Cambrian (Furongian) rhynchonelliform brachiopods from the Eastern Alborz Mountains, Iran

The Cambrian (Furongian) shallow water carbonates in the Mila Formation in the Tuyeh-Darvar area (eastern Alborz, northern Iran) contain numerous shell beds, entirely composed of disarticulated valves of the billingsellide brachiopods Billingsella? fortis sp. nov. and Hyrcanostrophia tuyehensis gen. et sp. nov. Higher up in the Mila Formation, the shallow water carbonates are replaced by nodular limestones, deposited in an open marine environment, containing Palaeostrophia tecta Nikitin & Popov, 1983 and the early polytoechioid Darvaretoechia prisca gen. et sp. nov. These two different brachiopod assemblages are assigned to the oligotaxic Billingsella and Palaeostrophia associations, respectively. These associations are considered to represent precursors to the brachiopod-dominated benthic assemblages of the Palaeozoic Evolutionary Fauna. The new brachiopod faunas from the Alborz Terrane are closely similar to contemporaneous Furongian faunas from the Australasian sector of Gondwana, in particular, to those from South China and the Kazakhstanian terranes.