The fossilized brain of a three-eyed shrimp-like creature that swam the oceans 500 million years ago could rethink the evolution of insects and spiders.
Named Stanleycaris hirpex, the creature is described as the “stuff of nightmares.”
It had two eyes “on stalks”, a third in the middle of its head, an impressive looking round mouth lined with teeth, and front claws with an impressive array of spikes.
Stanleycaris lived during the Cambrian “Explosion” – a period of rapid evolution when most of the large groups of animals appeared in the fossil record.
It belonged to an ancient, extinct offshoot of the arthropod evolutionary tree called Radiodonta—distantly related to modern insects and spiders.
Despite Stanleycaris’ bizarre appearance, it’s the contents of its head that excites scientists the most.
In a study of over 250 fossilized specimens of Stanleycaris dating back 506 million years, they found that the brain and central nervous system were preserved in 84 of the fossils.
They show that the Stanleycaris brain consisted of two segments – instead of three as in modern insects – and shed new light on the evolution of the arthropod brain, vision and head structure.
Fossil specimen of Stanleycaris hirpex collected from Burgess Shale – a fossiliferous deposit exposed in the Canadian Rocky Mountains of British Columbia. Dark material inside the head is the remains of nerve tissue
Stanleycaris had two eyes “on stalks”, a third in the center of its head, an impressive looking round mouth lined with teeth, and front claws with an impressive array of spikes
STANLEYCARIS STATISTICS
Species name: Stanleycaris hirpex
Mission: radiodonts
Lived: 500 million years ago
Environment: bottom of the seabed
Length: 8 inches (20 cm)
The Stanleycaris fossils were collected in the 1980s and 1990s from Burgess Shale – a fossiliferous deposit exposed in the Canadian Rocky Mountains of British Columbia.
Finding fossilized soft tissue is rare. Most fossils are bones or hard body parts like teeth or exoskeletons, while brains and nerves are made of fat-like substances that don’t typically survive.
“Although fossilized brains from the Cambrian Period are not new, this discovery stands out for the astonishing quality of preservation and the large number of specimens,” said Joseph Moysiuk, lead author of the research and a doctoral student at the University of Toronto’s Royal Ontario Museum.
“We can even see fine details like visual processing centers that feed the big eyes and traces of nerves that enter the limbs.
“The details are as clear as if we were looking at an animal that died yesterday.”
They show that the Stanleycaris brain consisted of two segments – the protocerebrum and the deuterocerebrum – connected to the eyes and frontal claws, respectively, which control vision and antennae signals in modern-day arthropods.
In modern-day arthropods such as grasshoppers and other insects, the brain consists of three segments – protocerebrum, deuterocerebrum, and tritocerebrum.
The tritocerebrum is connected to the labrum, a movable upper lip, and integrates sensory information from the other two lobes of the brain.
While one segment’s difference doesn’t sound groundbreaking, it actually has radical scientific implications, according to the researchers.
Because repeated copies of many arthropod organs are found in their segmented bodies, figuring out how segments arrange themselves between different species is crucial to understanding how these structures evolved.
“These fossils are like a Rosetta stone, helping to link features in radidonts and other early fossil arthropods with their counterparts in surviving groups,” Moysiuk said.
They show that the Stanleycaris brain consisted of two segments – the protocerebrum and the deuterocerebrum – connected to the eyes and frontal claws, respectively. Pictured: pair of fossil specimens of Stanleycaris hirpex
Abstract of paper showing interpretation of the nervous system from fossils of Stanleycaris and implications for understanding arthropod brain evolution. The brain is shown in red and the nerve cords in purple
New species found in 500 MILLION-year-old rocks in the Canadian Rocky Mountains
The remains of a new species of primitive arthropod that lived 500 million years ago have been discovered in the Canadian Rocky Mountains – and they dwarfed all of their conspecifics.
Titanokorys gainesi swam in the seas of Earth’s Cambrian period, reaching a length of 1.6 feet at a time when most species were only the size of a pinky finger.
Fossils of Titanokorys have been found in the Burgess Shale of Marble Canyon in Kootenay National Park by paleontologists at the Royal Ontario Museum.
The creature had multifaceted eyes, a tooth-lined mouth resembling a slice of pineapple, a pair of spiky claws, and a body with a row of armbands.
“We conclude that a two-part head and brain have deep roots in the arthropod lineage and that its evolution likely predates the tripartite brain that characterizes all living members of this diverse phylum.”
Stanleycaris was a member of the radiodonts, apex predators that were among the largest animals during the Cambrian period.
These include the famous “strange wonder” Anomalocaris, which could grow up to 1m long – making it a sea monster.
At no more than 20 cm long, Stanleycaris was small for its group, but at a time when most animals grew no larger than a human finger, it would have been a formidable predator.
Radodont means “radiant teeth”. The unusual animals were named for their toothy, rounded jaws and were adapted to the faint light of deep water.
According to the researchers, the sophisticated sensory and nervous systems of Stanleycaris would have made it possible to efficiently detect small prey in the dark.
In addition to its pair of stalked eyes, Stanleycaris possessed a large central eye at the front of its head – a feature never before seen in a radiodont.
“The presence of a giant third eye was unexpected,” said Dr. Jean-Bernard Caron, Richard Ivey Curator of Invertebrate Paleontology of ROM and PhD supervisor of Moysiuk.
“It underlines that these animals looked even more bizarre than we thought, but also shows us that the earliest arthropods had already evolved a variety of complex visual systems, like many of their modern relatives.
“Since most radiodonts are only sporadically known, this discovery is a crucial step forward in understanding what they looked like and how they lived.”
The study was published in Current Biology.
THE INCREDIBLE PRESERVATION OF THE BURGESS SHALE
Pictured: Artist’s rendering of the Cambrian Seas with Anomalocaris (top), Hallucigenia (bottom right), and Opabinia (bottom left)
The Burgess Shale is a fossiliferous rock deposit that outcrops in the Canadian Rocky Mountains.
The rock unit – a black shale – was deposited in an ancient sea some 500 million years ago during the Cambrian period of Earth’s history.
It is famous for its exceptional preservation of fossils – and is one of the oldest known deposits to contain evidence of mollusks.
Many strange-looking animal species have been found in the shale, including the large and streamlined predator Anomalocaris, the segmented Opabinia, and the alien-looking, spiny Hallucigenia.
The Burgess Shale outcrops in several locations near the town of Field in Yoho National Park and at Kicking Horse Pass and Kootenay National Park to the south.
The deposits were first discovered in August 1909 by paleontologist Charles Walcott. It was declared a UNESCO World Heritage Site back in 1980.