Chapter 17 Biogeographical distribution patterns in Early Palaeozoic Rostroconchia (Mollusca)

Abstract

Abstract The geographical distribution of rostroconch taxa of the orders Ribeirioida and Conocardiida, mostly across the equatorial continents and oceans, is compiled for six presumed diversity acmes in the early Early Ordovician ( c. 485 Ma), the late Early–early Middle Ordovician ( c. 475 Ma), the Late Ordovician ( c. 455 Ma), the Early Silurian ( c. 435 Ma), the late Early–early Late Silurian ( c. 425 Ma) and the early Early Devonian ( c. 415 Ma), based on our present, uneven knowledge. Rostroconchs show distribution patterns which enable a provisional separation of biogeographical provinces at least from the Silurian onward, comparable with Late Palaeozoic rostroconch distributional patterns. The distributions of tabulate corals, trilobites and bivalves appear roughly comparable, but not the nektic and planktic groups. A restriction to low latitudes (‘tropical’ realms) is clear for members of Ribeiria and Eopteria in the Early Ordovician, similar to proven patterns for hippocardiid rostroconchs from the Late Silurian onward until the Middle Permian. Preliminary rostroconch provinces or subprovinces, respectively, are currently discernable in the Silurian and Devonian for northwestern Laurentia, south-central Laurentia/Baltica and the north-central margin of Gondwana (i.e. Perunica, Bohemia). Rostroconch distributional data for SE Asia, China, Kazakhstan, Siberia and Australia are sparse and require further studies.