Great whites 'not descendants of megasharks'



Great whites `not descendants of megasharks` 	Washington: The evolutionary history of the great white shark, which is one of the largest living predatory animals, has been debated by paleontologists for the last 150 years.

In a new study, University of Florida researchers have named and described an ancient intermediate form of the white shark, Carcharodon hubbelli, suggesting that the modern white shark likely descended from broad-toothed mako sharks.

The study deviates from the white shark’s original classification as a relative of megatooth sharks such as the extinct Carcharocles megalodon, the largest carnivorous shark that ever lived.

Based on recalibrated dates of the excavation site in Peru, the study also concluded the new species was about 2 million years older than previously believed.

“We can look at white sharks today a little bit differently ecologically if we know that they come from a mako shark ancestor,” said lead author Dana Ehret, a lecturer at Monmouth University in New Jersey who conducted research for the study as a UF graduate student.

“That 2-million-year pushback is pretty significant because in the evolutionary history of white sharks, that puts this species in a more appropriate time category to be ancestral or kind of an intermediate form of white shark,” Ehret stated.

Most ancient shark species are named using isolated teeth, but analysis of C. hubbelli, also known as Hubbell’s white shark, was based on a complete set of jaws with 222 teeth intact and 45 vertebrae.

The species was named for Gainesville resident Gordon Hubbell, a collector who recovered the fossils from a farmer who discovered them in the Pisco Formation of southern Peru in 1988.

Hubbell donated the specimens to the Florida Museum of Natural History on the UF campus in December 2009.

Researchers determined Hubbell’s white shark was related to ancient broad-toothed mako sharks by comparing the physical shapes of shark teeth to one another.

While modern white sharks have serrations on their teeth for consuming marine mammals, mako sharks do not have serrations because they primarily feed on fish. Hubbell’s white shark has coarse serrations indicative of a transition from broad-toothed mako sharks to modern white sharks.

The study has been published in both print and online in the journal Palaeontology.

ANI