The Evolution of Shark
by Breuna McNair
You all may this animal as a Shark but, the shark today we all know looked nothing similar to the photo above. Lets look at the Evolution of the Great White Shark.
picture from google.com
picture from http://dinosaurs.about.com
This is the first every know record of the Great Shark. This animal is called Helicoprion. It was found 420 or 450 million years ago in the Ordovician period. Even though the picture above looks big to us, scientists said that the first shark every known was quite small. The size of a shark back 420 millions ago can be compare to a catfish today in size and lenght.
This is the next known shark scientists found naming it Cladoselache. The Cladoselache was known to be swimming around 370 millions ago. Found in the Late Devonian period. The reason it is compare to the shark is the the scales and the characteristics of the Cladoselache is very similar to the Shark today .
Not to long after the Cladoselache scientists found Orthacanthus. The Orthacanthus, the most important discover of the evolution of the shark because not only did the found this one, scientist founded fossils of two more similar animals named, Stethacanthus and Xenacanthus. All three were known for to have scales of a shark and shape teeth like the shark of today have. All were around 5-7 inches long and weighed about 100 pounds each.
The Cretoxyrhina is the closest relative to the shark today looking almost exactly like it. Scientists estimate the Cretoxyrhina was alive in the Middle-late Cretaceous and is about 25 feet long and weigh about a ton. Scientists found the fossil first in 1840's.
Leading back to's today shark. Today shark appeared in the Cenozoic period and is still roaming around today. This shark can weigh up to 7000 and can be as long as 52 ft.