Paleontologists discover a ‘three-eyed' predator that once roamed Earth's oceans 500 million years ago

Time of India

19-05-2025

Image source: New York Times
Paleontologists, aided by more than 60 fossil finds, discovered
Mosura fentoni
, an intriguing three-eyed predator that roamed in the oceans of Earth more than 500 million years ago. Also referred to as the "sea moth" because of its moth-like body, the ancient arthropod sheds important light on the early evolution and diversity of the arthropods.
The discovery illuminates the diverse ecosystems of the Cambrian Era, underlining the influence of Mosura and other predators on ocean life. Mosura fossils provide an unprecedented peek into early arthropod anatomy, giving us a greater appreciation of ancient existence and evolutionary creation.
'Three-eyed' predator Mosura fentoni and the early history of arthropods
Mosura fentoni was one of a group known as the radiodonts, a small but significant predator during the Cambrian Period.
Radiodonts are part of an ancient lineage of the arthropod branch of the family tree, an important group that gives rise to today's living insects, spiders, and crustaceans. The research, done by scientists who wrote in the Royal Society Open Science journal, provides new insight into what these early arthropods were and how much like modern versions they look.
The discovery of Mosura fentoni adds to the understanding of the history of arthropod evolution.
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Though extinct, radiodonts are crucial to studies of the evolution of current arthropods, which occupy over 80% of all living animal species. According to lead study author Dr. Joe Moysiuk, curator of paleontology at the Manitoba Museum, the fossils provide a rare glimpse into this extinct group's history.
Mosura fentoni characteristics
One of the most noticeable characteristics of Mosura fentoni is its then-unknown abdomen-shaped body segment, with 16 segments, such as gills at the rear.
It is a then-unknown body characteristic in any other radiodont. It has a shape resembling structures in its modern relatives such as horseshoe crabs, woodlice, and insects, where respiratory organs are borne by segments.
This feature likely helped Mosura to efficiently suck oxygen from its environment, potentially indicating evolutionary convergence—the mechanism by which bodily similarities develop in unrelated groups independently.
Study co-author Dr. Jean-Bernard Caron, a Royal Ontario Museum curator, noted that Mosura's diverse anatomy demonstrates early flexibility of arthropods.
Mosura's sea moth shape and its mysterious 'third eye'
Mosura's "sea moth" nickname is because of its body shape and size resemblance to moths today—about as long as an adult human index finger. Although it resembles one, no living creature is in Mosura's full form. Although the animal possessed insect-like and crustacean-like jointed claws, its strangest feature was its third eye.
Located in the middle of its head, this additional eye is distinct from the many eyes of present-day arthropods, in an orientation maintenance function. Moysiuk speculated that Mosura's significant third eye helped guide it through the underwater environment, as part of its life as a predator.
Secondly, Mosura's swimming style would also be the same as a ray fish by using its several swimming flaps in a smooth wave-like manner to drive it forward in water.
Its single pattern of locomotion along with its pencil-point mouth that was bordered by saw-like plates made Mosura stand apart from any other living being in the present world.
How Mosura's unique claws and features helped it survive
Although it is not known precisely how Mosura took its prey, front claws in some of the fossils are an indication. A fossil spiny claw was discovered by Dr. Jean-Bernard Caron while excavating one of the specimens with caution. Spiny claws were used by most related species to capture prey, but Mosura claws had smooth, extended sides and bifurcated ends, which might have assisted in grasping and moving small animals towards its mouth.
It is presumed that Mosura likely preyed upon smaller arthropods and worms that lived in its habitat. However, it too could have been a victim of the sea's larger predators, such as the Anomalocaris canadensis, a radiodont that looked like a shrimp, or the giant jellyfish Burgessomedusa phasmiformis.
The discovery of Mosura's unique features helps researchers to reimagine the evolution of early arthropods like radiodonts.
Harvard invertebrate paleontologist Rudy Lerosey-Aubril highlighted the way Mosura's unique body form can help researchers glimpse the developmental pathways that existed prior to evolutionary changes leading to more symmetrical body forms in subsequent species.
Mosura's fossils
from the Burgess Shale reveal its inner structure
The fossils that made the identification of Mosura fentoni arose were found in the Burgess Shale, a world-renowned fossil bed within the Canadian Rockies.
The Burgess Shale is renowned for preserving beautifully detailed remains of ancient creatures in the Cambrian Period, approximately 508 million years ago. Additional evidence of over 60 more specimens of Mosura were collected between 1975 and 2022, providing researchers with ample information about this enigmatic creature.
The biggest asset of the fossilised Mosura specimens is perhaps the ability to recognize impressions of the circulatory, digestive, and nervous systems.
The soft tissues are not usually preserved in fossils, giving the initial opportunity to view the inner works of an ancient arthropod.
Researchers were able to identify packs of nerves within the eyes, allowing Mosura to read visual cues, much like modern arthropods. Mosura also had an open circulatory system, where the blood was circulated into internal cavities with the reflective leftovers left behind that have been maintained in the fossil remains.
Mosura's role in the
Cambrian ecosystem
revealed
The discovery of Mosura fentoni not only enlightens us about the evolution of arthropods but also provides us with crucial information about life on our planet during the Cambrian Explosion—a time when the diversification of the animal kingdom was happening at high speed. In the view of Dr. Russell D.C. Bicknell, an American Museum of Natural History scientist, this discovery provides us with information regarding how early sea ecosystems functioned, particularly the role of predators like Mosura.
The extraordinary fossils of Mosura fentoni are proof of the diversity of life in Cambrian times and the level of sophistication of primitive arthropods. The perfect preservation of these fossils, especially at the Burgess Shale, is a goldmine for researchers who wish to know more about the history of life on Earth.
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