This Weird, 500 Million-Year-Old Spiky Worm With Legs Actually Has a Descendant

Modern-day velvet worms’ jaws are repurposed former claws

An artist's interpretation of what Hallucigenia sparsa looked like. Photo: Elyssa Rider

Around 505 million years ago, a spiky worm with clawed legs crawled around the ocean floor in what is today the Rocky Mountains in Canada. From the beginning, it was an oddity. As writes, "The spines along the creature's back were originally thought to be legs, its legs were thought to be tentacles along its back, and its head was mistaken for its tail." In honor of its far-out looks, the paleontologist who discovered it in the 1970s named it Hallucigenia, the New Scientist reports

A group of modern animals, however, still echoes those outlandish traits. Researchers just discovered that Hallucigenia does indeed have still-living relatives. That ancient worm's descendents are the velvet worms, a group of animals that live in tropical forests.

Researchers magnified fossilized Hallucigenia specimens 1,000 times to reveal that their claws contained multiple layers, "stacked one inside the other like a conical onion," the authors describe in The Conversation. Those claws are reminiscent of the jaws of modern velvet worms, they realized. When they compared the anatomy and the known family tree of velvet worms to Hallucigenia, they realized that they seemed to have a modern day match. "Hallucigenia was not an evolutionary dead end," they conclude on The Conversation. "Rather, it represents an early pit stop on the way to the velvet worm body plan, which arose gradually over time."

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