Brachiopods of the Orders Protorthida and Orthida from the Silurian of the Yass Syncline, southern New South Wales

Abstract

The Yass Syncline succession ranges in age from possibly late Wenlock to earliest Devonian, with reasonable correlation based on conodonts and graptolites for the late Ludfordian through Pridoli to earliest Lochkovian (i.e. uppermost Black Bog Shale to Elmside Formation). Numerous brachiopods have been recorded from the succession, but there are no published descriptions of protorthides or orthides. In this paper nine species are described, of which two (Skenidioides thrinax and Salopina mediocostata) were originally described from the late Wenlock of Canberra, while five are new: Dolerorthis exatripalude, Isorthis (Arcualla) salicipontis, Salopina pusilla, S. rainbowella, and Talentella yassensis. Only the two Canberra species and D. exatripalude occur in Gorstian levels below the Black Bog Shale. All except one species occur in the lower Ludfordian Black Bog Shale, S. rainbowella being restricted to the overlying upper Ludfordian Rainbow Hill Member (basal Rosebank Shale) which also contains very rare S. mediocostata. Both S. pusilla and T. yassensis extend to the lower Pridoli lower Cowridge Siltstone. T. yassensis is the oldest species of that genus so far recorded, and might be derived from S. mediocostata. The Lochkovian species Salopina? herkion (Garra Formation, central NSW) is here referred to Talentella.