From fossil records, the white shark, Carcharodon carcharias, first appeared around 11 million years ago, and whilst the evolution of sharks is well documented from fossilized teeth found worldwide, the white shark’s exact ancestry and evolution (as with the living animal) remains clouded. Some scientists believe the white shark is descended from the megatooth shark (Carcharocles megalodon, formerly known as Carcharodon megalodon) whilst other scientists believe the true line originates from Isurus (modern mako sharks). Originally the megatooth shark was grossly exaggerated as the first mock-up jaws were constructed from similarly sized teeth making the whole jaw and resulting estimated shark size truly enormous.
Reconstructed jaws of Carcharocles megalodon by the American Museum of Natural History, New York. This 1927 reconstruction is now thought to be about 30% too big, based on what is known about the teeth. Photo Credit: Wikimedia
It is unusual to find a cluster of fossil teeth from one shark. Normally, fossil shark teeth are found isolated. The way in which teeth grow into place in living sharks explains the abundance of single fossil teeth. In living sharks, old teeth are shed regularly as new teeth move into position in the jaws. The shed teeth fall to the sea floor where, because they are formed of resistant minerals, they fossilize readily. As more studies of the modern white shark (and other sharks) were made, scientists realized that as with the modern white shark, the megatooth shark teeth would not have all been the same size and, with more fossilized teeth being uncovered, and the rare discovery of a complete fossilized tooth set, a far more accurate jaw (and later, vertebrae) was mocked up. Carcharocles megalodon was still a huge animal (see comparison below), thought to prey on whales (fossil whale bone has been found on numerous occasions with the tail-tail lacerations from the megatooth teeth.)
Illustration showing size comparison between C. Megalodon and C.carcharias.
When you examine a megatooth shark tooth you can instantly see the resemblance to the modern great white shark and it is easy to see why so many scientists are convinced that Carcharocles megalodon is the evolutionary grandfather to the modern white shark. It is when entire tooth sets are compared that disparity occurs however.
Carcharocles megalodon teeth display the serrations synonymous with modern white sharks. Early mako shark ancestors such as Isurus hastalis lacked these serrations however the overall dentition shape of early Isurus sp. is close to that of juvenile modern white shark.
Carcharocles megalodon (left) and Isurus sp. upper jaw teeth
The third tooth from centre of the upper jaw of the white shark is prominently curved forward, as is C. megalodon, in stark difference to Isurus sp. which curves backward. Additionally, teeth grouping and numbers of Isurus are a far closer match to the modern white shark.