Ediacaran paleobiology and biostratigraphy of the Nama Group, Namibia, with emphasis on the erniettomorphs, tubular and trace fossils, and a new sponge, Arimasia germsi n. gen. n. sp.

Ediacaran fossils, obtained in stratigraphic context in 1993, 1995, and 1996, with the assistance of A. Seilacher, IGCP project 320 scientists, and the Geological Survey of Namibia, are described for the first time. Most are from the Kliphoek and Buchholzbrunn members of the Dabis Formation and the Huns and Spitskop members of the Urusis Formation, Witputs subbasin, but a significant number, including Pteridinium , are from the Kliphoek Member, Zaris Formation, and the Neiderhagen Member, Nudaus Formation, north of the Osis arch, which separates the two subbasins. We extend the stratigraphic ranges and geographic distributions of several important taxa, including Archaeichnium, Ernietta, Pteridinium, and Swartpuntia, provide reassessments of the paleobiology of these and other organisms, and describe a new sponge—possibly an unmineralized archaeocyath— Arimasia germsi n. gen. n. sp. We also describe and illustrate various ichnofossils (including the oldest known traces from the Nama Group), narrow down the first appearance of Treptichnus in the Nama succession, and reinforce the idea that there was a prolific infauna of micrometazoans during the latest Ediacaran by naming and describing previously reported microburrows found on the surfaces of gutter casts as Ariichnus vagus n. igen. n. isp.