The first dinosaur remains from the Cretaceous of Ecuador

Abstract

Yamanasaurus lojaensis gen. et sp. nov. is a new titanosaur (Saurischia, Sauropoda) from the Upper Cretaceous of the Alamor-Lancones Basin, southern Ecuador. The fossil remains were found in rocks of the Río Playas Formation, which is regarded as Campanian–Maastrichtian in age. Remains include a partial sacrum, a partial mid-caudal vertebra, and several associated limb bones. Yamanasaurus is characterized by: (1) anterior to mid-caudal vertebrae with a dorsoventrally compressed condyle, with the posterior tip elevated respect to the midline, no longitudinal ventral ridge, and spongy inner structure with absence of internal cavities (i.e., camellate bone, shared with Neuquensaurus); (2) last sacral centrum as long as tall, with small ovoid, shallow blind fossa on the lateral side; and (3) radius robust with flattened diaphysis and a marked neck or cingulum right under the epiphysis, with an heptagonal concave proximal surface. Morphology, size, and age suggest that Yamanasaurus is closely related to Neuquensaurus, being the northernmost saltasaurine known by far.