Abstract

Trilobites from the Lower Cambrian succession at Angorichina in the eastern Flinders Ranges, South Australia, are described. Silicified material from the Mernmerna Formation reveals the presence of a new assemblage from the Pararaia bunyerooensis Zone, including the eponymous species, Yorkella aff. australis, Eoredlichia sp., Redlichia sp., and the new species Wutingaspis euryoptilos and Yunnanocephalus macromelos. Trilobites of the Pararaia bunyerooensis Zone show a strong affinity with those from the Yu'anshan Member of the Heilinpu Formation in Chengjiang and Jinning Counties, Yunnan Province, southwest China. The Pararaia bunyerooensis Zone is correlated with the Yunnanocephalus Assemblage subzone (upper EoredlichiaWutingaspis Zone) of the Chiungchussuan (=Qiongzhusian) Stage of China. Additional trilobites from Angorichina include Elicicola calva from the Wilkawillina Limestone, Estaingia occipitospina (Jell) new combination from the Oraparinna Shale, and Redlichia guizhouensis Zhou from the Wirrealpa Limestone. Australian Early Cambrian trilobite biozonation is reviewed, with discussion of distinct assemblages within the Pararaia janeae Zone that have the potential for zonal subdivision, and evidence to support the placement of the northern Australian Ordian/Early Templetonian Stage within the late Early Cambrian.

A possible paedomorphic lineage between Pararaia bunyerooensis and P. janeae is proposed. Adult specimens of P. janeae retain juvenile characteristics of the progenitor P. bunyerooensis. Retardation in onset of maturity in P. janeae resulted in the attainment of a larger adult size than in P. bunyerooensis, indicating the former species evolved via neoteny.

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