Obelignathus

MEANING: Obelix jaw

PERIOD: Late Cretaceous

CONTINENT: Europe

Obelignathus is a rhabdodontomorph ornithopod dinosaur that lived during the Late Cretaceous in what is now France. It was a medium-sized bipedal herbivore, and like all rhabdodontomorphs, it had a beak used for processing vegetation. Obelignathus can be distinguished from other rhabdodontomorphs by its particularly robust jaw.

Abstract from paper: The origin and early diversification of ornithopods, a major clade of ornithischian dinosaurs, remain poorly understood, with conflicting phylogenetic hypotheses regarding rootward neornithischian relationships. Some topological stability is inferred near the basal divergence of Iguanodontia, though the ingroup relationships remain unclear. For instance, Rhabdodontidae, a clade of Late Cretaceous European ornithopods ‘traditionally’ considered to include eight to nine species, presents significant taxonomic challenges. We explore the diversity and disparity of European Rhabdodon-lineage iguanodontians. We assembled a novel dataset comprising morphological and morphometric data obtained from rhabdodontomorph dentaries, which are abundant, well-preserved in the majority of the taxa, and distinctive. Special attention is given to Rhabdodon septimanicus, a poorly known taxon from the upper Campanian to lower Maastrichtian of southern France, established based on a particularly robust dentary bone that has been subjected to conflicting taxonomic interpretations. Our restudy of the specimen, combined with a multivariate and phylogenetic assessment, shows that this taxon is a clear morphological outlier among European rhabdodontomorphs, providing a basis for its assignment to a new genus, Obelignathus. Although further large-scale studies, especially detailed osteological descriptions, are needed to clarify the taxonomic significance of certain European rhabdodontomorphs, our results indicate that the group exhibits greater diversity than currently recognized, with several sympatric taxa co-occurring, at least in southern France and possibly also in Romania.

Obelignathus is from the Late Cretaceous. The Cretaceous is the third and final geological period of the Mesozoic Era, with the Late Cretaceous making up roughly the second half of it, lasting from about 100 to 66 million years ago. It was a time of significant evolutionary change, with dinosaurs reaching their greatest diversity before the mass extinction at the end of the Cretaceous.

The Cretaceous was a period with a relatively warm climate, though the Late Cretaceous experienced a global cooling trend, caused by falling levels of carbon dioxide in the atmosphere. The continents were nearing their present positions, but high sea levels flooded low-lying regions, turning Europe into an archipelago, and forming the Western Interior Seaway in North America. These seas were home to a variety of marine reptiles, including mosasaurs and plesiosaurs, while pterosaurs and birds shared the skies.

On land, dinosaurs continued to thrive and diversify during the Late Cretaceous, producing many of the most well-known goups, including tyrannosaurs, hadrosaurs, and pachycephalosaurs. Established Cretaceous dinosaur clades like the ceratopsians, ankylosaurs, and dromaeosaurs continued to flourish. Sauropod species consisted almost exclusively of titanosaurs, which seemed to be confined to the Southern Hemisphere for much of the Late Cretaceous. Flowering plants and grasses diversified and spread, becoming the dominant flora similar to what we see today.

The Cretaceous (along with the Mesozoic) ended with the Cretaceous–Paleogene (K–Pg) extinction event, a large mass extinction in which many groups, including non-avian dinosaurs, pterosaurs, and large marine reptiles, died out. This event, likely triggered by an asteroid impact, is marked by the abrupt K–Pg boundary, a distinct geologic layer separating the Mesozoic and Cenozoic Eras. In its aftermath, mammals and avian dinosaurs rapidly diversified, becoming the dominant land animals of the Cenozoic Era.

Obelignathus is a rhabdodontomorph. Rhabdodontomorpha was a group of basal ornithopods that lived primarily during the Late Cretaceous, representing an early offshoot of the ornithopod lineage that would eventually give rise to the hadrosaurs. These dinosaurs were generally medium-sized, herbivorous, and adapted for bipedal locomotion, with powerful hind limbs and relatively short forelimbs. While not as specialized as their hadrosaurid cousins, rhabdodontomorphs retained more primitive characteristics, such as deep skulls and robust jaws suited for a strong bite force. Their teeth were arranged in tight rows and adapted for shearing plant material, suggesting a diet of tough, fibrous vegetation.

Fossils of rhabdodontomorphs have been found primarily in Europe, where they may have been part of isolated dinosaur faunas on European island landmasses during the Late Cretaceous. While other ornithopods spread across much of the globe, rhabdodontomorphs appear to have remained restricted to Europe and parts of Gondwana. Their survival in these regions—perhaps due to geographic isolation or reduced competition—makes them a fascinating example of how more basal dinosaur groups could persist and thrive in niche environments even as more derived forms evolved elsewhere.