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| | Shark Summary |
 | | Sharks do have hard teeth, and to a lesser degree hard scales and spines, which preserve well in the fossil record and are the main indicators of their presence in ancient times. |
 | | Shark eyes are similar to the eyes of other vertebrates, including similar lenses, corneas and retinas, though their eyesight is well adapted to their marine environment with the help of a tissue called tapetum lucidum. |
 | | Sharks include everything from the hand-sized pygmy shark, Euprotomicrus bispinatus, a deep sea species, to the whale shark, Rhincodon typus, which is known to grow to a maximum length of approximately 15 metres (49 feet) and which, like the great whales, feeds only on plankton. |
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