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Amargatitanis macni gen. et sp. nov. MACN PV N53. Anterior caudal vertebra in posterior (A), right (B), anterior (C), left (D), and ventral (E) views. MACN PV N51-A. Anterior caudal vertebra in posterior view (F). MACN PV N51-B. Mid caudal vertebra in right (G) and ventral (H) views. Scale bar: 50 mm.
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A study of the abundant and undescribed isolated and associated bones and teeth from the La Amarga Formation (Barremian of Neuquén, Argentina) permitted the recognition of additional clades of sauropod dinosaurs: basal titanosauriforms, both basal and derived titanosaurs, and rebbachisauroid diplodocoids, which are now added to the already known di...
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Context 1
... PV N53 and 51 (Figs. 5-7). Caudal vertebrae. There are six preserved caudal vertebrae presumably referable to the same specimen, and will be here referred here as 53 and 51-A, B, C, D, and E, respectively. 53 ( Fig. 6a-e) is an anterior caudal vertebrae. The centrum is slightly procoelous, not really circular but heart-shaped, as in several ornithischians. The neural arch is clearly positioned in the anterior part of the vertebra and the transverse process arises dorsolaterally. Spinodiapophysial laminae are well developed and the neural spine, although not preserved, seems to have pointed backwards. 51-A (Fig. 6f) is a poorly preserved anterior caudal vertebrae. The centrum is tall, anteroposteriorly short and slightly procoelous. The neural arch is on the anterior part of the vertebra and the transverse processes are still separated into visible diapophyses and parapophyses on the left side. This vertebra was found separated from the others and perhaps does not belong to the same ...
Context 2
... PV N53 and 51 (Figs. 5-7). Caudal vertebrae. There are six preserved caudal vertebrae presumably referable to the same specimen, and will be here referred here as 53 and 51-A, B, C, D, and E, respectively. 53 ( Fig. 6a-e) is an anterior caudal vertebrae. The centrum is slightly procoelous, not really circular but heart-shaped, as in several ornithischians. The neural arch is clearly positioned in the anterior part of the vertebra and the transverse process arises dorsolaterally. Spinodiapophysial laminae are well developed and the neural spine, although not preserved, seems to have pointed backwards. 51-A (Fig. 6f) is a poorly preserved anterior caudal vertebrae. The centrum is tall, anteroposteriorly short and slightly procoelous. The neural arch is on the anterior part of the vertebra and the transverse processes are still separated into visible diapophyses and parapophyses on the left side. This vertebra was found separated from the others and perhaps does not belong to the same ...
Context 3
... (Fig. 6g-h) and C (not figured) are similar to each other, with short and tall, rounded centra, and completely devoid of the neural arch. The transverse processes were not preserved but their scars remain on the lateral side of the centra. They were laterally directed. 51-D (not figured) is slightly longer. The base of the neural arch is preserved. The marks for diapophyses and parapophyses are distinct and both located on the upper half of the centrum. The neural arch is also located on the anterior half of the ...
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... Fossil vertebrates from the Anacleto Formation are less well-known than those from other stratigraphic units (e.g., Allen, Los Alamitos formations). Among non-dinosaurian vertebrates, dipnoans, lepidosaurs, chelid turtles, peirosaurid crocodyliforms, and dryolestoid mammals were reported (Goin et al., 1986;Turner & Calvo, 2005;Scanferla & Canale, 2007;Apesteguía et al., 2007;Brizuela & Albino, 2011;Martinelli et al., 2012;Forasiepi et al., 2012;Maniel et al., 2023). Among dinosaurs, the record includes ornithopods (Coria & Salgado, 1996), abelisaurid and megaraptorid theropods (Coria et al., 2002a;Sereno et al., 2008;Gianechini et al., 2015;Baiano et al., 2021), and titanosaurs (Chiappe et al., 1998(Chiappe et al., , 2001Chiappe & Coria, 2004). ...
