Revisiting hadrosaurid discoveries decades later: in-depth analysis of Salitral Moreno specimens at the Museo Provincial Carlos Ameghino collection.

BECERRA, M.G.; SALINAS, G.C.; JUAREZ VALIERI, R.D.; MESO, J. G.; GUZMÁN, F.A.; ROZADILLA, S.; BRISSÓN-EGLI, F.; FABIANELLI, M.N.; PRIETO-MARQUEZ, A.

Corrientes Capital

Jornada; XXXVII Jornadas Argentinas De Paleontología De Vertebrados; 2024

Asociación Paleontológica Argentina

Hadrosaurid ornithopods are the predominant faunistic component from middle Campanian – lower Maastrichtian outcrops of theAllen Formation at the SalitralMoreno, in the province of Río Negro, Argentina. During several field tripsconducted in the last decades of the twentieth century, multiple cranial andpostcranial remains of these dinosaurs were recovered from this site. Most ofthese elements were identified as belonging to Bonapartesaurus rionegrensis, the nomen vanum “Willinakaqe salitralensis”,and Hadrosauridae indet., but many pieces had not been previously identified ordescribed. Recent curatorial activities at the Museo Provincial Carlos Ameghinoof Cipolletti (MPCA) led to the identification of previously overlookedhadrosaurid bones from Salitral Moreno. The newly identified cranial bonescomprise the postorbital, prootic-opisthotic, paroccipital process of theopisthotic, basioccipital-basisphenoid, quadrate, jugal, frontal, and parietal.New axial elements include diverse cervical, dorsal, and caudal vertebrae, aswell as two partial sacra. Newly recognized appendicular elements consist ofmetacarpal IV, ischium, fibula, and astragalus bones. Additionally, new piecesof previously identified bones have been discovered, aiding in the clarificationof anatomical traits such as those of the dentary, maxilla, coracoid, andfemur. Newly identified features on these remains include: the frontal exhibitsconfluent articular facets for the prefrontal and postorbital and lacks anorbital margin, similar to Huallasaurus.The lateral surface of the postorbital is coarsely ornamented, as Kelumapusaura; however, this region isprominently overgrown, forming a bulging unevenness and a pit-like fossaventrally, features absent in the latter. The dentary symphysis appearsbilobate in lateral view due to a deep groove, similar to Kelumapusaura, but the dentary foramen is more widely open inproportion and lacks a crescent-shaped concavity at the articulation for thepredentary with the dentary, which is rather flat. The prootic-opisthoticfragment preserves the complete foramen metoticum, parts of the inner ear(including semicircular canals, the lagena, and the vestibulum), the foramenfor CN VIII that bifurcates into two branches before opening into the vestibulum,and several vascular passages. Notably, given the nature of the preservation inthe fossiliferous locality (a bonebed), many elements in the collection areduplicates, and represent several individuals. The ongoing identification andstudy of these remains at the MPCA, combined with the discovery of multiple newelements in Salitral Moreno and therecent advancements in the knowledge of South American hadrosaurids will helpto clarify the anatomy, diversity and evolutionary history of these dinosaursin the latest Cretaceous of Patagonia.