Late Ordovician and early Silurian rugose coral biogeography and world reconstruction of palaeocontinents

Abstract

Two epochs of Early Palaeozoic rugose coral diversification, Caradocian-Ashgillian and Middle Llandoverian-Early Wenlockian, are chosen for biogeographical analysis at the generic level, following an overall revised classification of the Rugosa (Wang et al., 1989a). World reconstruction maps are based on palaeomagnetic, palaeotectonic and palaeoblogeographic data, and were constructed through an autograph programme on an IBM PC-AT microcomputer. The Caradocian and Ashgillian rugose corals are in 16 families and 71 genera, including 15% Cystiphyllida, 40% Streptelasmatida and 44% Columnariida, in addition to the zaphrentoidid genus Protozaphrentis. Two biogeographical realms, the West Prototethyan and the East Prototethyan, may be discerned. The West Prototethyan Realm includes three provinces, the Siberian, the North American and the Kazakhstan-Hinganian. The East Prototethyan Realm also includes three provinces, the Southeast Asian (Yangtzean), the East Australian and the North European. The third area, the Gondwanan, is devoid of corals. In Middle and Late Llandoverian and Early Wenlockian, the rugose corals have 27 families and 130 genera, of which 26% are Cystiphyllida, 32% are Streptelasmatida and 41% are Columariida, in addition to the zaphrentoidid genus Duncanella. The West Prototethyan Realm contains three provinces, the Siberia-Mongolian, the North European and the North American. The East Prototethyan Realm consists of two provinces, the Southeast Asian (Yangtzean) and the Kazakhatan-Sinokorean, both bearing Ceriaster and Amplexoides.