https://rdi.uncoma.edu.ar/handle/uncomaid/272 2026-04-17T17:00:25Z https://rdi.uncoma.edu.ar/handle/uncomaid/19054 Estratigrafía de las bardas de la ciudad de Neuquén, Argentina. La Cuenca Neuquina, se halla desarrollada en la región occidental de Argentina y su historia geológica cubre desde el Triásico superior hasta el Cuarternario. El relleno sedimentario de esta cuenca fue subdividido por Groeber (1946) en tres super ciclos. Este último (Cretácico tardío al Paleoceno), está dividido en el Ciclo Neuqueniano del Albiano? al Campaniano bajo y el Malalhueyano del Maastrichtiano- Paleoceno. El Grupo Neuquén comprende depósitos fluviales y eólicos subordinados (Uliana, 1979; Uliana y Dellapé, 1981; Spalletti y Gazzera, 1989, Heredia y Calvo, 1997) resultando que el sector oriental de la cuenca fuera dominada por sedimentación molásica derivada del levantamiento de la Cordillera al oeste (Ramos, 1981; 1985). https://rdi.uncoma.edu.ar/handle/uncomaid/18960 Latest Ordovician-earliest Silurian chitinozoans from the Puna region, north-western Argentina (Western Gondwana) Late Ordovician–early Silurian chitinozoans from the Upper Member of the Salar del Rincón Formation of northwestern Argentina are described. The study area belongs to the Central Andean Basin situated on the western Gondwana margin during the Early Palaeozoic. Chitinozoan assemblages correlate with those from Northern Gondwana, where the effects of the glacial and postglacial events that occurred around the Ordovician–Silurian boundary, are quite well-documented. The recovered chitinozoan associations from the upper part of the Salar del Rincón Formation record the uppermost Ordovician–lowest Silurian deposits representing the postglacial stage of the late Hirnantian glaciation. Similar strata are usually absent in other parts of the Central Andean Basin. Tasmanites tzadiaensis is recovered for the first time outside of the northeast of Africa, supporting the northern Gondwana affinities. Associated land-derived components indicate a nearshore environment with terrestrial input. The other associated palynomorphs support the latest Hirnantian–earliest Rhuddanian postglacial stage correlation, as well. The ranges of several Late Ordovician– early Silurian Spinachitina and Cyathochitina species are discussed in terms of the Ordovician–Silurian boundary. Five new species are formally described: Spinachitina titae sp. nov., Cyathochitina brussai sp. nov., Cyathochitina lariensis sp. nov., Cyathochitina punaensis sp. nov. and Ramochitina deynouxi sp. nov. https://rdi.uncoma.edu.ar/handle/uncomaid/18958 Diuqin lechiguanae gen. et sp. nov., a new unenlagiine (Theropoda: Paraves) from the Bajo de la Carpa Formation (Neuquén Group, Upper Cretaceous) of Neuquén Province, Patagonia, Argentina Here we describe Diuqin lechiguanae gen. et sp. nov., a new unenlagiine taxon from the Upper Cretaceous (Santonian) Bajo de la Carpa Formation of the Neuquén Basin of Neuquén Province in northern Patagonia, Argentina that fills a substantial stratigraphic gap in the fossil record of these theropods. Although known only from a very incomplete postcranial skeleton, the preserved bones of Diuqin differ from corresponding elements in other unenlagiines, justifying the erection of the new taxon. Moreover, in several morphological aspects, the humerus of Diuqin appears intermediate between those of geologically older unenlagiines from the Neuquén Basin (e.g., Unenlagia spp. from the Turonian–Coniacian Portezuelo Formation) and that of the stratigraphically younger, larger-bodied Austroraptor cabazai from the Campanian–Maastrichtian Allen Formation. Consequently, the morphology of the new taxon appears to indicate a transitional stage in unenlagiine evolution. Phylogenetic analysis recovers Diuqin as a paravian with multiple plausible systematic positions, but the strongest affinity is with Unenlagiinae. The humerus of the new form exhibits subcircular punctures near its distal end that are interpreted as feeding traces most likely left by a conical-toothed crocodyliform, mammal, or theropod, the latter potentially corresponding to a megaraptorid or another unenlagiine individual. Thus, in addition to filling important morphological and temporal gaps in unenlagiine evolutionary history, the new taxon also offers information relating to the paleoecology of these theropods. https://rdi.uncoma.edu.ar/handle/uncomaid/18957 Juvenile specimen of Megaraptor (Dinosauria, Theropoda) sheds light about tyrannosauroid radiation Megaraptorids are a group of predatory dinosaurs that inhabited Gondwana from Cenomanian to Santonian times (Late Cretaceous). Phylogenetic relationships of megaraptorids have been matter of recent debate, being alternatively interpreted as basal coelurosaurs, carcharodontosaurian allosauroids, megalosauroids, and basal tyrannosauroids. One of the main reasons for such different interpretations is the incomplete nature of most available megaraptorid skeletons and, in particular, the scarce information about their cranial anatomy. Here we describe a partially preserved skeleton of a juvenile specimen of Megaraptor namunhuaiquii that provides substantial new information about the cranial morphology of this Patagonian taxon. The specimen comes from the Upper Cretaceous (Turonian–Coniacian) of the Portezuelo Formation, northwestern Patagonia, Argentina. The anatomy of the new specimen bolsters the recently proposed hypothesis that megaraptorids are nested within Coelurosauria, and possibly within Tyrannosauroidea. The most relevant features that megaraptorans share with tyrannosauroids include several foramina on the premaxillary body, extremely long and straight prenarial process of the premaxilla, incisiviform premaxillary teeth with a D-shaped cross-section, and cranially expanded supratemporal fossae separated from each other by a sharp sagittal median crest on frontals, which was presumably extended caudally above the parietals (not preserved). Information gathered from the present specimen allows to make for the first time a reconstruction of the skull of Megaraptor and hypothesize about evolutionary trends within Tyrannosauroidea.