![]() ![]() They suggested the branching mesh formations could be the fossil remains of a group known as keratosan sponges. Researchers found strikingly similar winding networks in rocks much younger than the Little Dal reef in several locations. In recent years, however, clues to their possible identity began to amass. "I just kind of thought, you know, I'll just let this fester away in my mind," she says. She didn’t know what to make of the odd forms' identity. Yet some odd samples from the structure displayed tube-like forms that branch apart and then rejoin in a polygonal three-dimensional network. The Little Dal reef is mostly "just a streaky set of laminated things," she says. "There was something fishy about it," Turner says. But a series of strange samples with complex structures caught her eye. At the time, she was interested in how the cyanobacteria built the reef. Turner began studying Little Dal decades ago as a graduate student at Queen's University in Ontario. Find out about the two major categories of fossils, how fossilization occurs, and how fossils can help paint a picture of the planet's history. Some date as far back as 3.5 billion years ago, providing some of the earliest convincing traces of any kind of life on Earth.įossils are echoes of an ancient past. When fossilized, the layered microbial structures are known as stromatolites. These microbes grow in slimy sheets, forming layered mounds over time as sands catch on their sticky surfaces and minerals dissolved in the waters turn into solid bits of fluff. Unlike many modern reefs that are built by corals, the architects of this ancient structure were cyanobacteria. The structure formed at a time when warm, shallow seas flooded a vast tract of land through what is now North America-time and tectonics dried out the inland seas and turned the reefs to stone. The newly described fossils were tucked in the nooks and crannies of the towering Little Dal reef. "It's time for it to be published and go out to the community for discussion and challenge." Fishy fossils But she acknowledges that the proposed animal identity will be controversial. "It seems almost like a no-brainer," says Turner, a field geologist at Ontario's Laurentian University. She points out the network of flexible tubes that give the sponge its squish, explaining that the mesh is "identical" to the newly analyzed fossils, as well as to several younger mesh-like fossils recently identified by other scientists. ![]() "What we have is essentially something a bit like a Rorschach inkblot test, where there are some squiggles in a rock," says Jonathan Antcliffe, a paleontologist specializing in early life at the University of Lausanne, Switzerland.ĭuring a Zoom interview, Elizabeth Turner, the sole author of the study, holds up a mustard yellow natural bath sponge-a modern relative to the newly proposed fossil sponge. And the Little Dal fossils are no different. The creatures that flourished in ancient seas may have looked quite different than those that swim through oceans today, and scientists disagree about how much and which types of evidence can distinguish animals from other forms of life-or geologic structures. However, most claims of extremely old fossilized life kick up controversy. If confirmed, the fossil sponges, found in the "Little Dal" limestones in northwest Canada, would predate the earliest undisputed fossils of any animal by more than 300 million years. Now, a study published in the journal Nature suggests that mesh-like structures in an ancient reef may be 890-million-year-old sponges. But exactly when that happened remains under debate. Their simplicity has led scientists to suggest sponges were the earliest animals to arise on our planet. Relatives of the humble sea sponge have filtered Earth's waters for hundreds of millions of years or more, long before the first plants took to land. ![]()
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