EARLY CAMBRIAN SMALL SHELLY FOSSILS FROM SOUTHEASTERN SHAANXI PROVINCE, CHINA

Phosphatized and phosphatic small shelly fossils are one of the major sources of information for understanding the evolution of animals during the Early Cambrian. Such fossils have long been reported from the later Early Cambrian (Qiongzhusian or Atdabanian) Xihaoping Member of the Dengying Formation from southeastern Shaanxi and northwestern Hubei provinces, China, deposited in shallow marine waters along the northern margin of the Yangtze Platform. Although a number of intriguing fossils from this unit have been described, most have not been studied in detail. We have collected new samples from Xiaowan, Xixiang County, Shaanxi, and here present preliminary results on the fossils found there. The most common taxa are conchs of orthothecimorph hyoliths, many of which have beautifully preserved microstructure, and isolated sclerites (parts of a multi-element external skeleton) of problematic cambroclaves. Also very common are a variety of coeloscleritophorans, a controversial group characterized by hollow aragonitic sclerites. These include multiple species of chancelloriids (sessile, superficially sponge-like animals), the probably allied form Cambrothyra, as well as curved sclerite of Aurisella (previously referred to as Ninella) and rare halkieriids. Other problematic forms include cap-shaped fossils and the bizarre spine-like Acidocharacus. More familiar taxa are represented by sponge spicules (including probable heteractinids) and rare molluscs. Microbes are recorded by endolithic microborings and encrusting filaments.