We describe a new semionotiform genus, which was recognized while studying Macrosemimimus fegerti, gen. et sp. nov., from the Late Jurassic Solnhofen Archipelago, Germany. Macrosemimimus (Lepidotes) lennieri from the early Kimmeridgian of Cap de la Hève, France, including Lepidotes toombsi from the Lower Kimmeridge Clay in Cambridgeshire, England, as a junior synonym, also belong to the new genus. Though different species, the presence of the same fish genus in different biodiversity zones suggests that semionotiforms might have been less sensible to the ecological and physical factors that caused the endemisms recognized in the invertebrate faunas. Macrosemimimus is mainly distinguished by the peculiar shape of the antorbital portion of the frontal bones, a single pair of extrascapular bones that do not reach the dorsal midline, anteriorly open circumborbital ring, only two suborbital bones, edentulous maxilla, a large quadratojugal involved in the jaw articulation, four postcleithra, and the pectoral fins placed very low and joining ventrally. The two included species differ in the ornamentation of the skull bones, the morphology of the scales, the relative size and position of the extrascapular bones, the dorsal extension of the preoperculum, and the kind of dentition. Although the phylogenetic relationships of Macrosemimimus are not yet established, the particular shape of the antorbital portion of the frontals and the patterns of the extrascapular and suborbital bones indicate possible systematic affinity with the macrosemiids, “Lepidotes” gloriae from the Oxfordian of Cuba, and “Lepidotes” microrhis and “Lepidotes” tanyrhis from the Barremian of Las Hoyas, Spain.