Mucronaspis mucronata (Brongniart) and allied taxa are common uppermost Ordovician trilobites throughout the world. A lectotype for M. mucronata mucronata is chosen and illustrated, and the Norwegian subspecies, M. mucronata kiaeri (Troedsson), redescribed. Limited evidence suggests that
dimorphism in glabellar proportions and palpebrallobe length is developed in the larger specimens and may indicate that sexual maturity is reached only in the later part of the holaspis phase.