A Canadian geologist has discovered 890 million-year-old sponge fossils in the Northwest Territories, leading to the retreat of the oldest known animal about 350 million years old. This work will help find other animals that do not have a skeleton or a shell.
tubes and skeletons
To date, the oldest identified animal fossil dates back 540 million years. “It was also a sponge, but with a skeleton,” says Elizabeth Turner, a geologist at Laurentian University in Sudbury and lead author of the study published Wednesday in the journal. nature. We think we’ve shown that our hole, which dates back 890 million years, is a sponge without a skeleton. “NSI Turner identified the structures in the rock as tubes, which are said to be traces of tubes surrounding a tissue stronger than a sponge without a skeleton. “It is well established that this tougher tissue degrades more slowly in modern sponges,” says the Sudbury researcher. Our hypothesis is that there are deposits around these tubes after the soft tissue decomposition of the sponge. If confirmed by other researchers, the analysis of M.I Turner can help identify other animals without a skeleton or shell. “The fossils that we know today are identifiable by these mineral tissues, which can be preserved under certain conditions. But the first animals without a skeleton are believed to have appeared a billion years ago. So we have to find other fossil traces, like the ones I describe in natureto get to know them. “NSI Turner recalls that an animal “is an organism that derives its energy and nutrients in part from the consumption of other living things.”
What other explanations have been considered to explain these tubular structures in the rocks examined by M.I Turner? “Some say it’s germs. But you have to realize that with the rock, there are a lot of structures that we don’t really understand. We tell ourselves, ‘Wow,’ and we move on. Why is she the first to suggest that it’s 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 far north, to places that are hard to reach. Applications for excavation permits are complicated because they are disputed lands, and we apply to the federal government, to the regions, to the guerrilla councils. They have other things. To do it other than get back to us quickly, and I get it. Then we spend the nights on our microscope, examining the rocks which for the most part contain nothing.”
Why did animals appear at this time in Earth’s history? “It appears to be related to Proterozoic oxygen from 830 to 540 million years ago,” says El Master.I Turner. Then, 540 million years ago, we witnessed the Cambrian explosion, with the emergence of many types of animals with skeletons and shells. There are also other animals that are slightly older, related to the Ediacaran Explosion, just before the Cambrian Explosion. Ediacaran fossils have been found in Newfoundland, in particular. But it is very difficult to understand whether they are really animals. Earth’s atmosphere had very little oxygen until the Great Oxygenation event, 3 billion years ago, and then it remained at 5% oxygen until the Proterozoic oxygenation, when the oxygen rate rose to 15%. The level of atmospheric oxygen is currently 21%. The Cambrian explosion lasted about 25 million years.
The first animals by numbers
200,000 to 300,000: Number of extinct species described from fossils
1.8 million: The number of living species identified on the planet today
From 2.5 to 8 million: the likely number of living species on the planet today
5 times faster: the speed of evolution of species during the Cambrian explosion compared to the speed of evolution today
Source: Smithsonian Institution
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