A new species of machaeridian from the Silurian of Podolia, USSR, with a review of the Turrilepadidae

Machaeridians are enigmatic marine fossils, known from rocks of Ordovician to Carboniferous age. Turrilepas modzalevskae sp. nov., from Podolia, Ukraine, USSR, is only the second turrilepadid machaeridian species to be represented by an articulated assemblage. It provides unequivocal evidence for the presence of minute marginal spines, and demonstrates the relationship between these spines and the ornament of the outer sclerite surface. A standardized system of terminology for turrilepadid machaeridians is presented, based on examination of many specimens of Turrilepas wrightiana (de Koninck) from the Wenlock of Britain, together with undescribed Canadian silicified material. The anterior structure of turrilepadids and plumulitids is very similar, both lacking outer series sclerites on the first two segments. The Family Turrilepadidae comprises the genera Turrilepas Woodward, Deltacoleus Withers, Clarkeolepis Elias, Spinacoleus Schallreuter, and Mojzcalepas Dzik. All but Turrilepas are inadequately known