New information about the hadrosaurids of Argentina (Dinosauria: Ornithischia).

SALINAS, G.C.; JUAREZ VALIERI, R.D.; BECERRA, M.G.; FABIANELLI, M.N.

La Rioja

Congreso; XXXVI Jornadas Argentinas De Paleontología De Vertebrados; 2023

Asociacion Paleontológica Argentina

An exhaustive bibliographic review allows us to provide new data on saurolophine hadrosaurids from the Upper Campanian - Lower Maastrichtian of Río Negro: Huallasaurus australis (Los Alamitos Fm.; MACN-RN 2, 142), Kelumapusaura machi (Allen Fm.; MPCN-PV- 807, 810), and Willinakaqe salitralensis (Allen Fm.; MPCA-Pv-SM7, 30–31, 34–38). Huallasaurus shares several features with Gryposaurus alsatei such as: development of three or more elongated denticles on the buccal margin of the premaxilla (also with Lophorhothon atopus); frontals forming a V-shaped naso-frontal articulation in which the ventral margin is more projected anteriorly (dorsal view); short diastema in the dentary; and long, sub-rectangular prepubic process of the pubis. Huallasaurus shares with the basal hadrosauroids Eolambia caroljonesa and Lophorhothon atopus the presence of a short and stout jugal process in the postorbital when laterally viewed (also with Kelumapusaura), and coracoid with a scapulocoracoid articular facet longer than the glenoid fossa, with both facets forming an angle greater than 115° (also with Willinakaqe). Kelumapusaura shares with Willinakaqe an anterior symphysis of the dentary with a bilobate outline in lateral view, a feature not identified in other hadrosaurids. Kelumapusaura has a predentary articular facet in the dentary that is crescent-shaped in lateral view. This feature is shared with Eotrachodon orientalis and Probrachylophosaurus bergei. However in Kelumapusaura the medial margin of this facet forms a medially prominent tubercle that is unique to this species. Kelumapusaura shares with brachylophosaurini saurolophines the presence of an elongated palatal process, an ectopterygoid crest oriented between 4–10° with the alveolarmargin (also in Willinakaqe). On the other hand, Kelumpausaura shares with  lambeosaurines the presence of apicobasally high dentary crowns with well-defined primary ridge and short accessory ridges, transversely narrow and anteroposteriorly elongated crest-shaped dorsal edge of the posterolateral process of the predentary. Furthermore, Kelumapusaura shares with lambeosaurines and basal hadrosauroids a scapular neck proportionally narrow to the scapular blade, and dorsally concave acromion process. Willinakaqe has a proportionally elongated deltopectoral crest of the humerus, similar to lambeosaurines or large saurolophines. This preliminary study allowed us to identify some features previously overlooked as shared among South American taxa, and with species from the northern hemisphere. It is necessary to include these comparisons in phylogenetic analyzes to establish whether the shared features between South American hadrosaurids  (always related to the kritosaurini saurolophines) and other species outside this group may affect their phylogenetic kinship, and thus verify their evolutionary history and dispersal patterns.