Diego Pino’s research while affiliated with National University of Río Negro and other places

The osteology of Pilmatueia faundezi Coria, Windholz, Ortega & Currie, 2019, a dicraeosaurid sauropod from the Lower Cretaceous of Patagonia, is reassessed from the perspective of a new specimen (MLL-Pv-010) that provides additional information on the axial skeleton and the pectoral girdle. The specimen MLL-Pv-010 is composed of three articulated anterior-middle cervical vertebrae (with their respective ribs in position and an associated fourth rib), seven dorsal vertebrae with associated dorsal ribs, a distal caudal vertebra, a left scapula and the proximal end of a right scapula. The new specimen shows features, especially in the middle cervical vertebrae, that link it to Pilmatueia faundezi. Additionally, the specimen MLL-Pv-010 shows features previously unknown for the species, such as the morphology and orientation of the bifid neural spines of the anterior and mid-cervical vertebrae. The information obtained from the specimen MLL-Pv-010 allows us to propose an expanded diagnosis of Pilmatueia faundezi. Moreover, two phylogenetic analyses focusing on South American dicraeosaurids show that Pilmatueia Coria, Windholz, Ortega & Currie, 2019 is well nested within Dicraeosauridae Huene, 1927. One of our phylogenetic hypotheses differs from previous contributions in showing South American dicraeosaurids as a monophyletic group. However, in the second hypothesis these are not recovered as a natural group. We think that it is reasonable to recover a South American dicraeosaurid clade, and that eventually it will be best supported once more evidence is recovered.

La Formación Allen (Campaniano medio-Maastrichtiano inferior; Cretácico Superior), con diversos afloramientos en el sector centro-oeste de Argentina, registra una interesante abundancia de restos fósiles de vertebrados. En particular, existen excelentes afloramientos en el Área Natural Protegida “Paso Córdoba”, 15 Km al suroeste de General Roca (Río Negro, Argentina), donde se la ha interpretado como un sistema eólico con desarrollo de facies de dunas e interdunas secas y húmedas. Las facies de dunas están compuestas por areniscas rojizas de grano medio con estratificación entrecruzada tangencial y paleocorrientes predominantes hacia el SE. En las facies de dunas de este sistema fueron hallados dos dientes aislados de terópodos (MPCN-PV-845.14 y 845.15, Museo Patagónico de Ciencias Naturales “Juan Carlos Salgado”), asociados a una acumulación formada por dos vértebras cervicales articuladas y restos parciales desarticulados de un dinosaurio titanosaurio indeterminado. Dadas las diferencias en sus morfologías, se reconocieron como dos morfotipos diferentes. El espécimen MPCN-PV-845.14 (Morfotipo 1) posee una corona baja (CHR<2) y comprimida labiolingualmente, la carena mesial posee una ligera desviación lingual, la carena distal está situada centralmente en el margen distal de la corona el cual es recto a ligeramente cóncavo, ambas carenas, mesial y distal, se extienden por debajo de la cerviz y el esmalte posee una textura irregular. Este elemento es interpretado como un diente mesial de la dentición lateral. El espécimen MPCN-PV-845.15 (Morfotipo 2) posee una carena mesial desarrollada solo hasta la cerviz, una sección transversal de contorno en forma de J o D, la superficie labial es fuertemente convexa, mientras que la lingual es levemente bicóncava y algo sigmoide, donde una depresión extendida apicobasalmente se presenta adyacente a la carena mesial, el esmalte posee una textura irregular. Este elemento se interpreta aquí como un diente mesial perteneciente a la dentición mesial. Sobre la base de la combinación de caracteres morfológicos y morfométricos diagnósticos de la dentición lateral y mesial de Theropoda Abelisauridae, se los identifica a este clado. Asimismo, la gran diferencia en tamaño de estas piezas dentales, sugiere que habrían pertenecido a individuos de distinto tamaño, en lugar de diferentes entidades posicionales a lo largo de la mandíbula de un individuo. El hallazgo de estos dientes junto a restos de un titanosaurio, mostraría una pequeña imagen del paleoecosistema cretácico, representando una posible interacción trófica entre abelisáuridos y titanosaurios.

The fluvial deposits of the Candeleros Formation widely outcrop in the Neuquén Basin, preserving an abundant and diversified saurian fauna of the “Middle” Cretaceous of northern Patagonia. The fossil record of the Candeleros Formation counts with many fossiliferous sites in Rio Negro andNeuquén Provinces; however, most of them come from the upper section of the unit. In this contribution, we report several saurian evidence from a new fossiliferous locality of El Sauce (Picún Leufú, Neuquén Province), where the lower section of the Candeleros Formation outcrops. Recent fieldworks allowed the finding of: several axial and appendicular sauropod remains, an almost complete femur that tentatively refers to an indeterminate, large-sized theropod dinosaur, some isolated plastron elements of indeterminate turtles, and isolated sauropod, pterosaur, and tridactyl dinosaur footprints. The sauropod specimens come from different sites on one laterally extended, fossiliferous level composed by grey, fine sandstones and green to purple mudstones, whereas the theropod femur and the footprints were found on brown coarse sandstones, all of which outcrop at the base of the Candeleros Formations. The diversified faunal composition recorded in the newlocality of El Sauce is concordant with the slightly older Lohan Cura Formation, suggesting the persistence of specific paleoenvironmental conditions on the southern Neuquén Basin, at leastduring the Early-Late Cretaceous transition. Furthermore, this new evidence shows part of the faunal components of Lohancuran tetrapod assemblage, allowing new morphological and taxonomical comparisons with the saurian fauna of the upper section of Candeleros Formation. New data from the Lohan Cura and Candeleros formations will improve the knowledge about the diversification and the paleobiogeographical evolution of the saurian fauna during the Cretaceous of Neuquén Basin.

