A new isopod species, Eonatatolana geisingensis gen. et sp. nov., is described from Middle Jurassic shallow-water sediments of southern Germany. It shows not only the almost completely preserved dorsal morphology but, in addition, details of the cephalic appendages, the pereiopods, pleopods and uropods. The presence of ambulatory pereiopods I–VII of a wide tridentate mandibular incisor with prominently developed posteriormost tooth and a narrow frontal lamina indicates that the new species belongs to the subfamily Conilerinae of family Cirolanidae within the suborder Cymothoida. It is closer to the species of the modern genus Natatolana Bruce than to any fossil isopod hitherto described. The isopod fossil record as well as current practices of isopod taxonomy in palaeontology are discussed, and the facies distribution and fossilization of isopods is reviewed with examples from the Jurassic.