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Carnotaurus sastrei Bonaparte, the Horned, Lightly Built Carnosaur from the Middle Cretaceous of Patagonia
... In particular, the stratigraphic record of abelisaurids encompasses all Patagonian Upper Cretaceous basins in which continental rocks are preserved (e.g., Neuquén Basin, Somuncura-Cañadón Asfalto Basin, Golfo San Jorge Basin, and Austral Basin). The knowledge of this family of theropods concerning their anatomy, evolutionary history, and phylogenetic relationships has increased notably in recent decades, with the Patagonian records providing the most novel information due to the abundance and diversity of the group to date (e.g., Bonaparte, 1985;Bonaparte & Novas, 1985;Bonaparte et al., 1990;Coria & Salgado, 1998;Coria et al., 2002;Calvo et al., 2004;Canale et al., 2009;Novas et al., 2013;Gianechini et al., 2015Gianechini et al., , 2021Filippi et al., 2016Filippi et al., , 2018bMéndez et al., 2018Méndez et al., , 2022Cerroni & Paulina-Carabajal, 2019;Cerroni et al., 2020;Aranciaga-Rolando et al., 2021;Baiano et al., , 2022. ...
... Diverse types of accessory structures are common in caudal vertebrae of abelisaurids, although they are also observed along the entire vertebral column of these theropods, a feature that led to an increase in structural rigidity of the axial skeleton (Coria et al., 2002;O'Connor, 2007;Méndez, 2014aMéndez, , 2014bFilippi et al., 2016). However, although movement restric- (Bonaparte et al., 1990;Coria et al., 2002;Filippi et al., 2016Filippi et al., , 2018b. However, in these taxa, the anterior projection of the transverse processes is more developed and it may have contacted the central part of the distal end of the transverse process of the preceding vertebra (Coria et al., 2002). ...
... One of these features is the low or no elevation of the processes with respect to the horizontal plane. Instead, the mid-caudals of more derived brachyrostran abelisaurids (i.e., furileusaurs), such asCarnotaurus(Bonaparte et al., 1990), Aucasaurus(Coria et al., 2002), and Viavenator(Filippi et al., 2018b), have more elevated transverse processes (25° or more with respect the horizontal plane). A second shared trait with basal brachyrostrans is the expanded distal end of the processes. ...
The Cerro Overo-La Invernada area in north Patagonia has provided a rich record of Cretaceous continental tetrapods in the last two decades, mainly from the Bajo de la Carpa Formation (Upper Cretaceous, Santonian). The dinosaur fauna from this area is diverse, including several new taxa, with abelisaurid theropods particularly abundant. Recently, a new isolated caudal vertebra (MAU-Pv-CO-598) was here
recovered. Although fragmentary, it shows features that differentiate it from other abelisaurid remains previously found in this area. It is considered a mid-caudal vertebra and is mainly characterized by a longitudinal groove on the ventral surface of the centrum; a scarcely elevated transverse process with an anteroposteriorly expanded and laterally concave distal end; a longitudinal dorsal crest anteriorly extended from the anterior border of the neural spine; and small tubercles extended from the ends of the zygapophyses, which are considered as accessory interlocking structures between vertebrae. Some characters, such as the dorsal longitudinal crest and the accessory tubercles of the zygapophyses, are present also in the non-brachyrostran abelisaurid Majungasaurus. However, the transverse process is similar to that of caudal vertebrae of non-furileusaur brachyrostrans, such as Ilokelesia, Ekrixinatosaurus, and Skorpiovenator. A phylogenetic analysis here conducted clusters MAU-Pv-Co-598 with the latter three taxa. MAU-Pv-CO-598 comes from lower levels of the Bajo de la Carpa Formation than the furileusaurs Viavenator and Llukalkan. The presence of a specimen with non-furileusaurian affinities in this formation indicates that a possible replacement from non-furileusaur to furileusaur brachyrostrans occurred during the Santonian, after the proposed Turonian faunal
turnover.
