Mystery of 'alien fish taco' solved!
Prehistoric oddity revealed to be among oldest ancestors of modern animals
THE mystery of a bizarre sea creature dubbed the “alien fish taco” has been solved, 500 million years after it prowled the oceans.
With its big eyes, its taco-like shell, and its tail like the rudder of a submarine, scientists were unsure what to make of the strange Odaraia.
Now a new study has found two mandibles on Odaraia fossils, revealing it to be one of the earliest ancestors of the majority of animal species on Earth today.
Lead author Alejandro Izquierdo-López, an evolutionary biologist at the University of Toronto, described the prehistoric critter’s weird biology.
He said: “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.”
It’s an otherwordly mix that’s seen the species branded an “alien fish taco”.
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“People like nicknames, but is not a fish at all,” said Alejandro.
“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.”
So strange is the Odaraia, that its classification had proved “enigmatic” for scientists, according to the Royal Ontario Museum (ROM).
But now paleontologists examining Odaraia fossils have discovered they had two mandibles, each brandishing six or seven teeth, placing it among the earliest mandibulates.
Izquierdo-López said: “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.”
Scientists also discovered the animal’s unusual hunting method.
Alejandro said: “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.”
Odaraia were first discovered in the 1910s in the Burgess Shale, a fossil site in British Columbia, Canada.
But it was analysis of 150 fossils collected between 1975 and 2000 that held the key to the new breakthrough.
Izquierdo-López said: “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.”
The biologist also paid tribute to Derek Briggs, a professor who hypothesised in the 1980s that Odaraia might have had mandibles.
“This tells us that when you do really good work on a fossil it can withstand for decades,” he said.
Alejandro and his co-author, Jean-Bernard Caron, a ROM palaeontologist, published their study in the journal Proceedings B.