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Late Cretaceous vertebrates from Bajo de Santa Rosa (Allen Formation), R??o Negro Province, Argentina, with the description of a new sauropod dinosaur (Titanosauridae)

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Abstract

A large and diverse collection of vertebrate remains from the Campanian-Maastrichtian Allen Formation (Malargüe Group) at the Bajo de Santa Rosa locality (Río Negro Province, Argentina) is described here. The vertebrates are represented by: chondrichthyans; diplomystid siluriform, lepisosteid, cf. percichthyid and dipnoid osteichthyans; pipid and leptodactylid anurans; chelid turthes; sphenodonts; elasmosaurid plesiosaurs; madtsoiid snakes; faveoolitid and megaloolithid eggshells; and hadrosaurid, cf. carcharodontosaurid and titanosaurid dinosaurs. A new small saltasaurine titanosaurid, Bonatitan reigi gen. et sp. nov., is described. It is diagnosed by the following association of characters: 1) longitudinal groove located on the suture between parietals that continues posteriorly over the supraoccipital to the foramen magnum; 2) basisphenoid tubera long and narrow (more than twice as long as wide); 3) dorsal to middle caudal vertebrae with deep oval to circular pits present on both sides of the prespinal lamina; 4) anterior caudal vertebra with spino-postzygapophysial and spino-prezygapophysial laminae; 5) neural arch of anterior caudals with deep interzygapophysial fossae with numerous pits; 6) anterior caudal vertebra with an accessory sub-horizontal lamina extending from the antero-ventral portion of the postzygapophysis to the mid-portion of the spino-prezygapophysial lamina; and finally, 7) anterior caudal vertebra with a prominent axial crest on the ventral surface of the cemtrum. The first record of sphenodonts and cf. carcharodontosaurid theropods is recognized for the upper Late Cretaceous of Patagonia, as well as the earliest record of percichthyids (Perciformes). The vertebrate record is mainly composed of terrestrial and freshwater taxa, but a few marine elements are found (elasmosaurids) indicating a marine influence during the deposition of the Allen Formation in the area of Bajo de Santa Rosa. The vertebrate remains support a Campanian-Maastrichtian age for the Allen Formation. Comparisons with other South American Campanian-Maastrichtian localities suggest a similar fossil vertebrate composition, with relatively few differences between the Patagonian and extra Patagonian South American records.
... Estos sedimentos aflorantes se pueden observar en las siguientes provincias: Neuquén, sur de Mendoza, noroeste de Río Negro y suroeste de La Pampa, con un área total de 120.000 km2 (Digregorio y Uliana, 1979;Legarreta y Uliana, 1999;Howell et al., 2005). Esta cuenca ha sido establecida como de tipo retroarco multiepisódica (Mpodozis y Ramos, 1989), cuya secuencia se encuentra conformada por sedimentos marinos, continentales y de tipo transicional (Casamiquela, 1964;Digregorio y Uliana, 1980;Bonaparte et al., 1984;Albino, 1986;Bonaparte, 1987;Uliana y Biddle, 1988;Barrio, 1990;Powell, 1992;Salgado y Coria, 1996;Salgado y Azpilicueta, 2000;Coria, 2001;de la Fuente et al., 2001;Hugo y Leanza, 2001;Martinelli y Forasiepi, 2004;Coria y Salgado, 2005;Franzese et al. 2007 Arregui et al., 2011;Cingolani et al., 2011;Armas y Sanchez, 2013y Paz et al., 2014. Su basamento se encuentra conformado por rocas metamórficas, ígneas y sedimentarias, cuyas edades van desde el Silúrico-Devónico hasta el Triásico Tardío (Digregorio y Uliana 1980;Franzese et al. 2007;Cingolani et al. 2011y Paz et al., 2014. ...
... Esta formación se encuentra ubicada en la base del Grupo Malargüe, separada del subyacente Grupo Neuquén por una discordancia erosiva (Andreis et al., 1974;Hugo y Leanza, 2001). La misma es portadora de restos fósiles de suma importancia a nivel mundial (Casamiquela, 1964;Bonaparte et al., 1984;Albino, 1986;Bonaparte, 1987;Powell, 1992;Salgado y Coria, 1996;Salgado y Azpilicueta, 2000;Coria, 2001;de la Fuente et al., 2001;Martinelli y Forasiepi, 2004;Coria y Salgado, 2005;Salgado et al., 2007a, b). La edad de la Formación Allen, establecida sobre la base del análisis de ostrácodos (Ballent, 1980), ha sido restringida al Campaniano medio-Maastrichtiano temprano. ...