... They are represented by numerous species that inhabited South America, continental Africa, Madagascar, India, southern Europe and possibly Australia during Cretaceous times (Novas et al. 2013, and references therein). Some abelisaurids are known from relatively complete and exquisitely preserved skeletons including the cranium and postcranium, as is the case for Carnotaurus (Bonaparte et al. 1990), Majungasaurus (Sampson et al. 1998;Krause et al. 2007), Aucasaurus (Coria et al. 2002) and Spectrovenator (Zaher et al. 2020). However, complete pelvic girdles and hind limbs of abelisaurids are not well documented in the literature, although they are well preserved in some taxa including Aucasaurus (Coria et al. 2002), Majungasaurus (Sampson et al. 1998), Rahiolisaurus (Novas et al. 2010) and Spectrovenator (Zaher et al. 2020); detailed descriptions have been provided for a few taxa with different degrees of completeness, such as Majungasaurus (Carrano 2007), Rahiolisaurus (Novas et al. 2010) and Xenotarsosaurus (Ibiricu et al. 2021). ...
... Over the caudolateral surface, just ventral to the iliac contact, there is a prominent tubercle probably related with the origin of the m. flexor tibialis internus 3, which is well-developed in Carnotaurus, Kurupi, Eoabelisaurus, Ceratosaurus and some tyrannosaurids (Bonaparte et al. 1990;Carrano & Hutchinson 2002;Iori et al. 2021). ...
... Scale bars ¼ 10 cm (A-D), 5 cm (E, F) and 2 cm (G). accessory trochanter to the proximal sector of the medial epicondylar crest of the femur (¼ mediodistal crest; Bonaparte et al. 1990). The intermuscular line is well developed and ornamented with small tubercles and rugosities (Fig. 5B). ...
Skorpiovenator bustingorryi is a derived abelisaurid theropod represented by a fairly complete skeleton from the Late Cretaceous sedimentary beds of north-western Patagonia. Although some features were described in the original paper, mainly related to the skull, the appendicular anatomy remains undescribed. The aim of the present contribution is to provide a detailed description and analysis of the available appendicular bones, including comparisons with other ceratosaurian theropods close to Skorpiovenator. In this way, new autapomorphies emerged to further distinguish Skorpiovenator from its relatives. Furthermore, a comprehensive phylogenetic analysis was performed and several characteristics of the hind limb, in particular some of the autopodium, resulted in the identification of new apomorphic traits for Ceratosauria and Abelisauridae. These features might prove to be useful for future phylogenetic analyses and may help to resolve the still confusing and debated internal relationships of abelisaurid theropods.
... This is probably because the larynx is cartilaginous in all tetrapods except neognath birds. Preserved hyoids in non-avian dinosaurs are only ceratobranchials except in the theropod Carnotaurus, Microraptor, and Confuciusornis (basihyal and ceratobranchial 1) 18,19 and some ankylosaurs (basihyal, and ceratohyal, and ceratobranchial 1 in Saichania chulsanensis and paraglossal, ceratobranchial 1, ceratobranchial 2, and epibranchial in Pinacosaurus grangeri) 17,20 . Pinacosaurus grangeri (IGM100/ 3186) has the best-preserved hyolaryngeal apparatus in non-avian dinosaurs. ...
A voice box (larynx) is unique for tetrapods and plays functional roles in respiration, airway protection, and vocalization. However, in birds and other reptiles, the larynx fossil is extremely rare, and the evolution of this structure remains largely unknown. Here we report the fossil larynx found in non-avian dinosaurs from ankylosaur Pinacosaurus grangeri. The larynx of Pinacosaurus is composed of the cricoid and arytenoid like non-avian reptiles, but specialized with the firm and kinetic cricoid-arytenoid joint, prominent arytenoid process, long arytenoid, and enlarged cricoid, as a possible vocal modifier like birds rather than vocal source like non-avian reptiles. Although bird-unique vocal source (syrinx) have never been reported in non-avian dinosaurs, Pinacosaurus could have employed bird-like vocalization with the bird-like large, kinetic larynx. This oldest laryngeal fossil from the Cretaceous dinosaur provides the first step for understanding the vocal evolution in non-avian dinosaurs toward birds.
