Shark week is almost here!! I just love those shows - the earliest known sharks date back more than 420 million years.
Wow that's really old? Have sharks changed much in that time?
Well the term shark has been used for extinct members so yes, they have changed a bit.
Interesting... Sharks really scare me ever since I saw Jaws...
Megalodon
Megalodon ("Carcharocles megalodon"), meaning "big tooth", is an extinct species of shark that lived approximately 23 to 3.6 million years ago (mya), during the Early Miocene to the Pliocene. It was formerly thought to be a member of the family Lamnidae, making it closely related to the great white shark ("Carcharodon carcharias"). However, presently there is near unanimous consensus that it belongs to the extinct family Otodontidae, which diverged from the ancestry of the great white shark during
eugenedontidans.
Under this broader definition, the earliest known sharks date back to more than 420 million years ago. Acanthodians are often referred to as "spiny sharks"; though they are not part of Chondrichthyes proper, they are a paraphyletic assemblage leading to cartilaginous fish as a whole. Since then, sharks have diversified into over 500 species. They range in size from the small dwarf lanternshark ("Etmopterus perryi"), a deep sea species of only in length, to the whale shark ("Rhincodon typus"