... Otherwise, this assemblage shares with coeval beds the abundance of rinconsaur titanosaurs and the occurrence of the dipnoan Metaceratodus kaopen (Apesteguía et al., 2007;Filippi & Garrido, 2008) (Fig. 20). One remarkable aspect that Marín Farm assemblage shares with late Campanian-Maastrichtian (Allenian sensu Leanza et al., 2004) is the low diversity, but numerical abundance, of chelid turtles, and particularly the occurrence of the genus Yaminuechelys (Leanza et al., 2004;de la Fuente et al., 2015;Maniel & de la Fuente, 2016Fig. ...
... As indicated by other authors, the limit between the Cenomanian and Turonian included an important extinction event and a faunistic turnover in Patagonia (Apesteguía, 2002;Coria & Salgado, 2005;Novas, 2009;Santamarina et al., 2022). Posterior to this extinction, titanosaurian sauropods underwent an extensive radiation (Coria & Salgado, 2005;Salgado et al., 2005;Gallina & Apesteguía, 2015;Apesteguía, 2007;Aranciaga-Rolando et al., 2022;Pérez-Moreno et al., 2024). The occurrence and abundance of Chadititan in the Marín Farm assemblage, together with the Turonian-Campanian rinconsaur radiation here depicted, indicates that it is possible that they were part of such turnover, and of the "evolutionary explosion" that occurred after the Cenomanian together with the appearance of aeolosaurines, saltasaurines, and diverse basal eutitanosaurs (Pérez-Moreno et al., 2024). ...
Here we describe a new fossil invertebrate and vertebrate assemblage from a previously unknown locality of the Anacleto Formation (Campanian, Upper Cretaceous), near General Roca city, Río Negro Province, Argentina. The specimens were found in a single fossiliferous layer, which yielded bivalves and gastropods, including the first fossil record of the terrestrial clade Megalomastomatidae and the first undoubted record for the terrestrial subulinid Leptinaria. Vertebrates are represented by fishes (lepisosteids, percomorphs, and the dipnoan Metaceratodus kaopen), chelid turtles, a single crocodyliform scute, an indeterminate pterosaur, an incomplete meridiolestidan mammalian jaw, and abelisaurid and rinconsaurian titanosaur dinosaurs. The latter is represented
by several individuals of a small and gracile-limbed form. The phylogenetic analysis recovers a monophyletic Rinconsauria including the new taxon, plus Rinconsaurus, Pitekunsaurus, Overosaurus, and Muyelensaurus. The new titanosaur indicates that rinconsaurians were characterized by a body shape that was different from
other titanosaurs, with brachiosaur-like posture, gracile limbs, and protonic tail. The faunistic assemblage is characterized by the abundance, but low diversity, of chelid turtles and a very low number of crocodyliforms. This taxonomic composition is reminiscent of other faunal assemblages of the latest Cretaceous of northern Patagonia, but differs markedly from Campanian assemblages known from North America and Europe.
... Moreover, a detailed analysis on dentitions can help in shedding light on previous assignations of isolated teeth to taxa -something of particular interest in polispecific beds and for monodont taxa-, a practice that has been repeatedly performed (e.g. Apesteguía, 2007;Christiansen, 2000;Janensch, 1935-36), but could potentially result in ambiguous palaeobiological inferences. ...
... Isolated individual teeth have been consistently assigned to sauropod -mainly suprageneric -taxa along the literature, based on morphological and/or taphonomical criteria (e.g. Apesteguía, 2007;Díez Díaz et al., 2013;Holwerda et al., 2018;Janensch, 1935-36;Mocho et al., 2017;Saegusa & Tomida, 2011). This is accurate in monospecific depositions (or at least within distant taxonomic taxa), such as is the criteria for associating non-articulated elements for individuals (e.g. ...
