A bizarre sea beast with a round mouth full of jagged teeth caused a prehistoric “arms race” when it evolved in the eyes, a new study has revealed.
Radiodonts lurked the oceans more than 500 million years ago and are one of the earliest species to appear on planet Earth.
Now a new study has revealed how their big eyes have given them an advantage in hunting for food, forcing their prey to adapt or die and fueling the wave of evolution.
While other animals at the time also had eyes, the radiodont’s eyes were particularly sophisticated, giving them an advantage in dimly lit areas of the ocean.
Radiodonta lurks the oceans more than 500 million years ago and is one of the earliest species to appear on planet Earth
WHAT ARE RADIODONTS?
Radiodonta, which means “emitting teeth”, were a group of arthropods during the Cambrian period.
They were the earliest known large predators. Some reach over a meter in length when most life forms are aquatic plants and multicellular organisms.
They had large, prickly predatory (or gripping) appendages at the front of the head and a round mouth adorned with serrated teeth.
No known member of Radiodonta is considered to have legs.
They are ancient relatives of spiders, insects and crustaceans.
John Patterson of the University of New England, the study’s lead author, 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 combination of different animal parts glued together.
– The head has a pair of large prickly appendages to catch prey, a round mouth with serrated teeth and a large pair of eyes.
“The rest of the body looks like a squid, with a series of floating flaps on either side of the body.”
He continued: “They are one 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 put a lot of pressure on their prey, especially when it comes to long-term survival.
“So the species of prey must adapt and develop in response to this pressure, otherwise they would face extinction.
“This so-called ‘arms race’ has been an ongoing 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. Patterson and his team came to their conclusions after studying fossils from the Emu Bay Shale on Kangaroo Island, South Australia
“Since animals began feeding on each other more than 500 million years ago, it has created an expanding network of complex ecological interactions that have undoubtedly led to the evolution of new species over time.”
Dr. Patterson and his team came to their conclusions after examining 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 an advantage when hunting for food, forcing their prey to adapt or die, and feeding the wave of evolution.
One eye sample had 28,000 lentils falling off – a number rival only to insects such as a dragonfly.
Dr Patterson said: “We have demonstrated that radiodonts have some of the largest and most complex eyes in the history of animal life.
“Not only did they have sharp eyesight, but they were able to see at different levels of light in the ocean.
Radiodonts have had some of the largest and most complex eyes in the history of animal life, giving them sharp eyesight and the ability to see at different levels of light in the ocean.
Some reach over a meter in length when most life forms are 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 today we will not see a huge variety of arthropods, including insects, spiders, crustaceans and centipedes.”
John Patterson of the University of New England, lead author of the study, said that it was this “arms race” that gave rise to the diversity of life we see today.
The oldest X-ray fossils date back about 518 million years, and – although it is not clear exactly when they disappeared – the creatures appear to have survived until 400 million years ago.
A diverse range of predators, they range in size from more than two meters in length to just a few centimeters.
“Many species are now known and it has become clear that they have had a varied diet,” said Dr. Patterson.
“Some of them would be the Great White Sharks in their time – that is, supreme predators that have eaten large prey.
“However, other species have probably eaten tiny plankton.
“Interestingly, the largest existing radiodonts are those that would eat these small organisms, which is similar to the diet of some of today’s giant whales.
“Because they are quite large, some may have had a significant life expectancy, perhaps on a decade-long scale, but this is speculative.”
Dr. Patterson and his colleagues Gregory Edgecomb and Diego Garcia-Bellido published their findings in the journal Science Advances.
WHAT WAS THE “CAMBRIAN BLAST”?
Scientists have long suggested that a large jump 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 when a wide variety of animals erupted on the evolutionary stage.
About 580 million years ago, most organisms were simple, made up of individual cells, 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 today.
It ended with the extinction of the Cambrian Ordovician about 488 million years ago.
A recent study linked the historical growth of 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 materials that helped keep them in oxygen.