The Classification and Evolution of the Superfamily Lichacea (Trilobita)

Abstract

Abstract The superfamily Lichacea is here considered to include two families : the Lichidae, composed of four subfamilies and twenty-four genera, and the Lichakephalidae, comprising only one species. Reed's interpretation of the glabellar and occipital lobes in the Lichidae is considered to be correct; the definition and degree of fusion of these lobes is the main criterion of generic discrimination. Hypostomal features are of assistance in defining subfamilies. The characters of the pygidium are constant in some genera, but unstable in others. The Lichinae and Homolichinae, stratigraphically the oldest subfamilies of the Lichidae, are chiefly European in occurrence during the Ordovician period. The Tetralichinae and the Ceratarginae occur earlier in North America than in Europe. Lichakephalus occurs in Lower Tremadoc beds of Bavaria.