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New information on Lessemsaurus sauropoides (Dinosauria: Sauropodomorpha) from the Upper Triassic of Argentina
Abstract
Postcranial remains of Lessemsaurus sauropoides are described herein, including elements of the vertebral column, pectoral girdle, forelimb, pelvis and hindlimb. These remains were closely associated with the cervicodor-sal neural arches previously described from this taxon. This assemblage of bones shows numerous derived characters, including some derived similarities exclusively shared with Antetonitrus ingenipes from the Upper Triassic of South Africa. Additionally, this material reveals an unusual com-bination of plesiomorphic character states present in many non-eusauropod sauropodomorphs together with derived characters that suggest affinities with eusauropods and rela-ted taxa.
... Our results show that the deep radial fossa of Bagualia is a synapomorphy of Eusauropoda ( Fig. 8 in Appendix S1), although some Triassic and Early Jurassic non-eusauropod sauropodomorphs also possess a moderately deep fossa (e.g. Lessemsaurus, Antetonitrus, Melanorosaurus; Pol and Powell, 2007;McPhee et al., 2014;Bonnan and Yates, 2007). This demonstrates that the development of a deep radial fossa occurred gradually in Sauropodomorpha towards the end of the Triassic, but it becomes more pronounced at the end of the Early Jurassic (Toarcian), accompanied by a more massive body and obligatory quadrupedal posture, as seen in Bagualia and Patagosaurus. ...
... Vulcanodon, Tazoudasaurus; Fig. 21 in Appendix S1). The ascending process of Bagualia is well-developed, occupying more than half of the anteroposterior length of the astragalus, a feature typical of sauropods (Otero et al., 2022), although a long ascending process also is present in the Upper Triassic sauropod Lessemsaurus (Pol and Powell, 2007). Except for Sefapanosaurus , most non-sauropod sauropodomorphs from the Late Triassic and Early Jurassic have foramina at the base of the posterior surface of the ascending process (e.g. ...
... As in most eusauropods, the flexor tubercle is slightly developed in the pedal unguals of Bagualia, although the reduction of this structure varies through Sauropodomorpha, and also is not marked in some early sauropodiforms (e.g. Mussaurus, Lessemsaurus, Antetonitrus, Vulcanodon; Otero and Pol, 2013;Pol and Powell, 2007;McPhee et al., 2014;Cooper, 1984). Similar to most non-eusauropod sauropodomorphs, the pedal ungual phalanges of Bagualia have both well-developed lateral and medial grooves (e.g. ...
Since their origin, sauropodomorphs have undergone numerous anatomical changes from small and bipedal early sauropodomorphs towards massive-bodied and quadrupedal sauropods. However, the timing of these changes in the evolution of the group is unclear. Here, we describe the appendicular skeleton of the early diverging eusauropod Bagualia alba from the late Early Jurassic of Patagonia, Argentina, and conduct a morphological disparity analysis based on a phylogenetic dataset of Sauropoda. The results reveal a change in morphospace occupation between the pre-Toarcian and Toarcian-Middle Jurassic sauropodomorphs and between the latter and Late Jurassic forms. The first shift corresponds with the extinction of non-sauropodan sauropodomorphs and the diversification of sauropods, while the second corresponds with the diversification of Neosauropoda and closely related eusauropods (mamenchisaurids, turiasaurians) in the Late Jurassic, leading to a substantial shift and increase in morphological disparity. Finally, we found that body mass is significantly correlated with the first principal coordinate axis of the morphospace in two-thirds of a random sample of optimal trees, which suggests that body size played a role in shaping the evolution of sauropod morphology. In this context, Bagualia provides insights into the evolution of Sauropoda, particularly regarding changes that occurred during the Early to Middle Jurassic.
... A, strict consensus tree obtained from the phylogenetic analysis; B, reduced consensus after pruning seven taxa. Numbers above the nodes represent bootstrap frequencies > 50%, and numbers below the nodes represent Bremer support values > 1. 2014;Pol & Powell, 2007;Y. H. Zhang & Yang, 1994;Q. ...
