Connor: Blog Of The Day

In order to give myself more of a challenge, I decided to research the evolution of sharks.  Modern sharks appeared about one hundred and fifty million years ago.  Because sharks existed for millions of years and only leave teeth fossils, it is hard to track their evolution.  Sharks are among the oldest creatures on the planet, the plankton being the oldest group.  Before researching I knew of one type of shark that was now extinct, The Megalodon shark.  It had a gigantic set of teeth, much bigger than that of modern predatory sharks.

The creature that evolved into sharks or stingrays was most likely a starfish or starfish like creature.  The first jawed fish swam about 400 million years ago at the earliest.  The Agnatha, which appeared 500 million years ago, was the first fish and bore a resemblance to modern sharks.  Following that ancient fish, we have the Chondrichthyes, the ancestor of modern sharks.  After that we have the first shark itself, Cladoselache, which lived 350 million years ago.  The best entire fossil of a shark was a fossil of Cladoselache,  the fossil was found in Lake Erie perfectly intact.  It had two low dorsal fins and pectoral fins and its eyes were far forward on the head.  The mouth was at the front of the head.

In short it looked like almost modern shark.  The teeth on the other hand had a central cusp and were extremely sharp.  It seems the diet of the first shark was the same as for modern sharks.  Modern sharks have a lower mouth than the first shark did.  Now with the perfect shark fossil people can find a good baseline for the other ancient sharks.  The first shark is not the first member of the kingdom that sharks are included in.  Modern sharks have changed for centuries.  Ancient sharks had bigger, sharper teeth and would be more dangerous if they were alive in modern times.  I mean that they would be dangerous to humans and sharks alike.