Proa valdearinnoensis

Proa valdearinnoensis is a basal styracosternan iguanodont from the lower Albian stage of the Early Cretaceous, known only from the Escucha Formation in Spain’s Teruel Province. The genus name comes from the Spanish word for “prow,” referring to the pointed shape of its predentary bone, and the species name honors Val de Ariño, the traditional name for the coal mines near the original discovery site. The species is based on three partial skeletons and several skull pieces from multiple individuals.

This dinosaur is set apart from other basal hadrosauriforms—especially other iguanodontids—by a predentary that extends to the front edge of the snout, with side processes that diverge outward. It also has a unique combination of features: a dentary tooth row that curves upward when viewed from the side; that tooth row extends behind the base of the coronoid process; a flat platform sits between the tooth row and the coronoid base; the coronoid process flares forward and backward; the maxilla lacks a front-facing upper process; the quadrate bone is straight in side view; the ilium has a convex upper margin, a non-hanging supraacetabular process, and a postacetabular process that tapers without a sudden change in slope along its top edge; and the cranial pubic process is concave along its top but does not widen at its tip.

Phylogenetic studies have placed Proa in different positions. McDonald and colleagues (2012) found it at the base of Hadrosauriformes alongside Iguanodon. Norman (2015) grouped it within a monophyletic Iguanodontidae, closer to the Asian Bolong and Jinzhousaurus than to other European iguanodontids. Verdu and coauthors (2017) recovered it in a Eurasian clade that includes Xuwulong, Altirhinus, Koshisaurus, and Gongpoquansaurus, with Proa as the most derived member and sister taxon to Batyrosaurus.