... Among Carnian sauropodomorphs, eight taxa are recognized: Saturnalia tupiniquim, Pampadromaeus barberenai, Buriolestes schultzi, and Bagualosaurus agudoensis (Cabreira et al., 2011(Cabreira et al., , 2016Langer et al., 1999;Pretto et al., 2019), from the Santa Maria Formation, Brazil; Panphagia protos, Chromogisaurus novasi, and Eoraptor lunensis (Ezcurra, 2010;Martinez & Alcober, 2009;Sereno et al., 2012), from the Ischigualasto Formation, Argentina; and Mbiresaurus raathi from Pebbly Arkose Formation, Zimbabwe (Griffin et al., 2022). These taxa are earlydiverging members of Sauropodomorpha, recognized mainly by their small, gracile forms, which are anatomically distinct from post-Carnian sauropodomorphs (Apaldetti et al., 2018;Bonaparte, 1967Bonaparte, , 1978Galton, 1973;Leal et al., 2004;Müller, Langer, et al., 2018;Novas et al., 2011;Pol & Powell, 2007). ...
Buriolestes schultzi is a small sauropodomorph dinosaur from Carnian beds (ca., 233 Ma) of southern Brazil. It is one of the earliest members of that lineage and is a key taxon to investigate the initial evolution of Sauropodomorpha. Here, we attribute a new specimen to B. schultzi from Late Triassic of southern Brazil, which represents the first occurrence of the taxon outside the type locality. The new specimen comprises a disarticulated and partial skeleton, including cranial and postcranial elements. It is tentatively regarded as an additional specimen of B. schultzi according to a unique combination of traits (including autapomorphies). Conversely, the new specimen is stouter than the other specimens of B. schultzi , as shown by femoral Robustness Index . Based on femoral circumference, the estimated body mass of the new specimen is approximately 15 kg, which is far higher than the previous estimations for other specimens of B. schultzi (i.e., approximately 7 kg). In fact, the new specimen and some specimens of Eoraptor lunensis and Saturnalia tupiniquim were found to be significantly stouter than coeval sauropodomorphs. Therefore, instead of all being constructed as gracile, the earliest sauropodomorphs experienced an unappreciated intraspecific variation in robustness. This is interesting because more precise data on species body mass are crucial in order to better understand the complex terrestrial ecosystems in which dinosaurs originated.
... It is also possible that stronger bites could have evolved in later-occurring basal loricatans with larger contemporaneous herbivores. For example, Fasolasuchus tenax size (8+ m long; no reliable body mass estimates exist) from the middle-late Norian Los Colorados Formation, Argentina, is exceeded by the sauropodomorph Lessemsaurus sauropoides (upper mass estimate of 10 tons, no length estimates exist; Apaldetti et al., 2018;Bonaparte, 1981;Nesbitt et al., 2013;Pol & Powell, 2007). However, the lack of three-dimensionally preserved skull material from this basal loricatan prevents robust functional investigations (Bonaparte, 1981;Nesbitt et al., 2013). ...
