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Getting Our Teeth Into the Origins of the Great White Shark

Trying to Unravel the Carcharodon Family Tree

The ancestry of the famous shark that starred in “Jaws” is better understood after the publication of a scientific paper by American researchers that provides details of a transitional fossil between prehistoric Mako sharks and extant Great Whites.

Carcharodon carcharias (Great White Shark), was considered by many scientists to be a direct descendant of the enormous Megalodon shark (Carcharodon megalodon), one of the largest fish to have existed in the last twenty million years. Fossil teeth of Megalodon have been found in Europe, Asia, the Americas and Australasia, this large predatory shark which could have reached lengths over sixteen meters seems to have been very widely distributed. However, scientists were unsure of the exact phylogenetic relationship between this giant shark that died out around 1.6 million years ago and extant species such as the Great White.

Did the great whites descend from the extinct megalodon?

The problem with Lamniformes, the Order to which sharks belong, is that they have skeletons made of cartilage. This is rarely preserved in the fossil record, so there are few body fossils (other than teeth) for paleontologists to study. However, the discovery of a remarkably well-preserved set of jawbones, some articulated bones and numerous teeth, a number of which are still “in situ” with the jawbones, from a remote location in Peru has provided scientists with a clue. important on the origins of today’s Great Whites. This fossil suggests that the Great Whites, although similar in body plan and lifestyle to Megalodon, probably did not evolve from the same line of sharks. It appears that great white sharks share a common ancestor with the Mako nektonic shark.

The phylogenetic relationship between the species of sharks that make up the genus Carcharodon remains somewhat confusing. Megalodon itself may turn out to be more closely related to tiger sharks (Galeocerdo cuvier) than today’s Great Whites.

Similar teeth compared to fossil sharks

It is true that today’s great white sharks have teeth similar to those of the extinct megalodon. The shape of the serrations along the edge of the teeth are very similar, but when examined under a microscope, one can see that the denticles (the scientific term for these serrations) are very different. The extinct Megalodon teeth show very fine serrations while the Great Whites denticles are very coarse and much larger in comparison.

Professor Dana Ehret, from Monmouth University (New Jersey, USA), the lead author of the research paper suggested that one of the reasons why Megalodon was considered the ancestor of Carcharodon carcharias was that large blanks were used by anatomists and paleontologists to make mounted displays of Megalodon for museums and other institutions. If a modern shark had been used as the basis for assembling Megalodon, it’s no surprise that Megalodon reconstructions look like a Great White.

Serrated teeth provide a clue

Since the two Carcharodon carcharias and Carcharodon megalodon have serrations (denticles) on the edge of their teeth, this was taken as an indication that these species were closely related. However, when examined under a microscope, differences can be seen. Today’s Great Whites have very coarse serrations while those of the extinct Megalodon are much finer.

Serrations on the edge of shark teeth can be found in many extant and extinct shark species. Some, indeed, indicate phylogenetic relationships, while other examples are likely the result of convergent evolution. Convergent evolution occurs when two organisms, not necessarily closely related, evolve in similar ways by adapting to particular circumstances and environmental pressures. For example, bats and most birds can fly, both have evolved wings but the structure of these wings is very different; birds and bats are not closely related.

Carcharodon hubbelli

The newly described species, known as Carcharodon hubbelli was named after a beautifully preserved shark specimen that was found at a fossil dig site, part of the Pisco Formation in southwestern Peru. The very dry atmosphere has made it possible to preserve fossils in exceptional conditions even when they have been eroded from sedimentary rock. Carcharodon hubbelli the material consisted of jaws, teeth some of which were still in situ in the jaws and other elements of the fossil including part of the animal’s spine. The Pisco Formation has already provided scientists with amazing fossils that provide insight into Pliocene marine fauna with the discovery of a gigantic predatory whale (leviathan melvillei), which probably fed on Megalodons.

Meet the fossil remains

The new shark species proves that Great Whites are descended from ancient Mako (mackerel) sharks. Described as a “transitional species”, C. hubbelli, named after Gordon Hubbell, the scientist who discovered the fossil, suggests that the Tall Whites are not the descendants of Carcharodon megalodon.

The mixture of Mako and Great White anatomical features includes the outward curvature of the third anterior tooth in the jaws of the Peruvian specimen. This is very similar to the dentition seen in modern Mako sharks today. Initially, the fossil was dated to around five million years old, but this posed a problem for paleontologists who suspected that this specimen represented an ancestor of today’s Tall Whites. Five million years ago, the lineage of the Great Whites already existed so how could it C. hubbelli to be the ancestor of this part of the Carcharodon family?

Dates of the biostratigraphic study until the Pliocene

A biostratigraphic study of invertebrate fossils found in the strata established that this fossil was in fact much older, around 6.5 million years old, making it more likely that this specimen represents an ancestor or intermediate to Great White.

Modified Mako Sharks

The American research team concluded that “Jaws” is essentially a highly modified Mako shark (genus Isurus). Mako sharks are highly streamlined, open-water predators. They are primarily fish eaters (piscivores), but have been known to become aggressive and attack people. The Great White line has adapted to eating larger prey such as dolphins, turtles and seals. Mako sharks are occasionally caught by anglers off Cornwall. These sharks having followed the Gulf Stream to the east, but Makos are more normally associated with warmer waters.

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