Evrim Yazgin
Cosmos science journalist
Scientists have found in museum collections more than 60 fossils belonging to a 506-million-year-old, 3-eyed hunter related to Earth’s first super predator.
The discovery sheds light on the evolution of a group of animals which includes modern insects and crabs.
Life on Earth was made up of single-celled organisms for billions of years. Then, about 600 million years ago, the first complex life emerged during a period known as the Ediacaran. These strange organisms puzzle scientists to this day.
It wasn’t until about 540 million years ago (mya) when creatures and plants recognisable today emerged. This was a time known as the “Cambrian explosion”.
This is the period when all the basic animal body plans – including segmented exoskeletons of arthropods and the first vertebrates – exploded onto the evolutionary scene.
Along with these basic body plans were evolutionary milestones like the first eyes, mouths and apex predators.
Earth’s first super predator was the 1m-long Anomalocaris canadensis. The creature lived from about 520 to 499 mya. It is an arthropod – the same group which includes modern spiders, insects, crabs and scorpions – and its name means “unlike other shrimps” owing to its foot-long frontal appendages which palaeontologists believe it used to grab prey.
Anomalocaris is an example of the extinct order of arthropods called radiodonts. They are distinguished by their frontal appendages, though not all used them in the same way as Anomalocaris.
The Manitoba palaeontologists announced a new radiodont species which has a feature seen in none of its cousins.
Mosura fentoni is described for the first time in a paper published in the Royal Society Open Science journal. M. fentoni is just a few cm long, has 3 eyes, a circular mouth lined with teeth, and a body with flaps on its side for swimming.
It also has similar frontal appendages to the much larger Anomalocaris.
But it was its back end which caught palaeontologists by surprise.
“Mosura has 16 tightly packed segments lined with gills at the rear end of its body,” says study lead Joe Moysiuk, Curator of Palaeontology and Geology at the Manitoba Museum. “This is a neat example of evolutionary convergence with modern groups, like horseshoe crabs, woodlice, and insects which share a batch of segments bearing respiratory organs at the rear of the body.”
Mosura has been nicknamed the “sea moth” because of its broad swimming flaps. It’s not clear why it has the gilled segments on its rear, but the palaeontologists think it may be related to habitat or behaviour which requires more efficient respiration.
“Radiodonts were the first group of arthropods to branch out in the evolutionary tree, so they provide key insight into ancestral traits for the entire group. The new species emphasizes that these early arthropods were already surprisingly diverse and were adapting in a comparable way to their distant modern relatives.” says co-author Jean-Bernard Caron, curator of invertebrate palaeontology at Royal Ontario Museum.
A total of 61 Mosura fossils were collected between 1975 and 2022, mostly from Raymond Quarry in Yoho National Park, British Columbia in Canada. One specimen had previously been studied but went unpublished.
“Museum collections, old and new, are a bottomless treasure trove of information about the past. If you think you’ve seen it all before, you just need to open up a museum drawer,” Moysiuk says.
