A bizarre sea creature with a circular mouth full of serrated teeth triggered a prehistoric ‘arms race’ as it developed eyes, new research has revealed.
Radio donors haunted the oceans more than 500 million years ago and are one of the earliest animal species to occur on planet Earth.
Now, a new study has revealed how their big eyes gave them a head start when hunting for food, forcing their prey to adapt or die, and promoting an increase in evolution.
While other animals at the time also had eyes, the radio donors’ eyes were particularly sophisticated, giving them the edge in dimly lit areas of the ocean.
Radiodonta pursued the oceans more than 500 million years ago and is one of the earliest animal species to appear on planet Earth.
WHAT IS RADIODONTA?
Radiodonta, meaning ‘radiating teeth’, was a group of arthropods in the Cambrian period.
They were the earliest known predators. Some reached over a meter in length at a time when most life forms were aquatic plants and multi-celled organisms.
They had large, spiny raptorial pendants (or gripping) pendants in front of their heads and a circular mouth adorned with tooth-like sawtooths.
No known member of Radiodonta is believed to have legs.
They are ancient relatives of spiders, insects and crustaceans.
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 mix of different animal parts sitting together.
‘The head has a pair of large, spiny pendants for catching prey, a circular mouth with serrated teeth and a large pair of eyes.
‘The rest of the body looks like an octopus with a series of floating flaps along 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 so well equipped for hunting, 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 were needed to adapt and evolve in response to this pressure, otherwise they would have been extinct.
‘This so-called “arms race” was a constant evolutionary battle between predators and prey over time, with predators adapting better “weapons” and prey 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 reached their conclusions after examining fossils from the Emu Bay Shale on Kangaroo Island, South Australia
‘When animals began eating each other over 500 million years ago, it started a growing network of complex ecological interactions that undoubtedly resulted in new species evolving over time.’
Dr Paterson and his team reached their conclusions after studying fossils from the 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 a head start when hunting for food, forcing their prey to adapt or die, and evoking a powerful development
One eye sample had jaw-dropping 28,000 lenses – a number that only competed with insects as a jeweler.
Dr Paterson said: ‘We demonstrated that radiodonts have some of the largest and most complex eyes in the history of wildlife.
Not only did they have sharp vision, but they were able to see at different light levels in the ocean.
Radiodonts had some of the largest and most complex eyes in the history of wildlife, giving them sharp vision as well as the ability to see at different light levels in the ocean
Some reached over a meter in length at a time when most life forms were aquatic plants and multi-celled organisms
‘This includes in dark depths in the twilight zone – down to 1,000 meters – where sunlight has almost disappeared.’
He added: ‘Radio donors represent some of the earliest and most primitive arthropods in existence.
‘Perhaps without them we would not see the enormous diversity of arthropods that live today, including insects, spiders, crustaceans and millipedes.’
John Paterson of the University of New England, lead author of the study, said it was this ‘arms race’ that gave rise to the diversity of life we see today.
The oldest fossil radiodont dates back to about 518 million years, and although it is unclear exactly when they became extinct, the creatures appear to have survived until 400 million years ago.
A different order of predators, they ranged in size from more than two meters long to only a few centimeters.
‘There are now many known species and it has become clear that they had different diets,’ said Dr Paterson.
‘Some would have been the great white sharks of their time – that is, topped predators that ate large prey.
‘But other species probably ate little plankton.
‘Interestingly, the largest radio donors in existence are those that would have eaten these small organisms, which is similar to the diet of some of today’s giant whales.
‘Being fairly large, it is possible that some had a significant lifespan, perhaps on a scale from decades, but this is speculative.’
Dr. Paterson and his colleagues, Gregory Edgecombe and Diego García-Bellido, published their findings in the journal Science Advances.
WHAT WAS ‘CAMBRIAN EXPLOSION’?
Researchers have long speculated that a large increase in oxygen during the ‘Cambrian Explosion’ was the key to the evolution of many animal species.
The Cambrian explosion, about 541 million years ago, was a period in which a large number of animals jumped onto the evolutionary stage.
Before about 580 million years ago, most organisms were simple, composed of individual cells occasionally organized in colonies.
Over the next 70 or 80 million years, the rate of development accelerated, and the diversity of life began to resemble that of today.
It ended with the Cambrian-Ordovician extinction event about 488 million years ago.
A recent study linked the historic rise in oxygen responsible for the formation of wildlife on Earth to fossil fuels. The image: This black slate, formed 450 million years ago, contains fossils of trilobites and organic material that helped support them in oxygen