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 ofDickinsonia, bilaterally symmetrical oval organisms, have been particularly difficult to classify. Bobrovskiyet al.conducted an analysis using lipid biomarkers obtained fromDickinsoniafossils and found that the fossils contained almost exclusively cholesteroids, a marker found only in animals (see the Perspective by Summons and Erwin). Thus,Dickinsoniawere 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

The taphonomic varieties of over 800 specimens of Kimberella (collected from the Vendian rocks of the White Sea region) provide new evidence of the animal's anatomy such as: shell morphology, proboscis, mantle, possibly respiratory folds and possibly musculature, stomach and glands. Feeding tracks, crawling trails and, presumably, escape structures preserved along with the body imprint provide insights on the mode of locomotion and feeding of this animal. The shield-like dorsal shell reached up to 15 cm in length, 5–7 cm in width, and 3–4 cm in height. The shell was stiff but flexible. Evidence of dorso-ventral musculature and fine transverse ventral musculature suggests arrangement in a metameric pattern. Locomotion may have been by means of peristaltic waves, both within the sediment and over the surface of the sea floor, by means of a foot resembling that of monoplacophorans. Respiration may have been through a circumpedal folded strip (possibly an extension of the mantle). Feeding was accomplished by a retractable proboscis bearing terminal hook-like organs and provided with a pair of structures interpreted here as glands. Whilst feeding, Kimberella moved backwards. The structural complexity of Kimberella poses questions about the time of origin of the triploblastic metazoans.

Rangea is the type genus of the Rangeomorpha, an extinct clade near the base of the evolutionary tree of large, complex organisms which prospered during the late Neoproterozoic. It represents an iconic Ediacaran taxon, but the relatively few specimens previously known significantly hindered an accurate reconstruction. Discovery of more than 100 specimens of Rangea in two gutter casts recovered from Farm Aar in southern Namibia significantly expands this data set, and the well preserved internal and external features on these specimens permit new interpretations of Rangea morphology and lifestyle. Internal structures of Rangea consist of a hexaradial axial bulb that passes into an axial stalk extending the length of the fossil. The axial bulb is typically filled with sediment, which becomes increasingly loosely packed and porous distally, with the end of the stalk typically preserved as an empty, cylindrical cone. This length of the axial structure forms the structural foundation for six vanes arranged radially around the axis, with each vane consisting of a bilaminar sheet composed of a repetitive pattern of elements exhibiting at least three orders of self-similar branching. Rangea was probably an epibenthic frond that rested upright on the sea bottom, and all known fossil specimens were transported prior to their final burial in storm deposits.

Six groups of fossil remains of Kimberella quadrata are described. They represent the imprints of the body in different types of preservation (including the group of specimens that are elongated more than twice in comparison with the common ones) and also the feeding traces and mucus secretions. The imprint is considered to be created only by the upper side of the body. The fossil material shows that Kimberella had hard sclerites, probably of aragonite, and several teeth in its mouth. Kimberella is suggested to have “the mantle” with sclerites, wider foot, which was spread over the outer surface of the mantle, and the strong transverse and longitudinal musculature.