Fossils discovered in the far north of Canada could push back the proven timeline of animals on Earth back by around 350 million years—a period of time longer than that between the first dinosaurs and the present day. Geologist Elizabeth Turner says the tiny fossils found in the Northwest Territories' Mackenzie Mountains could be the skeleton of an ancient sponge, the CBC reports. They were found in rock layers 890 million years old. The oldest confirmed sponge fossils date to around 535 million years ago. If the fossil is indeed a sponge, "the material described here would represent the oldest body-fossil evidence of animals known to date," Turner writes in a study published in the journal Nature. Turner says she puzzled over the samples for years until a study of sponge fossil formation made her realize there were no other "truly viable interpretations of the material."
The fossils were found in crevices of ancient reefs in what was once an inland sea. Some experts agree that the filaments strongly resemble the skeletons of modern sponges, though others believe they could have been formed by microbes, which emerged billions of years before the first animals. Sponges or sponge-like creatures are believed to have been the first animal groups to emerge, and some researchers say genetic evidence suggests they were around up to a billion years ago, the AP reports. "This would be the first time that a sponge fossil has been found from before the Cambrian, and not only before, but way before—that's what’s most exciting," says sponge expert Paco Cardenas at Uppsala University. (Read more fossils stories.)