... Dicraeosauridae has been stated to have teeth with labial facets (Holwerda et al., 2018;Sereno & Wilson, 2005), based on the assignation of isolated teeth in the Middle Saurian Beds (Tendaguru Formation) to Dicraeosaurus (Christiansen, 2000;Janensch, 1935-36) and several isolated teeth in the La Amarga Formation to Dicraeosauridae indet. or even Amargasaurus (based on their similarities to those of Dicraeosaurus; Apesteguía, 2007). However, no functional tooth was previously found attached to a dentigerous element within the clade. ...
The associated preservation between dentitions and dentigerous elements is crucial for understanding diverse biological features. Notwithstanding, their fossil record in Sauropoda is relatively seldom, compared to other skeletal elements. Here, the first partially complete dentition including upper and lower teeth in Dicraeosauridae is described, based on Bajadasaurus pronuspinax. This dentition lacks only one upper and two lower functional teeth. The dentigerous elements preserved replacement teeth, which reduce in length and number caudally. Tooth formation times and rates vary within the different elements, with a total mean replacement time of 40.7 days. The functional dentition shows three caudally directed patterns: reduction in size, reduction in curvature, and reduction in the occurrence of wear facets. The functional teeth number mirrors in the occlusal and sagittal planes. The replacement teeth ount in Bajadasaurus is lower than the same for other diplodocoids. In this taxon, the tooth-replacement process fits the Zahnreihen with a Z-space-of-two model on the lower dentition, but this model results in a chaotic arrangement of the developmental pattern dorsally, probably due to a replacement mechanism of the whole upper dentition similar to Dicraeosaurus and Apatosaurus. Overall, the dental traits of Bajadasaurus suggest a plausible low-level specialist-feeding ecological niche for this taxon.
... A similar hyposphene is recorded from the basal Rebbachisauridae indet. from La Amarga Formation MACN-Pv-N35 and in the 10 th dorsal vertebra of the African rebbachisaurid Nigersaurus (Apesteguía 2007;Sereno et al. 2007;Lerzo 2023). ...
... 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). ...
... Despite hosting an abundant and diverse sauropod assemblage (Apesteguía, 2007) very little is known about pterosaurs from the Barremian La Amarga Formation (Neuquén Province, Argentina). An incomplete femur (MACN-N 02) was reported by Montanelli (1987) and interpreted as an indeterminate pterodactyloid. ...
The Gondwanan pterosaur record is scarce when compared with that of Laurasia and is reviewed here. The majority of Gondwanan pterosaur remains are derived from South America; however, the relative richness of the South American record compared with other Gondwanan continents is largely a result of the ‘Lagerstätten’ effect. Nevertheless, the South American pterosaur assemblage represents the most speciose and diverse known from Gondwana, with several lineages represented, including the Raeticodactylidae, Rhamphorhynchoidea, Darwinoptera, Ctenochasmatidae, Gnathosaurinae, Nyctosauridae, Ornithocheiridae, Tapejaridae, Thalassodromidae, Dsungaripteridae, Chaoyangopteridae and Azhdarchidae. Gondwanan pterosauromorphs are known only from South America. From Africa rhamphorhynchids, archaeopterodactyloids, pteranodontians, nyctosaurids, ornithocheirids, tapejarids, dsungaripteroids, chaoyangopterids, and azhdarchids have been reported. The Arabian Peninsula has produced nyctosaurids, an istiodactyliform, ornithocheirids and azhdarchids. Non-pterodactyloid pterosaurs have been reported from India. A possible azhdarchid has been reported from Madagascar and rhamphorhynchids are known from isolated teeth. The Antarctic pterosaur assemblage also comprises isolated remains of indeterminate pterodactyloids, and a possible indeterminate rhamphorhynchoid. The pterosaur record from East Gondwana comprises ornithocheirids, azhdarchids and a possible ctenochasmatoid from Australia, as well as azhdarchids from New Zealand. Although our understanding of Gondwanan pterosaurs has greatly improved within the last three decades, the discovery and description of more specimens, particularly from Antarctica and East Gondwana, will enhance our understanding of pterosaurian biodiversity and palaeobiogeography.
