The trilobite Redlichia from the Ordian (Cambrian Series 2, Stage 4) Wirrealpa Limestone, South Australia.

Abstract

Trilobites of the genus Redlichia have been known from the Ordian (Cambrian Series 2, late Stage 4) Wirrealpa Limestone in the South Australia for over 100 years, yet only a small number of specimens have been described from this unit. Consequently, the taxonomic affinities of these remain poorly understood. Here, Redlichia from the Wirrealpa Limestone is described in detail based on abundant, newly collected material from the Bunkers Range area of the Flinders Ranges. This species is described under open nomenclature as Redlichia cf. versabunda, a species previously described from the Ordian Thorntonia Limestone in northern Australia. Ontogenetic trends in cranidial morphology are also described for this species. In addition, Redlichia is likely oversplit in Australia, with many species based on very few specimens or incomplete material, including of isolated cranidia. Therefore, the measurements of the new specimens from the Wirrealpa Limestone were compared to new measurements of other Australian Redlichia species based on figured specimens in existing literature, to reveal patterns of cranidial variation between species. Results show large overlap between species due to ontogenetic and intraspecific variation, including between species that are known to be separate due to differences in other sclerites. These results suggest that it is not possible to easily distinguish between Redlichia species based on cranidial measurements alone, and that species described only on cranidial material are problematic. Further research is required to comprehensively review this genus in Australia and elsewhere.