The femur of Omosaurus phillipsi Seeley from theCoralline Oolite Formation of Slingsby, Yorkshire, England is the only evidence for stegosaurian dinosaurs from the Oxfordian (basal Upper Jurassic). However, this taxon is a nomen dubium because the femur is poorly preserved and from a juvenile individual. Femora of Dacentrurus from the Kimmeridgian (Upper Jurassic) of Portugal and of Lexovisaurus from the Callovian (Middle Jurassic) of England are illustrated.