"A billion-year-old fossil of an organism, exquisitely preserved in the Scottish Highlands, reveals features of multicellularity nearly 400 million years before the biological trait emerged in the first animals, according to a new report in the journal Current Biology by an international team of researchers, including Boston College paleobotanist Paul K. Strother.." See https://www.eurekalert.org/news-releases/528947 and https://www.sheffield.ac.uk/news/billion-year-old-fossil-reveals-missing-link-evolution-animals for details.
The first article listed above says the following.
"The microfossil, discovered at Loch Torridon, contains two distinct cell types and could be the earliest example of complex multicellularity ever recorded, according to the researchers.
The fossil offers new insight into the transition of single celled organisms to complex, multicellular animals. Modern single-celled holozoa include the most basal living animals and the fossil discovered shows an organism which lies somewhere between single cell and multicellular animals, or metazoa."
The second article listed above says the following.
' “We have found a primitive spherical organism made up of an arrangement of two distinct cell types, the first step towards a complex multicellular structure, something which has never been described before in the fossil record.
discovery of this new fossil suggests to us that the evolution of
multicellular animals had occurred at least one billion years ago and
that early events prior to the evolution of animals may have occurred in
freshwater like lakes rather than the ocean.” '