Mystery of fossilised ‘alien fish taco’ finally solved 500 million years on

Scientists think they’ve finally solved the mystery of one of the strangest sea creatures ever discovered.

Nicknamed the ‘alien fish taco’, the Odaraia is a bit of an oddity with its large eyes, taco-like shell, and tail resembling the rudder of a submarine.

But a new study has found two mandibles on Odaraia fossils – which makes it one of the earliest ancestors of the majority of animal species on Earth today.

A mere 500 million years since the creature prowled our oceans, evolutionary biologist Alejandro Izquierdo-López led the study which discovered the Odaraia’s weird biology.

Alejandro, from the University of Toronto, explained: ‘Odaraia is an arthropod, an animal not very different from a crab or a shrimp.

‘It has a pair of large eyes, a couple of “jaws” on its mouth, and a long body with almost 30 pairs of legs.

‘Its tail looks exactly like the rudder of a submarine, or a shark’s tail.

‘Half of its body is enveloped in a shield or carapace, which has the shape of a tube, or “taco” as we nickname it.

‘People like nicknames, but is not a fish at all. The tail is what probably makes people call it a fish, as it does look like something we would see in today’s fishes.

‘Its shield or carapace envelops its body like a taco – you can also imagine an animal swimming inside a tube, with the tube being part of its body too.

‘I suppose it is a bizarre combination of traits, and thus alien.’

Classification of the Odaraia has proved ‘enigmatic’ for scientists, according to the Royal Ontatio Museum, but thanks to palaeontologists examining its fossils and discovering those mandibles, the creature can now officially be classed as a mandibulate.

Some 150 fossils, collected between 1975 and 2000, were analysed for the research that led to the major breakthrough.

Odaraia were first discovered in the 1910s in the Burgess Shale, a fossil site in British Columbia, Canada.

Alejandro explained why the classification is so crucial: ‘It’s a group of animals that today encompasses shrimps, centipedes or insects. These represent the majority of animal species on Earth.

‘Understanding how these animals looked and behaved 500 million years ago gives us some clues about why they became so successful.

‘We think Odaraia was hunting groups of small prey, detecting them with its large eyes.

‘Then, prey would go across its “taco” carapace, and there, they would have been captured by its 30 spiny legs.

‘The legs probably brought the food towards Odaraia’s mouth, where the mandibles would have broken the food apart.

‘The animals that lived in the Burgess Shale were tropical animals living in shallow seas.

‘We think Odaraia was probably able to swim across the water column, and was not stuck to the seafloor, as other animals of that time were.’

Alejandro and his co-author, palaeontologist Jean-Bernard Caron, published their study in the journal Proceedings B.

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