The Late Palaeozoic trilobites of Iran and Armenia and their palaeogeographical significance

Abstract

AbstractThe Iranian territory is composed of a mosaic of tectonic units, several of which underwent in the Permian and Triassic periods a migration from northern Gondwana to southern Laurussia associated with the opening of the Neo-Tethys Ocean. Although this broad outline of Permo-Triassic palaeogeographical evolution of Iranian microplates is now widely accepted, the individual timing of migration of these blocks, and their biogeographical relationships, remain insufficiently known. Here I review the Late Palaeozoic record of trilobites in Iran and Armenia, and discuss their palaeobiogeographical affinities in an attempt to shed light on the Permian palaeogeographical evolution of Iranian and Armenian terranes. Seven Iranian or Armenian localities, representative of five tectonic units, have yielded Carboniferous and Permian trilobites. Ten species are recognized, including two new taxa,Persia praecoxgen. nov. sp. nov. andPseudophillipsia(s.l.)parviziisp. nov.P. praecoxis the only Carboniferous (Tournaisian) species. The others are Wordian to Wuchiapingian in age and can be separated into three morphological groups, probably representing clades. One is composed of representatives ofAcropyge, while the two others (armenica-group andpaffenholzi-group) comprise species ofPseudophillipsia. OnlyP.(s.l.)parviziisp. nov. from the Zagros Mountains (Arabian Plate) is not attributed to one of these groups. The distribution of trilobites in Iran and Armenia strongly suggests that the Alborz, Central Iran and Transcaucasia microplates represented a single biogeographical unit in Middle and Late Permian times. Special relationships of this biochore with South China can also be stressed.