Earth’s ancient ‘goldilocks zone’ discovered in grand canyon depths

A newly discovered species of priapulid—commonly known as penis or cactus worms—has been unearthed in the Grand Canyon. Once abundant during the Cambrian period, these worms are now nearly extinct. This particular specimen featured an extensible mouth armed with hundreds of intricate, branching teeth used to sweep in food particles. Owing to its distinctive size and exotic dental arrangement, researchers named it Kraytdraco spectatus, inspired by the krayt dragon from the Star Wars universe. (Image: Rhydian Evans)

Under towering cliffs and twisting trails, the Grand Canyon has unveiled something quite unexpected: fossils of ancient soft-bodied animals from more than 500 million years ago. The finding, discovered along the Colorado River in 2023, is the first of its kind in this celebrated landscape and provides scarce insights into a dynamic and pivotal chapter of life's history.

A Window into the Cambrian World
Researchers from Cambridge University organised the expedition, and they discovered 507- to 502-million-year-old fossilised remains. This was the Cambrian explosion time when life accelerated fast in varied and unexpected ways. The fossilised remains are early molluscs, spiny worms, and filter-feeding crustaceans—most of which were preserved in fine detail. Scientists dissolved the mudstone samples in acid, filtered the sample, and then brought out the ancient remnants under high-powered microscopes.

These fossils are unique not just for their age but for their environment. Unlike previous discoveries from oxygen-poor settings, this fossil site sat in nutrient-rich, oxygenated waters. The conditions—neither too deep nor too shallow—created a perfect zone for evolutionary experimentation. Scientists describe it as a kind of "evolutionary sweet spot," where complex traits and behaviours had the best chance to develop.

From Star Wars to Prehistoric Worms
One of the most unusual finds was a newly identified species of priapulid worm. With rows of branching teeth and an extendable mouth, it was named Kraytdraco spectatus—after the krayt dragon from the Star Wars universe.

This creature likely swept food particles into its mouth with its complex anatomy. Other fossils show brine shrimp-like crustaceans using hairy limbs to feed and molluscs scraping algae from rocks using belts of tiny teeth.

The fine detail preserved in these fossils, including food particles near mouths and grooves on teeth, paints a vivid picture of early ecosystems. Tracks and feeding marks found throughout the canyon also helped researchers reconstruct daily activity.

Fossils That Speak to the Present
Lead researcher Giovanni Mussini said the fossils help us understand not just ancient life, but the conditions that foster innovation. Just as economies grow in times of abundance, so too did early life when resources allowed it. Evolution flourished through complexity, risk, and adaptation.

The study was published in Science Advances and supported by the UK’s Natural Environment Research Council and the US National Science Foundation. According to Mussini, even the tiniest creatures from the sea floor still have stories to tell.