A strange sea beast with a circular mouth full of jagged teeth unleashed a prehistoric “arms race” as its eyes evolved, new research has revealed.
Radiodonts chased the oceans more than 500 million years ago and are one of the first types of animals to emerge on planet Earth.
Now, a new study has revealed how their big eyes gave them an edge when looking for food, forcing their prey to adapt or die and fueling an increase in evolution.
While other animals of the time also had eyes, the eyes of radiodonts were particularly sophisticated, which gave them an advantage in dimly lit areas of the ocean.
Radiodonta chased the oceans more than 500 million years ago and is one of the first animals to emerge on planet Earth.
John Paterson, of the University of New England, the lead author of the study, said it was this “arms race” that gave rise to the diversity of life we see today.
He said: “Radiodonts are really weird, because they look like a mixture of various parts of the animals stuck together.
The head has a pair of large spiny appendages to capture prey, a circular mouth with jagged teeth, and a large pair of eyes.
“The rest of the body looks like a squid, with a series of swimming flaps on both sides of the body.”
He continued: “They are some of the first animals to appear in the history of the planet.
“Because they are very well equipped to hunt, especially with their excellent vision, they would have put a lot of pressure on their prey, especially when it came to long-term survival.
“So prey species needed to adapt and evolve in response to that pressure, otherwise they would have faced extinction.
“This so-called ‘arms race’ was a constant evolutionary battle between predators and prey over time, with predators better adapting ‘weapons’ and prey improving their defenses.”
He added: “It is possible that this arms race is primarily responsible for the diversity of life we see today.
Dr. Paterson and his team came to their conclusions after examining fossils from the shale of Emu Bay on Kangaroo Island in South Australia.
“Once animals began eating each other more than 500 million years ago, it began an expanding network of complex ecological interactions that no doubt caused new species to evolve over time.”
Dr. Paterson and his team came to their conclusions after examining fossils of the Emu Bay shale on Kangaroo Island, South Australia.
Until recently, relatively little was known about radiodont eyes, but the discovery of larger and better eye specimens paved the way for a breakthrough.
Their large eyes gave them an advantage in hunting for food, forcing their prey to adapt or die and feeding an increase in evolution.
One eye sample had 28,000 lenses that dropped the jaw, a number that only rivaled insects such as the dragonfly.
Dr Paterson said: “We have shown that radiodonts have some of the largest and most complex eyes in the history of animal life.
“Not only did they possess clear vision, but they were able to see at different levels of light within the ocean.
Radiodonts had some of the largest and most complex eyes in the history of animal life, which gave them clear vision and the ability to see at different levels of light within the ocean.
Some reached more than a meter in length at a time when most life forms were aquatic plants and multicellular organisms.
“This includes in the dark depths of the twilight zone, up to 1,000 meters, where sunlight has disappeared.”
He added: “Radiodonts represent some of the oldest and most primitive arthropods in existence.
“Perhaps without them, today we would not see the enormous diversity of arthropods, including insects, spiders, crustaceans and centipedes.”
John Paterson, of the University of New England, the lead author of the study, said it was this “arms race” that gave rise to the diversity of life we see today.
The oldest radiodont fossils date back to about 518 million years ago and, although it is not clear exactly when they became extinct, the creatures appear to have survived until 400 million years ago.
A diverse order of predators, they had a size that oscillated between more than two meters in length and only a few centimeters.
“Many species are now known and it has become quite clear that they had varied diets,” Dr. Paterson said.
Some would have been the great white sharks of their time, that is, apex predators that ate large prey.
However, other species are likely to eat tiny plankton.
Interestingly, the largest radiodonts that exist are the ones that would have eaten these tiny organisms, something similar to the diet of some of today’s giant whales.
“Being quite large, it is possible that some had a considerable useful life, perhaps on a scale of decades, but that is speculative.”
Dr. Paterson and colleagues, Gregory Edgecombe and Diego García-Bellido, published their findings in the journal Science Advances.
WHAT WAS THE CAMBRIAN EXPLOSION?
Scientists have long speculated that a large rise in oxygen during the “Cambrian explosion” was key to the development of many animal species.
The Cambrian explosion, about 541 million years ago, was a period in which a wide variety of animals burst onto the evolutionary scene.
Before about 580 million years ago, most organisms were simple, made up of individual cells that occasionally organized into colonies.
Over the next 70 or 80 million years, the rate of evolution accelerated and the diversity of life began to resemble that of today.
It ended with the Cambrian-Ordovician extinction, about 488 million years ago.
A recent study linked the historical increase in oxygen responsible for the formation of animal life on Earth to fossil fuels. Pictured: This black shale, formed 450 million years ago, contains fossils of trilobites and organic material that helped keep them in oxygen.