Studies on Silurian trilobites from Gotland, Sweden

Abstract: Trilobites of five families (Cheiruridae, Odontopleuridae, Encrinuridae, Phacopidae and Dalmanitidae) are described from the Silurian of Gotland. Fifty-five species (fourty-four named, of which twenty are new) are assigned to seventeen genera, of which Radiurus is new. The subgenera Dudleyaspis (Snoderaspis), Encrinurus (Australurus), and Encrinurus (Nucleurus) are new. One fairly distinct and some probable, morphologically directional, temporal lineages are recognised in members of three genera, and the material is interpreted as representing phyletic lineages. The stratigraphic distribution and succession of several trilobite associations on Gotland is discussed on the basis of quantitative data from more than 8500 specimens.