Paris (AFP)

Scientists have unearthed the fossil of a new extinct and "bizarre" species, dubbed the eagle shark, which likely fed on plankton before being replaced by manta rays, according to a study Thursday.

The 93-million-year-old specimen, Aquilolamna (eagle shark) milarcae, was discovered in an "exceptional conservation deposit" in northeastern Mexico, Romain Vullo, lead author of the study, told AFP. study published in Science.

Six feet long, its remarkable peculiarity is the thin pectoral fins extending on each side of its streamlined body, for a wingspan of 1.90 meter. Which made it, with a slender caudal fin, "an animal that moves slowly ".

- A glider -

"We can compare it by analogy with a glider (...), not at all adapted to a fast swim to pursue prey", according to the CNRS researcher at Géosciences Rennes, of the eponymous University.

If we add a large short head, and "no more teeth in the jaw of the specimen" found, - suggesting that they were very small -, we end up with "a combination of characters suggesting that he he's more of a plankton eater than a predator ".

At this time of the Cretaceous, we only know as the only lover of these tiny plant or animal organisms that the Pachycormidae, large bony fish, while the eagle shark has a cartilaginous skeleton.

That of all modern sharks.

The two groups will disappear with the great extinction of the species marking the end of the Cretaceous, 66 million years ago, when a gigantic meteorite hitting the Earth upset ecosystems and especially rarefied the source of plankton in the oceans.

The Pachycormidae have been replaced by large planktivorous sharks, like the current whale shark.

"The eagle sharks were gradually replaced by manta rays and devil rays, which developed at the beginning of the Tertiary era," says Vullo.

The researcher hopes that future excavations will make it possible to make the link between Aquilolamna and "isolated teeth, which could correspond to it", found in deposits of the same age.

They would belong to "a rather enigmatic plankton eater", which could be precisely the eagle shark.

- "Weird" animal -

The eagle shark was found in 2012, in a quarry which, when it hovered between two waters, "was well off the mainland, with a depth of several hundred meters".

This deposit, close to the border with Texas, "has preserved an entire oceanic ecosystem, that is to say of the high seas, with preserved oceanic sharks, fish, marine reptiles, ammonites", according to Mr. Vullo.

And it is by chance of a meeting with a specialist in ammonites, a kind of mollusks, that the eagle shark specimen came out of anonymity.

Romain Vullo met Professor Wolfgang Stinnesbeck, of the German University of Heidelberg, during a congress in Chile, "which had nothing to do with the paleontology of vertebrates, and even less of sharks".

The future co-author of the study "showed in his presentation an image of this shark, with a bizarre appearance, discovered five years earlier", to illustrate the richness of the Mexican site of Vallecillo.

They met there a year later to study the eagle shark, the first specimen of its species to be seen again.

A decidedly "bizarre" animal, as their study indicates in its introduction.

pcl / may / cb

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