Scientists from the Museum of Manitoba and the Royal Ontario Museum (ROM) have unveiled to the world a new ancient predator that lived about 506 million years ago. The creature's fossils were found in the Burgess Shale region of Canada. The results of the study were published in the scientific journal "Royal Society Open Science".
The new animal was called Mosura fentoni: it was the size of a human finger and possessed three eyes, a pair of spiky mobile limbs, a rounded mouth studded with teeth, and a body with lateral swimming blades.
These characteristics allowed us to attribute it to the extinct group of predatory marine creatures - radiodonts, which also included the famous Anomalocaris canadensis, which reached a length of one meter and lived in the same waters as Mosura.
However, Mosura is distinguished among its congeners by a unique feature - a segmented posterior body, resembling an abdomen and consisting of many closely adjoining areas.
Photo: phys.org
"Mosura has 16 consecutive segments with gills at the rear of the body. This is an amazing example of an evolutionary parallel to modern animals such as horseshoe crabs (swordtails), midge crabs and insects, which also have posterior segments that carry respiratory organs," says Joe Mojsiuk, curator of paleontology and geology at the Manitoba Museum and leader of the study.
The purpose of this unusual structure is still unclear. Scientists suggest that it could be related to habitat peculiarities or behavioral adaptations that required increased gas exchange.
Because of its body shape with wide fins in the middle and a narrowed rear end, Mosura has been given the unofficial nickname "sea moth". The creature's scientific name refers to the fictional Japanese monster Motra, known from kaiju (Japanese for "strange beast or monster") movies.
Photo: phys.org
Although Mosura superficially resembles insects, it is only distantly related to modern moths, as well as to spiders, crabs, and millipedes. It belongs to an ancient branch of
arthropod evolution, from which these groups later evolved.
"Radiodonts represent one of the first branches in the arthropod evolutionary tree, and as such they provide us with valuable insights into the primary traits of this group. Mosura demonstrates how diverse even the earliest life forms were, and how they adapted to their environment - just as their modern descendants do," notes Jean-Bernard Caron, curator of the ROM invertebrate collection and co-author of the study.
Some Mosura fossils contain exceptional details of internal structure, including elements of the nervous system, blood circulation, and digestive tract.
Photo: phys.org
"Few fossils give such a detailed view of soft-tissue anatomy. We see, for example, bundles of optic nerves in the eyes similar to those found in modern arthropods. It's really fascinating," adds Caron.
Unlike humans, Mosura had no arteries or veins. Its circulatory system was of the open type: the heart pumped fluid through the body into large cavities - lacunae. In the fossil record, these cavities can be seen as luminous spots covering the entire body and passing into swimming lobes.
"Lacuna-like structures have previously caused controversy in the paleontological community. We are now certain that they are indeed elements of the circulatory system. Their widespread occurrence in the fossil record proves the ancient origin of this feature," explains Mojsiuk, who is also a research associate at ROM.
Of the 61 known Mosura fossils, all but one were found by ROM staff between 1975 and 2022, mostly in the Raymond Quarry area of Yoho National Park, British Columbia.
Photo: phys.org
Several specimens have also been found near Marble Canyon in Kootenay National Park, 40 kilometers to the southeast, where other radiodonts have been found: Stanleycaris, Cambroraster, and Titanokorys. One previously undescribed specimen of Mosura was found as early as the early 20th century by Charles Wolcott, the discoverer of the Burgess Shale.
"Museum collections are an inexhaustible source of discovery. If you think that everything is already explored, just open another museum drawer," Mojsiuk notes with a smile.
The discovery sites in Yoho and Kootenay National Parks are protected by Parks Canada. "Parks Canada is actively working with scientists to expand knowledge of this key phase of
Earth's history and is making it available to the general public through tours and educational programs."
The Burgess Shale was designated a UNESCO World Heritage Site in 1980 for its exceptional scientific value and is now part of the larger Canadian Rocky Mountain Parks complex.
Photo: phys.org
Exhibits with radiodont fossils can be seen at the Willner Madge Gallery: Dawn of Life at the ROM (Toronto). Mosura will be presented to the public for the first time at the Museum of Manitoba in Winnipeg later this year.