Ancient steroids establish the Ediacaran fossil<i>Dickinsonia</i>as one of the earliest animals

Abstract

Confirming the identity of early animals The first complex organisms emerged during the Ediacaran period, around 600 million years ago. The taxonomic affiliation of many of these organisms has been difficult to discern. Fossils of Dickinsonia , bilaterally symmetrical oval organisms, have been particularly difficult to classify. Bobrovskiy et al. conducted an analysis using lipid biomarkers obtained from Dickinsonia fossils and found that the fossils contained almost exclusively cholesteroids, a marker found only in animals (see the Perspective by Summons and Erwin). Thus, Dickinsonia were basal animals. This supports the idea that the Ediacaran biota may have been a precursor to the explosion of animal forms later observed in the Cambrian, about 500 million years ago. Science , this issue p. 1246 ; see also p. 1198