... Los estratos de esta unidad han brindado una gran diversidad de tetrápodos continentales, con un dominio de los dinosaurios terópodos (Casamiquela, 1964;Bonaparte et al., 1984;Albino, 1986;Bonaparte, 1987;Powell, 1992;Salgado y Coria, 1996;Salgado y Azpilicueta, 2000;Coria, 2001;Fuente et al., 2001;Martinelli y Forasiepi, 2004;Coria y Salgado, 2005;Coria, 2007;Salgado et al., 2007ab;Novas et al., 2009;Salgado et al., 2009;Agnolin et al., 2012). Estos últimos, se encuentran representados por al menos cuatro clados, es decir, Abelisauridae, Alvarezsauridae, Dromaeosauridae y un tetanuro indeterminado (Coria, 2001;Coria y Salgado, 2005;Juárez Valieri et al., 2007;Novas et al., 2009;Salgado et al., 2009;Agnolin et al., 2012;. ...
Thesis
This Doctoral Thesis presents an exhaustive review of the Patagonian alvarezsaurids (Dinosauria, Theropoda). It includes a detailed osteological description of specimens of Patagonykus puertai (Holotype, MCF-PVPH-37), cf. Patagonykus puertai (MCF-PVPH-38), Patagonykinae indet. (MCF-PVPH-102), Alvarezsaurus calvoi (Holotype, MUCPv-54), Achillesaurus manazzonei (Holotype, MACN-PV-RN 1116), Bonapartenykus ultimus (Holotype, MPCA 1290), and cf. Bonapartenykus ultimus (MPCN-PV 738). A phylogenetic analysis and a discussion about the taxonomic validity of the recognized species and the taxonomic assignment of the materials MCF-PVPH-38, MCF-PVPH-102 and MPCN-PV 738 are presented. Different evolutionary and paleobiological studies were carried out in order to elucidate functional and behavioral aspects. Alvarezsaurus calvoi (MUCPv-54), Achillesaurus manazzonei (MACN-PV-RN 1116), Patagonykus puertai (MCF-PVPH-37) and Bonapartenykus ultimus (MPCA 1290) are valid species due to the presence of many autapomorphies. In this sense, the hypothesis proposed by P. Makovicky and collaborators that Achillesaurus manazzonei is a junior synonym of Alvarezsaurus calvoi is rejected. Likewise, certain morphological evidence allows hypothesizing that Alvarezsaurus calvoi represents a growth stage earlier than skeletal maturity. Specimen MCF-PVPH-38 is referable as cf. Patagonykus puertai, while MCF-PVPH-102 is considered an indeterminate Patagonykinae. In turn, MPCN-PV 738 is assigned as cf. Bonapartenykus ultimus based on the little overlapping material with the Bonapartenykus ultimus holotype. The results obtained from the mineralogical characterization through the X-ray diffraction method of specimens MPCN-PV 738 and the holotype of Bonapartenykus ultimus (MPCA 1290), allow to suggest that both specimens come from the same geographical area and stratigraphic level. The phylogenetic analysis, which is based upon the matrix of Gianechini and collaborators of 2018 with the inclusion of proper characters, and the database of Xu and collaborators of 2018, recovered the South American members of Alvarezsauria, such as Alnashetri cerropoliciensis (Candeleros Formation; Cenomanian), Patagonykus puertai (Portezuelo Formation, Turonian-Coniacian), Alvarezsaurus calvoi and Achillesaurus manazzonei (Bajo de La Carpa Formation, Coniacian-Santonian), and Bonapartenykus ultimus (Allen Formation, Campanian-Maastrichtian), nesting within the family Alvarezsauridae. In this sense, the forms that come from the Bajo de La Carpa Formation (Coniacian-Santonian) are recovered at the base of the Alvarezsauridae clade, while Alnashetri cerropoliciensis nests as a non-Patagonykinae alvarezsaurid. Regarding the type specimens of Patagonykus puertai and Bonapartenykus ultimus, they are recovered as members of the Patagonykinae subclade, a group that is recovered as a sister taxon of Parvicursorinae, both nested within the Alvarezsauridae. In addition, the topology obtained allows discerning the pattern, rhythm and time of evolution of the highly strange and derived alvarezsaurian skeleton, concluding in a gradual evolution. The Bremer and Bootstrap supports of the nodes (Haplocheirus + Aorun), [Bannykus + (Tugulusaurus + Xiyunykus)], and Patagonykinae, show indices that represent very robust values for these nodes. Likewise, these values suggest that two endemic clades originated early in Asia, while one endemic clade is observed in Patagonia, i.e., Patagonykinae. The analysis of the directional trends of the Alvarezsauria clade, tested by means of a own database on body masses based on the Christiansen and Fariña method, subsequently calibrated with the group's phylogeny using the R software, shows two independent miniaturization events in the alvarezsaurid evolution, namely the former originating from the base of the Alvarezsauridae (sustained by Alvarezsaurus), and the latter within the Parvicursorinae. Analysis of the Alvarezsauria dentition reveals possible dental synapomorphies for the Alvarezsauria clade that should be tested in an integrative phylogenetic analysis. The general characterization of the forelimb and a partial reconstruction of the myology of alvarezsaurs demonstrate different configurations for Patagonykinae and Parvicursorinae. The multivariate analyzes carried out from the databases of Elissamburu and Vizcaíno, plus that of Cau and collaborators, show that the Patagonykinae would have had ranges of movements greater than those observed in Parvicursorinae, although the latter would have had a greater capacity to carry out more strenuous jobs. The morphometric analysis of the hindlimb and the use of the Snively and collaborators equations, show that the configuration of this element in Alvarezsauria is indicative of a highly cursorial lifestyle, as well as possible particular strategies for more efficient locomotion. The topology obtained in the phylogenetic analysis that was carried out in this Doctoral Thesis, allowed clarifying the ontogenetic changes observed in the ontogenetic series of the manual ungueal element II-2 within the clade Alvarezsauridae. In addition, the multivariate analysis carried out from the manual phalanx II-2 allows us to infer that alvarezsaurs could have performed functions such as hook-and-pull and piercing, where the arm would function as a single unit. The anatomy and myology of the alvarezsaurian tail show that the caudal vertebrae of alvarezsaurians exhibit a combination of derived osteological features that suggests functions unique among theropods, such as considerable dorsal and lateral movements, as well as exceptional abilities to support distal loading of their long tail without compromising stability and/or mobility.
... (continued) (2009) Baurutitan B. britoi Marília Fm., Brazil Maastrichtian (LK) Powell (1986Powell ( , 1987, Kellner et al. (2005) Bonatitan (Martinelli and Forasiepi 2004) B. reigi (Martinelli and Forasiepi 2004) Allen Fm., Argentina late Campanian-early Maastrichtian (LK) Martinelli and Forasiepi (2004), Salgado et al. (2015) Brasilotitan (Machado et al. 2013) B. nemophagus (Machado et ...
... (continued) (2009) Baurutitan B. britoi Marília Fm., Brazil Maastrichtian (LK) Powell (1986Powell ( , 1987, Kellner et al. (2005) Bonatitan (Martinelli and Forasiepi 2004) B. reigi (Martinelli and Forasiepi 2004) Allen Fm., Argentina late Campanian-early Maastrichtian (LK) Martinelli and Forasiepi (2004), Salgado et al. (2015) Brasilotitan (Machado et al. 2013) B. nemophagus (Machado et ...
... (continued) (2009) Baurutitan B. britoi Marília Fm., Brazil Maastrichtian (LK) Powell (1986Powell ( , 1987, Kellner et al. (2005) Bonatitan (Martinelli and Forasiepi 2004) B. reigi (Martinelli and Forasiepi 2004) Allen Fm., Argentina late Campanian-early Maastrichtian (LK) Martinelli and Forasiepi (2004), Salgado et al. (2015) Brasilotitan (Machado et al. 2013) B. nemophagus (Machado et ...
Chapter
Titanosaurian sauropods were the most diverse and successful group of large-bodied terrestrial herbivores. Two aspects regarding their evolutionary history stand out, namely their great morphological diversity and their extensive record from various continental masses. In South America, and particularly in Argentina, the group has the richest record worldwide. This is mainly due to the conjunction of two factors: the extensive paleontological investigation carried out by South American researchers since the beginning of the twentieth century and the well-exposed outcrops of Cretaceous continental strata. With the exception of Tapuiasaurus from Brazil, the entire record of South American named titanosaurs discovered in the Berriasian–Santonian interval comes from Argentina, specifically from Patagonia, including the south of Mendoza, Neuquén, Río Negro, and Chubut Provinces. With a number of 22 valid taxa, the Early and ‘Mid’-Cretaceous titanosaur record of South America includes basally branching (‘basal’) forms (e.g., Andesaurus, Ninjatitan), basal and derived lithostrotians (e.g., Sarmientosaurus, Tapuiasaurus, and Epachthosaurus), and most of the colossosaurs (mainly the giant lognkosaurs Mendozasaurus, Futalognkosaurus, Patagotitan, and Notocolossus). After their origin in the Early Cretaceous, titanosaurians experienced a rapid increase in taxonomic diversity, which is maintained toward the Late Cretaceous. However, during the Berriasian–Santonian interval, the size of titanosaurs reached its climax, representing the largest vertebrate animals ever to inhabit the earth. Some South American titanosaurs from this time have been widely used to define new clades (e.g., Colossosauria, Lognkosauria, Rinconsauria) that clarified the main phylogenetic relationships at lower level. Moreover, studies in some key paleobiological aspects related with the estimation of size contributed to better understanding the biology of some species in the context of the process of gigantism.
... The Upper Member is interpreted by most authors as a restriction of the basin resulting in evaporitic deposition (Rodr ıguez 2011, and references therein). Its abundant fossil content also shows a mixture of continental and fresh-to brackish-water taxa (see Wichmann 1927, in 'the Lacustrine Senonian', equivalent to the Allen Formation; Hugo & Leanza 2001a, b;Leanza et al. 2004;Martinelli & Forasiepi 2004;O'Gorman et al. 2011;Garcia & Salgado 2013; and references therein). ...
Article
The most representative ankylosaurian remains from Argentina have been found in sediments of the Allen Formation (Campanian–Maastrichtian) in Salitral Moreno, Río Negro Province. Several authors have discussed the identity and history of these remains. In this study, we review all published material along with some new remains in order to summarize all the knowledge about these ankylosaurs. Previously published material includes a tooth, dorsal and anterior caudal vertebrae, a femur and several osteoderms. The new remains include synsacral and caudal elements, a partial femur and osteoderms. The anatomy of the tooth, the synsacrum, the mid-caudal vertebra, the femur and the osteoderms, and the histology of the post-cervical osteoderms, support a nodosaurid identification, as proposed in previous descriptions of the Salitral Moreno material. Patagopelta cristata gen. et sp. nov. is a new nodosaurid ankylosaur characterized by the presence of unique cervical half-ring and femoral anatomies, including high-crested lateral osteoderms in the half rings and a strongly developed muscular crest in the anterior surface of the femur. The ∼2 m body length estimated for Patagopelta is very small for an ankylosaur, comparable with the dwarf nodosaurid Struthiosaurus. We recovered Patagopelta within Nodosaurinae, related to nodosaurids from the ‘mid’-Cretaceous of North America, contrasting the previous topologies that related this material with Panoplosaurini (Late Cretaceous North American nodosaurids). These results support a palaeobiogeographical context in which the nodosaurids from Salitral Moreno, Argentina, are part of the allochthonous fauna that migrated into South America during the late Campanian as part of the First American Biotic Interchange. https://zoobank.org/urn:lsid:zoobank.org:pub:FBA24443-F365-49FD-A959-10D2848C2400
... Only a few species are recorded from the Early and Late Cretaceous: Arariphrynus placidoi (Leal et al., 2007;Báez et al., 2009), Eurycephalella alcinae , Cratia gracilis , Primaevorana cratensis (Moura et al., 2021), Kururubatrachus gondwanicus (Agnolin et al., 2020), Baurubatrachus pricei (Báez & Perí, 1989;Báez & Gómez, 2018) and Uberabatrachus carvalhoi (Báez et al., 2012) from Brazil; Hungarobatrachus szukacsi from Hungary (Szentesi & Venczel, 2010;Venczel et al., 2021); Indobatrachus pusillus from India (Noble, 1930;Špinar & Hodrová, 1985); and Beelzebufo ampinga from Madagascar (Evans et al., 2008). Additional Cretaceous neobatrachian records come from Chile and Argentina (calyptocephalellid neobatrachians, Báez, 1987;Martinelli & Forasiepi, 2004;Agnolin, 2012;Novas et al., 2019;Sterli et al., 2021;Moyano-Paz et al., 2022;Suazo-Lara & Gómez, 2022), from Sudan (neobatrachian indet., Báez & Werner, 1996) and Niger (neobatrachian indet., de Broin et al., 1974). It is noteworthy that the systematic position of the aforementioned extinct species remains blurred despite attempts to include them in phylogenetic studies. ...
... Este género pertenece a una rama tempranamente divergente entre los neobatracios, Australobatrachia (Frost et al., 2006), también distribuida en la región australiana. Si bien la presencia en Sudamérica de este grupo de neobatracios desde el Cretácico ha sido documentada por varios hallazgos fósiles (e.g., Báez, 1987;Martinelli y Forasiepi, 2004), los materiales del MLP que se detallan a continuación confirman que constituyó una parte importante de las comunidades batracológicas de agua dulce de Patagonia al oriente de los Andes por lo menos hasta el Mioceno (e.g., Báez, 2000;Muzzopappa y Nicoli, 2010;Fernícola y Albino, 2012;Muzzopapa, 2019). No obstante, debe señalarse algún sesgo en su reiterada representación en virtud de tratarse de formas hiperosificadas de hábitos acuáticos (e.g., Gómez et al., 2009). ...
Article
The Valcheta Petrified Forest is located in the northeast of the Río Negro Province, Argentina. This work provides a geological characterization of the site and a survey of the fossil logs exposed on the surface and their systematic study. The fossiliferous levels bearing the silicified logs are here referred to the Allen Formation (middle-upper Campanian – lower Maastrichtian, Malargüe Group). These deposits crop out in patches in the study area, and have been deposited on a paleorelief carved in Eopaleozoic rocks of the Nahuel Niyeu Formation being mostly covered by thin layers of Quaternary sediments. The Valcheta Petrified Forest was developed on the margins of a braided fluvial system. Numerous silicified logs have been located at the site. They consist of large axes, not found in life position, with monopodial growth, some of which retain the bases of lateral branches and flared-like base. The estimated height and ages of these trees suggests that it consisted of a mature forest. No other associated vegetative or reproductive structures have been found. Anatomically, a single xylological type has been distinguished and assigned to Podocarpoxylon mazzonii (Petriella) Müller-Stoll et Schultze-Motel, (Podocarpaceae). This taxon has been previously identified from other localities of the Upper Cretaceous to the Danian of Patagonia although never preserved in such complete tree grow architecture. This shows that, along others conifers, cycads and palms, P. mazzonii would have constituted an important element of the arboreal strata in the North Patagonian forest communities during the Campanian-Danian interval producing monotypic patches in some areas.
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Abelisaurids are medium–large-sized theropod dinosaurs that were predominant in the carnivorous fauna during the Late Cretaceous of Gondwana. These predators are abundant in the Cretaceous fossil strata of Patagonia, which yield the best record for this group. In the Late Cretaceous, abelisaurids appear in almost all regions of Gondwana and in all stages, except for the Coniacian, in which they are globally unknown. Here we describe a new abelisaurid, Elemgasem nubilus gen. et sp. nov., from the Portezuelo Formation (Turonian–Coniacian), Patagonia, Argentina. The palaeohistology of the appendicular bones of Elemgasem shows that the holotype was a subadult individual, but had achieved sexual maturity. This taxon is based on several axial and appendicular elements, and is diagnosed by the presence of a marked pattern of rugosity on the lateral surface of the fibula and a dorsoventrally deep lateral wall of the calcaneum. Moreover, the posterior caudal vertebrae have a morphology slightly different from any other abelisaurid. Elemgasem nubilus is recovered as an unstable taxon within Brachyrostra, given that it was recovered as sister taxon of Furileusauria or in several positions within this clade. Despite the problematic phylogenetic relationships of Elemgasem nubilus, it is important because it is the first abelisaurid from the Turonian–Coniacian interval and it increases the diversity of this theropod family at a time of marked turnover in the tetrapod fauna of South America, global climate change, and mass extinction events recorded worldwide in the marine realm.
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Full-text available
Titanosaurian sauropods are known to exhibit remarkable body size disparity, with some taxa famed for nearing the zenith of terrestrial vertebrate body size. Here, we describe a new titanosaurian – Ibirania parva gen. et sp. nov. – from the Upper Cretaceous (Santonian– Campanian) São José do Rio Preto Formation of Bauru Basin, in which represents one of the smallest sauropods known to date. The new taxon is diagnosed by seven autapomorphies and had an estimated body length of 5.7 m. Histological and μCT scan analyses showed that this new taxon is represented by skeletally mature individuals, which had attained somatic maturity prior to death. Phylogenetic analyses recovered the new taxon deeply nested within Saltasaurinae, a clade previously known by small-sized forms. Ibirania parva gen. et sp. nov. brings new information indicating that the body size reduction in some titanosaurians could be driven by recurrent ecophysiographical settings, present in South America prior to the diversity peak attained by the group during the Campanian–Maastrichtian.
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