Belemnites harleyi Mayer, 1866, originally described from the Jurassic of Normandy, has encountered diverging interpretations during the last 150 years of scientific research. It has subsequently been assigned to four different genera (Belemnopsis, Aulacoteuthis, Acrocoelites and Holcobelus). The detailed study of the rostrum morphology and its inner structure allows us to attribute it to a new genus, Lissajousibelus Weis gen. nov., in honour of the French geologist Marcel Lissajous (1863-1921). Key features of the new genus are the overall depressed rostrum, short dorsolateral apical grooves, a long intermediate ventral groove with splitting surface, and a shallow dorsoalveolar depression. Bed-by-bed sampling at the classic locality Feuguerolles-sur-Orne (Calvados) enables us to revise the stratigraphic position of Lissajousibelus harleyi (Mayer, in J de Conchyl 3:358-369, 1866) as lowermost Toarcian Tenuicostatum Chronozone. Lissajousibelus Weis gen. nov. is therefore amongst the earliest belemnites with belemnopseine morphology. However, its phylogenetic relationships with younger Belemnopseina from the Aalenian-Bajocian (Middle Jurassic) remain unclear