Pseudosuchian archosaurs, reptiles more closely related to crocodylians than to birds, exhibited high morphological diversity during the Triassic and are thus associated with hypotheses of high ecological diversity during this time. One example involves basal loricatans which are non-crocodylomorph pseudosuchians traditionally known as "rauisuchians." Their large size (5-8+ m long) and morphological similarities to post-Triassic theropod dinosaurs, including dorsoventrally deep skulls and serrated dentitions, suggest basal loricatans were apex predators. However, this hypothesis does not consider functional behaviors that can influence more refined roles of predators in their environment, for example, degree of carcass utilization. Here, we apply finite element analysis to a juvenile but three-dimensionally well-preserved cranium of the basal loricatan Saurosuchus galilei to investigate its functional morphology and to compare with stress distributions from the theropod Allosaurus fragilis to assess degrees of functional convergence between Triassic and post-Triassic carnivores. We find similar stress distributions and magnitudes between the two study taxa under the same functional simulations, indicating that Saurosuchus had a somewhat strong skull and thus exhibited some degree of functional convergence with theropods. However, Saurosuchus also had a weak bite for an animal of its size (1015-1885 N) that is broadly equivalent to the bite force of modern gharials (Gavialis gangeticus). We infer that Saurosuchus potentially avoided tooth-bone interactions and consumed the softer parts of carcasses, unlike theropods and other basal loricatans. This deduced feeding mode for Saurosuchus increases the known functional diversity of basal loricatans and highlights functional differences between Triassic and post-Triassic apex predators.
... This resembles the condition of B. schultzi (ULBRA-PVT280), Saturnalia tupiniquim (MCP 3844-PV), U. tolentinoi (UFSM 11069), and M. itaquii (CAPPA/UFSM 00101a). The phalanges are proportionately wider in more advanced sauropodomorphs (e.g., Otero & Pol, 2013;Pol & Powell, 2007). The larger phalanx (11 mm in length) is poorly preserved (Figure 4g-l). ...
The lineage of sauropodomorph dinosaurs raised some of the most impressive animals that ever walked on Earth. However, the massive titans of the Mesozoic Era originated from far smaller dinosaurs. The Triassic beds from Brazil yielded the earliest part of this evolutionary history. Despite the diverse fossil record of early sauropodomorphs, juvenile specimens, as well as certain species are poorly sampled. This is the case for Unaysaurus tolentinoi, an unaysaurid sauropodomorph from Caturrita Formation (ca. 225 Ma; early Norian, Late Triassic). The holotype and only specimen of U. tolentinoi was excavated from the Água Negra Locality (São Martinho da Serra, Rio Grande do Sul, Brazil) in 1998. More than two decades later, no other fossil vertebrates have been reported from the same fossiliferous site. Here we describe a skeletally immature specimen which was found in association with the holotype of U. tolentinoi. The specimen was discovered after a first-hand examination of the holotype and comprises some isolated vertebrae and elements from the posterior autopodium. According to linear regressions, its metatarsal I is approximately 41.7 mm in length, compared to approximately 75.9 mm in the holotype. The repeated elements and reduced size indicates that it does not belong to the elements originally used to erect U. tolentinoi. Rather, the specimen is assigned to U. tolentinoi by topotypy and shared morphology. In addition to the reduced size, distinct lines of evidence (e.g., neurocentral sutures; bone texture) support its assignment to a skeletally immature individual. In sum, the new material expands the record of U. tolentinoi, and represents an additional juvenile dinosaur from the Caturrita Formation.
The Early Jurassic Jenkyns Event (~183 Ma) was characterized in terrestrial environments by global warming, perturbation of the carbon cycle, enhanced weathering and wildfires. Heating and acid rain on land caused a loss of forests and affected diversity and composition of land plant assemblages and the rest of the trophic web. We suggest that the Jenkyns Event, triggered by the activity of the Karoo-Ferrar Large Igneous Province, was pivotal in remodelling terrestrial ecosystems, including plants and dinosaurs. Macroplant assemblages and palynological data show reductions in diversity and richness of conifers, cycadophytes, ginkgophytes, bennetitaleans, and ferns, and continuation of seasonally dry and warm conditions. Major changes occurred to sauropodomorph dinosaurs, with extinction of diverse basal families formerly called ‘prosauropods’ as well as some basal sauropods, and diversification of the derived Eusauropoda in the Toarcian in South America, Africa, and Asia, and wider diversification of new families, including Mamenchisauridae, Cetiosauridae and Neosauropoda (Dicraeosauridae and Macronaria) in the Middle Jurassic, showing massive increase in size and diversification of feeding modes. Ornithischian dinosaurs show patchy records; some heterodontosaurids and scelidosaurids disappeared, and major new clades (Stegosauridae, Ankylosauridae, Nodosauridae) emerged soon after the Jenkyns Event, in the Bajocian and Bathonian worldwide. Among theropod dinosaurs, Coelophysidae and Dilophosauridae died out during the Jenkyns Event and a diversification of theropods (Megalosauroidea, Allosauroidea, Tyrannosauroidea) occurred after this event with substantial increases in size. We suggest then that the Jenkyns Event terrestrial crisis was marked especially by floral changes and origins of major new sauropodomorph and theropod clades, characterized by increasing body size. Comparison with the end Triassic Mass Extinction helps to understand the incidence of climatic changes driven by activity of large igneous provinces on land ecosystems and their great impacts on early dinosaur evolution.
