Among thousands of impressions in a large rock surface, one stood out in the crowd. The imprint of a tough tubular exoskeleton with wavy tentacles, now frozen in time, looked strikingly familiar, unlike its neighbors.
It looked like a relative of corals, anemones and jellyfish from a sediment layer 20 million years before Cnidaria was thought to exist.
“It’s nothing like anything else we found in the fossil record at the time,” said paleontologist Frankie Dunn of the Oxford University Museum of Natural History.
“Most of the other fossils from this time have extinct body plans and it’s not clear how they are related to living animals. This one clearly has a skeleton, with tightly packed tentacles that would have swung in the water, catching passing food, much like corals and sea anemones do today.”
The discovery itself was made in 2007 when researchers from the British Geological Society removed debris from a boulder near the Bradgate Formation in Charnwood Forest, a well-known fossil site just outside Leicester.
The rock itself is already considered really old, dating back to about 557 to 562 million years old. It was a time of truly strange creatures, long before the rich biodiversity of the Cambrian explosion gathered the body plans we are now more familiar with.
The researchers took a cast of the textured rock for study. Amid the thousands of impressions depicting an assortment of ancient life forms, one looked less strange than the rest. In fact, it looked a little too much like the life we would see today.
The 20-centimeter cnidarian resembles something we might see snare a passing crustacean on a modern coral reef and now represents the earliest example of a predator.
“The ‘Cambrian Explosion’ was remarkable. It is known as the time when the anatomy of living animal groups was fixed for the next half a billion years,” Dunn explains.
“Our discovery shows that the cnidarians’ body plan [corals; jellyfish; sea anemones, etc.] was repaired at least 20 million years earlier, so it’s hugely exciting and raises a lot more questions.”
The Ediacaran period is known for its scarce but strange, very alien fossils that bear no resemblance to anything currently living. The new find supports the theory that this period is also the beginning of modern animals. The seeds of at least one animal group we know today were first planted then, just in time to truly bloom and diversify during the fertile Cambrian era.
So Dunn and his colleagues named the fossilized animal’s genus auroralumina, which means dawn lantern because of its resemblance to a burning torch. Much to the delight of Sir David Attenborough, who hunted fossils nearby as a boy, they gave it the species name attenboroughii.
This strange but familiar creature has the same characteristics as early Cambrian cnidarians; unlike them, however, the tough exoskeleton is smooth rather than decorated.
“It’s the earliest creature we know to have a skeleton,” Dunn says. “So far we’ve only found one, but it’s hugely exciting to know that there must be others who hold the key to when complex life on Earth began.”
Auroralumina attenboroughiis large size, compared to other known relatives, may mean it doesn’t have the free-swimming medusa stage of its life cycle like jellyfish and corals, the team suspects. Anemones also lack this stage – they are sessile animals that always stay in place.
The researchers believe that a deluge of volcanic ash sent this lone little predator into deeper water from a shallower house on the flank of a volcanic island. It lies at a strange angle compared to its neighbors in death, who were all flattened and kept forever in that direction when the Flood struck.
This research was published in Nature Ecology & Evolution.