A brand new species of ‘penis worm’ was found within the Grand Canyon

An historic cradle of evolution could have been found within the striped cliffs of the Grand Canyon.

Paleontologists have discovered an exceptionally well-preserved trove of fossils within the greenish shales of the Bright Angel Formation. Today, these shales overlook the Colorado River from varied factors all through the canyon, however they fashioned roughly half a billion years in the past, through the Cambrian Period.

The fossilized fauna embody refined organisms like a newly identified species of penis worm with a retractable mouth, in addition to mollusks and crustaceans that share similarities with fashionable animals, researchers report July 23 in Science Advances. The fossils paint an image of a thriving ecosystem during which organisms developed more and more advanced options, leading to a form of evolutionary arms race.

“There are only some kinds of settings which can really launch evolutionary innovation forward,” says paleontologist Giovanni Mussini of the University of Cambridge. “And the Grand Canyon was probably one of them back in the Cambrian.”

Fossil proof from all over the world suggests that the majority fashionable animal teams first appeared through the early Cambrian Period, amid a biodiversity growth referred to as the Cambrian Explosion. Many Cambrian fossils originated in areas as soon as comparatively far offshore that had been oxygen-poor, which lowered decomposition and promoted preservation. But such websites, which embody the well-known Burgess Shale within the Canadian Rockies, could not inform the story of life in additional liveable Cambrian ecosystems, Mussini says.

Half a billion years in the past, a lot of western North America would have been inundated in a shallow sea. The forms of sediments within the Bright Angel Formation counsel the layer fashioned on the traditional continental shelf at a depth of “at most, a couple dozen meters,” the place daylight might illuminate the seabed, Mussini says. “There was probably much more photosynthesis going on” in contrast with the Burgess Shale’s atmosphere.

What’s extra, the positioning would have in all probability been nearer to deltas and estuaries that delivered vitamins into the ocean. And in distinction to the darkish Burgess Shale, the sunshine coloration of the Bright Angel formation means that a lot of the natural materials was being recycled by a prolific fauna, Mussini says.

In 2023, he and colleagues spent weeks touring downriver on a dinghy by way of the Grand Canyon, stopping at seashores to pattern shales. Mussini was trying to find small carbonaceous fossils, which may protect in beautiful element animal stays missing bones or different laborious elements.

Finding such fossils “is partly a game of luck,” Mussini says, as they’re too small to identify by eye. So after gathering dozens of shale samples from all through the canyon, the researchers checked their bounty again within the lab by dissolving the samples in acid and selecting by way of the residue underneath a microscope. In whole, they recovered over 1,500 specimens, together with “the first exceptionally preserved Cambrian animals from the Grand Canyon,” Mussini says.

The fauna embody crustaceans with arrays of bristles that had been in all probability used to seize meals particles within the water column. These crustaceans “would have looked very similar to modern day brine shrimp … the kind of things that flamingos tend to eat,” Mussini says. And a mollusk had overlapping, blunt enamel that might have been good at scraping, very like a contemporary backyard snail or sea slug.

Then there’s the penis worm. While penis worms had been already recognized to have existed right now, this species has advanced enamel with finely branching projections lining its pharynx, together with different sturdy and spiny enamel, which Mussini says “are much more complex than any of its counterparts from the Burgess Shale.”

The fashionable and complicated traits discovered within the Bright Angel biota counsel the atmosphere was plentiful sufficient for competing species to spend money on advanced variations, Mussini says. These organisms could have then unfold into settings like that of the Burgess Shale, the place assets would have been extra restricted, he speculates.  

“The information that they offered is in step with that … [but] I don’t suppose the ebook is closed says paleontologist Karma Nanglu of the University of California, Riverside, who was not concerned within the work. The biota of the Bright Angel Formation and the Burgess Shale are each fairly biodiverse, so it’s not clear that one represents the supply of traits discovered within the different, he says. If the researchers might discover older fossils that present shallower environments had been extra biodiverse than deeper ones, that might make their case stronger, he says.

Mussini plans to proceed trying to find refined specimens even older than the Cambrian Period. It’s “in the spirit of trying to see if some of these innovations are actually older than we thought,” he says. “This record is still relatively untapped.”