Alocodon is a genus of ornithischian dinosaur known from multiple teeth from the Middle or Late Jurassic. The taxon was first described in 1973 by Richard A. Thulborn for an assemblage of teeth from the Pedrógão locality of Portugal, distinguished by an enlarged central denticle on the teeth, with the name taken from the Greek alox and odon meaning 'furrow tooth'. The type specimen, a single tooth, is stored in the Museu Geológico do Instituto Geológico e Mineiro in Lisbon, Portugal, formerly having been kept in the collections of the Free University of Berlin as IPFUB P X 1, and comes from an individual under in length. Though it was originally described as having been found in an unnamed deposit in the Portuguese Leiria District of upper Callovian age, it was identified as having come from the lower Oxfordian Cabaços Formation. Alongside the 158 isolated teeth from Portugal assigned to Alocodon, some isolated teeth from the Bathonian Forest Marble and Chipping Norton Formations of England have been assigned to as cf. Alocodon sp. based on similarity. Alocodon was originally referred to as a member of the ornithopod family Fabrosauridae by Thulborn in 1973, closest to Fabrosaurus but also related to Echinodon and Trimucrodon. Peter M. Galton retained it in the family in 1978, though he noted that there were significant differences between Alocodon and Fabrosaurus, and the Middle to Late Jurassic fabrosaurids Alocodon, Trimucrodon and Echinodon were representative of three independent branches of the family, with Nanosaurus not preserving enough material to determine its relationships. Galton then suggested in 1983 that Alocodon was related to Othnielia, based on similarities of the teeth, placed within the ornithopod family Hypsilophodontidae. Given that the species was only represented by teeth, Alocodon was designated as a nomen dubium in 1990 by David B. Weishampel and Lawrence M. Witmer, as an indeterminate member of Ornithischia outside Ornithopoda. While a basal ornithischian position outside Ornithopoda was retained by Paul Sereno in 1991, it was considered a possibly valid taxon based on its broad central denticle. José Ruiz-Omeñaca reclassified Alocodon in 1999, based on a reconsideration of features and classifications specified previously. Though it had similarities to ornithopod, Ruiz-Omeñaca instead placed it within Thyreophora as an intermediate taxon, as the tooth crown was asymmetrical, with the cingulum on one side higher than the other, and no ridges present on the crown. Weishampel, Witmer and colleague David B.