... In dorsal view the neural spine is rhomboidal in shape, with rounded and prominent edges, as in Haplocanthosaurus and several diplodocoids, such as Apatosaurus, Diplodocus, Rebbachisaurus, and the indeterminate rebbachisaurid MACN-Pv N35 (Marsh 1877(Marsh , 1878Hatcher 1903;Janensch 1914;Lavocat 1954;Apesteguía 2007;Foster and Wedel 2014;Wilson and Allain 2015). On the lateral surface of the spine the spinodiapophyseal laminae (spdl) are robust and prominent, being anteroposteriorly expanded close to the spinal apex ( Figure 5A), as in Rebbachisaurus (Wilson and Allain 2015). ...
... On the lateral surface of the spine the spinodiapophyseal laminae (spdl) are robust and prominent, being anteroposteriorly expanded close to the spinal apex ( Figure 5A), as in Rebbachisaurus (Wilson and Allain 2015). The spdl, together with prespinal (prsl) and postspinal (posl) laminae, frame oval and dorsoventrally extended spinoprezigapophyseal (sprf) and spinopostzygapophyseal (spof) fossae, as seen in dorsal neural spines of several rebbachisaurids, such as Comahuesaurus, Katepensaurus, Rebbachisaurus, and MACN-Pv N35 (Apesteguía 2007;Carballido et al. 2012;Ibiricu et al. 2013Ibiricu et al. , 2015Wilson and Allain 2015). In lateral view, the posl is convex and more prominent than prsl ( Figure 5A), and the spinopostzygapophyseal lamina (spol) is thin, slightly prominent, and anterolaterally inclined. ...
... Carballido et al. 2012;Wilson and Allain 2015;Canudo et al. 2018;Whitlock and Wilson Mantilla 2020;Salgado et al. 2022;Bellardini et al. 2022a), two main dispersal events and a main diversification area are considered. In this sense, a first dispersal event was during the Early Cretaceous (Hauterivian-Barremian), with evidence from Europe, Africa, and South American (Dalla Vecchia 1998;Pereda Suberbiola 2003;Salgado et al. 2006;Apesteguía 2007;Mannion 2009;, whereas a last spread occurred during the Late Cretaceous (Cenomanian), where only Patagonian taxa are known (Bellardini et al. 2022a). On the other hand, most of the rebbachisaurid come from Gondwana, especially from Patagonia, with the Neuquén Basin playing a crucial role in the diversification of the clade. ...
The Lohan Cura Formation (Albian) at the Cerro de los Leones locality (Neuquén Province, Patagonia, Argentina) yielded several fossil materials, especially sauropod specimens. Among these, Agustinia ligabuei includes postcranial elements of a single individual, with widely debated taxonomy and phylogeny. Here, we provide an extended osteological description and illustrations of the axial and appendicular elements of Agustinia, as well as a revised diagnosis. Moreover, the phylogenetic analysis including a new combination of morphological features recognises Agustinia as a basal Rebbachisauridae, closely related with other South American rebbachisaurids. Our results suggest a more diversified sauropod fauna in the Neuquén Basin, where different members of both neosauropod lineages (i.e. Macronaria and Diplodocoidea) survived in the same region during the Albian age. The reassessment of Agustinia as a basal rebbachisaurid improves our knowledge about the early stages of evolutionary history of Rebbachisauridae, adding new information on the morphological and taxonomic diversification of the clade during the Early Cretaceous of southwestern Gondwana.
