oddball

Look: Ancient shrimp-like creature sheds light on an evolutionary mystery

This five-eyed wonder is no longer in a class of its own.

by Jennifer Walter
Updated: 
Originally Published: 
F. Anthony

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During the Cambrian period, Earth’s oceans exploded with new species of swimming, segmented invertebrates — many that look more alien than Earthly.

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Take Opabinia regalis, for example.

The shrimp-like creature sported five beady eyes and a trunk-like appendage, used to shovel food into its mouth — kind of like an elephant.

It’s tough to picture exactly how opabiniids lived, and how they evolved into the species we see today.

That’s partially due to the fact that Opabinia regalis was the only opabiniid species on record. But an analysis adds new characters to its story.

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Researchers writing Wednesday in the journal Proceedings of the Royal Society B describe a new opabiniid species — one that was hiding in plain sight.

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S. Pates

The discovery stems from a fossil specimen unearthed in Utah at the Cambrian Wheeler Formation.

Researchers originally identified it in 2008 as a radiodont — cousins of opabiniids.

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Radiodonts were predators in the Cambrian world and lived all over the globe.

Though they had elongated bodies similar to opabiniids, radidonts didn’t have the same head structure or eyes as their cousins.

The head and eyes on the Wheeler Formation specimen weren’t well-preserved, meaning it wasn’t easy to identify the opabiniid without in-depth analyses.

S. Pates

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The research team compared the specimen to 43 other fossils and 11 living descendants of Cambrian arthropods.

That led them to conclude that the fossil was a member of a new species: Utaurora comosa.

U. comosa has similarities to both Opabinia and some radiodonts.

But it’s distinct enough to be an opabiniid species of its own, giving researchers new insight into how they evolved into the arthropods we see today.

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The Cambrian arthropods are the ancestors of centipedes, butterflies, and crabs.

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U. comosa’s classification reveals opabiniids survived longer into the Cambrian period and lived in more areas than previously realized.

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“This means Opabinia was not the only opabiniid, [and] Opabinia was not as unique a species as we thought.”

Stephen Pates, study co-author, in a statement.

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