A bizarre sea animal with a circular mouth full of toothed teeth caused a prehistoric ‘arms race’ when it developed eyes, new research has revealed.
Radiodonts stalked the oceans more than 500 million years ago and are one of the earliest animal species that originated on planet Earth.
Now a new study has revealed how their big eyes gave them an edge when searching for food, forcing their prey to adapt or die and fueling an increase in evolution.
While other animals at the time also had eyes, the radiodonts’ eyes were particularly sophisticated, giving them the forefront in dimly lit parts of the sea.
Radiodonta crept across the oceans more than 500 million years ago and is one of the earliest animal species to appear on earth.
John Paterson of the University of New England, lead author of the study, said it was ‘arms race’ that gave rise to the variety of lives we see today.
He said: ‘Radiodonts are really weird because it looks like a mixture of different animal parts stuck together.
‘The head has some large prickly appendages for catching prey, a round mouth with toothed teeth and a large pair of eyes.
“The rest of the body looks like an octopus, with a series of swimming pools on either side of the body.”
He continues: ‘These are some of the first animals to appear in the history of the planet.
‘Because they are so well equipped to hunt, especially with their excellent vision, they would have put a lot of pressure on their prey, especially in terms of long-term survival.
‘So prey species had to adapt and evolve in response to this pressure, otherwise they would have faced extinction.
“This so-called ‘arms race’ has been a constant evolutionary battle between predators and prey over time, with predators adapting better ‘weapons’ and improving their defenses.”
He added: ‘It is possible that this arms race is largely responsible for the diversity of life we see today.
Dr Paterson and his team came to their conclusions after examining fossils from Emu Bay Shale on Kangaroo Island, South Australia
“After animals began eating each other more than 500 million years ago, it began an extensive network of complex ecological interactions, which undoubtedly led to the evolution of new species over time.”
Dr Paterson and his team came to their conclusions after examining fossils of Emu Bay Shale on Kangaroo Island, South Australia.
Until recently, relatively little was known about radiodont eyes, but the discovery of larger, better eye samples paved the way for a breakthrough.
Their large eyes gave them an edge in the hunt for food, forcing their prey to adapt or die, and inciting an increase in evolution
In one eye sample, there were 28,000 lenses falling on the jaw – a number that only competes with insects such as the dragonfly.
Dr Paterson said: ‘We have shown that radiodonts are some of the largest and most complex eyes in the history of animal life.
‘They not only had sharp vision, but also at different light levels in the ocean.
Radiodonts had some of the largest and most complex eyes in the history of animal life, giving them sharp vision, as well as the ability to see at different light levels in the sea.
Some reached more than a meter long at a time when most life forms were aquatic plants and multicellular organisms.
“This includes the dark depths of the twilight zone – up to 1,000 meters – where sunlight has almost disappeared.”
He added: ‘Radiodonts are some of the earliest and most primitive arthropods in existence.
“Perhaps without them we would not see the great variety of arthropods today that include insects, spiders, crustaceans and millipedes.”
John Paterson of the University of New England, the lead author of the study, said that this ‘arms race’ has given rise to the diversity of life we see today.
The oldest radiodont fossils date to about 518 million years and – although it is unclear exactly when they became extinct – the creatures appear to have survived to 400 million years ago.
It was a diverse order of predators and ranged in size from more than two meters long to only a few centimeters.
“Many species are now known, and it has become clear that they have different diets,” said Dr. Paterson said.
‘Some would have been the Great White Sharks of their time – that is, top predators that ate large prey.
‘Other species probably ate small plankton.
‘Interestingly enough, the largest radio donuts in existence would have eaten the small organisms, which are similar to the diet of some of today’s giant whales.
“Because it’s quite large, it is possible that some have had a substantial lifespan, perhaps on a scale of decades, but that’s speculative.”
Dr. Paterson and his 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 oxygen peak during the ‘Cambrian Explosion’ was the key to the evolution of many animal species.
The Cambrian Explosion, about 541 million years ago, was a time when a wide variety of animals erupted on the evolutionary scene.
Before about 580 million years ago, most organisms were simple, composed of individual cells that were sometimes 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 extinction event of Cambrian-Ordovician, about 488 million years ago.
In a recent study, the historical increase in oxygen responsible for the formation of animal life on earth was linked to fossil fuels. In the photo: this black shale, formed 450 million years ago, contains fossils of trilobites and organic matter that help carry them in oxygen