BBC has an up-close look at the tiny, primitive face of the great-great-great-great-etc. grandaddy of anything with a backbone:
They say that fossilised traces of the 540-million-year-old creature are “exquisitely well preserved”.
The microscopic sea animal is the earliest known step on the evolutionary path that led to fish and – eventually – to humans.
The research team says that Saccorhytus is the most primitive example of a category of animals called “deuterostomes” which are common ancestors of a broad range of species, including vertebrates (backboned animals).
Saccorhytus was about a millimetre in size, and is thought to have lived between grains of sand on the sea bed.
The researchers were unable to find any evidence that the animal had an anus, which suggests that it consumed food and excreted from the same orifice.
The study was carried out by an international team of researchers, from the UK, China and Germany. Among them was Prof Simon Conway Morris, from the University of Cambridge.
He told BBC News: “To the naked eye, the fossils we studied look like tiny black grains, but under the microscope the level of detail was jaw-dropping.
“We think that as an early deuterostome this may represent the primitive beginnings of a very diverse range of species, including ourselves. All deuterostomes had a common ancestor, and we think that is what we are looking at here.”