It seems to be a fungus of some sort:
When the Ediacaran period began, the planet was recovering from a catastrophic ice age, also known as the “snowball Earth.” At that time, ocean surfaces were frozen to a depth of more than a kilometer and it was an incredibly harsh environment for virtually any living organism, except for some microscopic life that managed to thrive. Scientists have long wondered how life ever returned to normalcy — and how the biosphere was able to grow larger and more complex than ever before.
With this new fossil in hand, Tian and Xiao are certain that these microscopic, low profile cave dwellers played numerous roles in the reconditioning of the terrestrial environment in the Ediacaran time. One role involved their formidable digestive system.
Fungi have a rather unique digestive system that plays an even greater role in the cycling of vital nutrients. Using enzymes secreted into the environment, terrestrial fungi can chemically break down rocks and other tough organic matter, which can then be recycled and exported into the ocean.
“Fungi have a mutualistic relationship with the roots of plants, which helps them mobilize minerals, such as phosphorus. Because of their connection to terrestrial plants and important nutritional cycles, terrestrial fungi have a driving influence on biochemical weathering, the global biogeochemical cycle, and ecological interactions,” said Gan.
Although previous evidence stated that terrestrial plants and fungi formed a symbiotic relationship around 400 million years ago, this new discovery has recalibrated the timeline of when these two kingdoms colonized the land.
Virginia Tech, “635 million-year-old fungi-like microfossil that bailed us out of an ice age discovered” at ScienceDaily
The study is open access.
In short, complex life got started even earlier than we had thought, which leaves even less time for unguided, Darwinian evolution.