Paleontologists have identified a species of medium-sized iguanodontian ornithopod dinosaur from two specimens found in northwestern Patagonia, Argentina.
Life reconstruction of the early rhabdodontomorph dinosaur Iani smithi. Image credit: Jorge Gonzalez.
Emiliasaura alessandrii lived in what is now Patagonia during the Valanginian age of the Early Cretaceous epoch, some 138 million years ago.
“Knowing Early Cretaceous dinosaurs is critical for gaining insights into the evolution of those clades that are characteristic of younger Cretaceous faunas,” said first author Dr. Rodolfo Coria and his colleagues from Argentina, Canada and Europe.
“Dinosaur diversity around the Jurassic-Cretaceous boundary represents a unique chapter characterized by the establishment of several major lineages.”
“However, our knowledge of dinosaur diversity during the earliest part of the Cretaceous is poor, especially in South America.”
Emiliasaura alessandrii belongs to Rhabdodontomorpha, a group of early iguanodontian dinosaurs within the clade Ornithopoda.
This dinosaur group consists of small to large plant-eaters from Europe and Gondwana.
“Emiliasaura alessandrii represents the first Rhabdodontomorpha record from South America and is currently the oldest and more primitive member of the clade,” the paleontologists said.
“This new species formed part of a diverse Early Cretaceous (Valanginian) dinosaur assemblage, which also includes diplodocid and dicraeosaurid sauropods and carcharodontosaurid theropods.”
Emiliasaura alessandrii is represented by two fossilized specimens collected from different sites and stratigraphical levels of the Mulichinco Formation.
“The holotype specimen includes the coracoid, the proximal end of a scapula, a humerus and a complete right hind limb, whereas the paratype specimen preserves vertebral elements, haemal arches, an incomplete pelvis, and nearly complete hind limbs,” the researchers said.
“The new species has an anteroposteriorly elongate ilium with a sigmoidal dorsal border and broad brevis shelf, a femur shaft with an extensive, proximally positioned fourth trochanter, and a second pedal digit with a short, robust, blunt ungual phalanx similar to those in Ankylopollexia ornithopods.”
The findings were published this week in the journal Cretaceous Research.
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R.A. Coria et al. First Valanginian (Early Cretaceous) ornithopod (Dinosauria, Ornithischia) from Patagonia. Cretaceous Research, published online October 16, 2024; doi: 10.1016/j.cretres.2024.106027