The first animals just got a little older.

Researchers say a fossil site in Canada’s Northwest Territories contains 567-million-year-old organisms that may be among the earliest animals to move, reproduce sexually and develop recognizable body plans. The findings suggest those milestones happened 5 to 10 million years earlier than previous evidence showed.

The fossils belong to the Ediacaran biota, a group of mostly soft-bodied organisms that lived on ancient seafloors more than 500 million years ago. The study was led by scientists at the American Museum of Natural History and Dartmouth and published in Science Advances.

“For 3 billion years, life on Earth was dominated by microbes. Then, all the sudden, we get these strange-looking marine animals big enough to see and capable of behaviors we would find familiar today,” said lead author Scott Evans, assistant curator of invertebrate paleontology at the American Museum of Natural History. “If we want to understand this transition, when life first became large, complex and unmistakably animal, this new site has tremendous potential.”

Ediacaran fossils have been found on every continent except Antarctica, but sites with more than 10 species are extremely uncommon. Scientists have had only limited evidence from this period, which lasted roughly 40 million years.

Before this discovery, fossils from the White Sea assemblage had been documented in Europe, Asia and Australia, but not in North America. Researchers found the new fossils in ancient rock layers in Canada’s Mackenzie Mountains on the traditional lands of the Sahtú Dene and Métis. Members of those communities gave the researchers guidance and permission to enter and study the area.

Scientists identified more than 100 fossils, including six groups never previously recorded in North America. Some date to about 567 million years ago, making them 5 to 10 million years older than other known White Sea fossils.

“Not only is this new site highly diverse, but also it is from a part of the rock succession where we have previously lacked fossil remains,” said study co-author Justin Strauss, an associate professor of Earth and Planetary Sciences from Dartmouth, who has been exploring the area for about 15 years. “This is really exciting. Given our understanding of the regional geology in northwestern Canada, there is great potential here to revisit our understanding of Ediacaran Earth history.”

Several of the fossils represent organisms never before found in North America. They include Dickinsonia, a flat animal that traveled across the seafloor and apparently absorbed nutrients through its lower surface, and Funisia, a tube-shaped organism that lived in clusters and provides the oldest known fossil evidence of sexual reproduction.

The site also includes Kimberella, which moved with a muscular foot and scraped food from the seafloor. Scientists commonly interpret it as an early relative of mollusks. The newly discovered specimens may also make it the oldest known fossil bilaterian, the group of animals with distinct front, back, top and bottom and symmetric left and right sides that makes up more than 99 percent of all known animals.

Researchers also found Eoandromeda, described as a possible comb jelly with eight arms arranged in a spiral.

The fossils indicate these organisms lived in deeper water than scientists had previously linked to the White Sea assemblage. The researchers said that supports the idea that early animals may have first appeared in offshore, deep marine environments before spreading into shallower coastal waters.

“These results suggest a pattern where evolutionary innovation begins in deeper environments and later spreads toward the coast,” Evans said. “We think of the deep ocean as a dark, inhospitable place, but it is also relatively stable, with few fluctuations in things like temperature and oxygen essential to most animal life. This stability may have provided key opportunities to support early animal life.”

The fossils will eventually become part of the permanent collection at the Prince of Wales Northern Heritage Centre in Yellowknife, Northwest Territories.

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