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PROTEROCHAMPSA REIG, 1959 Type species: Proterochampsa barrionuevoi Reig, 1959. Diagnosis: Trotteyn et al. (2013) defined Proterochampsa as an archosauriform genus with the following combination of features (autapomorphies are marked by an asterisk*): temporal surface of skull depressed; external nares placed close to the anterior tip of the snout and dorsally oriented; antorbital fenestra, orbits and supratemporal fenestra dorsally oriented; notably developed ornamentation composed of nodular crests on the skull and mandibles*; exclusion of jugal from the suborbital fenestra by the maxilla–ectopterygoid contact; premaxilla forming half of the border of the external nares*; nasals extended anteriorly along the medial border of the external nares between the premaxillary dorsal processes., Published as part of Simão-Oliveira, Daniel De, Pinheiro, Felipe Lima, Andrade, Marco Brandalise De & Pretto, Flávio Augusto, 2022, Redescription, taxonomic revaluation and phylogenetic affinities of Proterochampsa nodosa (Archosauriformes: Proterochampsidae) from the early Late Triassic of the Candelaria Sequence (Santa Maria Supersequence), pp. 1310-1332 in Zoological Journal of the Linnean Society 196 (4) on page 1314, DOI: 10.1093/zoolinnean/zlac048, http://zenodo.org/record/7390673, {"references":["Reig OA. 1959. Primeros datos descriptivos sobre nuevos reptiles arcosaurios del Triasico de Ischigualasto (San Juan, Argentina). Revista de la Asociacion Argentina de Geologia 13: 257 - 270.","Trotteyn MJ, Arcucci AB, Raugust T. 2013. Proterochampsia: an endemic archosauriform clade from South America. In: Nesbitt SJ, Desojo JB, Irmis RB, eds. Anatomy, phylogeny and palaeobiology of early archosaurs and their kin, Vol. 379. London: Geological Society, Special Publication, 59 - 90."]}

PROTEROCHAMPSA NODOSA BARBERENA, 1982 Holotype: MCP 1694 PV (Fig. 2), well-preserved skull with articulated mandible missing most of the occiput, right temporal region and posterior right lower jaw ramus. Locality: The specimen comes from a now-gone outcrop located 6 to 8 km west of the Botucaraí hill, located at km 136 of the BR-287 highway, on the outskirts of Candelária municipality, Rio Grande do Sul State, Brazil (Barberena, 1982; Abdala et al., 2002). Age and horizon: Late Carnian–Earliest Norian (Rogers et al., 1993; Langer, 2005; Furin et al., 2006; Martínez et al., 2011) from the Upper Triassic of Candelaria Sequence, Hyperodapedon Assemblage Zone, Rosário do Sul Group, Paraná Basin (Barberena, 1982; Langer et al., 2007; Horn et al., 2014). Emended diagnosis: Proterochampsid archosauriform with a skull similar in proportions to Proterochampsa barrionuevoi; dorsoventrally flattened, highly ornamented skull; rostrum elongated with respect to the temporal region; external nares, antorbital fenestrae, orbits, supratemporal fenestrae and infratemporal fenestrae facing dorsally; elongated piriform nares with anteroposteriorly extended narial fossae; ornamentation consisting of dermal sculpturing in the shape of longitudinally disposed ridges along the dorsal face of the skull; a complex arrangement of ridges with interspersed nodules in the interorbital region of the prefrontals and frontals; curved ridges in the postorbitals, along the posterior border of the orbits; periodic and small nodular protrusions along the dorsal midline of the skull; well-developed nodular growths aligned along the dorsolateral portion of the premaxillae, maxillae, lateroventral corner of the jugals and lateral surface of the quadratojugals; jugal excluded from the infraorbital fenestra; prominent horizontal shelf on the surangular, dorsal to the mandibular fenestra; wide adductor fossa in the mandible; ventrally curved lamina on the angular; absence of retroarticular process; hook-shaped projection on the posterolateral side of the quadratojugal. Proterochampsa nodosa can be distinguished from Proterochampsa barrionuevoi by having overall fewer nodules and ridges, but larger nodular growths on the dorsolateral side of the skull; elevated medial rim of the orbits along the postorbital, frontal and prefrontal, shaping the orbit in an elliptic, almost subquadrangular manner; nasal pair wider than the minimum interorbital space (while, in Pr. barrionuevoi, the space between the orbits is virtually the same width as that of the nasal pair); elongated and laterally straighter frontal with contribution to the medial border of the orbit diminished by the prefrontal, which in comparison is lateromedially wider in dorsal view; rounded anterior margin of the antorbital fenestra and less angular than in Pr. barrionuevoi; small supratemporal fenestra comprising one-fourth or less of the length of the infratemporal fenestra, compared to one-third in Pr. barrionuevoi; postorbital posteriorly elongated past the posterior border of the supratemporal fenestra; presence of a quadrate foramen; occiput region proportionally higher and less depressed, with the quadrate and squamosal forming a nearly 90° angle; proportionally