New bradoriids from the lower Cambrian Mernmerna Formation, South Australia: systematics, biostratigraphy and biogeography

Abstract

An assemblage of bradoriid arthropods from the Mernmerna Formation in the Donkey Bore Syncline, central Flinders Ranges, South Australia contains eleven species, including three species of the enigmatic ornamented spine 'Mongolitubulus'. Four new taxa are described, 'Onagrocharion tuberosus' gen. et sp. nov., 'Amphikeropsis myklosis' gen. et sp. nov., 'Hipponicharion australis' sp. nov. and 'Mongolitubulus unispinosa' sp. nov. The presence of 'Hipponicharion australis' sp. nov. in the upper Mernmerna Formation represents the first occurence of the genus in Australia and extends the biogeographic range of Hipponicharion to eastern Gondwana. Bradoriid specimens of 'Mongolitubulus unispinosa' sp. nov. exhibiting a single mature ornamented spine attached to the central portion of the carapace provides definitive evidence of a bradoriid affinity for the enigmatic, widespread 'Mongolitubulus' small shelly fossil taxon. The assemblage includes several species that facilitate correlation with the Stansbury Basin of South Australia, but also with faunas from other Cambrian palaeocontinents, including Antarctica and Laurentia.