Taphonomy

Gene

Structural basin

Geology

Paleontology

Trace fossil

Archaeology

Phanerozoic

Ecology

Most recent common ancestor

Geography

Lineage (genetic)

Ancestor

Biota

Biochemistry

Cenozoic

Evolutionary biology

Biology

Paleobiology

Phylogenetics

Proceedings of the National Academy of Sciences

Significance The transition from simple, microscopic forms to the abundance of complex animal life that exists today is recorded within soft-bodied fossils of the Ediacara Biota (571 to 539 Ma). Perhaps most critically is the first appearance of bilaterians—animals with two openings and a through-gut—during this interval. Current understanding of the fossil record limits definitive evidence for Ediacaran bilaterians to trace fossils and enigmatic body fossils. Here, we describe the fossil Ikaria wariootia, one of the oldest bilaterians identified from South Australia. This organism is consistent with predictions based on modern animal phylogenetics that the last ancestor of all bilaterians was simple and small and represents a rare link between the Ediacaran and the subsequent record of animal life.

Discovery of the oldest bilaterian from the Ediacaran of South Australia