Uncovering the Missing Link: Rare Fossils Shed Light on Major Animal Group Evolution.
Rare, well-preserved fossils of an extinct invertebrate called Rotadiscus grandis have helped fill a gap in our understanding of the origin and evolution of major animal groups alive today. The fossils, from the Cambrian period, have revealed how some characteristics of living species may have evolved independently rather than originating in a single common ancestor. The analysis of the fossils has helped place Rotadiscus in the animal tree of life, showing that it is a very early member of the ambulacrarians, a group that includes starfish and acorn worms. The discovery also suggests that some features, such as a post-anal tail, may have evolved independently in different animal groups through convergent evolution.