Article: Cambroclaves and paracarinachitids, early skeletal problematica from the Lower Cambrian of south China

Cambroclaves are a major group of sclerite-bearing metazoans, known from the Lower Cambrian of China (south China, Xinjiang), USSR (Kazakhstan) and Australia. Zhijinites longistriatus Qian is redescribed on the basis of abundant material from the Hongchunping Formation at Maidiping, Sichuan. Sclerites show extensive morphological variability and have a taphonomic history of endolithic infestation and diagenetic phosphatization, the latter leading to replication of wall ultrastructure. Deiradodavus trigonus gen. et sp. nov. and Deltaclavus graneus gen. et sp. nov. are younger cambroclaves recovered from the Guojiaba Formation near Kuanchuanpu, Shaanxi, and the Shuijingtuo Formation at Taishanmiao, Hubei. Both taxa bore a cataphract scleritome, composed of interlocking sclerites. In Deltaclavus articulated series of sclerites include 'arm-like' structures. Paracarinachitids may be related to cambroclaves, and are described on the basis of isolated sclerites of Paracarinachites spinus Yu from the Yuhucun Formation of Meishucun, Yunnan. Protopterygotheca leshanensis Chen from the Hongchunping Formation of Maidiping is included in the paracarinachitids, and is described on the basis of isolated sclerites bearing prominent flanges on either side of the spatulate axis. The primary function of the scleritomes of cambroclaves and paracarinachitids may have been protective, but in the absence of intact scleritomes both the palaeoecology and affinities of these groups are uncertain. The new class Cambroclavida is proposed.