Carcharodon vs. Carcharocles

There is a major disagreement among scientists as to how C. megalodon should be classified. The controversy is that whether C. megalodon is a close relative of the extant great white shark or whether the two species are distant relatives. The trend among shark researchers is to dismiss the statement that C. megalodon is a close relative of the great white shark, in favor of citing convergent evolution as the reason for the dental similarity.

One school of thought insists that both megalodon and the White Shark are derived from Cretalamna via 'Carcharodon' orientalis, and are thus both members of the same genus (Carcharodon) and family (Lamnidae). Proponents of this theory include paleontologists Shelton Applegate, John Maisey, Robert Purdy and shark systematist Leonard Compagno.

The opposing school of thought insists just as strongly that Megalodon is derived from Cretalamna via Otodus obliquus, and that Carcharodon derived from a separate lineage. Further, 'Carcharodon' orientalis belongs in its own genus, Paleocarcharodon, and was an evolutionary dead end that did not give rise to any extant shark. Thus megalodon belongs in a separate genus (Carcharocles) and family (Otodontidae) from the modern white shark:

Proponents of this school include paleontologists Henri Cappetta, John Long, Mikael Siverson, and David Ward.

This table provides a brief point-counterpoint synopsis of some of the arguments on both sides of the Carcharodon-Carcharocles debate.

Although the Carcharodon cartel raises some compelling points, their evidence shows enough weaknesses to warrant caution in lumping Megalodon in the same genus as the modern White Shark. Extrapolation from one species to another is risky in practice, being fraught with inherent problems and perils. Several shark lineages have independently evolved teeth with a triangular, serrated blade, probably due to convergence borne of similar dietary and feeding habits. Interpreting fossil shark teeth is a highly subjective combination of training and experience; since no two researchers have exactly the same backgrounds, differences of opinion are bound to appear. And lastly, taphonomy (the science of puzzling out by what happened to a fossil or artifact after it was deposited - including how it was moved from its original resting place to where it was eventually found) can be quite convoluted and tricky. Fossil shark teeth that happen to be found together may not have come from the same individual, any more than leaves clogging a storm drain necessarily all came from the same tree.