All About Shark Evolution Through The Years

ByJames Luthor

The sharks have known to be evolved about 400 million years ago which makes it 200 million years before the dinosaurs existed. They are thought to have descended from a small leaf-shaped fish without any eyes, fins or bones. They are known to have evolved into 2 main groups existing even today, namely, bony fish (Osteichthyes) and cartilaginous fish (Chondrichthyes which include the sharks, skates, rays and chimaera).

The document records of the fossils hold information of over 3000 shark species. It is believed that many more sharks have existed but have disappeared without leaving any trace and so there have been no record of fossils. After a shark dies, its skeleton rots away because it is made of cartilage and not bone. This is the reason why the only shark fossils found are teeth, dermal denticles and fin spines.

The scientists can tell a lot from only these fossils, especially from the teeth. They can easily determine what the shark fed on and also identify the family of species it belonged to. The fossil records of the sharks are abundant and diverse. They have revealed that many species living around 150 million years ago were identical to the ones existing today.

Sharks have always been the ones dominating the marine food chain. They were joined by the other huge marine reptiles, Mosasaurs and Plesiosaurs for a brief time but they made their place to the top again alone. They are the only group of the three to have survived till today.

The animal history of our planet can be broken down into 4 stages:

  • The Precambrian Supereon
  • This is the era which had absolutely no animal life to be seen.
  • The Paleozoic Era
  • The Paleozoic shark refers to the sharks that existed in the Paleozoic era of the shark evolution. This era started 542 million years ago and ended about 251 million years ago. This time is known to be the time of great change on Earth. Their fossils are also very famous and you can also find the Paleozoic shark teeth for sale.
  • The Mesozoic Era
  • Some of the shark of the previous Paleozoic era survived into this one. The end of this era saw a fall of the great marine reptiles. This era began 250 million years ago and ended around 65 million years ago.
  • The Cenozoic Era
  • This era began 65 million years ago and persists till date. This era is seeing sharks as the most threatened group of animals on the planet.

Author’s Bio: The author is an avid blogger. This article is about Paleozoic shark.