Figure 3 - uploaded by Martin Ezcurra
Content may be subject to copyright.
The Early Cretaceous theropods Ligabueino andesi (A, C), Tyrannotitan chubutensis (B, D), an indeterminate abelisaur (E, F), and Genyodectes serus (G−I). Right ilium in medial view (A), right jugal in lateral view (B), left femur in anterior view (C), right dentary in lateral view (D), anterior caudal vertebra in anterior (E) and dorsal (F) views, premaxillae in anterior view (G), and left maxilla (H) and dentary (I) in lateral views. Abbreviations: amf, anteromedial fossa; at, anterior trochanter; ef, extensor fossa; ip, ischiadic peduncle; pp, pubic peduncle; pop, postacetabular process; prp, preacetabular process; prz, prezygapophysis; tp, transverse process. Scale bars equal 2 cm in (A, C), 5 cm in (B, D, G−I), and 2 cm in (E, F).
Source publication
Theropoda includes all the dinosaurs more closely related to birds than to sauropodomorphs (long-necked dinosaurs) and ornithischians (bird-hipped dinosaurs). The oldest members of the group are early Late Triassic in age, and non-avian theropods flourished during the rest of the Mesozoic until they vanished in the Cretaceous-Palaeogene mass extinc...
Contexts in source publication
Context 1
... some of the best known Early Cretaceous tetrapods from South America, such as the dicraeosaurid sauropod Amargasaurus cazaui and the cladotherian mammal Vincelestes neuquenianus (Bonaparte, 1996). The theropod record from this unit is currently limited to the tiny partial postcranium of the abelisauroid Ligabueino andesi (femoral length 62.4 mm) (Fig. 3A, C) and several isolated teeth comparable with those of large basal tetanurans (Apesteguía, 2007). Ligabueino andesi has been recently found within Noasauridae (Tortosa et al., 2014) and a detailed description of its anatomy is currently under preparation by the senior author. Del Corro (1974) described an isolated tooth crown from the ...
Context 2
... richest diversity of Argentinean Early Cretaceous theropods comes from the Aptian−Albian Cerro Barcino Formation of the Chubut Province. The first theropod specimen described for these beds was the ceratosaur Genyodectes serus, which is based on a partial snout of a single specimen (Woodward, 1901;Rauhut, 2004) (Fig. 3G−I). This species has been recently recovered as the sister-taxon of the Late Jurassic North American ceratosaur Ceratosaurus (Pol & Rauhut, 2012). More recently, Rauhut et al. (2003) described two anterior caudal vertebrae of an abelisaurian (probably abelisaurid) theropod from the Hauterivian−Barremian La Paloma Member of the same ...
Context 3
... 3G−I). This species has been recently recovered as the sister-taxon of the Late Jurassic North American ceratosaur Ceratosaurus (Pol & Rauhut, 2012). More recently, Rauhut et al. (2003) described two anterior caudal vertebrae of an abelisaurian (probably abelisaurid) theropod from the Hauterivian−Barremian La Paloma Member of the same formation (Fig. 3E, F). Novas et al. (2005) erected the new genus and species Tyrannotitan chubutensis based on two partial skeletons from the Aptian Cerro Castaño Member of this formation (Fig. 3B, D). The skeletons that compose the hypodigm of Tyrannotitan chubutensis belonged to animals with a total body length of around 13 metres and are the most ...
Context 4
... (2003) described two anterior caudal vertebrae of an abelisaurian (probably abelisaurid) theropod from the Hauterivian−Barremian La Paloma Member of the same formation (Fig. 3E, F). Novas et al. (2005) erected the new genus and species Tyrannotitan chubutensis based on two partial skeletons from the Aptian Cerro Castaño Member of this formation (Fig. 3B, D). The skeletons that compose the hypodigm of Tyrannotitan chubutensis belonged to animals with a total body length of around 13 metres and are the most complete Early Cretaceous theropod specimens known so far from Argentina. Abbreviations: anfe, antorbital fenestra; anfo, antorbital fossa; bf, brevis fossa; co, coracoid; d, dentary; ...
Similar publications
The reproductive biology of living birds differs dramatically from that of other extant vertebrates. Although some attributes of modern avian reproduction had their origin within theropod dinosaurs like oviraptors and troodontids, even the most derived non-avian theropods lack key features of modern birds. We review the current knowledge of reprodu...
The Late Devonian envelops one of Earth’s big five mass extinction events at the Frasnian–Famennian boundary (374 Ma). Environmental change across the extinction severely affected Devonian reef-builders, besides many other forms of marine life. Yet, cause-and-effect chains leading to the extinction remain poorly constrained as Late Devonian stratig...
Background
Living anguilliform eels represent a distinct clade of elongated teleostean fishes inhabiting a wide range of habitats. Locomotion of these fishes is highly influenced by the elongated body shape, the anatomy of the vertebral column, and the corresponding soft tissues represented by the musculotendinous system. Up to now, the evolution o...
Late Cretaceous dinosaur assemblages of North America—characterized by gigantic tyrannosaurid predators, and large-bodied herbivorous ceratopsids and hadrosaurids—were highly successful from around 80 million years ago (Ma) until the end of the ‘Age of Dinosaurs’ 66 Ma. However, the origin of these iconic faunas remains poorly understood because of...
Citations
... By the end of the Cretaceous Period, the continental ecosystems of the Gondwanan land masses were dominated by dinosaurs and crocodilians (e.g., Pol and Leardi, 2015). South America holds one of the most complete records, documenting a diversification of titanosaurian sauropods (Campos et al., 2005;Casal, 2007;Salgado and Carvalho, 2008;Carballido et al., 2017;Hechenleitner et al., 2020) and ceratosaurian theropods (Ezcurra and Novas, 2016;Zaher et al., 2020;Iori et al., 2021), among dinosaurs, as well as notosuchians, among crocodyliforms (Fiorelli et al., 2016;Lio et al., 2016). Information on these Upper Cretaceous vertebrate faunas is abundant but is geographically restricted mostly to Patagonia, in Argentina (Bonaparte and Novas, 1985;Canale et al., 2009;Lio et al., 2016;Carballido et al., 2017), and Southeastern Brazil (e.g., Tavares et al., 2014;Martinelli and Teixeira, 2015;Menegazzo et al., 2016). ...
... Paleontological discoveries over the past three decades have substantially improved the fossil record of latest Cretaceous (Campanian-Maastrichtian) non-avian dinosaurs and other terrestrial vertebrates from landmasses that formerly comprised the Gondwanan supercontinent. Phylogenetically and paleobiogeographically informative Campanian and/or Maastrichtian dinosaur finds have come from South America (Bonaparte, 1986(Bonaparte, , 1996Leanza et al., 2004;Novas, 2009;Novas et al., 2013;de Jesus Faria et al., 2015;Ezcurra and Novas, 2016;Rozadilla et al., 2021), Madagascar (Krause et al., 1999(Krause et al., , 2006(Krause et al., , 2019, and even Antarctica (Reguero et al., 2013(Reguero et al., , 2022Lamanna et al., 2019). Nevertheless, the latest Cretaceous dinosaur records of two major Gondwanan land areas-Australasia and mainland Africa (i.e., Africa to the exclusion of Madagascar)-remain woefully incomplete, hindering meaningful insights into the evolutionary and paleobiogeographic relationships of their respective dinosaur faunas during this time (Krause et al., 1999(Krause et al., , 2006(Krause et al., , 2019Wilson et al., 2001;Ali and Krause, 2011;Lamanna, 2013;Sallam et al., 2018). ...
Dinosaur fossils from the latest Cretaceous (Campanian–Maastrichtian) of Africa and the Arabian Peninsula are rare. Most discoveries to date have consisted of limited fossils that have precluded detailed phylogenetic and paleobiogeographic interpretations. Fortunately, recent discoveries such as the informative Egyptian titanosaurian sauropod dinosaur Mansourasaurus shahinae are beginning to address these long-standing issues. Here we describe an associated partial postcranial skeleton of a new titanosaurian taxon from the Upper Cretaceous (Campanian) Quseir Formation of the Kharga Oasis, Western Desert of Egypt. Consisting of five dorsal vertebrae and 12 appendicular elements, Igai semkhu gen. et sp. nov. constitutes one of the most informative dinosaurs yet recovered from the latest Cretaceous of Afro-Arabia. The relatively gracile limb bones and differences in the coracoid and metatarsal I preclude referral of the new specimen to Mansourasaurus. Both model-based Bayesian tip-dating and parsimony-based phylogenetic analyses support the affinities of Igai semkhu with other Late Cretaceous Afro-Eurasian titanosaurs (e.g., Mansourasaurus, Lirainosaurus astibiae, Opisthocoelicaudia skarzynskii), a conclusion supported by posterior dorsal vertebrae that lack a postzygodiapophyseal lamina, for example. Igai semkhu strengthens the hypothesis that northern Africa and Eurasia shared closely related terrestrial tetrapod faunas at the end of the Cretaceous and further differentiates this fauna from penecontemporaneous assemblages elsewhere in Africa, such as the Galula Formation in Tanzania, that exhibit more traditional Gondwanan assemblages. At present, the specific paleobiogeographic signal appears to vary between different dinosaur groups, suggesting that Afro-Arabian Cretaceous biotas may have experienced evolutionary and paleobiogeographic histories that were more complex than previously appreciated.
... Several authors have proposed that an extinction event occurred during the Cenomanian-Turonian boundary, affecting many vertebrate groups in both hemispheres 68,70,71 . Some authors discussed the impact of such an event, considering the posibility that this extinction was a step-wise process involving several million of years 69 . Nevertheless, there is a consensus that after the Cenomanian-Turonian time interval, many dinosaurian groups became extinct in tandem with the origin, diversification, and increased numerical abundance of others 2,68,[70][71][72][73] . ...
Megaraptora is a theropod clade known from former Gondwana landmasses and Asia. Most members of the clade are known from the Early to Late Cretaceous (Barremian–Santonian), with Maastrichtian megaraptorans known only from isolated and poorly informative remains. The aim of the present contribution is to describe a partial skeleton of a megaraptorid from Maastrichtian beds in Santa Cruz Province, Argentina. This new specimen is the most informative megaraptoran known from Maastrichtian age, and is herein described as a new taxon. Phylogenetic analysis nested the new taxon together with other South American megaraptorans in a monophyletic clade, whereas Australian and Asian members constitute successive stem groups. South American forms differ from more basal megaraptorans in several anatomical features and in being much larger and more robustly built.
... Carnotaurus sastrei is one of most complete and best preserved theropods from Gondwana (Bonaparte 1996b;Ezcurra and Novas, 2016). This large-bodied abelisaurid (~7.8 m in body length, and a body mass around 1.5e1.7 tonnes; Mazzetta et al. 2004;Benson et al. 2014;Grillo & Delcourt 2017) is characterized by a short-snouted and tall cranium adorned with two prominent frontal horns as well as atrophied forelimbs with four reduced digits (Bonaparte et al. 1990;Ruiz et al. 2011;Cerroni et al. 2020;Fig. ...
The integument of the theropod dinosaur Carnotaurus sastrei from the Upper Cretaceous of Argentina is here described in detail for the first time. The scaly skin of this abelisaurid is the most completely preserved of any theropod and the only example of this form of integument known outside of Tetanurae (excluding footprints). The skin is preserved in the shoulder, thoracic, tail and, possibly, neck regions and consists of medium to large (20-65 mm in diameter) conical feature scales surrounded by a network of low and small (<14 mm) basement scales separated by narrow interstitial tissue. Contrary to previous interpretations, the feature scales are randomly distributed and neither form discrete rows nor show progressive variations in their size along parts of the body. They also show little difference in morphology along the body, although their apices are variously positioned in different body parts. Conversely, the basement scales vary from small and elongated, large and polygonal, and circular-to-lenticular in the thoracic, scapular, and tail regions, respectively. Given the presumed active lifestyle of Carnotaurus and the necessity of shedding excess heat, particularly at large body sizes (>1000 kg), we speculate that the skin may have played a vital role in thermoregulation; a role consistent with integument function in extant mammals and reptiles.
... Fossil discoveries within the last few decades have revealed an important diversity of abelisauroid theropod dinosaurs from Cretaceous localities in southern South America, especially from Upper Cretaceous beds in Patagonia (Coria, 2007;Novas, 2009;Novas et al., 2013;Ezcurra and Novas, 2016). Nevertheless, the fossil record of Abelisauroidea also indicates that members of this group were diverse and abundant in other areas of the continent plus other Gondwanan and Laurasian landmasses as well (e.g., Kellner and Campos, 2002;Carrano et al., 2002;Wilson et al., 2003;Krause et al., 2007;} Osi and Buffetaut, 2011;Farke and Sertich, 2013;Tortosa et al., 2014;Chiarenza and Cau, 2016;Langer et al., 2019). ...
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.
... Fossil discoveries within the past three decades have revealed an unexpected diversity of tetanuran theropod dinosaurs from Cretaceous localities in the Southern Hemisphere landmasses, especially South America (e.g., Bonaparte 1991;Coria and Salgado 1995;Kellner and Campos 1996;Martill et al. 1996;Novas 1997Novas , 1998Novas and Puerta 1997;Kellner 1999;Naish et al. 2004;Makovicky et al. 2005Makovicky et al. , 2012Novas and Pol 2005;Novas et al. 2005Novas et al. , 2008aNovas et al. , 2008bNovas et al. , 2012Coria andCurrie 2006, 2016;Martínez and Novas 2006;Martinelli and Vera 2007;Sereno et al. 2008;Kellner et al. 2011;Porfiri et al. 2011aPorfiri et al. , 2018Agnolín et al. 2012;Apesteguía et al. 2016;Motta et al. 2016Motta et al. , 2020Coria et al. 2020; see reviews in Novas et al. 2013;Ezcurra and Novas 2016). Among the most enigmatic of these predominantly Gondwanan tetanuran clades is Megaraptora, definitively represented in South America by the Argentinean Late Cretaceous species Aerosteon riocoloradensis (Sereno et al. 2008), Megaraptor namunhuaiquii (Novas 1998;Calvo et al. 2004;Porfiri et al. 2007aPorfiri et al. , 2007bPorfiri et al. , 2008Porfiri et al. , 2014Paulina-Carabajal and Porfiri 2018), Murusraptor barrosaensis (Coria and Currie 2016;Paulina-Carabajal and Currie 2017;Aranciaga Rolando et al. 2019), Orkoraptor burkei (Novas et al. 2008a), and Tratayenia rosalesi , as well as multiple taxonomically indeterminate (e.g., Aranciaga Rolando et al. 2015Novas et al. 2019;Ibiricu et al. 2020) or as-yet undescribed (e.g., Porfiri et al. 2011b;Casal et al. 2019;Méndez et al. 2019) specimens. ...
... 8)-are positioned as tyrannosauroids of otherwise unresolved phylogenetic position. Despite these results, however, we regard the recovered position of Megaraptora and Gualicho within Tyrannosauroidea with caution, and concur with many previous authors (e.g., Apesteguía et al. 2016;Coria and Currie 2016;Ezcurra and Novas 2016;Novas et al. 2016;Porfiri et al. 2018) that further discoveries are needed to definitively resolve the higher-level affinities of these taxa within Avetheropoda. ...
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.
... The Upper Cretaceous deposits of Patagonia (southern Argentina) have yielded an outstanding number of theropod species from several different clades (e.g., Noasauridae, Abelisauridae, Carcharodontosauridae, Megaraptoridae, Alvarezsauridae, Unenlagiinae), documenting a high diversity of predatory dinosaurs in South America during the Late Cretaceous (Novas et al., 2013;Ezcurra and Novas, 2016). Among them, Aerosteon riocoloradensis is particularly interesting because it represents an early Campanian (Garrido, 2010) basal avetheropod with extreme cranial and postcranial pneumatization . ...
... This fossil is important in that it constitutes the only known record of a continental vertebrate from this stratigraphic unit and the oldest dinosaurian fossil from the Antarctic Cretaceous (Schweitzer et al., 2012). As such, although such a study would be beyond the scope of the present paper, we believe that MLP 89-XII-1-1 requires reanalysis in light of the numerous Cretaceous non-avian theropod discoveries that have been made on Gondwanan continents during the past quarter-century (e.g., Novas et al., 2013;Ezcurra and Novas, 2016). For example, spinosaurids (e.g., Spinosaurus aegyptiacus, Stromer, 1915) are the only megalosauroids known to have survived into the Late Cretaceous, and as such, MLP 89-XII-1-1 should be compared to the distal tibiae of these distinctive semi-aquatic theropods. ...
Although the fossil record of non-avian dinosaurs from the Cretaceous of Antarctica is the poorest of any continent, fossils representing at least five major taxonomic groups (Ankylosauria, early-diverging Ornithopoda, Hadrosauridae, Titanosauria, and Theropoda) have been recovered. All come from Upper Cretaceous (Coniacian–Maastrichtian) marine and nearshore deposits belonging to the Gustav and Marambio groups of the James Ross Basin at the northern tip of the Antarctic Peninsula. The majority of these finds have come from the Campanian–Maastrichtian Snow Hill Island and López de Bertodano formations of James Ross and Vega islands. Given the rarity of Antarctic Cretaceous non-avian dinosaurs, discoveries of any fossils of these archosaurs, no matter how meager, are of significance. Here we describe fragmentary new ornithischian (ankylosaur and ornithopod) material from the upper Campanian–lower Maastrichtian Cape Lamb Member of the Snow Hill Island Formation and the Maastrichtian Sandwich Bluff Member of the López de Bertodano Formation. One of these specimens is considered to probably pertain to the holotypic individual of the early-diverging ornithopod Morrosaurus antarcticus. We also provide an up-to-date synthesis of the Late Cretaceous non-avian dinosaur record of the James Ross Basin and analyze the biostratigraphic occurrences of the various finds, demonstrating that most (including all named taxa and all reasonably complete skeletons discovered to date) occur within a relatively condensed temporal interval of the late Campanian to early Maastrichtian. Most or all James Ross Basin dinosaurs share close affinities with penecontemporaneous taxa from Patagonia, indicating that at least some continental vertebrates could disperse between southern South America and Antarctica during the final stages of the Mesozoic.
... Finally, and most recently, in their analysis of the unnamed megaraptoran represented by specimen SMNS 58023, Aranciaga Rolando et al. (2018) recovered Megaraptora in the same positions as did Apesteguía et al. (2016): within Carcharodontosauria [using a modification of Carrano et al.'s (2012) dataset] or as non-tyrannosauroid basal coelurosaurs [using a modification of Porfiri et al.'s (2014) dataset]. The possible positions of Megaraptora within Tetanurae were summarized by Ezcurra and Novas (2016: fig. 1). ...
... The discovery of Tratayenia in a Santonian horizon of the Bajo de la Carpa Formation constitutes a new stratigraphic occurrence in the megaraptorid fossil record of the Neuqu en Basin (Fig. 11). Following the stratigraphy proposed by Garrido (2010), megaraptorid taxa from this basin include, in stratigraphic order from oldest to youngest, Megaraptor from the upper Turonianelower Coniacian Portezuelo Formation (Novas, 1998;Calvo et al., 2004;Porfiri et al., 2014), Murusraptor from the middle Coniacian Sierra Barrosa Formation (Coria and Currie, 2016), and Aerosteon from either the upper Coniacianelowermost Santonian Plottier Formation (Novas et al., 2013;Ezcurra and Novas, 2016) or the lower Campanian Anacleto Formation (Sereno et al., 2008). Consequently, Tratayenia is either intermediate in age between Murusraptor and Aerosteon or (if the latter is from the Plottier Formation) the geologically youngest megaraptorid yet known from the Neuqu en Basin. ...
... Indeed, and notably, given its Santonian age, Tratayenia may be the latest-surviving representative of Megaraptoridaedand perhaps Megaraptora as a wholedyet discovered anywhere in the world. The megaraptorid Orkoraptor from the Austral Basin of southern Patagonia was originally regarded as Maastrichtian in age (Novas et al., 2008), prompting Benson et al. (2010) to propose that Megaraptora survived to the end of the Mesozoic; however, Orkoraptor is now suspected to be substantially more ancient than initially considered (Cenomanianeearly Coniacian; Novas et al., 2013;Ezcurra and Novas, 2016). Similarly, Casal et al. (2016) recently reported two manual unguals (one partial, the other complete and well preserved) and a probable metatarsal III that are likely referable to Megaraptoridae from the Lago Colhu e Huapi Formation of the Golfo San Jorge Basin in central Patagonia. ...
We describe Tratayenia rosalesi gen. et sp. nov., a new megaraptoran theropod dinosaur from the Upper Cretaceous of Patagonia, Argentina. The holotype consists of a well-preserved, mostly articulated series of dorsal and sacral vertebrae, two partial dorsal ribs, much of the right ilium, and pubis and ischium fragments. It was found in a horizon of the Upper Cretaceous (Santonian) Bajo de la Carpa Formation of the Neuquén Group in the Neuquén Basin exposed near the town of Añelo in Neuquén Province of northwestern Patagonia. Phylogenetic analysis recovers Tratayenia within the Gondwanan megaraptoran subclade Megaraptoridae. The new taxon exhibits similarities to other megaraptorids such as Aerosteon riocoloradensis, Megaraptor namunhuaiquii, and Murusraptor barrosaensis, but also presents differences in the architecture of the dorsal and sacral vertebrae and the morphology of the ilium. Tratayenia is the first megaraptoran that unequivocally preserves the complete sequence of sacral vertebrae, thereby increasing knowledge of the osteology of the clade. Moreover, depending on the chronostratigraphic ages of the stratigraphically controversial megaraptorids Aerosteon and Orkoraptor burkei, as well as the phylogenetic affinities of several fragmentary specimens, the new theropod may be the geologically youngest megaraptorid or megaraptoran yet discovered. Tratayenia is also the largest-bodied carnivorous tetrapod named from the Bajo de la Carpa Formation, reinforcing the hypothesis that megaraptorids were apex predators in southern South America from the Turonian through the Santonian or early Campanian, following the extinction of carcharodontosaurids.
... The Cretaceous theropod record of South America is mainly restricted to Argentina and Brazil (Novas, 2009). In particular, the Argentinean record of the group is taxonomically diverse, including ceratosaurids, noasaurids, abelisaurids, carcharodontosaurids, basal coelurosaurs, megaraptorans, alvarezsaurids, basal paravians, and birds (e.g., Novas, 2009;Novas et al., 2013;Ezcurra and Novas, 2016). The theropod Brazilian record is less abundant, but considerably diverse though, including abelisaurids, noasaurids, carcharodontosaurids, spinosaurids, megaraptorans, basal coelurosaurs, and birds (e.g., Kellner and Campos, 2002;Novas, 2009;Bittencourt and Langer, 2011;Lindoso et al., 2012;Martinelli et al., 2013;Carvalho et al., 2015;Brusatte et al., 2017). ...
A specimen composed of a partial sacrum articulated to two anterior caudal vertebrae and an ilium (SMNS 58023) from the Lower Cretaceous (Albian) Santana Formation of Brazil was originally described as an oviraptorosaur, but it is here re-interpreted as the oldest megaraptoran of South America. The phylogenetic relationships of SMNS 58023 were tested quantitatively for the first time including it in the two most comprehensive phylogenetic data sets focused on non-maniraptoran theropods –including megaraptorans. The Brazilian specimen was consistently found as a megaraptoran in both analyses because of the presence of sacral centra longer than tall, absence of a median transverse constriction of sacral centra, and the morphology and position of sacral pleurocoels. SMNS 58023 sheds light on a region of the body that is poorly known in megaraptorans and pulls back the temporal range of the clade in South America. This re-interpretation reinforces the absence of oviraptorosaurs in Gondwana.
