Bizarre ‘manta shark’ slowly cruised the oceans 93 million years ago

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An artist’s reconstruction of the ancient shark Aquilolamna milarcae

Vullo et al., Science (2021)

The discovery of a fossil in a Mexican quarry has revealed that a bizarre shark with manta ray-like wings slowly cruised the oceans more than 90 million years ago.

Named Aquilolamna milarcae, the shark was unique in being wider than it was long, with a wingspan of 1.9 metres and a body length of about 1.6 metres. Romain Vullo at the University of Rennes in France, who helped describe the species, says the shark’s distinct body shape and wide mouth suggests it hoovered up plankton.

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“As this shark probably fed on plankton, it didn’t need to go fast. Like modern manta rays, relatively slow swimming was enough to eat plankton,” says Vullo. But unlike manta rays, which use their pectoral fins for propulsion, the shark probably used them more like a stabiliser, relying on the fin at its rear to propel it along.

As the only known specimen, it is unclear whether the fossil belonged to a juvenile or mature shark. However, Vullo suspects it was probably an adult and the species was probably a medium-sized shark, growing to 3 metres long at most. Its teeth were probably very small.

Vullo and his colleagues compared the fossil with 26 modern shark species and, based on the shape of its vertebrae and the skeleton of its tail fin, assigned it to the order Lamniformes, which includes great white sharks.

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The fossil specimen of the “manta shark” called Aquilolamna milarcae

Vullo et al., Science (2021)

Found in 2012 in the Vallecillo limestone quarry in Nuevo León, north-eastern Mexico, the shark lived 93 million years ago in the Late Cretaceous epoch, 30 million years before manta and devil rays. Vullo suspects that the species was wiped out in the global mass extinction event that happened 66 million years ago, which killed off most dinosaurs and three quarters of life on the planet.

While the shape of Aquilolamna milarcae is exceptional – “really weird, strange”, says Vullo – the time it lived was known as an incredibly diverse period for sharks, judging from fossil shark teeth. “On evolution, it tells us that sharks occupied some ecological niches that today are restricted to other groups, such as rays,” says Vullo.

Journal reference: Science, DOI: 10.1126/science.abc1490

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