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The first shark-like chondrichthyans appeared in the oceans 400 million years ago, [1] developing into the crown group of sharks by the Early Jurassic. [2] Listed below are extant species of shark. Sharks are spread across 512 described and 23 undescribed species in eight orders. The families and genera within the orders are listed in ...
In most oviparous shark species, an egg case with the consistency of leather protects the developing embryo(s). These cases may be corkscrewed into crevices for protection. The egg case is commonly called a mermaid's purse. Oviparous sharks include the horn shark, catshark, Port Jackson shark, and swellshark. [80] [82]
Sharks portal; Sharks constitute the superorder Selachimorpha in the subclass Elasmobranchii in the class Chondrichthyes.The Elasmobranchii also include rays and skates; the Chondrichthyes also include Chimaeras.
The International Union for the Conservation of Nature reports 35% of all shark species are threatened with extinction. That number has grown nearly 50% in a decade’s time. That number has grown ...
Over 1.5 million living animal species have been described—of which around 1 million are insects—but it has been estimated there are over 7 million in total. Animals range in size from 8.5 millionths of a metre to 33.6 metres (110 ft) long and have complex interactions with each other and their environments, forming intricate food webs .
Older than dinosaurs and trees, sharks have endured a lot throughout their 450 million years on Earth. They’ve even survived five mass extinctions, including the asteroid that wiped out 75% of ...
A mysterious shark that may count as the world’s largest predatory fish appears to be in decline off the U.S., prompting a rush to gather as much information as possible about the secretive ...
List of fatal shark attacks in the United States; Jersey Shore shark attacks of 1916 – series of shark attacks along the coast of New Jersey between July 1 and July 12, 1916 [4] Summer of the Shark – the name given to the summer of 2001 by American media outlets capitalizing on a bull shark attack and subsequent shark attacks [5]