Burgess Shale Worm
A fossilized Spartobranchus tenuis from the Burgess shale in Canada. The animal contains features of modern acorn worms and modern tube worms called pterobranches.
Spartobranchus tenuis in a tube. The worms look like modern free-living acorn worms, but resided in tubes. Modern mini-tube worms called pterobranches may have evolved from worms like this.
The modern acorn worm Harrimania planktophilus. The acorn worms are about 1.2 inches (32 millimeters) long when uncoiled.
Undescribed Acorn Worm
A modern-day acorn worm about 3.5 inches (88 mm) long.
A modern pterobranch, Rhabdopleura normani. Each of these tube-dwelling worms is only 0.02 inches (0.5 mm) long.
A modern tubular colony created by pterobranches. These tubes are similar to those seen fossilized in the Burgess shale.
A reconstruction of Spartobranchus tenuis within and outside of their tubes.
Worm in Tube
A close-up of Spartobranchus tenuis in its tube.
The Burgess shale in Yoho National Park, British Columbia, where the Spartobranchus tenuis fossils are found.
Burgess shale quarries on Fossil Ridge in Yoho National Park.
Burgess Fossil Quarry
A close-up of a fossil quarry in the Burgess shale in Yoho National Park.
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Stephanie Pappas is a contributing writer for Live Science, covering topics ranging from geoscience to archaeology to the human brain and behavior. She was previously a senior writer for Live Science but is now a freelancer based in Denver, Colorado, and regularly contributes to Scientific American and The Monitor, the monthly magazine of the American Psychological Association. Stephanie received a bachelor's degree in psychology from the University of South Carolina and a graduate certificate in science communication from the University of California, Santa Cruz.