The fossilized brain of a prawn-like creature with three eyes that sailed the waters 500 millions years ago may provoke a reconsideration of the development of insects and spiders.
The Stanleycaris hirpex monster is described as “the stuff of nightmares.”
It featured two eyes “on stalks” and a third eye in the center of its head, a circular mouth lined with fangs, and frontal claws with a terrible array of spines.
Stanleycaris existed during the Cambrian ‘explosion,’ a period of rapid evolution in which the majority of significant animal species first appeared in fossils.
It was a member of Radiodonta, an extinct branch of the arthropod evolutionary tree that was distantly related to current insects and spiders.
Scientists are particularly intrigued by the contents of Stanleycaris’s brain, despite the creature’s peculiar appearance.
In an examination of over 250 fossilized Stanleycaris specimens dating back 506 million years, the brain and central nervous system were discovered to be preserved in 84 of the fossils.
It sheds fresh light on the evolution of the arthropod brain, vision, and head anatomy by demonstrating that Stanleycaris had a two-segmented brain as opposed to the three segments found in modern insects.
The Stanleycaris fossils were recovered in the 1980s and 1990s from the Burgess Shale, a fossil-bearing layer exposed in the Canadian Rockies of British Columbia.
It is uncommon to find fossilized soft tissue. The majority of fossils consist of bone or hard body parts, such as teeth or exoskeletons, whereas brains and nerves are composed of lipid-like substances that do not typically fossilize.
“Although fossilized brains from the Cambrian Period are not new, this discovery stands out for the astounding quality of preservation and a large number of specimens,” said Joseph Moysiuk, the study’s lead author and a Ph.D. candidate at the Royal Ontario Museum affiliated with the University of Toronto.
Even minute elements such as visual processing centers serving the big eyeballs and nerves entering the appendages are discernible.
The features are so distinct that it’s as if we’re staring at a dead animal from yesterday.
They demonstrate that Stanleycaris’ brain consisted of two segments, the protocerebrum, and the deutocerebrum, which were related to the eyes and frontal claws, respectively. In modern arthropods, these brain parts control vision and antenna signals.
Protocerebrum, deutocerebrum, and tritocerebrum are the three segments of the brain in modern arthropods, such as grasshoppers and other insects.
The tritocerebrum is connected to the labrum, an upper lip muscle, and combines sensory input from the other two brain lobes.
According to the experts, although the difference in one segment may not sound game-changing, it has profound scientific ramifications.
Since repeated copies of many arthropod organs may be found in their segmented bodies, it is crucial to comprehend how these structures originated to determine how segmentation varies between species.
Moysiuk remarked, “These fossils serve as a Rosetta Stone to link features in radiodonts and other early fossil arthropods with their counterparts in living populations.”
We conclude that a two-segmented head and brain has deep roots in the arthropod lineage and that its evolution likely predates the three-segmented brain that is present in all living members of this varied animal phylum.
Stanleycaris was a member of the radiodonts, which were some of the largest animals during the Cambrian Period and were apex predators.
This contains the well-known “strange wonder” Anomalocaris, which measured at least 1 meter in length.
Stanleycaris was small for its group, measuring no more than 8 inches (20 cm) in length, but at a time when most animals grew no larger than a human finger, it would have been a formidable predator.
Radiodont is short for “radiating teeth.” The odd creatures were named for their round, toothy jaws and were adapted to the limited light of the deep sea.
According to the researchers, Stanleycaris’ excellent sensory and neurological systems would have enabled it to efficiently select small victims in the darkness.
In addition to its pair of stalked eyes, Stanleycaris has a big central eye in the front of its head, a trait never before observed in a radiodont.
Dr. Jean-Bernard Caron, the Richard Ivey Curator of Invertebrate Palaeontology at the Royal Ontario Museum and Moysiuk’s Ph.D. advisor, stated, “The existence of a massive third eye was unexpected.”
It emphasizes that these animals were even stranger-looking than previously believed, but also demonstrates that the oldest arthropods had already evolved a variety of complex visual systems, similar to those of many of their current relatives.
This discovery is a significant step forward in understanding what radiodonts looked like and how they lived, given that most are known solely through fragmentary evidence.
