Oldest animal fossil found in Canada

A Canadian geologist has found sponge fossils in the Northwest Territories that are 890 million years old, pushing back the age of the oldest known animal by 350 million years. This work will make it possible to find other animals that did not have a skeleton or a shell.

Posted Jul 29 2021Mathieu Perreault The Press

Tubing and Skeletons

Until now, the oldest identified animal fossil dates back 540 million years. "It was also a sponge, but with a skeleton," said Elizabeth Turner, a geologist from Laurentian University in Sudbury who is the lead author of the study published Wednesday in the journal Nature. “We believe we have demonstrated that our fossil, which dates back 890 million years, is that of a sponge without a skeleton. ^Ms. Turner identified structures in the rock in the form of tubing, which would be the traces of tubing enclosing the firmer tissue of the sponges without skeleton. “There is good evidence that this firmer tissue decomposes more slowly in modern sponges,” says the Sudbury researcher. Our hypothesis is that there were deposits around these tubings after the softer tissues of the sponge had broken down. If confirmed by other researchers, ^Ms. Turner's analysis could help identify other animals without skeletons or shells. “The fossils that we currently know are identifiable by these mineralized tissues, which can be preserved under certain conditions. But it is believed that the first animals without a skeleton appeared 1 billion years ago. So you have to find other fossil traces, like those I describe in Nature, to identify them. ^Ms. Turner points out that an animal is “an organism that derives its energy and nutrients in part from the consumption of other organisms”.

Oldest animal fossil found in Canada

Microbes

What are the other explanations considered to explain these tubular structures in the rocks examined by Mrs. ^Turner ? “Some say they are germs. But you have to realize that with rock, there are a lot of structures that you don't really understand. We say to ourselves: “How weird” and we move on. Why is she the first to suggest that it is a sponge fossil? “Our field of study is very difficult,” says the geologist. We don't have a lot of funding, we have to go to the Far North, to places that are difficult to access. Excavation permit applications are complicated because it concerns lands whose ownership is disputed, applications are made to the federal government, to the territories, to the band councils. They have other things to do than answer us quickly, and I understand that. Then, you spend nights on your microscope, examining rocks which, most of the time, contain nothing. »

Oxygenation

Why did animals appear at this time in Earth's history? “It seems to be related to Proterozoic oxygenation, 830 to 540 million years ago,” says ^Ms. Turner. It was after that, 540 million years ago, that we had the Cambrian explosion, with the appearance of many species of animals with skeletons and shells. There are also other possible animals a little older, linked to the Ediacaran explosion, a little before the Cambrian explosion. Ediacaran fossils have been found in Newfoundland, in particular. But it is exceptionally difficult to understand if they are indeed animals. The Earth's atmosphere had very little oxygen until the Great Oxygenation 3 billion years ago, then remained at 5% oxygen until the Proterozoic Oxygenation, when the rate oxygen increased to 15%. The atmospheric oxygen level is currently 21%. The Cambrian explosion lasted about 25 million years.