... (a) Alligator mississippiensis and (b) Psittacus erithacus modified from Homberger (2017). ar, arytenoid;bh, basihyal;bmc, m. branchiomandibularis caudalis;bmr, m. branchiomandibularis rostralis;cg, m. ceratoglossus;cr, cricoid;crh, m. cricohyoideus;eb, epibranchial;esb, m. episternobranchialis;esbt, m. episternobranchiotendineus;gg, m. genioglossus;gh, m. geniohyoideus;hg, m. hyoglossus;hol, m fossilized intact as hyolaryngeal fossils are mainly ceratobranchials and a few basihyals (Bonaparte et al., 1990;Li et al., 2018;Jiang et al., 2020;Yoshida et al., 2021). Since the qualitative comparison (i.e., classical comparative anatomy) of ambiguous-homology musculoskeletal elements is not suited for understanding anatomical evolution as a whole system, the issue requires quantitative musculoskeletal data and analytical methods to compare the hyolarynx of archosaurs that are independent from homology. ...
Adaptive radiation of archosaurs, represented by crocodilians, non‐avian dinosaurs, and birds, since the Mesozoic has been studied mainly based on their major skeletal elements (skull, vertebrae, and limbs). However, little is known about the evolution of their hyolaryngeal apparatus, which is involved with feeding, respiration, and vocalization, because of poor fossil preservation and the difficulty in determining the musculoskeletal homology of the apparatus. Network analysis is a framework to quantitatively characterize the topological organization of anatomical structures for comparing structural integration and modularity regardless of ambiguous homology. Herein, we modeled the musculoskeletal system of hyolarynx in six species of extant archosaurs and its sister‐taxon turtle, and conducted a network analysis using network parameters, modular partition, and bone centrality in a phylogenetic framework. The network parameters reveal that ancestral archosaurs have reduced the numbers of elements and links and acquired complex networks as a whole domain with strong modularity in the hyolarynx. Furthermore, the modular partition and centrality reveal that the hyoids are highly evolvable, while the larynx is constrained and less evolvable. The archosaur hyolarynx exhibits different evolutionary trends: crocodilians with the system integration, basihyal simplification, and ceratobranchial centralization; and birds with the simplicity, weak integration, and modularity of the hyolarynx, laryngeal integration with cricoid centrality, and tongue‐module expansion with the acquisition of paraglossal. Four hyolaryngeal bones (ceratobranchial, basihyal, paraglossal, and cricoid) have played important roles in archosaur evolution, and their fossil records are keys to understanding the two major archosaur lineages toward crocodilians and birds.
... 5A, 5C, 6B-6D), though this is only preserved on the left side. These structures are superficially similar to the lacrimal processes identified in some tyrannosaurids as well as in Carnotaurus (Bonaparte, Novas & Coria, 1990, fig. 2), Ceratosaurus (Madsen & Welles, 2000, plate 3) and some allosauroids (Currie & Zhao, 1994, fig. ...