New material of Melanorosaurus readi HAUGHTON, 1924 from the Carnian of the Cape Province represents two incomplete specimens of this early prosauropod. The species is more lightly built than the somewhat younger M. thabanensis GAUFFRE, 1993 a from Lesotho and the South American melanorosaurid Riojasaurus BONAPARTE 1969. The sixth cervical vertebra has an inclined anterior articular surface, pointing to a natural curvature in the neck. The forelimbs are shorter and more slender than in Riojasaurus. M. readi also has four sacral vertebrae, the additional one being incorporated from the dorsal series. The pubes are long, slender elements compared to the same in Riojasaurus. M. readi was probably facultatively bipedal, whereas Riojasaurus was probably an obligatory quadruped.
The sauropod dinosaur from the Kota formation of India, Lower Jurassic in age, is the earliest which is known from adequate material. This preliminary account mentions the occurrence of the material, establishes a name and holotype, presents a diagnosis of its characters and comments on those which are typical of sauropods. Some of the characters which collectively distinguish the new genus and species, Barapasaurus tagorei, from other sauropods are briefly indicated.
Continental strata of Early Jurassic age are seldom exposed, and little is known of the history of sauropod dinosaurs prior to the Middle Jurassic radiation of neosauropods. Well-preserved skeletons and skulls have not been recovered from strata older than the Middle Jurassic. Here we report, in the Early Jurassic of the Moroccan High Atlas, the discovery of the skeleton, including cranial material, of a new vulcanodontid sauropod. Tazoudasaurus naimi n.g., n.sp. represents with Vulcanodon the sister group of the eusauropods and the most complete basal sauropod material available to date. To cite this article: R. Allain
The holotype of the prosauropod dinosaurBlikanasaurus cromptoni
Galton & van Heerden 1985, a partial hindlimb, is described from the lower Elliot Formation (Red Beds; Carnian, Upper Triassic) of the Eastern
Cape, South Africa.Blikanosaurus, along with the sympatricEuskelosaurus andMelanorosaurus, probably represent the oldest record of the Prosauropoda (certainly so for articulated remains). The prosauropod family
Blikanasauridae is characterized by a hind-limb that is extremely stocky, especially the metatarsus.Blikanasaurus was an early heavily-built, quadrupedal saurischian, but it was probably not the ancestor for the Sauropoda. The other tetrapods
of the lower Elliot Formation are reviewed with particular emphasis on the carnivorous dinosaurAliwalia rex.
Der Holotyp (ein unvollständig erhaltenes Hinterbein) des prosauropoden DinosauriersBlikanasaurus cromptoni
Galton & van Heerden 1985 wird aus der unteren Elliot Formation (Red Beds, Karn, Obertrias) beschrieben.Blikanasaurus bildet, zusammen mit den sympatrischen GattungenEuskelosaurus undMelanorosaurus, das älteste Vorkommen der Prosauropoda (zumindest was artikulierte Reste betrifft). Die prosauropode Familie Blikanasauridae
ist durch ein extrem plumpes Hinterbein — insbesondere im Metatarsus — charakterisiert.Blikanasaurus kann als ein schwergewichtiger quadrupeder Saurischier angesehen werden, steht aber wahrscheinlich nicht in der Vorfahrenlinie
zu den Sauropoden. Es wird ein Überblick über die übrigen Tetrapoden der unteren Elliot Formation mit besonderer Berücksichtigung
des carnivoren DinosaurierAliwalia rex gegeben.
