If you visited the oceans more than 500 million years ago, you would find yourself in an alien world. Creatures with quilted folds of soft tissue sat like carpets on the sea floor, and life forms that looked like leafy plants but were actually animals were anchored on the ocean floor. But one organism may be somewhat familiar: a stalked, cup-like creature with wavy tentacles that resemble those of a jellyfish. The newly described fossil of this organism, called Auroralumina attenboroughii after naturalist and broadcaster David Attenborough, is between 556 million and 562 million years old and is perhaps the oldest example of an evolutionary group still alive.
When Oxford University co-author and paleobiologist Frances Dunn saw a cast of the fossil, she said, “It was immediately clear that this was very special and very rare.” With other fossils from the Ediacaran period, between 635 million and 541 million years ago, her first impression is often, “What is this? How can I relate this to anything alive today?” But with this one, she thought, “I know what this is.”
Classical scientific wisdom places the origin of modern animals about 539 million years ago during what is called the Cambrian explosion. At this point, creatures with specialized tissues, organs, guts, and symmetrical left and right sides — all traits we recognize in today’s animals — began to emerge.
In more recent years, fossil finds from the earlier Ediacaran period began to question this dogma. That’s especially true of creatures that can be classified as cnidarians, a group of marine animals that includes today’s jellyfish, corals, and sea anemones. A cup-shaped creature with a tangle of tentacles called Haootia quadriformis dates about the same age as A. attenboroughiibut the relatively poor preservation makes the exact relationship with extant animals difficult to parse.
Paleobiologist Philip Wilby and colleagues at the British Geological Survey discovered the new fossil in the Charnwood Forest, a hotbed of pre-Cambrian paleontology in a hilly area of Leicestershire in central England. They dated the rocks around the fossil to between 556 million and 562 million years ago using the radioactive decay of uranium into lead.
The eight-inch fossil — about the length of a dinner fork — is an impression of a bipartisan creature with long stems topped by tentacled cups. The organism appears to be in the polyp stage, the life cycle in which a cnidarian clings to the ocean floor and uses its tentacles to grab tasty larvae and floating plankton. The body of A. attenboroughi has fourfold symmetry, meaning it is symmetrical around all four corners of a center point, much like modern jellyfish.
The researchers made a cast and a detailed drawing of the fossil, which they examined and manipulated on a computer to better see the creature in different exposures. They then used another computer program to count the fossil’s physical properties and place it on an evolutionary tree.
The team concluded that A. attenboroughi is a cnidarine and a member of the subgroup called medusozoans, which includes modern jellyfish, they report today in Nature Ecology & Evolution. If true, “our fossil will be the oldest animal with direct living descendants in the fossil record — period,” Dunn says.
“It looks more like a modern animal group than anything this age or older,” agrees Alexander Liu, a paleobiologist at the University of Cambridge who was not involved with the new find; he was part of the team that described Haootia in 2014. Still, he wishes the authors had compared the new fossil better to groups such as the coral-containing cnidarian subgroup anthozoa.
As for the creature’s alliterative name, the researchers chose: auroralumina because of its early animal status and because Dunn’s shape was reminiscent of the Olympic torch; in Latin, Aurora means dawn and lumina means light. And they chose attenboroughii because Attenborough spent his childhood near Charnwood and has drawn attention to its fossils. “He grew up stomping those ancient forests, so we wanted to name the species after him,” Dunn says.