Sharks are an aggregation of fish described by a cartilaginous skeleton, five to seven gill openings on the sides of the head, and pectoral balances that are not intertwined to the head. Present day sharks are ordered inside the clade Selachimorpha (or Selachii), and are the sister gathering to the flashes. Nonetheless, the expression "shark" has moreover been utilized for wiped out parts of the subclass Elasmobranchii outside the Selachimorpha, for example Cladoselache and Xenacanthus. Under this broader definition, the soonest known sharks date from more than 420 million years prior. 
Sharks
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Sharks
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