The holotype of the large prosauropod Camelotia borealis GALTON from the basal Westbury Formation (Rhaetic, Upper Triassic) of Wedmore, Somerset, England is illustrated in detail. The femur has two synapomorphic characters of the Melanorosauridae, the lesser trochanter of the femur is sheet-like and the transverse width of the shaft at mid-length is greater than the antero-posterior width. The centra of the most anterior caudal vertebrae are tall but short, as in Melanorosaurus HAUGHTON (Upper Triassic, South Africa), the probable sister group of Camelotia. These characters also show that Camelotia borealis is not a junior synonym of Plateosaurus engelhardti MEYER, the common large plateosaurid from the Upper Triassic of western Europe. The associated teeth of Avalonianus KUHN are referred to the possible carnosaurian theropod ?Megalosaurus cambrensis NEWTON.
Three classifications of the Dinosauria have been proposed, which differ from each other in the principles on which their authors proposed to make the divisions. First in time is Professor Cope’s classification (‘Philadelphia, Acad. Nat. Sci. Proc.,’ November 13th, 1866, and December 31st, 1867; ‘Amer. Phil. Soc. Trans.,’ vol. 14, Part I). He relied upon the characters of the tarsus and the ilium; and on their varied condition divided Dinosaurs into three orders named Orthopoda, Goniopoda, and Symphopoda. In the Orthopoda , the generic types associated are Scelidosaurus, Hylæosaurus, Iguanodon, and Hadrosaurus. And in this group the relations of the tibia and fibula are compared to those of modern Lizards, the proximal tarsals being distinct from each other and from the tibia. The ilium has a narrowed anterior prolongation.
The femur of the anchisaurid (= plateosaurid) prosauropoddinosaur Euskelosaurus browniiHuxley, 1866 from the lower Elliot Formation (Upper Triassic) of South Africa is sigmoidal in posterior view with the fourth trochanter well removed from the medial edge. The sympatric Melanorosaurus readiHaughton, 1924 is not a junior synonym of Euskelosaurus brownii because the femur is straight in posterior view with the fourth trochanter close to the medial edge. In addition to Melanorosaurus, the Melanorosauridae Huene, 1929 includes Camelotia borealis nov. gen. and nov. sp. from the Upper Triassic of England, Riojasaurus incertusBonaparte, 1969 from the Upper Triassic of Argentina, and possibly some of the posteranial material referred to the? rauisuchian the codontian Sinosaurus triassicusYoung, 1948 from the Lower Jurassic of China.frLe fémur du dinosaure prosauropode anchisauridé(= platéosauride) Euskelosaurus browniiHuxley, 1866des couches inférieures de la formation Elliott (Trias supérieur) d'Afrique du Sud est sigmoïde, en vue postérieure, le quatrième trochanter se détachant bien du bord médian. Le sympatrique Melanorosaurus readiHaughton, 1924n'est pas un synonyme plus récent d'Euskelosaurus brownii, puisque son fémur apparaît droit en vue postérieure, le quatrième trochanter se rapprochant du bord médian. En plus de Melanorosaurus, les Melanorosauridae Huene, 1929includes regroupent Camelotia borealis nov. gen. et nov. sp. du Trias supérieur d'Angleterre, Riojasaurus incertusBonaparte, 1969du Trias supérieur d'Argentine, et éventuellement, on leur attribue une certaine partie du matériel post-crânien du Thécodonte rauisuchien, Sinosaurus triassicusYoung, 1948du Jurassique inférieur de Chine.