Paleontologists from the Manitoba Museum and the Royal Ontario Museum (ROM) have uncovered an incredible fossil of a 506-million-year-old predator in the Burgess Shale of Canada.
The new species, named Mosura fentoni, is part of an ancient group called radiodonts, which also includes the well-known Anomalocaris canadensis.
Unlike its larger relative, Mosura fentoni is only about the size of an index finger, yet it packs an array of fascinating features.
With three eyes, spiny jointed claws, a circular mouth lined with sharp teeth, and a series of swimming flaps along its body, Mosura fentoni was well-equipped for life in the ancient seas. But what really sets this creature apart is its unique abdomen-like structure.
While other radiodonts do not have such features, Mosura has 16 tightly packed segments at the rear of its body, each lined with gills.
This design is surprisingly similar to modern-day arthropods like horseshoe crabs, woodlice, and insects, which also have segmented rear ends with respiratory organs.
According to Joe Moysiuk, Curator of Paleontology and Geology at the Manitoba Museum and the lead author of the study, this is an example of “evolutionary convergence,” where unrelated species develop similar features independently.
The reason for this unusual adaptation remains a mystery. However, the research team suspects it may be connected to the creature’s habitat or its unique behavior.
Its broad swimming flaps near the middle of its body and its narrow, segmented back led field collectors to nickname it the “sea-moth,” drawing inspiration from its wing-like appearance.
This name also inspired its scientific name, Mosura, after the Japanese kaiju “Mothra.” Despite its name, Mosura is only distantly related to real moths, as well as other arthropods like spiders, crabs, and millipedes. It belongs to a much deeper branch of the evolutionary tree.
Radiodonts like Mosura were the first group of arthropods to emerge in the evolutionary timeline.
This means they provide vital clues about the origins of modern arthropods. Jean-Bernard Caron, co-author of the study and Curator of Invertebrate Paleontology at ROM, explains that Mosura highlights the surprising diversity and adaptability of these early creatures.
Fossils of Mosura also reveal details of its internal anatomy, which is rare in fossils of this age. The preserved remains include elements of its nervous system, circulatory system, and digestive tract.
What makes this discovery even more special is the level of detail visible in the fossils. Scientists could observe nerve bundles in its eyes, suggesting that Mosura processed images similarly to living arthropods.
Its circulatory system was also well-preserved. Unlike humans, who have closed circulatory systems with veins and arteries, Mosura had an “open” system. Its heart pumped blood into large internal spaces called lacunae, which allowed blood to flow freely through its body and into its swimming flaps.
These lacunae appeared as reflective patches in the fossils, providing clear evidence of how its circulatory system functioned. This remarkable preservation helps scientists understand similar, less visible features in other ancient fossils.
Of the 61 fossils of Mosura studied, all but one were collected by ROM between 1975 and 2022. Most came from the Raymond Quarry in Yoho National Park, British Columbia, with some new finds from Marble Canyon in Kootenay National Park.
These sites are part of the Burgess Shale, one of the world’s most important fossil beds. The Burgess Shale is managed by Parks Canada and is part of a UNESCO World Heritage Site, recognized for its incredible contribution to understanding the history of life on Earth.
Mosura is now set to go on display for the first time at the Manitoba Museum in Winnipeg, while other radiodont fossils are featured in the ROM’s Willner Madge Gallery, Dawn of Life, in Toronto.
For those interested in the dawn of life on Earth, these exhibits offer a glimpse into a world half a billion years old, where predators like Mosura ruled the ancient seas.
