Researchers have discovered a miniature world of marine life hidden within a rocky outcrop near a herd of grazing sheep.
Paleontologists Lucy Muir and Joseph Botting have discovered a pint-sized pile of fossils within walking distance of their home in the Castle Bank quarry in central Wales. At a time when aquatic life lived, the area was a rocky sea shelf fringed by volcanic islands.
In a new study published online May 1 in the journal natural ecology and evolution, the duo and their colleagues from England, Sweden and China describe the site’s ancient inhabitants. Most are only a few millimeters long and include nozzle-mouthed worms, horseshoe crabs, starfish and early barnacles. Also in the fossil pile are small, cryptic remnants from a preceding Cambrian explosion that began about 540 million years ago when diverse life forms exploded.
A couple of paleontologists first discovered the deposits in 2013 when they found sponge fossils in a small quarry surrounded by sheep pastures. For many years Muir and Botting, Honorary Fellows of the National Museum of Wales Amgedfa Kiml, have returned to the site in search of further fossils. However, they were unable to find any traces other than sponges.
During the 2020 COVID lockdown, they started describing their local sponge suite as a pandemic project. One day, Botting headed to the quarry to look for more sponges. “And of course that was the first time I found a little tube with tentacles sticking out of it,” he recalls.
The fossil, just 3.5 mm tall, resembled a lanky alien spaceship and was unlike anything paleontologists had ever seen. They soon realized they were just scratching the surface of the site. Botting and Muir found evidence of a thriving ecosystem within the two-meter-thick band of rock. Like the photo in progress, paleontologists cracked the rock and the fossil was revealed seconds later. “Split them and after 30 seconds they magically appear,” he says Botting.
Over several months, paleontologists have found fossils of about 170 different species that may have lived on the rocky slopes along the sinking volcano. In addition to sponges and worms, there were trilobites, arthropods with grasping appendages, and six-legged animals very similar to primitive insects that didn’t appear until millions of years later. There was also an animal that made me think. obabinia, a strange wonder of the Cambrian period that had five eyes and a trunk-like proboscis. Many of these evolutionary oddities were delicately etched in gray stone, and soft body features that rarely fossilized, such as gills, digestive tracts, optic nerves, and nervous tissue, were easily visible.
The impressive preservation of Castle Bank fossils, similar to those found in the iconic 500-million-year-old Cambrian deposits of the Burgess Shale in the Canadian Rockies, represent some of the oldest complex animals on Earth. Producing some fossils. Researchers have found equally impressive Cambrian fossils around the world.
But in the subsequent Ordovician period, beautifully maintained animals are much rarer. According to Alicia Stigal, a paleontologist at the University of Tennessee, Knoxville, this could be due to changes in Ordovician ocean chemistry, or an increase in burrowing organisms that exposed other animal carcasses to decay. I have. Without these remnants, scientists know very little about the majority of mollusks that lived in the aftermath of the Cambrian explosion. [around] 70% of all animals,” she says, referring to soft-bodied creatures. “A snapshot of the history of non-biomineralizing animals, such as the fauna of Castle Bank, is very important for a more complete understanding of the history of life,” she said, not involved in the new study. adds Stigall.
The newly discovered fossils also offer a glimpse into a dynamic chapter in evolution called the great Ordovician biodiversity event. “This is when life really started to get interesting,” says Muir. “As animals diversified, ecosystems became more complex.” Although animal sizes remained constant throughout the Cambrian, some ecosystems appear to have shrunk during the Ordovician. Castle her bank fossils are generally small. Most of them measure between 1 and 5 mm.
Such shrinkage is usually attributed to fossilization peculiarities in which giant organisms were washed away before being buried. But Botting and Muir believe that Castle Bank truly represents an ecosystem dominated by tiny life forms. The remarkable preservation of the soft tissues of these fossils reveals that entire ecosystems were likely buried instantly, possibly by sudden rock slides. If larger creatures had roamed around the ecosystem, they would have been buried alive as well. Paleontologists believe the site’s relatively large sponges and algae (several centimeters) provided the perfect habitat for these tiny creatures.
The small world of sea creatures may seem strange, but Muir stresses that they continue to be staples of the marine environment. says Muir. “It’s just that they’re hard to see.”
Researchers are still working to better describe dozens of Castlebank fossils, including tentacle creatures living in tubes and animals resembling marine life that could be the predecessors of insects. Just like during the lockdown, their home is now overrun with fossils from the scene. “The spare room is full and you can’t sleep on the bed,” says Botting.
