Revision of the middle Cambrian trilobite Paradoxides jemtlandicus

Paradoxides jemtlandicus Wiman, 1903, from strata near the boundary between the oelandicus Stage and the paradoxissimus Stage of the middle Cambrian in central Sweden, is redescribed using more complete specimens than were known hitherto. It is one of the earliest species of the genus Paradoxides sensu stricto, and though the form of the dorsal exoskeleton and the transverse shape of the hypostome are normal for the genus, compared with typical Paradoxidessuch as P. paradoxissimus it shows features that can be regarded as primitive. These features include the shape of the glabella, the lack of strong fusion of the rostrum with the hypostome, the acute inner spine angle of the librigena and the short pygidium; they are reminiscent of some species of Hydrocephalus.