Morphologic variation in the P1 element of Mississippian species of the conodont genus Pseudognathodus

A revision of the Austin Conodont Collection at the Natural History Museum, London, has revealed a diverse assemblage of P1 elements of Pseudognathodus . Pseudognathodus homopunctatus, Ps. lineatus, Ps. mermaidus and Ps. symmutatus are di?erentiated and a new species, Ps. posadachaconae , is de?ned from material from North Wales. The systematic of these species is updated. A revised diagnosis is provided for the genus Pseudognathodus , as well as for the species Ps. lineatus and Ps. symmutatus . The types of Ps. symmutatus cannot be differentiated from immature specimens of Ps. homopunctatus . The evolutionary relationships of Pseudognathodus species are discussed. Stratigraphic distribution indicates that diversity increased moderately from the upper Tournaisian and lower Visean to the upper Visean (Mississippian, Carboniferous). Pseudognathodus homopunctatus and Ps. symmutatus are widely distributed palaeogeographically whereas Ps. lineatus and P s. posadachaconae sp. nov. are endemic.