The fluvial deposits of the Candeleros Formation widely outcrop in the Neuquén Basin, preserving an abundant and diversified saurian fauna of the “Middle” Cretaceous of northern Patagonia. The fossil record of the Candeleros Formation counts with many fossiliferous sites in Rio Negro and Neuquén Provinces; however, most of them come from the upper section of the unit. In this contribution, we report several saurian evidence from a new fossiliferous locality of El Sauce (Picún Leufú, Neuquén Province), where the lower section of the Candeleros Formation outcrops. Recent fieldworks allowed the finding of: several axial and appendicular sauropod remains, an almost complete femur that tentatively refers to an indeterminate, large-sized theropod dinosaur, some isolated plastron elements of indeterminate turtles, and isolated sauropod, pterosaur, and tridactyl dinosaur footprints. The sauropod specimens come from different sites on one laterally extended, fossiliferous level composed by grey, fine sandstones and green to purple mudstones, whereas the theropod femur and the footprints were found on brown coarse sandstones, all of which outcrop at the base of the Candeleros Formations. The diversified faunal composition recorded in the new locality of El Sauce is concordant with the slightly older Lohan Cura Formation, suggesting the persistence of specific paleoenvironmental conditions on the southern Neuquén Basin, at least during the Early-Late Cretaceous transition. Furthermore, this new evidence shows part of the faunal components of Lohancuran tetrapod assemblage, allowing new morphological and taxonomical comparisons with the saurian fauna of the upper section of Candeleros Formation. New data from the Lohan Cura and Candeleros formations will improve the knowledge about the diversification and the paleobiogeographical evolution of the saurian fauna during the Cretaceous of Neuquén Basin.

A state of the knowledge of the Andean cycle is presented, mainly based on our recent works, but also on highlights of recent research of many colleagues. This synthesis allowed us to update the geochronology of its different units. New absolute ages through U-Pb analysis in zircons by different methods complement those previously carried out and made it possible to accurately limit the age of these units. We have been able to define the boundary between the Tordillo and Vaca Muerta Formations very precisely between 147 and 146 Ma; the age of the Agrio Formation between 132 and 126 Ma, and to present the first absolute ages of the Huitrín Formation. All these data are screened through precise biostratigraphy, sequence stratigraphy, and astrochronology. The Troncoso Member of the Huitrín Formation yielded an age of 123 Ma that placed it in the Barremian. This is partially corroborated by the finding of fossils in the La Tosca Member with trigonioids and foraminifera of undoubted marine origin, dated with nannofossils of early Barremian age indicating the permanence of communication with the Pacific during the deposition of the Huitrín Formation.

En esta contribución se dan a conocer las primeras edades U-Pb en circones detríticos de una muestra de los depósitos sinorogénicos del Cretácico Superior (Formación Anacleto) aflorantes en el extremo oriental de la cuenca Neuquina, en Paso Córdoba, Río Negro, Argentina. La edad máxima depositacional obtenida es de 78,6 ± 1,7 Ma (Campaniano medio). La edad se calculó sobre la base de un grupo de circones jóvenes cretácicos (n=11), a partir del análisis de una muestra extraída de los depósitos de interduna húmeda, asignados a la Formación Anacleto del Grupo Neuquén.

Osteological knowledge of the sauropod dinosaur Ligabuesaurus leanzai is increased by the description of new postcranial elements assigned to the holotype MCF-PVPH-233. Furthermore, a newly referred specimen, MCF-PVPH-228, is recognized after a detailed revision of the abundant sauropod material collected from the Lohan Cura Formation outcrops in the Cerro de los Leones locality (southern Neuquén Basin, Patagonia, Argentina). Recent laboratory preparation and fieldwork allowed us to recognize several new morphological features of the pectoral and pelvic girdles and the cervical and caudal anatomy. Thus, a new diagnosis of Ligabuesaurus is proposed that includes new autapomorphies and a unique combination of features. A phylogenetic analysis based on this new material recovers Ligabuesaurus as a non-titanosaurian somphospondylan, more derived than Sauroposeidon. Therefore, we discuss the palaeobiogeographical implications for the diversification and distribution of South American somphospondylans, especially in the Neuquén Basin, which are closely related to the early stages of evolution of Titanosauria. In this context, Ligabuesaurus represents one of the more complete Early Cretaceous Titanosauriformes and the earliest non-titanosaurian somphospondylan of South America. Finally, the new information on Ligabuesaurus contributes not only to reconstruction of the sauropod faunal composition of south-western Gondwana, but also sheds light on the early stages and emergence of titanosaurians.