Article: The taxonomy and stratigraphical significance of the Anglo-Welsh Cryptolithinae (Trinucleidae, Trilobita)

The taxonomic status of the stratigraphically-important Caradoc genera Salterolithus Bancroft, 1929, Broeggerolithus Lamont, 1935 and Smeathenia Dean, 1960 and the species therein is critically reviewed. The radial alignment patterns of the fringe pits within the E arcs are used to distinguish Salterolithus from Broeggerolithus; fringe morphology and pit counts are used to distinguish species within these genera. 'Broeggerolithus'harnagensis is reassigned to Salterolithus and S. praecursor, S. caractaci paucus and Smeathenia smeathenensis are all regarded as junior synonyms of Salterolithus harnagensis. This revision of the Anglo-Welsh Cryptolithinae reveals the evolution of morphologically very variable populations and environmentally constrained morphotypes and species. Eight species and subspecies of Salterolithus and Broeggerolithus are retained and redescribed and their stratigraphical distribution in the Caradoc of Britain, Ireland, Belgium and Scandinavia is clarified.