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About 506 million years agoPeer-reviewed · 2 sourcesWell documented

Anomalocaris: the apex predator that was mistaken for three animals

On the timeline · around About 506 million years ago · The Preserved WindowsThe Preserved WindowsThe New Cast of AnimalsAnomalocaris: the apex predator that was mistaken for three animals

What happened

At up to a metre long, Anomalocaris was the largest hunter of the Cambrian seas, a swimming predator with grasping spiked appendages and a circular, tooth-lined mouth. For nearly a century it was not recognized as one animal at all. In 1892, Joseph Whiteaves described its grasping arms as the tail of a separate shrimp-like creature; Charles Walcott, working the Burgess Shale, identified its mouth as a jellyfish he named Peytoia; and Simon Conway Morris mistook its body for a sponge he called Laggania. Only in 1985 did Harry Whittington and Derek Briggs recognize that all three fossils were fragments of the same single animal. In 2011, a study in Nature examining fossilized eyes from an Australian Anomalocaris relative found each eye held at least 16,700 individual lenses, rivaling the resolution of a modern dragonfly's eye.

Why it matters

Anomalocaris shows both how alien the Cambrian could be and how easily fragmentary fossils mislead even careful scientists. Its eyes also settle one small piece of the causes debate directly: sophisticated predator vision existed in the Cambrian, whatever role it played in starting the explosion.

How we know

The single-animal identity rests on complete specimens found later that showed the mouth, arms, and body still attached to one another. The eye's lens count comes directly from counting individual lens facets preserved in fossilized eye tissue under a microscope, not from an estimate.

Sources

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Part of a timelineThe Cambrian Explosion9 events · How nearly every animal body plan alive today appeared within a geological blink, from the first mineral skeletons to the apex predators, calcite eyes, and first fish the fossil record preserves.View all →