A lowermost Ordovician tabulate-like coralomorph from the Precordillera of western Argentina: a main component of a reef-framework consortium

Abstract

Although putative corals of uncertain affinities occur in the early Cambrian, the earliest definite tabulatecorals have not been described prior to the Early Ordovician in North America. This paper reports a new findingof a tabulate-like coralomorph forming part of biostratigraphically well-constrained reef mounds in the latestCambrian?Early Ordovician La Silla Formation in the Argentine Precordillera. The oldest record of the coralomorphgenus Amsassia is reported and a new species, A. argentina, is erected. The discovery of this genus in the lowermostOrdovician modifies the previously proposed paleogeographic distribution and patterns of origination and migrationroutes of this coral-like organism. Amsassia argentina n. sp. constitutes a main framework builder together with acomplex microbial consortium. This oldest occurrence of Amsassia as a reef builder represents a new record of askeletal organism in the gap of metazoan reef constructors after the demise of archaeocyaths in the late early Cambrian