Article: Early Cambrian button-shaped phosphatic microfossils from the Siberian Platform

Button-shaped phosphatic microfossils from the uppermost Atdabanian (Lower Cambrian) of the Siberian Platform (middle reaches of the River Lena, Yakutia, U.S.S.R.) are described as Lenargyrion knappologicum n. g., n. sp. The fossils have a mean diameter of about 150 ^m. One side is smooth and slightly convex, the other conical with a flat crest on which are set minute nodes. The internal structure is double-layered: the conical and nodular surfaces are formed by a dense layer capping the more porous core, which contains fine canals. No growth structures can be seen, and there is evidence of mechanical abrasion on the nodular surface. The 'buttons' were probably dermal sclerites in an animal of unknown systematic position. The possibilities of vertebrate affinities are briefly discussed, but the evidence is considered inconclusive.