... Rebbachisauridae represents a diplodocoid neosauropod clade less nested than Flagellicaudata (Dicraeosauridae+ Diplodocidae), known from the Hauterivian of Europe (Dalla Vecchia, 1998Vecchia, , 2005 to the Cenomanian-Turonian of Patagonia (Calvo & Salgado, 1995;Gallina & Apesteguía, 2005;Ibiricu et al., 2013Ibiricu et al., , 2015. Histriasaurus; Dalla Vecchia, 1998, 2005, or even earlier if we consider the recent reassessment of Xenoposeidon from the Berriasian of England as a rebbachisaurid sauropod (Taylor, 2018 Vecchia, 1998;Pereda Superbiola, 2003;Salgado et al., 2006;Apesteguía, 2007;Mannion, 2009;Mannion et al., 2011) and the last dispersion event (Fig. 8.3) during the early Late Cretaceous (Cenomanian) in Patagonia (e.g., Whitlock, 2011;Wilson & Allain, 2015;Canudo et al., 2018). In this context, the evidence of different taxa in the Hauterivian-Barremian of Laurasia (i.e., Histriasaurus, Demandasaurus) and Gondwana (Zapalasaurus; Salgado et al., 2006) suggests a wide geographical dispersion since the Early Cretaceous, a condition that would support the early origin of the clade. ...
... 4.3). The dorsal surface of the neural spine is convex in anterior view, Photo and line drawings of the anterior-to-middle dorsal vertebra MAU-PV-EO-634 in anterior view; and 2, detail of the amedl on the basal portion of the neural spine; 3, line drawings in anterior view of the mid-to-posterior dorsal neural arch of indeterminate rebbachisaurid MACN PV N35 (modified fromApesteguía, 2007;Carballido et al., 2012;Wilson & Allain, 2015); 4, line drawings in anterior view of the dorsal vertebra of Rebbachisaurus MNHN-MRS 1958 (modified fromApesteguía, 2007;Carballido et al., 2012;Wilson & Allain, 2015); 5, line drawings in anterior view of the anterior dorsal vertebra of Comahuesaurus MOZ-PV 6656 (modified fromApesteguía, 2007;Carballido et al., 2012;Wilson & Allain, 2015). Scale bar= 100 mm. as in the Rebbachisaurus MNHN-MRS 2000 and the MMCH-PV-49 (Fig. 7.1) ...
... 4.3). The dorsal surface of the neural spine is convex in anterior view, Photo and line drawings of the anterior-to-middle dorsal vertebra MAU-PV-EO-634 in anterior view; and 2, detail of the amedl on the basal portion of the neural spine; 3, line drawings in anterior view of the mid-to-posterior dorsal neural arch of indeterminate rebbachisaurid MACN PV N35 (modified fromApesteguía, 2007;Carballido et al., 2012;Wilson & Allain, 2015); 4, line drawings in anterior view of the dorsal vertebra of Rebbachisaurus MNHN-MRS 1958 (modified fromApesteguía, 2007;Carballido et al., 2012;Wilson & Allain, 2015); 5, line drawings in anterior view of the anterior dorsal vertebra of Comahuesaurus MOZ-PV 6656 (modified fromApesteguía, 2007;Carballido et al., 2012;Wilson & Allain, 2015). Scale bar= 100 mm. as in the Rebbachisaurus MNHN-MRS 2000 and the MMCH-PV-49 (Fig. 7.1) ...
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.
... Berriasian-Hauterivian deposits in Brazil have also yielded putative titanosaurs, including Triunfosaurus [151,152], although these have more recently been regarded as non-titanosaurian somphospondylans [17,131]. In Argentina, Hauterivian-Barremian deposits have produced remains of titanosauriforms [153,154], but dicraeosaurids dominate the Barremian deposits [155][156][157][158][159][160][161]. Terminal Barremian deposits in Colombia have produced the titanosauriform Padillasaurus, originally described as a brachiosaurid by Carballido et al. [162] but reinterpreted as a somphospondylan by Mannion et al. [71], whereas upper Barremian-lower Aptian deposits in Argentina host rebbachisaurids [163]. ...
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.
... 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). ...
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.
