Obelignathus (meaning "Obelix jaw") is an extinct genus of rhabdodontomorph ornithopod dinosaurs from the Late Cretaceous 'Grès àReptiles' Formation of France. The genus contains a single species, O. septimanicus, known from a right dentary. The species was initially classified as a species of the coeval Rhabdodon.
The Obelignathus holotype specimen, MDE D30, was discovered in 1990 in outcrops of the 'Grès àReptiles' Formation near Montouliers in Saint-Chinian commune of Hérault, southern France. The specimen consists of an isolated right dentary, missing the anterior (front) part.
The specimen was first described in 1991 by ÃÂric Buffetaut and Jean Le Loeuff. Based on the general morphology and dental anatomy, they identified it as belonging to the genus Rhabdodon, named as a hypsilophodont in 1869. However, they described it as a new species, R. septimanicus due to other differing anatomical characteristics. The specific name references Septimania, a historic region of France corresponding to Languedoc, where the type locality in Montouliers is.
In 2025, Czepià Âski & Madzia described Obelignathus as a new genus of rhabdodontomorphs for "Rhabdodon" septimanicus based on these fossil remains. The generic name, Obelignathus, combines a reference to Obelix, a fictional character in the cartoon Asterix and Obelix, with the Greek óýìøÿà(gnáthos), meaning "jaw", referencing the similar strength of the character and robust morphology of the holotype dentary.
To determine the phylogenetic affinities of Obelignathus, Czepià Âski & Madzia (2025) used an updated version of the comprehensive phylogenetic dataset of Fonseca et al. (2024), who had independently recovered "Rhabdodon" septimanicus outside of the genus Rhabdodon and suggested it may represent a taxon distinct from Rhabdodon priscus.
Czepià Âski & Madzia included the 'Quarante rhabdodontomorph' as a separate operational taxonomic unit (OTU); the specimens comprising this OTU were referred to cf. "R." septimanicus in a doctoral thesis but have not yet been formally described. Using implied weighting and K-values of 15 and 21, the authors recovered Obelignathus as the most basal member of the Rhabdodontomorpha. These results are displayed in the cladogram below: