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Xenotarsosaurus bonapartei Nov. Gen. et Sp. (Carnosauria: Abelisauridae),un nuevo Theropoda de la Formación Bajo Barreal, Chubut, Argentina

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... The former clade includes small-bodied, gracile forms, whereas the latter is generally characterized by medium-to large-bodied and more robust forms, with some exceptions (e.g., Farke and Sertich, 2013;Canale et al., 2016;Grillo and Delcourt, 2017;Cerroni et al., 2020). Although the Neuqu en Basin of northern Patagonia has yielded the most abundant and diverse fossil record of Abelisauroidea (see Leanza et al., 2004;Garrido, 2010; Table 1), recent and historical discoveries in the Golfo San Jorge Basin of central Patagonia have also added important information about the group (Martínez et al., 1986(Martínez et al., , 2004aLamanna et al., 2002;Casal et al., 2016;Ibiricu et al., 2020). The record of Abelisauroidea from the Golfo San Jorge Basin comes entirely from the Upper Cretaceous (lower Cenomanianeupper Turonian) Bajo Barreal Formation. ...
... Dinosauria Owen, 1842Saurischia Seeley, 1888Theropoda Marsh, 1881Ceratosauria Marsh, 1884Abelisauroidea Bonaparte and Novas, 1985 Abelisauridae Novas, 1985 Xenotarsosaurus Martínez, Gim enez, Rodríguez, andBochatey, 1986 Xenotarsosaurus bonapartei Martínez, Gim enez, Rodríguez, and Bochatey, 1986 Figs. 3e8 ...
... Dinosauria Owen, 1842Saurischia Seeley, 1888Theropoda Marsh, 1881Ceratosauria Marsh, 1884Abelisauroidea Bonaparte and Novas, 1985 Abelisauridae Novas, 1985 Xenotarsosaurus Martínez, Gim enez, Rodríguez, andBochatey, 1986 Xenotarsosaurus bonapartei Martínez, Gim enez, Rodríguez, and Bochatey, 1986 Figs. 3e8 ...
Article
Xenotarsosaurus bonapartei was the third abelisaurid theropod dinosaur to be named from Argentina. The holotype comprises two partial anterior dorsal vertebrae and a complete right hind limb from the Upper Cretaceous (lower Cenomanian–upper Turonian) Bajo Barreal Formation, central Patagonia, Argentina. The materials display morphological features that undoubtedly position Xenotarsosaurus within Abelisauroidea. Moreover, detailed comparisons with members of that theropod group confirm the close relationship of this taxon to abelisaurids. Here we provide an emended diagnosis of Xenotarsosaurus bonapartei that includes five newly recognized autapomorphies: (1) anterior dorsal vertebrae with large, strongly dorsoventrally developed parapophyses; (2) anterior dorsal vertebrae with well-developed centroprezygapophyseal fossae that are taller dorsoventrally than wide mediolaterally; (3) fibular condyle of femur triangular in shape and projecting posteriorly; (4) well-marked groove on the anterolateral corner of the proximal fibula; and (5) iliofibularis tubercle of fibula distally interrupted by a hook-like shaped concavity. To determine its systematic position within Abelisauroidea, we incorporated Xenotarsosaurus into a phylogenetic analysis, recovering this theropod as a non-carnotaurine abelisaurid more derived than Eoabelisaurus mefi. Xenotarsosaurus displays several plesiomorphic traits when compared with penecontemporaneous abelisaurids from the Neuquén Group. Similarly, other non-avian dinosaur taxa from the Bajo Barreal Formation are frequently postulated as more phylogenetically basal than coeval forms from northern Patagonia. This scenario suggests the potential existence of provincialism in early Late Cretaceous continental vertebrate faunas of southern South America. The present study increases knowledge of abelisaurid systematics, evolution, and paleobiogeography and augments our understanding of the Late Cretaceous dinosaur assemblage of central Patagonia.
... Xenotarsosaurus bonapartei UNPSJB-PV 184, 612 Femur, fibula, tibia and astragaluscalcaneum complex (UNPSJB-PV 184), dorsal vertebrae (UNPSJB-PV 612) Martínez et al., 1986;Ibiricu et al., 2021 USLM SE-PF (FA-SF) Martínez et al., 1986 Ibiricu et al., 2020; this paper Abelisauroidea indet. 224,225,226,229,230,231,232,233,981,982,983,984,985 Chelidae indet. ...
... Xenotarsosaurus bonapartei UNPSJB-PV 184, 612 Femur, fibula, tibia and astragaluscalcaneum complex (UNPSJB-PV 184), dorsal vertebrae (UNPSJB-PV 612) Martínez et al., 1986;Ibiricu et al., 2021 USLM SE-PF (FA-SF) Martínez et al., 1986 Ibiricu et al., 2020; this paper Abelisauroidea indet. 224,225,226,229,230,231,232,233,981,982,983,984,985 Chelidae indet. ...
... The sedimentological section conducted on Outcrop A links two important paleontological sites, including quarries of the basal titanosaur Epachthosaurus sciuttoi (Martínez et al., 2004), and the abelisaurid theropod Xenotarsosaurus bonapartei (Martínez et al., 1986;Ibiricu et al., 2021), but also several associated abelisauroid materials , among other remains. Outcrop B involves several vertebrate fossils such as an isolated abelisaurid maxilla (Lamanna et al., 2002), numerous dinosaur teeth (Casal et al., 2009), crocodyliform teeth (this paper), and rebbachisaurid remains , among others. ...
Article
We present the first integrate paleoecological study which includes both previous and new sedimentological, paleoclimate, fauna and flora analyses in the Bajo Barreal Formation (Upper Cretaceous), Golfo San Jorge Basin, Patagonia, Argentina. The study was carried out principally at the Estancia (=Ranch) Ocho Hermanos Locality, although other significant paleontological localities of the Bajo Barreal Formation are included. In the Estancia Ocho Hermanos Locality, the paleoenvironment is characterized by low sinuosity single-channelized fluvial systems, with well-developed proximal floodplains. Paleoclimate was interpreted as warm and humid with marked seasonality. This locality was dominated by dinosaurs, including sauropods (titanosaurs and rebbachisaurids) and theropods (abelisaurids and megaraptorids), but other vertebrates, such as pterosaurs, crocodyliforms, turtles and fishes were also part of the paleoecosystem. In addition, the first stable isotope analysis on Mesozoic teeth (dinosaurs and crocodyliforms) from the Golfo San Jorge Basin was conducted. This new information revealed different sources of water utilized by theropod and sauropod dinosaurs, allowed to infer preliminary modes of lyfe for crocodyliforms, and provided information about diet of these Mesozoic organisms. Ground-level and mid-height feeding are interpreted for rebbachisaurid and titanosaurid sauropods, respectively. Ferns are considered the main non-arboreal component of this ecosystem and possibly an important source of the diet of sauropods, whereas angiosperms (eudicots and monocots) would have been present as well. On the other hand, gymnosperms, mainly Araucariaceae, and in a minor proportion Podocarpaceae, and Cheirolepidiaceae, would encompass the arboreal component of this environment. Abelisaurids could be recognized as one of the top predators of this paleoecosystem, in part due to their relative abundance, in relation to other carnivores. Finally, in a broad context, this study augments our understanding of Cretaceous terrestrial ecosystems of south-central Patagonia and contributes for future comparisons with other chronologically equivalent localities, principally, from the Southern Hemisphere.
... In this context, we have scored several previously unknown character states for Skorpiovenator (Supplemental material Table S2). The sample of taxa has been modified with the addition of Afromimus tenerensis (Sereno 2017;Cerroni et al. 2019), Llukalkan aliocranianus , Niebla antiqua (Aranciaga-Rolando et al. 2021), Quilmesaurus curriei (Coria 2001) and Xenotarsosaurus bonapartei (Mart ınez et al. 1986;Ibiricu et al. 2021), whereas other fragmentary taxa have been removed (i.e. 'Spinostropheus-type', Camarillasaurus, Deltadromeus and USNM 8415) due to their questioned ceratosaurian affinity (Rauhut & Carrano 2016;Langer et al. 2019;Samathi et al. 2021). ...
... The fibular facet is sculptured by abundant rugosities which are predominant over the midshaft and gradually diminish towards the distal end, near the lateral malleolus, and the facet it is much less rugose. A wrinkled fibular facet is usually Appendicular osteology of Skorpiovenator present in abelisaurids (Mart ınez et al. 1986;Carrano 2007) and may have marked the lateral extension of the m. tibialis cranialis attachment (Carrano & Hutchinson 2002;Cerroni 2021). ...
Article
Skorpiovenator bustingorryi is a derived abelisaurid theropod represented by a fairly complete skeleton from the Late Cretaceous sedimentary beds of north-western Patagonia. Although some features were described in the original paper, mainly related to the skull, the appendicular anatomy remains undescribed. The aim of the present contribution is to provide a detailed description and analysis of the available appendicular bones, including comparisons with other ceratosaurian theropods close to Skorpiovenator. In this way, new autapomorphies emerged to further distinguish Skorpiovenator from its relatives. Furthermore, a comprehensive phylogenetic analysis was performed and several characteristics of the hind limb, in particular some of the autopodium, resulted in the identification of new apomorphic traits for Ceratosauria and Abelisauridae. These features might prove to be useful for future phylogenetic analyses and may help to resolve the still confusing and debated internal relationships of abelisaurid theropods.
... En cuanto al registro de terópodos, en el yacimiento de estancia Ocho Hermanos el clado está dominado por los abelisauroideos. Entre los restos se destaca Xenotarsosaurus bonapartei Martínez et al. (1986) representados por dos vértebras dorsales anteriores, y una extremidad posterior derecha incompleta que incluye fémur, tibia, fíbula, astrágalo y calcáneo (Fig. 10). Los restos estaban preservados en areniscas verdes medianas con intraclastos pelíticos y tobáceos de un depósito de canal. ...
... Los restos estaban preservados en areniscas verdes medianas con intraclastos pelíticos y tobáceos de un depósito de canal. Xenotarsosaurus es un terópodo de tamaño medio, de entre 5 y 6 m aproximadamente de largo (Lamanna et al. 2002, Grillo y Delcourt 2017, y fue propuesto originalmente como miembro de Abelisauridae (Martínez et al. 1986), particularmente basado en las similitudes morfológicas con Carnotaurus sastrei (Bonaparte 1985). Coria y Rodríguez (1993) ponen en duda esa asignación y proponen a Xenotarsosaurus como un Neoceratosauria incertae sedis. ...
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En la cuenca del Golfo San Jorge se encuentran unidades de origen continental reunidas en el Grupo Chubut (Barreamiano-Maastrichtiano) que son portadoras de un alto contenido fosilífero. Este registro paleontológico de vertebrados continentales cretácicos de la cuenca es una de los más diversos de América del Sur. Es relativamente escaso al momento en la Formación Matasiete (Aptiano), pero mucho más abundante en las formaciones Bajo Barreal (Cenomaniano temprano-Turoniano tardío) y Lago Colhué Huapi (Conianciano-Maastrichtiano). Incluye una importante cantidad de grupos de vertebrados, destacándose los dinosaurios saurópodos, terópodos y ornitópodos. También están bien documentados otros taxones como cocodrilos y tortugas, pero son escasos hasta el momento los restos de reptiles voladores, anuros y peces. Muchos de los hallazgos son de gran importancia y han contribuido al conocimiento de diferentes grupos y de sus relaciones filogenéticas y paleobiogeográficas. Se describe en este trabajo, solo el registro paleontológico más relevante y especies válidas conocidas hasta el momento.
... Aucasaurus;Gilmore, 1920;Martínez et al., 1986;Accarie et al., 1995;Madsen & Welles, 2000;Coria, 2001; ...
Article
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The Late Cretaceous theropod fauna of South America is composed of Abelisauridae, Noasauridae, Spinosauridae, Carcharodontosauridae, Megaraptora, and Coelurosauria. These groups include mostly small (Noasauridae and Coelurosauria) and medium- tolarge-sized taxa (Carcharodontosauridae, Abelisauridae, and Megaraptora). Some of these lineages are predominantly Gondwanic (Abelisauridae, Noasauridae, Carcharodontosauridae, Megaraptora) and poorly represented in Laurasian landmasses. Particularly, several theropods have been reported from Patagonia, known either due to distinct anatomical features or due to their high degree of preservation, such as Carnotaurus, Skorpiovenator, Giganotosaurus, Megaraptor, Alvarezsaurus, and Unenlagia. Here we describe a new incomplete tibia (MAU-PV-CM-653) from the Sierra Barrosa Formation (middle Coniacian, Upper Cretaceous), Patagonia, Argentina. MAU-PV-CM-653 shows an anteroposteriorly reduced cnemial crest that is strongly curved laterally. Finally, the tibia lacks a proximal extension of the fibular crest. These traits are reminiscent of tetanuran morphology and, together with the stratigraphic provenance of MAU-PV-CM-653, they allow us to assign it to an allosauroid theropod, thus improving the Allosauroidea global record for the middle Late Cretaceous.
... Among them, abelisaurids are undoubtedly the bestknown theropods. This group of mid-sized, meat-eating dinosaurs is represented by almost 20 nominate species, half of them from Patagonia (Bonaparte, 1985;Bonaparte and Novas, 1985;Martínez et al., 1986;Coria and Salgado, 1998;Calvo et al., 2004;Canale et al., 2009;Filippi et al., 2016;Cerroni et al., 2020). The increase of osteological knowledge of these theropods has been exponential since the recognition of the family, more than 30 years ago. ...
Article
Abelisaurids are among the most abundant and diverse Patagonian Late Cretaceous theropods. Here, we present a new furileusaurian abelisaurid, Llukalkan aliocranianus gen. et sp. nov., represented by cranial remains from the Bajo de la Carpa Formation (Santonian) at La Invernada fossil area, northwestern Patagonia. Features characterizing this taxon include a possible caudal tympanic recess posterior to the columellar recess, a T-shaped lacrimal with jugal ramus lacking a suborbital process, and large foramina for caudal middle cerebral veins widely separated from the median supraoccipital crest. In addition to this, a bulge on the anteromedial border of the supratemporal fossa, tall and posteriorly projected paroccipital processes, basal tubera interconnected distally, a triangular basisphenoid recess, and a single foramen for the sphenoidal artery on the basisphenoid, differentiate Llukalkan from Viavenator exxoni. The latter is the other furileusaurian taxon from the same area and stratigraphic unit. Although the holotype of Llukalkan probably corresponds to a sub-adult—as the lacrimal morphology suggests— the possibility that it represents a juvenile of V. exxoni is discarded based mainly on the presence of a caudal tympanic recess (which is absent in V. exxoni). The probable coexistence of two abelisaurid taxa demonstrates that the abelisaurids were one of the most important—and likely the main—predator component of the ecosystems, not only in this area, but also in all of Patagonia, during the Late Cretaceous.
... Two Cretaceous sedimentary units are widely exposed in the region, the lower Cenomanian-upper Turonian Bajo Barreal Formation (from which the megaraptorid fossils described herein were recovered) and the Coniacian-Maastrichtian Lago Colhué Huapi Formation (Casal et al. 2015(Casal et al. , 2016. Apart from the generically unassigned megaraptorid reported here, theropod dinosaurs from the former unit include abelisauroids (possibly all of which are abelisaurids; Xenotarsosaurus bonapartei [Martínez et al. 1986] and indeterminate forms [e.g., Lamanna et al. 2002Lamanna et al. , 2011Lamanna et al. , 2012Martínez et al. 2004Martínez et al. , 2005Casal et al. 2009Casal et al. , 2016Ibiricu et al. 2020]), a putative carcharodontosaurid (represented Fig. 13.-Synopsis of fossil record, body size evolution, and paleobiogeography of Megaraptoridae. A, stratigraphic distribution of definitive and probable megaraptorid fossils through the Cretaceous. ...
Article
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We describe two partial postcranial skeletons belonging to the enigmatic theropod dinosaur clade Megaraptoridae from the Upper Cretaceous (lower Cenomanian-upper Turonian) Bajo Barreal Formation of southern Chubut Province, central Patagonia, Argentina. The specimens are assigned to Megaraptoridae due to their possession of multiple anatomical features that are considered synapomorphies of that predatory dinosaur group, such as a greatly enlarged, laterally compressed ungual of manual digit I that possesses asymmetrical lateral and medial vascular grooves. Overlapping elements of the two skeletons are nearly identical in morphology, suggesting that they probably represent the same taxon, a large-bodied theropod that was previously unknown from the early Late Cretaceous of southern South America. The Bajo Barreal specimens constitute the most ancient unquestionable records of Megaraptoridae from that continent, and exhibit particularly strong osteological resemblances to penecontemporaneous megaraptorids from the Winton Formation of Australia. Phylogenetic analysis recovers the unnamed Bajo Barreal taxon as the earliest-diverging South American megaraptorid and the oldest-known representative of this clade that likely attained a body length of at least seven meters and a mass of at least one metric ton. Overall, the balance of the evidence suggests that megaraptorids originated in eastern Gondwana (Australia) during the Early Cretaceous, then subsequently dispersed to western Gondwana (South America) during the mid-Cretaceous, where they attained substantially larger body sizes, ultimately coming to occupy the apex predator niches in their respective habitats.
Article
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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The deposits corresponding to the Upper Cretaceous Neuquén and San Jorge Gulf basins from northern and central Patagonia have provided two of the most complete sequences of terrestrial vertebrate faunas of all Gondwanan landmasses. Among the carnivorous components, the carcharodontosaurid theropods appeared as common elements during the Early Cretaceous and the earliest Late Cretaceous in northern and central Patagonia. Although recorded mostly in the lower Turonian, isolated teeth suggest their presence in younger strata in northern and central Patagonia, reaching the clade in the region as late as the early Maastrichtian. Here, we verify the assignment of such isolated teeth previously identified as belonging to Carcharodontosauridae from the Upper Cretaceous strata of northern and central Patagonia. Using three different methods, namely a cladistic analysis performed on a dentition-based data matrix, and discriminant and cluster analyses conducted on a large dataset of theropod crown measurements, we assign a tooth from Candeleros Formation to carcharodontosaurid theropods and teeth from Cerro Lisandro, Bajo Barreal, Portezuelo, Plottier and Allen formations to abelisaurid theropods. These new reappraisals provide additional evidence about the extinction of Carcharodontosauridae in South America at about the late Turonian–earliest Coniacian as part of a general faunistic turnover event, with the last clear evidence of this lineage in Patagonia coming from the early–middle Turonian.
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