... Amazonsaurus maranhensis (Carvalho et al. 2013); Tapuiasaurus macedoi (Zaher et al. 2011); Laplatasaurus araukanicus (Huene 1929); Amargasaurus cazaui (Salgado and Bonaparte 1991); Amargatitanis macni (Apesteguía 2007); Rinconsaurus caudamirus (Calvo and González Riga 2003); Muyelensaurus pecheni (Calvo et al. 2007a, b, c); Sarmientosaurus musacchioi (Martínez et al. 2016); Saltasaurus loricatus (Bonaparte and Powell 1980); Rocasaurus muniozi (Salgado and Azpilicueta 2000); Brasilotitan nemophagus (Machado et al. 2013) Overosaurus paradasorum (Coria et al. 2013); Trigonosaurus pricei (Bonaparte 1996(Bonaparte , 1997; Comahuesaurus windhauseni (Carballido et al. 2012); Bonitasaura salgadoi (Apesteguía 2004); Panamericansaurus schroederi (Calvo and Porfiri 2010); Narambuenatitan palomoi (Filippi et al. 2011); Epachthosaurus sciuttoi (Powell 1990); Pitekunsaurus macayai (Filippi and Garrido 2008); Ligabuesaurus leanzai (Bonaparte et al. 2006); Kaijutitan maui (Filippi et al. 2019); Elaltitan lilloi (Mannion and Otero 2012); Drusilasaura deseadensis (Navarrete et al. 2011); ...
... Aeolosaurus maximus (Santucci and Arruda-Campos 2011); Katepensaurus goicoecheai (Ibiricu et al. 2013); Choconsaurus baileywillisi (Simón et al. 2017); Zapalasaurus bonapartei (Salgado et al. 2006); Agustinia ligabuei. Bonaparte (1999b); Nullotitan glaciaris (Novas et al. 2019); Atacamatitan chilensis (Kellner et al. 2011); Punatitan coughlini (Hechenleitner et al. 2020); Limaysaurus tessonei (Calvo and Salgado 1995;Salgado et al. 2004); Quetecsaurus rusconii (González Riga and Ortiz David 2014); Barrosasaurus casamiquelai (Salgado and Coria 2009); Maxakalisaurus topai (Kellner et al. 2006); Adamantisaurus mezzalirai (Santucci and Bertini 2006); Baurutitan britoi ; Aeolosaurus rionegrinus rionegrinus (Powell 1987); Aeolosaurus colhuehuapensis (Casal et al. 2007); Andesaurus delgadoi (Calvo and Bonaparte 1991); Triunfosaurus leonardii (Carvalho et al. 2017); Pellegrinisaurus powelli (Salgado 1996); Cathartesaura anaerobica (Gallina and Apesteguía 2005); Padillasaurus leivaensis (Carballido et al. 2015); Baalsaurus mansillai (Calvo and González Riga 2018); Nopcsaspondylus alarconensis (Apesteguía 2007). Antarctosaurus wichmanianus (Huene 1929). ...
Most taphonomy studies of South American sauropodomorphs have addressed extrinsic factors such as sedimentary environments, bone dispersal, and mineralogical processes that occurred during fossil diagenesis. These studies provide important data on the taphonomic modes which are associated with bone accumulations in different paleoenvironmental contexts. However, these analyses have generally not considered intrinsic factors like the shape, size, and structural integrity of the skeletal elements, variables that can produce some taphonomic bias. Sauropodomorphs include dinosaurs of highly varied sizes, ranging from small (less than 8 m long) to remarkably giant forms (around 30 m long). In the largest sauropods, such as the huge titanosaurs, very incomplete skeletons are commonly found and most notably skull and articulated pedes rarely are preserved. We focus here on some intrinsic anatomical factors as they relate to articulation in some key parts of the skeletons. Further, this study suggests that the preservation of fragile portions of sauropodomorph skeletons was possible only under specific combinations of sedimentological and biological processes.
