The bivalved arthropod Caudicaella aff. bispinata from the Heatherdale Shale (Cambrian Stage 3), South Australia

Abstract

Sunellids are early Cambrian bivalved arthropods first recognized in South China that are important for understanding the early evolution of the group. However, their taxonomic affinity and distribution beyond South China is poorly known. Furthermore, the relationship between members of the Sunellidae and the globally dispersed Isoxys remains unclear. Recently, rare specimens of the sunellid Caudicaella aff. bispinata have been recovered from the lower Cambrian (Series 2, Stage 3) Heatherdale Shale, eastern Stansbury Basin, South Australia, representing the first record of the group from East Gondwana. Caudicaella aff. bispinata from Australia bears a semicircular carapace, a pair of anterodorsal sulci, anterior and posterior cardinal spines, as well as a distinct thick border or margin. It most closely resembles Caudicaella bispinata from the Shuijingtuo Formation in western Hubei Province, South China. The new discovery adds support for strong faunal similarity of the Konservat-Lagerstätten of South Australia and South China and extends the known geographical range of Cambrian sunellids to East Gondwana. The occurrence of Caudicaella bispinata in South China and Caudicaella aff. bispinata in East Gondwana strengthens the biostratigraphic correlation between those two palaeo-continents.