Eotyrannus lengi Hutt et al., 2001 from the Lower Cretaceous Wessex Formation (part of the Wealden Supergroup) of the Isle of Wight, southern England, is described in detail, compared with other theropods, and evaluated in a new phylogenetic analysis. Eotyrannus is represented by a single individual that would have been c. 4.5 m long; it preserves the anterior part of the skull, a partial forelimb and pectoral girdle, various cervical, dorsal and caudal vertebrae, rib fragments, part of the ilium, and hindlimb elements excluding the femur. Lack of fusion with regard to both neurocentral and sacral sutures indicates subadult status. Eotyrannus possesses thickened, fused, pneumatic nasals with deep lateral recesses, elongate, tridactyl forelimbs and a tyrannosaurid-like scapulocoracoid. The short preantorbital ramus of the maxilla and nasals that are approximately seven times longer than they are wide show that Eotyrannus was not longirostrine. A posterodorsally inclined ridge on the ilium's lateral surface fails to reach the dorsal margin: a configuration seen elsewhere in Juratyrant. Eotyrannus is not arctometatarsalian. Autapomorphies include the presence of curving furrows on the dentary, a block-like humeral entepicondyle, and a distoproximally aligned channel close to the distolateral border of the tibia. Within Tyrannosauroidea, E. lengi is phylogenetically intermediate between Proceratosauridae and Yutyrannus and the clade that includes Xiongguanlong, Megaraptora, Dryptosaurus and Tyrannosauridae. We do not find support for a close affinity between Eotyrannus and Juratyrant. Our analysis supports the inclusion of Megaraptora within Tyrannosauroidea and thus increases Cretaceous tyrannosauroid diversity and disparity. A proposal that Eotyrannus might belong within Megaraptora, however, is based on character states not present in the taxon. Several theropods from the Wessex Formation are based on material that overlaps with the E. lengi holotype but none can be shown to be synonymous with it. Subjects Paleontology, Zoology
... The general morphology of abelisaurids is rather peculiar compared to that of other theropods by having extremely short skulls and almost vestigial arms (Bonaparte et al., 1990;Canale et al., 2009;Delcourt, 2018;Sampson and Witmer, 2007), but the caudal vertebrae of the South American abelisaurids are also peculiar. Their transverse processes can be anteroposteriorly or only anteriorly projected, increasing the rigidity of the tail (Méndez, 2014;Persons and Currie, 2011). ...
Abelisauridae is a diverse clade of theropod dinosaurs, geographically well-distributed especially in the southern continents during the Cretaceous. The record of abelisaurids in South America comes mainly from Patagonia, whereas in Brazil they are mostly represented by numerous dental crowns and isolated bones, with few formally named species, mostly coming from the Late Cretaceous beds of the Bauru Group. In this contribution, we describe a small abelisaurid mid-caudal vertebra (LPRP/USP L0020) from the Presidente Prudente Formation, Bauru Group. LPRP/USP L0020 bears several abelisaurid features, such as an almost flat ventral surface, a poorly constrict centrum, lack of pneumatization, and distally positioned transverse processes. Body length estimation suggest that LPRP/USP L0020 belonged to a roughly 3.4 m long adult animal, representing one of the smallest known abelisaurids. The discovery of LPRP/USP L0020 indicates that Late Cretaceous abelisaurids from central South America were more diverse in body size than previously known, and possibly as diverse as their Patagonian counterparts.
Despite nearly 200 years of scientific collecting and study, none of the extinct, bipedal, predatory, theropod dinosaurs have been reliably shown to exceed 12 m in length. Using digital 3D models of theropods with lengths spanning 80 cm to 12 m, their body masses were found to scale to the 3.5 power of body lengths. The lateral area of the pelvis and the cross-sectional area of the tail base of these animals corresponds to the cross-sectional areas of key muscle groups important for balance and locomotion, and both scale to the 2.4 power of body length. Body accelerations in the lateral and forward directions are, using F = ma, given by dividing muscle area (force proxy) by body mass. Plotting these acceleration estimates against body length shows them to decrease exponentially. The largest theropods with body lengths of 10–12 m have less than 10% of the acceleration capacity of the smaller forms. The distinct lack of fossil remains of theropods demonstrably longer than 12 m suggests that the theropod body plan had an upper size limit based on a minimum acceleration threshold. Rotational inertia of the theropod body was found to be proportional to body length raised to the 5.5 power, and with increasing length, the capacity for agility would rapidly diminish. The tight relationship between theropod pelvic area and body length allows for the estimation of body lengths of specimens lacking complete axial skeletons, and this is done for four, large, well-preserved pelves.
