Grand Canyon Gives Up New Species From 'Goldilocks Zone'

A previously unknown species of penis worm navigated what's now the Grand Canyon half a billion years ago—making up part of a fascinating, first-of-its-kind discovery at the iconic US site. By dissolving fist-size rocks discovered along the Colorado River within the canyon, researchers led by the University of Cambridge revealed thousands of tiny fossils representing worms, mollusks, and crustaceans that lived between 507 million and 502 million years ago during the Cambrian Period, along with some of the planktonlike particles they consumed. They're the oldest set of well-preserved animal fossils to be found in the canyon, per the Washington Post, and point to an evolutionary hotbed.

Fossils of nonskeletonized Cambrian animals are extremely hard to come by, making the discovery of soft-bodied creatures especially important. These are "the first soft-bodied, or nonmineralized, Cambrian fossils from an evolutionary 'Goldilocks zone' that would have provided rich resources for the evolution of early animals to accelerate," per a release. "By combining these fossils with traces of their burrowing, walking, and feeding—which are found all over the Grand Canyon—we're able to piece together an entire ancient ecosystem," says paleontologist Giovanni Mussini, lead author of the study published Wednesday in Science Advances.

This part of the world was located closer to the equator and submerged beneath a warm, shallow, oxygen-rich sea during the Cambrian Period. "Where you have this high availability of resources, evolution was essentially going into overdrive," with animals developing risky adaptations, Mussini tells the Post. The newly discovered species of penis worm, or priapulid, is an example of that. Dubbed Kraytdraco spectatus after the toothy krayt dragon featured in Star Wars, the tiny worm could fold itself inside out, like the finger of a glove, exposing rows of teeth used to sweep up food particles. The team also discovered three other previously unknown species: two mollusks and a shrimplike animal with hairy limbs used to sweep plankton into its mouth, per the Post and New York Times.