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Meet Our Weirdest Ever Cousins

A school of vetulicolians swimming in the Cambrian ocean

Our strangest relatives? A school of vetulicolians swimming in the Cambrian ocean, 515 million years ago. Credit: Katrina Kenny

By Diego García-Bellido & Michael Lee

Strange-sounding and even stranger-looking, vetulicolians are close relatives of vertebrates.

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“Vetulicolians” sounds like a new race out of Star Trek. Indeed these 500 million-year-old fossils are so bizarre that they could be mistaken for aliens. They were tough-skinned blind creatures shaped like a figure-of-eight, with a drum-shaped head-end and a segmented tail. They were also important elements of Cambrian ecosystems. Larger than most of their fellow creatures, perhaps rendering them less prone to predation, they are some of the most abundant animals in Cambrian fossil sites after trilobites.

Yet their unfamiliar body plan has long challenged palae­ontologists. First discovered in 1911, they were put in the “too hard” basket and not described formally until new specimens were found in 1997 – and yet remained enigmatic.

The vetulicolians were a diverse group, with 14 species in four different families, they were 8–15 cm in length and spread over several continents: North America, China, Greenland and Australia.

Their lifestyle has been debated. It had been suggested that they grubbed about in the mud, though most people now think they swam in the water column.