Emiliasaura
Emiliasaura is an extinct genus of iguanodontian ornithopod dinosaurs from the Early Cretaceous Mulichinco Formation of Neuquén Province, Argentina. The genus contains a single species, Emiliasaura alessandrii, known from three individual specimens. Emiliasaura was initially described as a rhabdodontomorph. If this identification is correct, it would represent the oldest member of this clade and the first named from South America. However, a later analysis of rhabdodontomorphs failed to recover Emiliasaura within this clade, instead placing it as a styracosternan.
Discovery and naming
During the summer of 2009, Carlos Alessandri discovered productive outcrops of the Mulichinco Formation northeast of the city of Las Lajas in Neuquén Province, Argentina. The partial skeleton of a medium-sized ornithopod was collected in March of that year, comprising part of the left and, the left, and a complete right hindlimb. During fieldwork conducted two years later, on the shore of Pilmatué Creek northeast of the previous quarry, a second partial ornithopod skeleton was found, comprising much of the right hindlimb and foot, parts of both, three and eight vertebrae, nine, and associated. An isolated was also recovered in association with a partial skeleton referred to the sauropod Pilmatueia.After being announced in October 2024 in a non-finalized preprint, Coria et al. described Emiliasaura alessandrii as a new genus and species of ornithopod based on these fossil remains. The first collected specimen, cataloged as MLL-Pv-001, was established as the holotype, and the second specimen, MLL-Pv-006, as the paratype. The isolated dorsal vertebra was also referred to the species. The specimens are accessioned at the Museo de Las Lajas in Argentina. The generic name, Emiliasaura, honors Emilia Ondettia de Fix, the founder of the first museum in Las Lajas. The specific name, honors Carlos Alessandri, discoverer of the holotype.
Description
Based on histological research, Coria et al. identified the specimens of Emiliasaura as belonging to somatically immature, or subadult, individuals. Since bone modeling was still occurring at the time of death, the animals were likely still growing and had not reached their full body size.Classification
In their 2025 description of Emiliasaura, Coria et al. scored it in the phylogenetic dataset of Poole. They found it to be the most basal member of the Rhabdodontomorpha. This would makes it the oldest known member of the clade and the first one known from South America. Their results are displayed in the cladogram below:In a later 2025 publication focused on European rhabdodontomorphs, Czepiński & Madzia included Emiliasaura in an updated version of the comprehensive phylogenetic dataset of Fonseca et al.. This matrix consistently recovered Emiliasaura within Dryomorpha, as an early-diverging styracosternan. The authors concluded that, while they had not observed the material in detail, Emiliasaura can most likely be regarded as a genus outside Rhabdodontomorpha. These results are displayed in the cladogram below: