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Cretaceous tetrapods of Argentina
... A record of a rebbachisaurid from Asia has recently been reported (Averianov and Sues 2021), but its taxonomic assignment has been questioned (Lerzo et al. 2021), and the enigmatic North American taxon Maraapunisaurus (formerly Amphicoelias) fragillimus has been referred to Rebbachisauridae, albeit on the basis of missing material (Carpenter 2018). Despite the broad paleogeographic distri-bution of the group, the greatest diversity and abundance of rebbachisaurid sauropods are known from the Cretaceous of South America, especially in Neuquén Basin from Argentina (Calvo and Salgado 1995;Bonaparte 1996Bonaparte , 1997Dalla Vecchia 1998;Sereno et al. 1999;Carvalho et al. 2003; Gallina and Apesteguía 2005;Salgado et al. 2006;Apesteguía 2007;Taylor and Naish 2007;Carballido et al. 2010;Torcida et al. 2011;Salgado et al. 2012;Fanti 2013Fanti , 2015Ibiricu et al. 2013Ibiricu et al. , 2015Canudo et al. 2018;Lindoso et al. 2019;Bellardini et al. 2022). ...
... This stratigraphic unit has provided a diverse fauna of fossil reptiles and other continental vertebrates from the Neuquén Basin, among which the sauropod dinosaurs stand out. Candeleros Formation sauropods include the titano saur Andesaurus delgadoi (Calvo and Bona parte 1991) and the rebbachisaurids Limaysaurus tessonei (Calvo and Salgado 1995), Nopcsaspondylus alarconensis (Apesteguía 2007), and Rayososaurus agrioensis (Bonaparte 1996;Carballido et al. 2010). The anterior caudal vertebrae described herein, MDPA-Pv 007, is from the Candeleros For mation and is referred to the family Rebbachisauridae. ...
... MDPA-Pv 007 adds to the known fossil record of rebba chisaurid genera from the Candeleros Formation, so far represen ted by Limaysaurus (Calvo and Salgado 1995), Nopcsaspondylus (Apesteguía 2007), Rayososaurus (Bonaparte 1996;Carbal lido et al. 2010) and some remains of Rebbachisauridae indet. (Paulina Carabajal et al. 2016). ...
... Calvo (1991) y Heredia et al. (2019), reportaron huellas tridáctilas asignadas a terópodos no avíanos. Asimismo, los registros de saurópodos también son numerosos, entre ellos Nopcsaspondylus alarconensis (Apesteguía, 2007), Andesaurus delgadoi (Calvo y Bonaparte, 1991), Limaysaurus tessonei ( (Bonaparte, 1996). También se presentan registros de huellas asignadas a saurópodos, ornitisquios y pterosaurios (Calvo, 1991). ...
... En sección transversal, es tan alta dorsoventralmente como ancha transversalmente (n.b., 10% más alta dorsoventralmente). Esta morfología se correlaciona con una vértebra dorsal media en función de los diferentes sectores de la serie conocidos para Alvarezsauridae (Bonaparte, 1996;Perle et al., 1994;Karhu y Rautian, 1996;Xu et al., 2010;Averianov y Lopatin, 2022). Respecto a la vértebra dorsal posterior (Fig. IV.6), su fuerte compresión transversal también observada en Parvicursorinae (e.g., Parvicursor, Mononykus, Xixianykus;Perle et al., 1994;Karhu y Rautian, 1996;Xu et al., 2010;Averianov y Lopatin, 2022) respalda su asignación dentro de la serie como un elemento posterior. ...
... Transversalmente, este centro se comprime fuertemente (Fig. IV.46C), recordando la condición presente en las vértebras dorsales 9-12 en Xixianykus . Otro carácter presente en la serie dorsal de Alvarezsauridae (Bonaparte, 1996;Novas, 1997;Perle et al., 1994;Karhu y Rautian, 1996;Xu et al., 2010;Lee et al., 2019;Averianov y Lopatin, 2022) es que carece de fosas neumátcas (pleurocelos), aunque se observa una leve excavación poco profunda debajo de la parapófisis (Fig. IV.46C). Estas se ubican craneodorsalmente en el centro, siendo algo robustas, dirigidas en sentido laterodorsal, y con superficies articulares elípticas para las costillas (Fig. IV.46C). ...
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.
... The specimens include valuable anatomical information and most bones are represented by multiple individuals. Bonaparte (1996) compared 'Kritosaurus' australis with Secernosaurus and noted important differences in ilium shape. Wagner (2001), in an unpublished MSc thesis, indicated that Secernosaurus koerneri and 'Kritosaurus' australis were phylogenetically close to each other, coining the combination Secernosaurus australis for the latter. ...
... A detailed comparison between the holotype specimens of 'Kritosaurus' australis and Secernosaurus koerneri (FMNH P13423) demonstrates several differences, including features previously noted by Brett-Surman (1979), Bonaparte (1996) and Coria (2016). First, the postacetabular process is notably elongate and narrow (both dorsoventrally and transversely) in Secernosaurus, resembling Edmontosaurus annectens and Kundurosaurus (Godefroit et al. 2012a), but different from 'K.' australis and other Patagonian taxa that have deeper processes. ...
... We follow the criteria of Bonaparte (1996) and Coria (2014Coria ( , 2016 in regarding Secernosaurus koerneri as different from 'K.' australis and other Patagonian hadrosaurids. Furthermore, we concur with Horner et al. (2004) and Coria (2014Coria ( , 2016 ...
Here we describe a new hadrosaurid from the Upper Cretaceous (Campanian-Maastrichtian) Allen Formation of R ıo Negro Province, northwest Patagonia. The new taxon is based on cranial and postcranial elements from subadult and adult specimens. The new taxon may have reached 8-9 m in total body length, and it is diagnosed by a unique combination of characters, including a very low maxilla with respect to the dentary, and a dentary with a prominent and elongate anterior process with a deep groove on its anterior end, among other features. The new taxon is known from well-preserved elements and constitutes one of the most complete hadrosaurids known from South America. Features of the teeth, cranial and postcranial bones of the new taxon overlap with those of other hadrosaurid specimens previously recorded from this continent. This new evidence allows us to recognize that Secernosaurus koerneri, Bonapartesaurus rionegrensis and 'Kritosaurus' australis are valid taxa. The latter can be distinguished from the other South American taxa, as well as from Kritosaurus from North America. Thus, a new generic name is proposed for the species 'Kritosaurus' australis. Phylogenetic analysis recovers a new clade of South American hadrosaurids composed of the new taxon, 'Kritosaurus' australis, Bonapartesaurus and Secernosaurus. The new South American clade is tentatively nested among Kritosaurini and is supported by several traits, including an ilium with a subhorizontal ridge separating the preacetabular notch from the pubic pedicle, a longitudinal ridge on the dorsal surface of the postacetabular process, and a twisted distal end of the postacetabular process. The recovery of a monophyletic clade of South American hadrosaurids indicates that the history of the clade on Gondwanan landmasses is far from well understood, and new discoveries may change the current picture of the taxonomy and phylogenetic relationships of southern duck-billed dinosaurs. http://zoobank.org/urn:lsid:zoobank.org:pub:6C6F0056-9D3A-4097-A10E-2E33C9DB76B9
... 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 skeleton and associated skin were found in a hematite concretion (Appendix A1, figure A1B) from the Maastrichtian (Rauhut et al. 2003;Novas et al. 2013;Vera et al. 2019;Clyde et al. 2021) La Colonia Formation at the Estancia "Pocho Sastre" in Bajada Moreno, Chubut Province, Argentina (43.0 S, 67.5 W; paleocoordinates 45.7 S, 53.8 W; The Paleobiology Database; Bonaparte et al. 1990;Bonaparte 1996b;Fig. 1B-D). ...
... Czerkas and Czerkas (1997, p. 155) wrote that the skeleton of Carnotaurus was articulated in a typical death pose with the head pulled back and was "lying upon its right side which is were the skin was preserved". It is possible that the 'mummified' carcass was preserved entirely within the hematite concretion, which limited weathering of the well-preserved remains (Bonaparte 1996b;Fernando Novas, pers. comm. ...
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.
... Remains of rebbachisaurids were found in Africa (Lavocat, 1954;Sereno et al., 1999), South America (Calvo & Salgado, 1995;Bonaparte, 1996;Gallina and Apesteguía, 2005;Salgado et al., 2004Salgado et al., , 2006Apesteguía, 2007), and Europe (Dalla Vecchia, 1998;Suberbiola et al., 2003). ...
... For more than fifteen years, the sole record of Rebbachisauridae in Brazil came from the Albian Itapecuru Formation (Amazonsaurus maranhensis and cf. Rayososaurus Bonaparte, 1996), but recently, Lindoso et al. (2019) described a new species for the Albian-Cenomanian beds of Alcântara Formation, as well as disarticulated remains tentatively attributed to cf. Rayososaurus (=Limaysaurus) tessonei. ...
... All other occurrences of rebbachisaurids in South America during the mid-Cretaceous are reported from Argentina, with seven nominal species (Calvo and Salgado, 1995;Bonaparte, 1996;Gallina and Apesteguía, 2005;Salgado et al., 2006;Apesteguía, 2007;Carballido et al., 2012;Ibiricu et al., 2013;Canudo et al., 2018). An unidentified Rebbachisauridae has also been reported for Huincul Formation (Calvo, 1999;Haluza et al., 2012) and Candeleros Formation (Carabajal et al., 2015). ...
... The most distinctive feature of Dicraeosauridae is a set of long dorsally projected bifid neural spine in most presacral vertebrae (Janensch, 1929;Salgado and Bonaparte, 1991;Rauhut et al., 2005;Coria et al., 2019;Gallina et al., 2019). The Dicraeosauridae biochron extends from the Middle Jurassic to the Early Cretaceous, and its fossil record comes from Argentina, Tanzania, United States and China (Janensch, 1929;Bonaparte, 1986;Salgado and Bonaparte, 1991;Bonaparte, 1996;Harris and Dodson, 2004;Upchurch et al., 2004;Rauhut et al., 2005;Apesteguía, 2007;Xu et al., 2018;Coria et al., 2019;Gallina et al., 2019). ...
... The La Amarga Formation (BarremianeAptian, Lower Cretaceous) assemblage includes a great diversity of tetrapod taxa, collected in field works carried out by Dr. Jos e F. Bonaparte and collaborators (Bonaparte, 1986(Bonaparte, , 1996Chiappe, 1988;Leanza et al., 2004;Otero and Salgado, 2015). Specifically, the sauropod diversity is represented by the dicraeosaurids Amargasaurus cazaui (Salgado and Bonaparte, 1991) and Amargatitanis macni (Apesteguía, 2007) and the rebbachisaurid Zapalasaurus bonapartei (Salgado et al., 2006). ...
Dicraeosauridae is a family of small body-sized sauropod dinosaurs that diversified from the Middle Jurassic to the Lower Cretaceous, whose distinctive feature is a long dorsally projected, bifid neural spines in most of the presacral vertebrae. The dicraeosaurid fossil record is limited to few taxa, therefore each new finding, however fragmentary, allows to improve the knowledge about this group. Here, we report new dicraeosaurid remains, consisting of two associated anterior dorsal vertebrae (MOZ-Pv 6126-1; MOZ-Pv 6126-2) collected from the La Amarga Formation (Barremian–Aptian, Lower Cretaceous). MOZ-Pv 6126-1 is represented by an almost complete anterior dorsal vertebra, while MOZ-Pv 6126-2 is an anterior dorsal vertebral centrum with a portion of the neural arch. The morphological features of these axial elements, as well as the absence of lateral fossae, the orientation of the transverse processes and an elongated bifid neural spine, allow us to refer them to the dicraeosaurid sauropods (Janensch, 1929; Salgado y Bonaparte, 1991; Rauhut et al., 2005; Coria et al., 2019; Gallina et al., 2019). However, due to the lack of more diagnostic features, we prefer to consider MOZ-Pv 6126-1 and MOZ-Pv 6126-2 as Dicraeosauridae indet. The new materials increase the fossil record of dicraeosaurid sauropods from La Amarga Formation and enrich the poor worldwide fossil record of the Dicraeosauridae.
... The description of numerous new taxa and identification of new groups have greatly changed our understanding of Cretaceous theropod evolution and biogeography (e.g. Bonaparte, 1985Bonaparte, , 1991aBonaparte, , 1996Sereno et al. 1994Sereno et al. , 1996Sereno et al. , 1998Coria & Salgado, 1995;Novas, 1996Novas, , 1997Sampson et al. 1998;Sampson, Carrano & Forster, 2001). Whereas Late Cretaceous Laurasian theropod faunas are dominated by coelurosaurs (tyrannosaurids, dromaeosaurids, ornithomimosaurs, oviraptorosaurs, therizinosaurs, etc.), Cretaceous theropod communities from the Southern Hemisphere are now known to consist of a mixture of a diverse assemblage of highly derived basal theropods (abelisaurs), several groups of basal tetanurans, and rare coelurosaurs (e.g. ...
... Whereas Late Cretaceous Laurasian theropod faunas are dominated by coelurosaurs (tyrannosaurids, dromaeosaurids, ornithomimosaurs, oviraptorosaurs, therizinosaurs, etc.), Cretaceous theropod communities from the Southern Hemisphere are now known to consist of a mixture of a diverse assemblage of highly derived basal theropods (abelisaurs), several groups of basal tetanurans, and rare coelurosaurs (e.g. Rauhut, 1995Rauhut, , 1999Bonaparte, 1996;Sereno et al. 1996Sereno et al. , 1998Novas, 1997). Unfortunately, however, the origin of the Cretaceous theropod faunas in the Southern Hemisphere is still poorly understood, mainly due to the poor Jurassic dinosaur record from Gondwana. ...
Small theropod post-cranial material from Tendaguru, Tanzania, the only known Late Jurassic theropod locality in the Southern Hemisphere, is reviewed. Material originally described as ‘coelurosaurs’ includes at least one taxon of basal tetanuran and one taxon of small abelisauroid. Together with the abelisauroid Elaphrosaurus and the presence of a larger ceratosaur in Tendaguru, this material indicates that ceratosaurs were an important faunal element of Late Jurassic East African theropod faunas. One bone furthermore shares derived characters with the holotype of the poorly known Middle Jurassic Australian theropod Ozraptor and allows the identification of the latter as the oldest known abelisauroid, thus indicating an early divergence of ceratosaurids and abelisauroids within ceratosaurs. Abelisauroids might have originated in Gondwana and represent important faunal elements of Cretaceous Gondwanan theropod faunas in general.
... The fossil record of theropods in the Cretaceous of Patagonia is relatively rich and is represented by several groups of coelurosaurs, carcharodontosaurids and abelisaurids (Novas, 2009). The latter is probably the most diverse and specious clade, which includes a high number of medium to large-sized forms (Bonaparte, 1991(Bonaparte, , 1996Novas et al., 2013). ...
... Abelisauroids were traditionally divided into two main clades that are comfortably separated by body mass: large-sized Abelisauridae and small-sized Noasauridae (Carrano and Sampson, 2008). Because body mass is usually indicative of an ecological niche, these predatory dinosaurs were considered as pertaining to different carnivoran guilds (Bonaparte, 1991(Bonaparte, , 1996. ...
... Supporting the possibility of such a migratory scenario, other groups of terrestrial vertebrates appear to have reached South America from Laurasia, North America in particular, during the Campanian -Maastrichtian interval (Bonaparte 1986). Among those recently advanced as such are the nodosaurine ankylosaur Patagopelta (Riguetti et al. 2022;however, Agnolín, Rozadilla et al. 2023 considered it as a Gondwanan parankylosaurian) and hadrosaurs (Alarcón-Muñoz et al. 2023;Bonaparte 1996;Prieto-Márquez 2010; though this was put into question by Rozadilla et al. 2021). Most of the hadrosaurs from the Upper Cretaceous of South America have been recovered as a monophyletic group Alarcón-Muñoz et al. 2023), which raises the possibility that the radiation of hadrosaurs in Patagonia involves a substantial amount of time to result in the observed endemic diversity. ...
... Strict consensus tree exhibits several polytomies in different clades (Figure 16). To evaluate the causes of this low resolution in those points of the phylogeny and detect if it is due to a combination of taxa and characters, or if, on the contrary, it is due to the presence of one or more unstable taxa ('wildcard' sensu Nixon and Wheeler 1992), the iterative PCR method was used ('Positional Congruent Reduced'; iterPCR [Pol and Escapa 2009] (Lapparent and Zbyszewski 1957;Nowinski 1971;Bonaparte 1996;Buffetaut et al. 2000;González Riga et al. 2009;González Riga et al. 2016). Most of the polytomies are resolved by pruning these taxa from the MPTs (Figure 16). ...
... The huge fossil content of the Neuquén Group comprises abundant and diverse dinosaur groups, including not only body fossils but also eggs and footprints; moreover, there are crocodiles, sphenodonts, serpents, anurans, birds, and mammals (Bonaparte 1996;Leanza et al. 2004;Calvo et al. 2011 and references there, see Biostratigraphy and Geochronology below). There are also a few body and trace fossil of invertebrates (see Garrido 2010 for references), and micro and megafloras (Vallati 2001(Vallati , 2010(Vallati , 2013Morel et al. 2011). ...
The Neuquén Basin, located at the foothills of the Central Andes of Argentina, with superb and extended exposures is a natural laboratory. It is important not only for its continuous sedimentary record and superb palaeontological biota but also for its significant economic hydrocarbon resources. This synthesis is intended to provide an update only on the Cretaceous timespan in the basin development. It is characterized by a succession of sedimentary rocks that were deposited in different environments over time, interspersed with volcanic rocks associated with an active volcanic arc. High-precision geochronology dating on the tuffs establishes robust chronological ages to constrain the different stages. As this brief review only shows a fragment of the information presently available, an effort has been made to compile a comprehensive and up-to-date bibliography to compensate for the brevity of the text.
... Cerda et al. (2015) proposed a ligamentous origin for this structure, based on histological observations of sauropod specimens. However, cartilaginous (Bonaparte, 1996) or tendinous (Giménez, Salgado & Cerda, 2008) origins were also suggested for the supraspinous rod that connects the dorsal portion of the neural spines of the sacral vertebrae. The function (and homology) of the supraspinous ligamental ossification is so far unknown, but it may be related to stressing forces acting on this region of the skeleton (e.g., tensile forces; Cerda et al., 2015); however, it is not clear to what extent this condition has an ontogenetic component (Cerda et al., 2015). ...
Aucasaurus garridoi is an abelisaurid theropod from the Anacleto Formation (lower Campanian, Upper Cretaceous) of Patagonia, Argentina. The holotype of Aucasaurus garridoi includes cranial material, axial elements, and almost complete fore- and hind limbs. Here we present a detailed description of the axial skeleton of this taxon, along with some paleobiological and phylogenetic inferences. The presacral elements are somewhat fragmentary, although these show features shared with other abelisaurids. The caudal series, to date the most complete among brachyrostran abelisaurids, shows several autapomorphic features including the
presence of pneumatic recesses on the dorsal surface of the anterior caudal neural arches, a tubercle lateral to the prezygapophysis of mid caudal vertebrae, a marked protuberance on the lateral rim of the transverse process of the caudal vertebrae, and the presence of a small ligamentous scar near the anterior edge of the dorsal surface in the anteriormost caudal transverse process. The detailed study of the axial skeleton of Aucasaurus garridoi has also allowed us to identify characters that could be useful for future studies attempting to resolve the internal phylogenetic relationships of Abelisauridae. Computed tomography scans of some caudal vertebrae show pneumatic traits in neural arches and centra, and thus the first reported case for an abelisaurid taxon. Moreover, some osteological correlates of soft tissues present in Aucasaurus and other abelisaurids, especially derived brachyrostrans, underscore a previously proposed increase in axial rigidity within Abelisauridae.
... Diplodocoid sauropods can be considered as the classic low-level browsers, with diplodocids and dicraeosaurids as an abundant component of large herbivorous fauna during the Late Jurassic across North America, Europe, and Gondwana, and also during the earliest Early Cretaceous in western Gondwana McPhee et al., 2016;Gallina et al., 2019). Nevertheless, the archetype of a groundlevel browser sauropod is represented by the rebbachisaurids, which survived (and partially replaced) the other families of diplodocoids, becoming an important component of the Cretaceous sauropod faunas in South America, Africa, and Europe until CenomanianeTuronian times (Lavocat, 1954;Calvo & Salgado, 1995;Bonaparte, 1996;Sereno et al., 1999;Carvalho et al., 2003;Torcida Fern andez-Baldor, F. et al., 2011;Mannion et al., 2011;Fanti et al., 2013). The highly derived design present in rebbachisaurids that tended towards low or ground-level browsing adaptations is indicative of feeding specialization, and probably, based on snout shape of Nigersaurus, generalist sauropods (Sereno et al., 2007). ...
A new titanosaur sauropod genus including an almost complete skull and axial elements to the hips, reflecting a convergent bauplan with the older rebbachisaurids sauropods.
... 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.
... The group was originally erected (Bonaparte and Powell, 1980) to encompass only Noasaurus leali, from the Maastrichtian of Salta, Argentina. The description of several new species expanded the taxonomic and morphological diversity of the group, containing species described in South America, Africa, Madagascar, India, Europe and Australia (Bonaparte, 1996;Coria and Salgado, 2000;Sampson et al., 2001;Carrano et al., 2002;Agnolin and Martinelli, 2007;Carrano et al., 2011;Pol and Rauhut, 2012;Tortosa et al., 2014;Poropat et al., 2020). However, noasaurids are still mainly known by rather incomplete records from the Cretaceous of Gondwana (Brum et al., 2018;Brougham et al., 2020;de Souza et al., 2021). ...
... They calculate the total length of the femur (just represented by an incomplete shaft) as being 2.5 m in maximum length. Bonaparte (1998) referred to Argentinosaurus a femur (that was not described nor illustrated) that was found close to the holotype specimen and that measured 2.5 m in maximum length, which is congruent with the referral of MLP-DP 46-VIII-21-3 to Argentinosaurus. Specimen MLP-DP 46-VIII-21-3 includes a partial right humerus, an incomplete dorsal rib, and incomplete left and right femora (Fig. 11). ...
... Lower Albian deposits in Neuquén Province have yielded rebbachisaurids and non-titanosaurian somphospondylans including Ligabuesaurus [75,77,88,[172][173][174], whereas upper Albian deposits in Chubut Province have produced the lognkosaurian titanosaur Patagotitan [175,176], but no rebbachisaurids. Rebbachisaurids are represented in the Albian-Cenomanian of Brazil [177], and dominate Cenomanian-Turonian sauropod faunas across Argentina [178][179][180][181][182][183][184][185][186][187][188]. The latter deposits also preserve a variety of titanosaurs, including early branching forms, such as Andesaurus, Epachthosaurus and Sarmientosaurus, as well as lognkosaurians including Argentinosaurus [58,74,84,85,[189][190][191][192][193][194][195][196][197][198]. ...
The Upper Cretaceous Winton Formation of Queensland, Australia, has produced several partial sauropod skeletons, but cranial remains—including teeth—remain rare. Herein, we present the first description of sauropod teeth from this formation, based on specimens from three separate sites. An isolated tooth and a dentary fragment from the Diamantinasaurus matildae type locality are considered to be referable to that titanosaurian taxon. A single tooth from the D. matildae referred specimen site is similarly regarded as being part of that individual. Seventeen teeth from a new site that are morphologically uniform, and similar to the teeth from the two Diamantinasaurus sites, are assigned to Diamantinasauria. All sauropod teeth recovered from the Winton Formation to date are compressed-cone-chisel-shaped, have low slenderness index values (2.00–2.88), are lingually curved at their apices, mesiodistally convex on their lingual surfaces, and lack prominent carinae and denticles. They are markedly different from the chisel-like teeth of derived titanosaurs, more closely resembling the teeth of early branching members of the titanosauriform radiation. This provides further support for a ‘basal’ titanosaurian position for Diamantinasauria. Scanning electron microscope microwear analysis of the wear facets of several teeth reveals more scratches than pits, implying that diamantinasaurians were mid-height (1–10 m) feeders. With a view to assessing the spatio-temporal distribution of sauropod tooth morphotypes before and after deposition of the Winton Formation, we provide a comprehensive continent-by-continent review of the early titanosauriform global record (Early to early Late Cretaceous). This indicates that throughout the Early–early Late Cretaceous, sauropod faunas transitioned from being quite diverse at higher phylogenetic levels and encompassing a range of tooth morphologies at the start of the Berriasian, to faunas comprising solely titanosaurs with limited dental variability by the end-Turonian. Furthermore, this review highlights the different ways in which this transition unfolded on each continent, including the earliest records of titanosaurs with narrow-crowned teeth on each continent.
... El estudio integral de estos materiales, sumado a los diversos ejemplares de arcosaurios atesorados en el IML (descubiertos e interpretados por J. F. Bonaparte en la década de 1970), resultaron en trabajos que sustentaron la monofilia de Dinosauria (Novas, 1996), temas que fueron ahondados a partir de allí por otros paleontólogos, varios de ellos argentinos. Amarga, Lohan-Curá, Bajo de la Carpa, Angostura Colorada, Allen y Loncoche, entre otras (e.g., Bonaparte, 1996aBonaparte, , 1996bMartinelli y Forasiepi, 2004 (Bonaparte et al., 2003;Bonaparte y Migale, 2015;Rougier et al., 2021). ...
... Almost simultaneously, J. Bonaparte described Rayososaurus agrioensis from a well-preserved scapula and fragmentary appendicular bones and indeterminate fragments from Agrio del Medio, also in Neuquén Province, from sedimentary levels that he assumed belonged to the Lower Cretaceous Rayoso Formation (Bonaparte 1996), and which are currently considered to be the Cenomanian Candeleros Formation (Carballido et al. 2010), recognizing certain similarities with Rebbachisaurus garasbae. The following year, the same author proposed a new sauropod clade, naming it Rebbachisauridae, although without providing a phylogenetic definition or discussing its phylogenetic relationships within Sauropoda (Bonaparte 1997). ...
With 17 species formally identified throughout the world, Rebbachisauridae is, at present, the best-represented group of South American diplodocoids, and it has a temporal record ranging from the Barremian up to the Turonian. Defined as all diplodocoids more closely related to Rebbachisaurus garasbae than to Diplodocus carnegii, these sauropods are characterized by postcranial synapomorphies (e.g., absence of the hyposphenal ridge on anterior caudal vertebrae; presence of spinodiapophyseal lamina in caudal vertebrae). Although relatively complete skulls are known in only a few genera (Limaysaurus, Lavocatisaurus, and Nigersaurus), the whole cranial evidence indicates that they were highly specialized with respect to other diplodocoids (for instance Diplodocidae). South America counts ten genera of Rebbachisauridae, most of them from the Argentine Patagonia. They embrace a rather diverse group of basally branching forms (Amazonsaurus, Zapalasaurus, Comahuesaurus, and Lavocatisaurus), derived forms (as the limaysaurines Limaysaurus and Cathartesaura and the rebbachisaurines Katepensaurus and Itapeuasaurus), together with forms of uncertain phylogenetic filiation (Rayososaurus). Rebbachisaurids were important in South America toward the end of the Early Cretaceous, integrating, at that time, the sauropod faunas together with macronarians (Titanosauriformes) and other diplodocoids (Dicraeosauridae). They persisted up to at least the Turonian, being the last diplodocoids in becoming extinct globally.
... quadrupedal stance with small heads, long necks and long tails), sauropods showed a highly morphological variation in the skeleton, particularly in the vertebrae, which exhibit a strong degree of anatomical disparity amongst the different lineages (Salgado & Powell, 2010;Wilson, 1999). Perhaps one of the most extreme examples of vertebral disparity is found in Dicraeosauridae, a clade of diplodocoid sauropods, whose fossil record comes from Argentina, Tanzania, United States and China (Bonaparte, 1986;Bonaparte, 1996;Coria et al., 2019;Gallina, 2016;Gallina et al., 2019;Harris & Dodson, 2004;Janensch, 1929;Rauhut et al., 2005;Salgado & Bonaparte, 1991;Upchurch et al., 2004;Windholz et al., 2021;Xu et al., 2018). Presacral vertebrae of dicraeosaurid sauropods are characterized by the presence of elongate bifid neural spines, which are therefore composed by two hemispinous processes (following Harris [2006] and referring to one half of a bifurcated spine. ...
Dicraeosaurid sauropods are iconically characterized by the presence of elongate hemispinous processes in presacral vertebrae. These hemispinous processes can show an extreme degree of elongation, such as in the Argentinean forms Amargasaurus cazaui, Pilmatueia faundezi and Bajadasaurus pronuspinax. These hyperelongated hemispinous processes have been variably interpreted as a support structure for a padded crest/sail as a display, a bison‐like hump or as the internal osseous cores of cervical horns. With the purpose to test these hypotheses, here we analyze, for the first time, the external morphology, internal microanatomy and bone microstructure of the hemispinous processes from the holotype of Amargasaurus, in addition to a second dicraeosaurid indet. (also from the La Amarga Formatin; Lower Cretaceous, Argentina). Transverse thin‐sections sampled from the proximal, mid and distal portions of both cervical and dorsal hemispinous processes reveal that the cortical bone is formed by highly vascularized fibrolamellar bone interrupted with cyclical growth marks. Obliquely oriented Sharpey's fibres are mostly located in the medial and lateral portions of the cortex. Secondary remodelling is evidenced by the presence of abundant secondary osteons irregularly distributed within the cortex. Both anatomical and histological evidence does not support the presence of a keratinized sheath (i.e. horn) covering the hyperelongated hemispinous processes of Amargasaurus, and either, using a parsimonious criterium, in other dicraeosaurids with similar vertebral morphology. The spatial distribution and relative orientation of the Sharpey's fibres suggest the presence of an important system of interspinous ligaments that possibly connect successive hemispinous processes in Amargasaurus. These ligaments were distributed along the entirety of the hemispinous processes. The differential distribution of secondary osteons indicates that the cervical hemispinous processes of Amargasaurus were subjected to mechanical forces that generated higher compression strain on the anterior side of the elements. Current data support the hypothesis for the presence of a ‘cervical sail’ in Amargasaurus and other dicraeosaurids. Life restoration of Amargasaurus cazaui. Current data support the hypothesis for the presence of a ‘cervical sail’ in Amargasaurus and other dicraeosaurids. Illustration made by Gabriel Lio.
... The most diverse and specious clade among abelisauroids is the Abelisauridae, which includes a large number of forms found in South America, Africa, Madagascar, India, and also southern Europe (Bonaparte, 1991(Bonaparte, , 1996Novas et al., 2013; see Tortosa et al., 2013). These have not been recorded in the rich Cretaceous beds from North America and Asia (Bonaparte and Kielan-Jaworowska, 1987) or Antarctica. ...
The fossil record of abelisaurid theropods in South America is mostly limited to Brazil and Argentina. In Argentina, abelisaurids are generally known from Patagonia, where their record is relatively abundant and includes well-known and complete specimens. However, for Northwestern Argentina, abelisaurids are represented by incomplete and isolated bones and teeth that remain largely unpublished. The aim of this contribution is to report a nearly complete abelisaurid braincase from the Late Cretaceous Los Blanquitos Formation (Campanian), Amblayo Valley, Salta province, Argentina. The specimen shows plesiomorphic features for abelisaurids, including a thin skull roof, absence of skull projections like horns or bulges, and low and narrow parietal eminence that lie at the same level as the sagittal crest. Furthermore, the specimen possesses some autapomorphies that support its status as a new taxon and its small size allows it to be assigned as one of the smallest abelisaurids recorded up to date. The finding of this specimen constitutes the first unequivocal occurrence of an abelisaurid in Northwestern Argentina and brings new evidence concerning the geographic distribution of the clade during Late Cretaceous times in South America.
... Several previous contributions analyzed the notably diverse sauropod assemblages from Patagonia (e.g., Bonaparte, 1996;Leanza et al., 2004;Salgado and Bonaparte, 2007;Novas, 2009;Ju arez-Valieri et al., 2010). Patagonian titanosaurs are almost grouped in three main clades: the small-sized Saltasaurinae, the gracile-limbed Aeolosaurini, and the gigantic Colossosauria. ...
The record of sauropods in the Upper Cretaceous of Patagonia is rich. However, there are still several blanks on this record. Here it is described a new sauropod assemblage coming from the Salitral Ojo de Agua Area, Río Negro province, northern Patagonia, Argentina (Allen Formation; Maastrichtian). Remains of indeterminate saltasaurines, aeolosaurines, as well as new specimens of the small saltasaurine Rocasaurus muniozi and the new eutitanosaur Menucocelsior arriagadai gen. et sp. nov., are described.. The new eutitanosaur is represented by an incomplete caudal series and some appendicular bones that indicate that it does not belong to any previously recognized eutitanosaur clade (e.g, Colossosauria, Saltasaurinae, Aeolosaurini). The co-occurrence of several roughly coeval titanosaurs in a restricted area (as occur in Bajo de Santa Rosa, Salitral Moreno and Salitral Ojo de Agua sites) with different body plans, indicates that they probably occupied particular ecological niches and that probably competition for resources was limited, allowing the connivance of several taxa in a single locality and age. This pattern is not observed in other sites of the world. Based on these records and on the high diversity of osteoderm morphotypes recovered, it appears to be certain that palaeoecological conditions in the area were able to sustain and promote the flourishing of many species of titanosaurs.
... The Neuqu en Group (Cazau and Uliana, 1973;Stipanicic et al., 1968), part of the sedimentary filling of the Neuqu en Basin, is widely exposed in northwestern Patagonia. Since the late 19th Century, it has yielded numerous fossils that document a taxonomically diverse vertebrate assemblage that largely contributes to our understanding on the evolutionary histories of the represented groups throughout most of the Late Cretaceous (e.g., Bonaparte, 1996;Bonaparte and Gasparini, 1978;Calvo and Lockley, 2001;Calvo et al., 2007;Carballido et al., 2012). Recent extensive fieldwork recovered a large assortment of vertebrate remains, including those of basal snakes, chelyid turtles, sphenodontians, pterosaurs, and sauropod and theropod dinosaurs, from the red beds of the Candeleros Formation, the lowermost unit of the Neuqu en Group (Candia-Halupczok et al., 2018). ...
An incomplete anuran skeleton collected from outcrops of the Candeleros Formation on the western shore of the Ramos Mexia Reservoir, Neuquén Province, Patagonia, is described herein. It consists of several partially articulated postcranial bones that are exposed in ventral view and belong to a post-metamorphic frog that is probably an adult. The axial column consists of eight opisthocoelous presacral vertebrae; fusion of the first two anterior vertebrae cannot be determined. Most of the sacrum is formed by the expanded diapophyses of Vertebra IX. However, Vertebra X also has distally expanded diapophyses that fuse to those of Vertebra IX. Traces of a suture between the urostyle and sacrum are evident. The morphology of the sacro-urostylic region casts doubts on the previous interpretation of the fused condition of sacrum and urostyle in the holotype of Avitabatrachus uliana from the same stratigraphic unit. The material described here contributes new information about the formation of the sacrum and suggests that different ontogenetic pathways are involved in formation of different sacral morphologies. The sacrum formed only by Vertebra IX probably is plesiomorphic in pipimorphs. It is hypothesized that the more complex structure described here evolved from it and incorporates postsacral vertebrae as well as synostotic fusion with the urostyle. Complete synostotic fusion of sacrum and urostyle, when present, seems to have been an event that occurred relatively late in the ontogeny of early pipimorphs. This fusion might have shifted to earlier developmental stages relative to the ancestor independently on different branches of the pipimorph tree.
... A. cooperensis possesses a smaller femur compared to the specimen referred to as Argentinosaurus huinculensis (Bonaparte, 1996). A. cooperensis differs from Aegyptosaurus baharijensis (Stromer, 1932) by being larger and possessing a mediolaterally broad midshaft for both the femur and humerus. ...
A new giant sauropod, Australotitan cooperensis gen. et sp. nov., represents the first record of dinosaurs from the southern-central Winton Formation of the Eromanga Basin, Australia. We estimate the type locality to be 270–300 m from the base of the Winton Formation and compare this to the semi-contemporaneous sauropod taxa, Diamantinasaurus matildae Hocknull et al., 2009, Wintonotitan wattsi Hocknull et al., 2009 and Savannasaurus elliottorum Poropat et al., 2016. The new titanosaurian is the largest dinosaur from Australia as represented by osteological remains and based on limb-size comparisons it reached a size similar to that of the giant titanosaurians from South America. Using 3-D surface scan models we compare features of the appendicular skeleton that differentiate Australotitan cooperensis gen. et sp. nov. as a new taxon. A key limitation to the study of sauropods is the inability to easily and directly compare specimens. Therefore, 3-D cybertypes have become a more standard way to undertake direct comparative assessments. Uncoloured, low resolution, and uncharacterized 3-D surface models can lead to misinterpretations, in particular identification of pre-, syn- and post-depositional distortion. We propose a method for identifying, documenting and illustrating these distortions directly onto the 3-D geometric surface of the models using a colour reference scheme. This new method is repeatable for researchers when observing and documenting specimens including taphonomic alterations and geometric differences. A detailed comparative and preliminary computational phylogenetic assessment supports a shared ancestry for all four Winton Formation taxa, albeit with limited statistical support. Palaeobiogeographical interpretations from these resultant phylogenetic hypotheses remain equivocal due to contrary Asian and South American relationships with the Australian taxa. Temporal and palaeoenvironmental differences between the northern and southern-central sauropod locations are considered to explain the taxonomic and morphological diversity of sauropods from the Winton Formation. Interpretations for this diversity are explored, including an eco-morphocline and/or chronocline across newly developed terrestrial environments as the basin fills.
... In addition to the bone fossil record, thyreophoran and probably ankylosaurian footprints are variously known from several sites in Africa, South America, India and Australia from Jurassic and Cretaceous beds (Thulborn, 1998;Apesteguía and Gallina, 2011;Mateus et al., 2011aMateus et al., , 2011bLeahey et al., 2015;Pereda-Suberbiola et al., 2015;Galton and Ayyasami, 2017;Francischini et al., 2018;Pazos et al., 2019;Leonardi and Carvalho, 2021;Riguetti et al., 2021). However, because of the presence of stegosaurs in Lower Cretaceous and Jurassic beds of Africa and South America (Hennig, 1915;Bonaparte, 1996;Han et al., 2018;Maidment et al., 2020), the producers of the tracks should be considered as indeterminate eurypodans. ...
The fossil record of ornithischians in South America is sparse, and they are clearly underrepresented when compared with sauropod dinosaurs. However, recent discoveries indicate that ornithischians were more diversified than thought. The aim of the present contribution is to describe isolated remains belonging to ankylosaurs, and ornithopods, including basal euiguanodontians and hadrosaurs coming from the Chorrillo Formation (upper Campanian–lower Maastrichtian), Santa Cruz province, southern Argentina. The fossil remains of ankylosaurs reported here are the southernmost recorded for the continent. They show a unique combination of plesiomorphic features, indicating that they may belong to a basal ankylosaur. Ankylosaurs and hadrosaurids are thought to have arrived in South America during the latest Cretaceous through Central America. However, a detailed overview of the fossil record of Gondwana indicates that both clades were present and probably diversified along southern continents. This indicates that their presence in South America may be alternatively interpreted as the result of migration from other landmasses, including Africa and Europe, or may even be the result of Jurassic–Early Cretaceous vicariance from their northern counterparts.
... Based on the distribution of their earliest occurrences, rebbachisaurids are likely to have dispersed into Africa from Europe (via the 'Apulian route'), then from north-west Africa into northeast South America before or during the Barremian (Lindoso et al., 2019;Pereira et al., 2020). During the mid-Cretaceous, rebbachisaurids proliferated in northern Africa (Sereno et al., 1999(Sereno et al., , 2007Fanti et al., 2013Fanti et al., , 2014Fanti et al., , 2015Mannion & Barrett, 2013;Wilson & Allain, 2015), north-east South America (Carvalho et al., 2003;Medeiros & Schultz, 2004;Castro et al., 2007;Lindoso et al., 2019;Pereira et al., 2020) and Patagonia (Calvo & Salgado, 1995;Bonaparte, 1996;Calvo, 1999;Salgado et al., 2004Salgado et al., , 2006Salgado et al., , 2012 ...
The titanosaurian sauropod dinosaur Diamantinasaurus matildae is represented by two individuals from the Cenomanian-lower Turonian 'upper' Winton Formation of central Queensland, northeastern Australia. The type specimen has been described in detail, whereas the referred specimen, which includes several elements not present in the type series (partial skull, atlas, axis and postaxial cervical vertebrae), has only been described briefly. Herein, we provide a comprehensive description of this referred specimen, including a thorough assessment of the external and internal anatomy of the braincase, and identify several new autapomorphies of D. matildae. Via an expanded data matrix consisting of 125 taxa scored for 552 characters, we recover a close, well-supported relationship between Diamantinasaurus and its contemporary, Savannasaurus elliottorum. Unlike previous iterations of this data matrix, under a parsimony framework we consistently recover Diamantinasaurus and Savannasaurus as early-diverging members of Titanosauria using both equal weighting and extended implied weighting, with the overall topology largely consistent between analyses. We erect a new clade, named Diamantinasauria herein, that also includes the contemporaneous Sarmientosaurus musacchioi from southern Argentina, which shares several cranial features with the referred Diamantinasaurus specimen. Thus, Diamantinasauria is represented in the mid-Cretaceous of both South America and Australia, supporting the hypothesis that some titanosaurians, in addition to megaraptoran theropods and possibly some ornithopods, were able to disperse between these two continents via Antarctica. Conversely, there is no evidence for rebbachisaurids in Australia, which might indicate that they were unable to expand into high latitudes before their extinction in the Cenomanian-Turonian. Likewise, there is no evidence for titanosaurs with procoelous caudal vertebrae in the mid-Cretaceous Australian record, despite scarce but compelling evidence for their presence in both Antarctica and New Zealand during the Campanian-Maastrichtian. These later titanosaurs presumably dispersed into these landmasses from South America before the Campanian (~85 Mya), when seafloor spreading between Zealandia and Australia commenced. Although Australian mid-Cretaceous dinosaur faunas appear to be cosmopolitan at higher taxonomic levels, closer affinities with South America at finer scales are becoming better supported for sauropods, theropods and ornithopods.
... Other than these records, stegosaurs from South America have also been reported from the Lower Cretaceous (Barremian-Early Aptian) La Amarga Formation of the Neuquén Basin (Bonaparte, 1996). Although Maidment et al. (2008) considered the material to be undiagnostic beyond Ornithischia indet., its stegosaurian identity was supported in a later paper by Pereda- Suberbiola et al. (2013). ...
A stegosaurian humerus from the Oxfordian–Tithonian(?) Cañadón Calcáreo Formation of Chubut, Argentina, extends the fossil record of this clade of thyreophoran ornithischian dinosaurs to the Upper Jurassic of South America. The element shares the derived character of an oblique ridge extending from the deltopectoral crest towards the medial distal condyle with taxa such as Kentrosaurus and Stegosaurus and thus represents a derived representative of the clade. The presence of stegosaurs in the Cañadón Calcáreo Formation underlines the similarities of its dinosaur fauna with other Late Jurassic dinosaur faunas, such as the Morrison Formation of North America or the Tendaguru Formation of Tanzania, in at least broad systematic terms.
... In such analysis, 176 more parsimonious trees (MPTs) of 865 steps were recovered, with a consistency index (CI) of 0,610 and a retention index (RI) of 0,723. The topology obtained is consistent with those of some previous works (Tortosa et al., 2013;Filippi et al., 2016;Cerroni et al., 2020), in which Ligabueino (Bonaparte 1996) is obtained as the sister taxa of Abelisauroidea, and Eoabelisaurus as the sister taxa of the clade comprising Ligabueino + Abelisauroidea. The enigmatic Austrocheirus (Ezcurra et al., 2010) nests within Noasauridae (Fig. 11), a phylogenetic relationship that is supported by a single character: presence of a flat surface in the anterior face of the tibia (Ch. ...
Abelisaurid theropods are well known in Cretaceous beds along South America, particularly Patagonia. However, the record of latest Cretaceous abelisauroids is still far from satisfactory. Until recently, few taxa were described from Maastrichtian beds: Carnotaurus sastrei and Quilmesaurus curriei, but also perhaps Abelisaurus comahuensis. In this contribution, we describe a new genus and species (Niebla antiqua gen. et sp. nov.), of medium-sized abelisaurid coming from Late Cretaceous (Maastrichtian) beds from Río Negro province, northern Patagonia, Argentina. The paleohistological analysis shows that this individual has reached the somatical maturity and that it represents an adult of a mid-sized abelisaurid. The specimen is represented by a nearly complete braincase, fragmentary jaw and teeth, relatively complete scapulocoracoid, dorsal ribs and incomplete vertebrae. The new taxon is relatively small, much smaller than other coeval abelisaurids such as Carnotaurus and Abelisaurus. The braincase shows autapomorphic features such a dorsoventrally tall basal tuber and postemporal foramen enclosed by parietal and exoccipitals. The scapulocoracoid is notably similar to that of Carnotaurus in having a posterodorsally oriented glenoid, a dorsoventrally expanded and wide coraco-scapular plate, and a very narrow and straight scapular blade. These features are very different from those of other abelisaurids, which may indicate a unique conformation of the pectoral girdle among these South American theropods.
... To clarify its origin and to facilitate the description, we refer to these laminae as single TPRL (sTPRL) and single TPOL (sTPOL). Saurischia Seeley, 1887Sauropoda Marsh, 1878 Neosauropoda Bonaparte, 1996 Macronaria Wilson & Sereno, 1998 Camarasauromorpha Salgado et al., 1997 Genus Europasaurus Mateus, Laven, & Knötschke in Sander et al., 2006 Europasaurus holgeri Mateus, Laven, & Knötschke in Sander et al., 2006 (Figs 1-28) Downloaded by [José L. Carballido] A right angular, initially listed as part of the holotype (Sander et al. 2006) is excluded from this specimen, as the size of it is too small compared with the other mandible bones (Maprmann et al. 2011). ...
... Some saurischians with large cervical epipophyses develop a lamina that crosses the SDF, linking the epipophysis and prezygapophysis (Wilson 2012). Among non-avian theropods, this lamina is restricted to ceratosaurians and is well developed in Carnotaurus (Bonaparte 1996(Bonaparte , 1986bM endez 2014, figs 4-9), Majungasaurus (O'Connor 2007, figs 7, 8) and Dahalokely (Farke & Sertich 2013, figs 2, 3), where a smooth, sharp lamina demarcates the dorsal and lateral surfaces of the neural arch. Among sauropods, a similar feature was first noted in Nigersaurus, where it was figured in the fifth cervical vertebra and termed the 'prezygapophyseal-epipophyseal lamina' (Sereno et al. 2007, fig . ...
Fossil-rich deposits from the Middle and Late Jurassic of China have yielded a diverse array of sauropod dinosaurs, including numerous species referred to Mamenchisaurus and Omeisaurus. Despite an abundance of fossils and a proliferation of taxa, the anatomy of Middle–Late Jurassic Chinese sauropods remains poorly documented. Here, we comprehensively redescribe and illustrate Klamelisaurus gobiensis from the Middle–Late Jurassic Shishugou Formation of northwest China. Phylogenetic analyses conducted under parsimony and time-calibrated Bayesian optimality criteria consistently recover Klamelisaurus as a member of a predominantly Chinese radiation of exceptionally long-necked eusauropods that includes Mamenchisaurus spp., Chuanjiesaurus, Qijianglong and Wamweracaudia. In most analyses, this lineage also includes Euhelopus, reviving a ‘traditional’ Euhelopodidae and calling into question the macronarian affinities of Euhelopus. Klamelisaurus shares several features with Euhelopus that are unique to a subset of East Asian taxa or rare among sauropods, including a convex ventral margin of the prezygodiapophyseal lamina in middle–posterior cervical vertebrae, a ventrally bifurcated postzygodiapophyseal lamina in posterior cervical vertebrae, and development of a rugose projection extending anteriorly from the epipophysis into the spinodiapophyseal fossa in most cervical vertebrae. Anatomical comparisons of the cervical vertebrae of Klamelisaurus to several other sauropodomorphs and insights from myological studies of extant archosaurs strongly suggest that this latter structure, often considered part of an epipophyseal-prezygapophyseal lamina, is an epaxial muscle scar that is distinct from pneumatic structures of the lateral surface of the neural spine. The phylogenetic and comparative anatomical data presented here provide a foundation for future revision of the taxonomy and systematics of sauropods from the Junggar and Sichuan basins.
... The Jurassic forms include the Bathonian-Callovian Spinostropheus gautieri (Sereno et al., 2004;Rauhut and Lopez-Arbarello, 2009), the Kimmeridgian Elaphrosaurus bambergi from Tendaguru, Tanzania (Janensch, 1920;Rauhut and Carrano, 2016) and Limusaurus inextricabilis from the late Oxfordian of China (Xu et al., 2009). The richest noasaurid record comprises Cretaceous forms like the Barremian Ligabueino andesi, Argentina (Bonaparte, 1996), the Albian Genusaurus sisteronis (the so far only known European noasaurid, Accarie et al., 1995), the Santonian-Campanian Velocisaurus unicus from Argentina (Bonaparte, 1991), the Maastrichtian taxa Noasaurus leali (also from Argentina, Bonaparte and Powell, 1980), Masiakasaurus knopfleri from Magadascar (Sampson et al., 2001), Laevisuchus indicus from India (Huene and Matley, 1933) and a recently described, new noasaurid from the Late Cretaceous of Brazil (Langer et al., 2019). Further Late Cretaceous noasaurids are represented as well by fragmentary material from Argentina, Brazil and Morocco (Agnolin and Martinelli, 2007;Lindoso et al., 2012;McFeeters, 2013;Evans et al., 2015;Brum et al., 2018) and eventually by the controversial Cenomanian Deltadromeus agilis, whether it is confirmed as a basal ceratosaurian (Delcourt, 2017;Delcourt and Iori, 2018), or as a noasaurid (Rauhut and Carrano, 2016;Wang et al., 2017;Delcourt, 2018), instead of as a tetanuran (Sereno et al., 1996;Apesteguía et al., 2016). ...
A new ceratosaurian theropod dinosaur, Huinculsaurus montesi gen. et sp. nov., is described here. This taxon is based on the last three dorsal vertebrae and the first and second sacral vertebrae found in association at Aguada Grande, Neuquén Province, Argentina. Although fragmentary, Huinculsaurus shows a unique mix of features which differentiates it from all other theropods, including the sympatric abelisaurid Ilokelesia, and is diagnosed by prezygapophyseal articular facets twice longer than wide, anterior centroparapophyseal lamina strongly developed as an extensive lateral lamina in the posterior dorsal vertebrae, pneumatic foramina located ventrally to the postzygodiapophyseal lamina in the posterior dorsal vertebrae, posteriorly tapering postzygapophysis pointed posteriorly, and an accessory lamina bisecting the parapophyseal centrodiapophyseal fossa in the posterior dorsal neural arches. Phylogenetic analyses recovered Huinculsaurus as most closely related to the Late Jurassic Elaphrosaurus than to other Cretaceous abelisauroids, suggesting the persistence of the elaphrosaurine lineage in South America up to the early Late Cretaceous.
... Remarks. Abelisauroid theropods are relatively abundant in the southern continents (Delcourt, 2018), with those from Argentina perhaps being the most informative and complete [e.g., Abelisaurus comahuensis (Bonaparte and Novas, 1985), Carnotaurus sastrei (Bonaparte, 1985;Bonaparte et al., 1990), Ligabueino andesi (Bonaparte, 1996), Skorpiovenator bustingorryi (Canale et al., 2009), Viavenator exxoni , among others]. Indeed, Abelisauroidea, which comprises the mid-to large-sized Abelisauridae and the small to mid-sized Noasauridae, is the best-represented theropod clade in the Cretaceous of Patagonia (Novas et al., 2013). ...
In this paper, we present an updated revision of fossil vertebrates from the Chubut Group, Golfo San Jorge Basin, while also describing some new remains. Extensive exposures of both Lower and Upper Cretaceous sedimentary sequences are present in central Patagonia. These outcrops have, over the past several decades, yielded a varied vertebrate fauna, including fishes, turtles, crocodyliforms, pterosaurs, and dinosaurs, currently herein characterized and described. Although vertebrate diversity in the Chubut Group in central Patagonia is remarkable, the most abundant vertebrates recovered are dinosaurs. The Matasiete Formation (Hauterivian?–Albian) is markedly less prolific in terms of fossils discoveries than either the Bajo Barreal Formation (Cenomanian–early Turonian) or the recently recognized Lago Colhué Huapi Formation (Coniacian–Maastrichtian). The Bajo Barreal fauna is, at a high level, typical of coeval Gondwanan faunas. However, interestingly, several taxa occupy a basal position within their respective groups. The Lago Colhué Huapi Formation has produced a more derived vertebrate fauna, again similar to those from other Gondwanan regions. Finally, in a broad context, the new materials described augment our understanding of Cretaceous terrestrial vertebrate assemblage of central Patagonia and add to the generally meager record of vertebrate in the Cretaceous of the Southern Hemisphere.
... In South America, Rebbachisauridae is diverse and frequently recorded in an interval extending from the Barremian to Turonian, particularly in Argentina. Additionally, their remains are composed mainly of postcranial elements (Calvo and Salgado, 1995;Bonaparte, 1996;Calvo, 1999;Salgado et al., 2004;Gallina and Apesteguía, 2005;Apesteguía, 2007;Carballido et al., 2010Carballido et al., , 2012Haluza et al., 2012;Ibiricu et al., 2012Ibiricu et al., , 2013. This diversity has been also complemented by a few cranial remains (Calvo and Salgado, 1995;Carabajal et al., 2016;Canudo et al., 2018). ...
A new genus and species of Rebbachisauridae sauropod from the Cenomanian of the São Luís Basin, Alcântara Formation, Itapeuasaurus cajapioensis gen. et sp. nov., is described, the first from this temporal interval in northern Brazil. It is characterized by the presence of large and deep fossae on ventro-lateral aspect of the dorsal neural arch split by laminae obliquely oriented; posterior centrodiapophyseal lamina forked ventrally forming the dorsal edge of the centrodiapophyseal fossa; dorsal and ventral components of anterior caudal transverse process thinner than the usual bony bar. This latter feature is associated with the presence of a prezygodiapophyseal centrodiapophyseal fossa accessory lamina. The phylogenetic analysis performed herein identifies the subclade Nigersaurinae as a South American – African/European clade, suggesting a vicariant event before Cenomanian times. In addition, continental vertebrate taxa recorded in the Alcântara Formation offer support to a minor evolutionary change after major vicariant event in Western Gondwana.
Noasaurus leali is a small (~2 m) carnivorous theropod and the nominal genus of the clade Noasauridae, one of the two radiations of abelisauroid ceratosaurs predominantly present in the Southern Hemisphere during the Mesozoic. This eponymous theropod from the Maastrichtian Lecho Formation of Salta, Argentina, is known from an incomplete skeleton of which the strongly curved manual ungual is the most peculiar element. We here provide for the first time a comprehensive description of the holotypic specimens of Noasaurus, whose phylogenetic position was explored using three independent datamatrices on theropod relationships. This species is diagnosed by several apomorphies such as a dorsal ridge in the maxillary fossa, a strongly arched quadrate, a cervical neural arch with anterior epipophyseal prongs, and a manual ungual with a subtriangular flexor fossa delimited by a V-shaped ridge. Results of the phylogenetic analyses recovered Noasaurus closely related to Velocisaurus, Masiakasaurus, and Laevisuchus, which together form a Late Cretaceous radiation of small-bodied noasaurids restricted to the Southern Hemisphere. The peculiar morphology of the lateral dentition and manual unguals suggests that Noasaurus was an opportunistic carnivore feeding on small prey items and a possible piscivore gaffing fish with its specialized hand claws.
ABSTRACT—Small-bodied theropod dinosaurs are rare on southern landmasses but have been known from India for a century. Excavations by Charles Matley and rgansankar Bhattacharji in uppermost Cretaceous sediments at Bara Simla, central India in 1917–1919 recovered small theropod vertebral and limb elements originally interpreted as coelurosaurians and separated into at least three species compsosuchus solus, Laevisuchus indicus, Jubbulpuria tenuis) based on features that can now be attributed to their serial position in the vertebral column. The comparatively recent discoveries of Noasaurus leali and Masiakasaurus knopfleri from similar-aged rocks in South America and Madagascar, respectively, and advances in basal theropod systematics led to a revised interpretation of most small-bodied Indian theropods as noasaurid abelisauroids. Here we review and redescribe Laevisuchus, Jubbulpuria, and Compsosuchus, including several elements that until now were thought lost, and describe a new partial noasaurid dentary from central India. The dentary bears the characteristic procumbent dentition of Masiakasaurus, which apparently is absent in Noasaurus. Likewise, cervical vertebrae of Laevisuchus more closely resemble those of Masiakasaurus than those of Noasaurus. Despite these similarities, phylogenetic analyses indicate that the balance of character data supports the Indian noasaurid species outside the sister-taxon pairing of South American and Malagasy species. Bones of small-bodied theropods have been recovered exclusively from the youngest Mesozoic localities in India (e.g., Pisdura, Bara Simla); to date they have not been reported from the slightly older localities in western and central India, from southern Indian sites in the Cauvery Basin, nor from the Vitakri Formation of Pakistan.
Gondwanan dinosaur faunae during the 20 Myr preceding the Cretaceous-Palaeogene (K/Pg) extinction included several line-ages that were absent or poorly represented in Laurasian landmasses. Among these, the South American fossil record contains diverse abelisaurids, arguably the most successful groups of carnivorous dinosaurs from Gondwana in the Cretaceous, reaching their highest diversity towards the end of this period. Here we describe Koleken inakayali gen. et sp. n., a new abelisaurid from the La Colonia Formation (Maastrichtian, Upper Cretaceous) of Patagonia. Koleken inakayali is known from several skull bones, an almost complete dorsal series, complete sacrum, several caudal vertebrae, pelvic girdle and almost complete hind limbs. The new abelisaurid shows a unique set of features in the skull and several anatomical differences from Carnotaurus sas-trei (the only other abelisaurid known from the La Colonia Formation). Koleken inakayali is retrieved as a brachyrostran abeli-saurid, clustered with other South American abelisaurids from the latest Cretaceous (Campanian-Maastrichtian), such as Aucasaurus, Niebla and Carnotaurus. Leveraging our phylogeny estimates, we explore rates of morphological evolution across ceratosaurian lineages, finding them to be particularly high for elaphrosaurine noasaurids and around the base of Abelisauridae, before the Early Cretaceous radiation of the latter clade. The Noasauridae and their sister clade show contrasting patterns of morphological evolution, with noasaurids undergoing an early phase of accelerated evolution of the axial and hind limb skeleton in the Jurassic, and the abelisaurids exhibiting sustained high rates of cranial evolution during the Early Cretaceous. These results provide much needed context for the evolutionary dynamics of ceratosaurian theropods, contributing to broader understanding of macroevolutionary patterns across dinosaurs.
In the central Neuquén Basin, the Huincul Formation comprises thick successions of Upper Cretaceous fluvial deposits widely exposed at the south and north-west of Huincul High. The vertebrate fossil record from the Huincul Formation is very abundant, especially
considering the saurischian dinosaurs, including several theropod (Mapusaurus, Taurovenator, Aoniraptor, Skorpiovenator, Ilokelesia, Gualicho, Overoraptor, Tralkasaurus, and Huinculsaurus) and sauropod specimens (Choconsaurus, Argentinosaurus, Cathartesaura, Limaysaurus, and the indeterminate rebbachisaurid MMCH-Pv-49). In this contribution, we describe new rebbachisaurid sauropod findings from the El Orejano locality (Neuquén Province, Argentina), where coarse sandstones outcrop referred to the lower section of the Huincul Formation. The new material includes three axial elements that we refer to Rebbachisauridae: a partial dorsal neural arch (MAU-Pv-EO-633), an incomplete dorsal vertebra (MAU-Pv-EO-634), and an almost complete caudal vertebra (MAU-Pv-EO-666). These new findings share different features with other members of that family, although show some morphological differences with other rebbachisaurid taxa, which suggest a more diversified fauna in the central Neuquén Basin than previously known, at least during the Cenomanian/Turonian interval. This record from the new fossiliferous locality of El Orejano allows us to improve our knowledge about the morphological diversity of the Rebbachisauridae during the early Late Cretaceous. Furthermore, it represents one of the most modern records of the family, adding new information on the last stages of the evolutionary history of rebbachisaurids.
After the extinction of rebbachisaurids during the Cenomanian–Turonian interval, titanosaurs were the only group of sauropods to face the K–Pg event. This same global pattern also holds for the end-Cretaceous (Campanian–Maastrichtian) titanosaur record in South America, where their remains can be found from southern Argentina to Ecuador, with more frequent findings in Argentina and Brazil. In this chapter, we review these fossil findings and the main aspects of the taxonomy, systematics, and paleogeographic implications of this record and briefly discuss the importance of these occurrences for the understanding of titanosaur evolution. The diversity and abundance of end-Cretaceous titanosaur taxa in South America represent about 25% of the known Titanosauria species in the world, which makes them the most common group of large terrestrial herbivores of that time. Cretaceous titanosaurs from South America also vary highly in morphology and size, comprising small to large-sized taxa, for example. Their record mainly consists of appendicular and axial remains, including rare skull material, but also comprises eggs, nests, footprints, and coprolites. In South America, by the end of the Late Cretaceous, titanosaurs were generally represented by more derived titanosaurians that are mainly taxonomically assigned to more derived species within Aeolosaurini and Saltasaurinae.
Given that bone microstructure is a very important source of paleobiological information, several paleohistological studies have been conducted on sauropodomorph dinosaurs, possibly making this clade the most studied histologically. Despite these paleohistological studies on sauropodomorph dinosaurs from South America are relatively scarce in comparison with other regions of the world, significant progress on this matter (i.e. paleohistology of South American sauropodomorphs) has been made during the last decade. Following an order from rather specific to more generalized issues, the most important advances are related to the origin of particular skeletal elements (i.e. osteoderms, sacral supraspinous ossifications and extremely elongated cervical ribs), the growth patterns of basal sauropodomorphs and the variation on sauropod growth dynamics and its relationship with gigantism. Regarding the origin of osteoderms and extremely elongated cervical ribs, these structures have been formed by metaplastic ossification of dermal and tendinous tissues, respectively. Their histological characterization has been helpful to discover that the alleged osteoderms of Agustinia ligabuei were actually dorsal and cervical ribs. The long bone histology of basal sauropodomorphs has revealed that the cyclical growth pattern assumed for this group actually showed some degree of variation. Finally, a clade of basal sauropods (i.e. lessemsaurids) was characterized by a cyclical growth pattern, not previously reported for other sauropods, combined with episodes of highly accelerated growth rates. The gigantic body sizes obtained by lessemsaurids were therefore reached through a growth strategy different from that developed by eusauropods (i.e. rapid and continuous growth).
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.
Dzharatitanis kingi gen. et sp. nov. is based on an isolated anterior caudal vertebra (USNM 538127) from the Upper Cretaceous (Turonian) Bissekty Formation at Dzharakuduk, Uzbekistan. Phylogenetic analysis places the new taxon within the diplodocoid clade Rebbachisauridae. This is the first rebbachisaurid reported from Asia and one of the youngest rebbachisaurids in the known fossil record. The caudal is characterized by a slightly opisthocoelous centrum, ‘wing-like’ transverse processes with large but shallow PRCDF and POCDF, and the absence of a hyposphenal ridge and of TPRL and TPOL. The neural spine has high SPRL, SPDL, SPOL, and POSL and is pneumatized. The apex of neural spine is transversely expanded and bears triangular lateral processes. The new taxon shares with Demandasaurus and the Wessex rebbachisaurid a high SPDL on the lateral side of the neural spine, separated from SPRL and SPOL. This possibly suggests derivation of Dzharatitanis from European rebbachisaurids. This is the second sauropod group identified in the assemblage of non-avian dinosaurs from the Bissekty Formation, in addition to a previously identified indeterminate titanosaurian.
The Middle Jurassic sauropod Cetiosaurus is significant both historically and in terms of its potential phylogenetic relationships. The anatomy and taxonomy of this form are poorly understood because inadequate diagnoses have allowed the proliferation of species names and the referral of very fragmentary specimens. A review of Cetiosaurus species indicates that all, except C. oxoniensis, are unavailable or nomina dubia. The current type species, C. medius, can no longer be regarded as a valid taxon. Previous suggestions that Cardiodon is a senior subjective synonym of Cetiosaurus cannot be sustained because the two forms do not share any autapomorphies. It is proposed that the generic name Cetiosaurus be retained, with C. oxoniensis as the new type species. The most complete specimen of C. oxoniensis (a partial skeleton from Bletchingdon Station, Oxfordshire) is redescribed and compared with other sauropods. Cetiosaurus is rediagnosed on the basis of autapomorphies, including: (1) ‘pyramid’-shaped neural spines in posterior cervical and anterior dorsal vertebrae; (2) loss of the spinodiapophyseal lamina on all dorsal vertebrae; (3) anterior chevrons with anteroposteriorly compressed distal shafts; (4) distal caudal centra have a ‘tongue’-like projection at the dorsal midline of their articular ends; and (5) a distinct triangular hollow on the lateral surface of the ilium at the base of the pubic process.
Based on a detailed morphological comparison of the original figures, the lost holotype of "Ornithocheirus hilsensis" is identified as the distal part of the proximal pedal phalanx from digit I of a large-sized theropod. The distinctness in the morphology of the distal epiphysis of this element from that present in the manus and in pedal digits II-IV of most theropods may have contributed to the ambiguous interpretation of this specimen in the course of discussion since the 1880s. Features that have been interpreted as indicating pneumaticity that would support a pterosaur affiliatio can be alternatively explained by taphonomic and dia-genetic processes. Aside of this unresolved question, the published information do not indicate the presence of any pterosaur synapomorphies. Although clearly a nomen dubium, "Ornithocheirus hilsensis" is a precious record of a large-sized theropod near the Valanginian/Hauterivian boundary of Central Europe. It is furthermore of significance as one of the historically earliest documented remains of a dinosaur from Germany.
Elaphrosaurinae is an enigmatic clade of gracile ceratosaurian theropod dinosaurs known from the Late Jurassic of Africa (Elaphrosaurus bambergi) and Asia (e.g., Limusaurus inextricabilis), and the early Late Cretaceous of Argentina (Huinculsaurus montesi). Elaphrosaurinae is often placed within Noasauridae as the sister taxon to Noasaurinae, a clade of small-bodied theropods that lived in South America, Africa, Madagascar and India throughout much of the Cretaceous. Herein, we report the first evidence of Elaphrosaurinae from Australia: a nearly complete middle cervical vertebra from the upper Lower Cretaceous (lower Albian) Eumeralla Formation of Cape Otway, Victoria, Australia. The fact that this site would have been situated at ~76°S towards the end of the Early Cretaceous (~110–107 Ma) implies that elaphrosaurines were capable of tolerating near-polar palaeoenvironments, whereas its age indicates that elaphrosaurines persisted in Australia until at least the late Early Cretaceous. The new Australian elaphrosaurine, in tandem with the recently described Huinculsaurus montesi from the Cenomanian–Turonian of Argentina, implies that the spatiotemporal distribution of Elaphrosaurinae has heretofore been greatly underestimated. Historic confusion of elaphrosaurines with coelurosaurs, especially ornithomimosaurs, coupled with our generally poor understanding of noasaurid evolution, might explain the apparent dearth of fossils of this theropod clade worldwide.
The diversity of Australia’s theropod fauna from the ‘mid’-Cretaceous (Albian–Cenomanian) is distinctly biased towards the medium-sized megaraptorids, despite the preponderance of abelisauroids in the younger but latitudinally equivalent Patagonian theropod fauna. Here, we present new evidence for the presence of ceratosaurian, and specifically abelisauroid, theropods from the Cenomanian Griman Creek Formation of Lightning Ridge, New South Wales. A partial cervical vertebra is described that bears a mediolaterally concave ventral surface of the centrum delimited by sharp ventrolateral ridges that contact the parapophyses. Among theropods, this feature has been reported only in a cervical vertebra attributed to the noasaurid Noasaurus. We also reappraise evidence recently cited against the ceratosaurian interpretation of a recently described astragalocalcaneum from the upper Barremian–lower Aptian San Remo Member of the upper Strzelecki Group in Victoria. Inclusion of the Lightning Ridge cervical vertebra and Victorian astragalocalcaneum into a revised phylogenetic analysis focused on elucidating ceratosaurian affinities reveals support for placement of both specimens within Noasauridae, which among other characters is diagnosed by the presence of a medial eminence on the ascending process of the astragalus. The Lightning Ridge and Victorian specimens simultaneously represent the first noasaurids reported from Australia and the astragalocalcaneum is considered the earliest known example of a noasaurid in the world to date. The recognition of Australian noasaurids further indicates a more widespread Gondwanan distribution of the clade outside of South America, Madagascar and India consistent with the timing of the fragmentation of the supercontinent.
Isolated cervical vertebrae from the mid Cretaceous Kem Kem beds of south east Morocco are referred to the theropod dinosaur clade Abelisauroidea, and represent the first axial remains from this deposit referred to this group. An isolated axis is referred to Abelisauroidea on account of the invaginated spinopostzygapophyseal lamina; the extremely large, projecting and pointed epipophyses; and the anteroposteriorly long, transversely compressed neural spine with a gently convex and unexpanded dorsal margin. In addition, postzygapophyseal facets which completely overhang the centrum posteriorly and lack lateral orientation indicate abelisaurid affinities. An anterior cervical (C4?) is referred to Noasauridae based on an anteriorly-positioned, reduced neural spine and extremely well developed centroprezygapophyseal fossae. This specimen represents both the smallest dinosaur and the first definitive small-bodied dinosaur from the Kem Kem beds. The affinities of the new material are discussed in the context of other abelisauroid remains reported from the Kem Kem assemblage and elsewhere in Africa.
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