Polycotylids were a clade of shorth-necked plesiosaur that achieved a worldwide distribution and a peak of diversity during the Albian-Turonian, reaching the K/Pg mass extinction with a relative low diversity. One of the youngest polycotylids worldwide recorded is Sulcusuchus erraini, from Los Alamitos and La Colonia formations (Patagonia). Here, a new polycotylid specimen, also from Maastrichtian levels of the La Colonia Formation, is described; and the affinities of the new material and Sulcusuchus erraini are evaluated. Additionally, the phylogenetic position of Sulcusuchus erraini is reevaluated recovering Sulcusuchus erraini outside the Occultonectia, the latter comprising only Cenomanian-Turonian polycotylids. However, additional analysis indicate that the position of S. erraini is far from being well resolved.
Giant carnivorous dinosaurs such as Tyrannosaurus rex and abelisaurids are characterized by highly reduced forelimbs that stand in contrast to their huge dimensions, massive skulls, and obligate bipedalism.¹,² Another group that follows this pattern, yet is still poorly known, is the Carcharodontosauridae: dominant predators that inhabited most continents during the Early Cretaceous3, 4, 5 and reached their largest sizes in Aptian-Cenomanian times.6, 7, 8, 9, 10 Despite many discoveries over the last three decades, aspects of their anatomy, especially with regard to the skull, forearm, and feet, remain poorly known. Here we report a new carcharodontosaurid, Meraxes gigas, gen. et sp. nov., based on a specimen recovered from the Upper Cretaceous Huincul Formation of northern Patagonia, Argentina. Phylogenetic analysis places Meraxes among derived Carcharodontosauridae, in a clade with other massive South American species. Meraxes preserves novel anatomical information for derived carcharodontosaurids, including an almost complete forelimb that provides evidence for convergent allometric trends in forelimb reduction among three lineages of large-bodied, megapredatory non-avian theropods, including a remarkable degree of parallelism between the latest-diverging tyrannosaurids and carcharodontosaurids. This trend, coupled with a likely lower bound on forelimb reduction, hypothesized to be about 0.4 forelimb/femur length, combined to produce this short-armed pattern in theropods. The almost complete cranium of Meraxes permits new estimates of skull length in Giganotosaurus, which is among the longest for theropods. Meraxes also provides further evidence that carchardontosaurids reached peak diversity shortly before their extinction with high rates of trait evolution in facial ornamentation possibly linked to a social signaling role.
Little is known about the large‐scale evolutionary patterns of skull size relative to body size, and the possible drivers behind these patterns, in Archosauromorpha. For example, the large skulls of erythrosuchids, a group of non‐archosaurian archosauromorphs from the Early and Middle Triassic, and of theropod dinosaurs are regarded as convergent adaptations for hypercarnivory. However, few investigations have explicitly tested whether erythrosuchid and theropod skulls are indeed disproportionately large for their body size, and whether this trend is driven by hypercarnivory. Here, we investigate archosauromorph relative skull size evolution, examining the scaling relationships between skull and body size of Palaeozoic and Mesozoic archosauromorphs using a robust phylogenetic framework and assessing the influence of potential drivers, such as taxonomy, diet, locomotory mode and inhabited biotope. Our results show that archosauromorph relative skull sizes are largely determined by phylogeny and that the other drivers have much weaker levels of influence. We find negative allometric scaling of skull size with respect to body size when all studied archosauromorphs are analysed. Within specific groups, skull size scales with positive allometry in non‐archosaurian archosauromorphs and, interestingly, scales isometrically in theropods. Ancestral reconstructions of skull–femur size ratio reveal a disproportionately large skull at the base of Erythrosuchidae and proportionately sized skulls at the bases of Theropoda, Carnosauria and Tyrannosauroidea. Relative skull sizes of erythrosuchids and theropods are therefore distinct from each other, indicating that disproportionately large skulls are not a prerequisite for hypercarnivory in archosauromorphs, and that erythrosuchids exhibit a bauplan unique among terrestrial Mesozoic carnivores.
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