Scientists' new discovery is a very old shark

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Say hello to Megalolamna paradoxodon(Credit: Kenshu Shimada)

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Megalodon fans, take note: in a paper published today, an international team of scientists announced the past existence of a shark that was closely related to the infamous prehistoric super-predator. Although it wasn't as large as the Carcharodon megalodon shark, the newly-described Megalolamna paradoxodon was similar in size to the present-day great white – and just as toothy.

Due to the fact that sharks' cartilaginous skeletons don't fossilize, paradoxodon was identified based solely on fossilized teeth found in California, North Carolina, Peru and Japan, which measured up to 4.5 cm (1.8 inches) in length. It lived approximately 20 million years ago during the early Miocene epoch, and was a member of the Lamniformes order – great whites and mako sharks are modern members of that same order.

A map showing locations where paradoxodon teeth have been found(Credit: Kenshu Shimada)

Focusing down a bit more, paradoxodon also belonged to the now-extinct Otodontidae family of "mega-toothed" sharks, of which the megalodon was a member. That said, although megalodons are estimated to have reached lengths of around 18 metres (59 ft), paradoxodon likely topped out at about 4 meters (13 ft).

Its front teeth were designed for grasping its prey (likely medium-sized fish), while those in the rear were aimed more at cutting. Although features of those teeth are in keeping with those of other members of the Otodontidae family, they also look somewhat like an oversized version of teeth from the existing salmon shark, which is a member of the Lamna genus. With that in mind, the new shark was given the genus name Megalolamna.

The species name paradoxodon (Latin for "paradoxical teeth") comes from the fact that there appears to be a 45 million-year gap between the time that it likely split from its closest relative to form its own species, and the time at which its fossilized teeth enter the geological record.

"It's quite remarkable that such a large lamniform shark with such a global distribution had evaded recognition until now, especially because there are numerous Miocene localities where fossil shark teeth are well sampled," says Prof. Kenshu Shimada, a paleobiologist at Chicago's DePaul University, and lead author of the study.

Other institutions taking part in the research include North Carolina State University, The University of Hong Kong and The Natural History Museum, London. The paper appears in the journal Historical Biology.

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