species of sharks today, which can all be placed under 8 scientific orders that contain 30 families. They are placed into these categories by their shared characteristics, this is called taxonomy. The more closeley related species are placed in another family in the order.
SQUAINIFORMES: The angel shark as they are commonly known are characterized by their RAY like flattened bodies. This order has one family which is called SQUATINDAE that contains about 13 species. The maximum size that can be attained by any one of these species is 4-6 feet in length.
PRISTIOPHORIFORMES: These shark are known as the saw shark. This order has only has one family PHISTOPHORIFORMES which contains five species. These sharks are easy to recongnize due to the fact that they posses an ellongated blade like snout that is lined with sharp teeth along the edges, thus, the name saw sharks.
SQUALIFORMES: The order possesses three family which consist of about 82 species. These sharks are characterized by their slender, cylinder-shaped bodies, long snouts with shortened mouths.
HEXANCHIFORMES: The Hexanchiformes or cow sharks, comprise of two families. Recognized by their six or seven pairs of gill slits, there sharks can often be found in deep water. The frilled shark (CHLAMYDISELACHUS ANGUINEUS) who?s appearance is quite unmistakable due to it?s “eel” like appearance, is perhaps one the strangest shark that exist today.
Shark fossil record is fargmentery at best. Most fossils found so far consist of nothing but teeth in some cases a few vertebra have been found. This is rare due to the fact that sharks have bones instead, they have cartiladge which countrary common belief is rather solid. In the rarest of cases complete fossil have been discovered. Scientific data shows that following a period of great physiological changes. There was not to many changes in the sharks fossil in the millions of years, of studying the shark fossils.
The Hybodonts who made their appearance some 320 million (years ago the age of the dinosaurs) where quite common through out both oceanic and fresh water. Due to reasons unknown to science both oceanic and fresh water hybodonts because exticnt at about the same time as the dinosaurs.
The largest shark to ever swim the oceans is called the megalodon. Many think that it?s ancestor to the great white shark however there is great controversy surrounding this matter. The size of the shark is 40 to 50 feet in length it is safe to say that megalodon is still considered to be largest predatory fish to have ever existed.
THE PERFACT PREDATOR:
The shark is considered by many to be the perfect predator. It?s perhaps the most perfectly adapted predator in it?s environment. The shark jaws another facinating development of evolution. Each species jaws are perfectly adapted to that sharks eating habits some sharks have long pointed teeth for cathing fish others have teeth contains the most of the species of sharks are harmless botton dwellers, like catsharks or houndsharks. However the most of those sharks are in danger of be coming extinct.
THE SHAPE OF SHARKS:
The sharks has all different kinds of shapes and sizes or sharks one can find in the ocean. Sharks posse a richness of diversity and body forms, ranging from the popular sharks. A good example of this is a Bizzare Goblin Shark. This sharks has a horn-like protrusion coming from it?s head. The body forms of sharks can be related to their way of life. Some like the angel and wobbegong sharks the shape of these sharks of these sharks is perfectly adapted to their environment and their way of life. All sharks swim by snaking their way through the water while using their pectoral fins for lift and direction.
Most attacks take place within 100 feet of the shoreline. However, it?s not impossible to be stuck on open sea. Sharks have been recorded following boats for many years. Sailors used to consider this a bad omen and would throw one man overboard to please the shark. If there is one drop of blood from a person a shark and sense 200 feet where the blood is coming from. The people most at risk of shark attacks are men from a shipwreck just floating in the open ocean. This is because there are usually large amounts of blood in the water. The most know shipwrecks that involved with sharks in the U.S.S. More then 500 people died by shark attacks. The most common shark that attacks is the blue shark.