Early Cambrian Trilobites from Angorichina, Flinders Ranges, South Australia, with a New Assemblage from the 'Pararaia bunyerooensis' Zone

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 'Yunnaocephalus 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 Countries, Yunnan Province, southwest China. The 'Pararaia bunyerooensis' Zone is correlated with the 'Yunnanocephalus' Assemblage subzone (upper 'Eoredlichia-Wutungaspis' Zone) of the Chiungchussuan (=Qiongzhusian) Stage of China. Additional trilobites from Angorichina include 'Elicicola calva' from the Wilkawillina Limestone, 'Estaingia occipitospina' (Jell) new combination form 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 bunyeriiensis' 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.