Sharks: A Timeline Of Shark Evolution

Sharks: The Evolution For roughly 420 million years, the greatest predator of the ocean has been swimming freely around in the water (450 Million Years of Sharks). Fish scurry away escape the rows of teeth in the jaws of a shark. With over 400 species of shark, how did they all get here? (A Timeline of Shark Evolution). Most importantly, how did they get such unique features that help them become the rulers of the ocean? In the article titled “Sharks,” it states, “[Sharks] range in size from the length of a human hand to more than 39 feet (12 meters) long” (Frost). All of these different sized sharks evolved from the same species, that roamed millions of years ago. Sharks have roamed the waters 200 million years longer than dinosaurs have

This shark lived around 360 million years ago and swam in North American and European waters (Britannica). How does the Cladoselache differ from modern day sharks? For starters, Cladoselache sharks did not have ‘claspers’, which is what modern day male sharks use during reproduction. Scientists are still unsure on how Cladoselache sharks mated, being that they didn’t have the claspers to transfer sperm (Pepper). The structure of the mouth was also something scientists noticed was different. The mouth of a Cladoselache was aligned properly, not like modern day sharks that have their top jaw hang over their bottom jaw. Darren Pepper, author of the article titled “Cladoselache” wrote, “The jaw joint appears to have been quite weak, but was supported by powerful muscles, something that would have enabled Cladoselache to tackle larger prey” (Pepper). The last difference Pepper talks about is the number of gills these sharks had. A Cladoselache shark could have had up to seven gill slits, meanwhile modern day sharks only have up to

Prehistoric sharks weren’t very large, as mentioned earlier. Being so small, they were often meals for bigger animals swimming in the ocean. Now, sharks such as the hammerhead shark and the great white shark are apex predators, meaning they are at the top of the food chain. Sharks have grown into a variety of sizes, ranging from the smallest shark, the dwarf lantern reaching a maximum of 8.5 inches long, to the largest shark, the extinct megalodon shark, reaching a maximum of 59 feet long (Megalodon & 20 Smallest Sharks). All of these different sharks descended from the prehistoric sharks, and have evolved from 16 inches to being up to 59 feet, moving sharks way up the food chain. Their fins have evolved into the perfect size for their body, to help them swim more swiftly through the water. Sharks pectoral fins are now as long or longer than the shark’s dorsal fin to provide fast movements. The tails of a shark now have more muscle, to let them swim further than they used to be able to. The male sharks, now have developed the claspers they need in order to reproduce properly and more effectively, like said before. Involving the head of the shark, they have changed in two major ways. Firstly, the teeth of sharks used to be flat. Now, shark teeth are very sharp, in order to be able to cut through the flesh of their prey with ease. Secondly, the jaws of sharks have become more