Scientists have discovered a billion-year-old fossil in the Scottish Highlands that could reveal a new link in the evolution of animals.
The microfossil was unearthed by a team of researchers, led by the University of Sheffield at Loch Torridon in north-west Scotland. Their discovery, which contains two separate types of cells, could be the earliest multicellular animal ever found.
It has been formally named Bicellum Brasieri in a research paper published in Current Biology, a peer-reviewed scientific journal. Professor Charles Wellman, one of the lead investigators from the university's department of animal and plant sciences, said the fossil was the first of its kind to be recorded.
"The origins of complex multicellularity and the origin of animals are considered two of the most important events in the history of life on Earth, our discovery sheds new light on both of these," he explained.
"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. The 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."
Bicellum Brasieri offers new insight into the transition of single-celled organisms to complex multicellular animals and its "exceptional preservation" allowed the team to analyse it at a cellular and subcellular level.