large (relative to Pr. barrionuevoi) contribution of the pterygoid on the occipital region; opisthotic isolated from contacting the quadrate by the squamosal and the pterygoid. Comparative description Skull: The skull of Proterochampsa nodosa is overall triangular. It has a slender and elongated snout, forming approximately two-thirds of the total skull length, and a comparatively wide and robust temporal region. The rostral region gradually tapers anteriorly in dorsal view. The cranium is dorsoventrally flattened, and the temporal fenestrae, nasal openings and orbits face dorsally. All dermal bones present, to some extent, ornamentation in the form of nodular protrusions and complex ridges that vary in size and are commonly swollen in width (Figs 2–5). These are notably large in the maxilla, jugal and quadratojugal, where they form a continuous single line of nodules. The overall cranial shape and proportions are similar to the Argentinian species, Proterochampsa barrionuevoi (see: Reig, 1959; Barberena, 1982; Dilkes & Arcucci, 2012; Trotteyn et al., 2013). The external nares are located at the dorsal midline of the snout and are separated from each other by a thin ridge formed by the premaxillae and nasals. Although the external openings can be identified in the specimen, the segmentation of the nasal cavity was hampered by the quality of the CT slices. Therefore, most of the information on its morphology is based on first-hand observation of the holotype. The external nares are piriform and anteroposteriorly extended, with anterior depressions in the premaxilla and elongated posterior fossae in the nasals, a characteristic shared by all Proterochampsidae (Sill, 1967; Bonaparte, 1971; Kischlat, 2000; Trotteyn et al., 2013). The temporal region is wider and taller than the snout. The supratemporal fenestra is small and oval-shaped, being one-quarter or less of the length of the infratemporal fenestra, while the infratemporal fenestra of Pr. barrionuevoi is approximately one-third of the length of the infratemporal opening (Barberena, 1982; Dilkes & Arcucci, 2012). The orbital and temporal regions of MCP 1694 PV present complex arrangements of protuberant ridges, which make the orbits of Pr. nodosa appear less rounded than those of Pr. barrionuevoi in dorsal view. At the interorbital region, the prefrontals and frontals form a complex ornamentation around the anteromedial and posterior orbital rims. In the dorsal view, the ridges extend anterolaterally from the midline of the frontals towards the lacrimals, forming a tall and U- or V-shaped ridge from the medial to anteromedial region of the interorbital zone (Fig. 4). Most Pr. barrionuevoi specimens show a smoother surface in this region (Dilkes & Arcucci 2012), and while some individuals may present some degree of ornamentation surrounding the orbits, they are never as rough as in Pr. nodosa. A similar condition is also seen in Chanaresuchus (Romer, 1971; Trotteyn et al., 2012; Trotteyn & Ezcurra, 2020). A well-marked set of ridges surrounding the anteromedial margin of the orbit is reported for Rugarhynchus sixmilensis (Wynd et al., 2020). Differing from that of Proterochampsa and Chanaresuchus, however, these ridges connect to a maxillary ridge in Ru. sixmilensis. Additionally, the ridge that connects the orbits in Pr. nodosa seems to be unique to the taxon, not occurring in other proterochampsids or doswelliids. Posteriorly, the postorbitals and frontals form tall and curved ridges around the posterior rims of the orbits and the anteromedial edge of the infratemporal fenestrae, anteriorly to the supratemporal fenestrae. Notably, the lateral borders of the skull present larger nodules extending from the posterolateral edge of the premaxillae, through the maxillae, jugals and quadratojugals (Fig. 5), ending in a hook-like projection in the posterodorsal corner of the quadratojugal, in lateral view. Indeed, the general arrangement and size of the nodules is one of the most evident distinctions between Pr. nodosa and Pr. barrionuevoi. While the nodules in the Brazilian species are larger, mainly laterally arranged and evenly spaced between each other, the nodules in the skulls of the Argentinian species are comparatively smaller, more densely concentrated and evenly distributed through most of the skull (Reig, 1959; Barberena, 1982; Dilkes &Arcucci, 2012). A hook-like projection in the quadratojugals is present in both Pr. nodosa and Pr. barrionuevoi, and it was suggested to be a shared feature of the genus Proterochampsa (Dilkes & Arcucci, 2012). Premaxillae (Figs 2–4): The premaxillae are rostrally rounded and extend from the tip of the snout to the posterior limit of the external nares. In dorsal view, the premaxillae contact each other medially, anteriorly to the nares. A smooth premaxillary depression can be seen anterior to each external naris. The premaxilla– maxilla suture is clear. In lateral view, it arises at the level of the midpoint of the premaxilla–maxilla diastema, running obliquely to reach the dorsal surface of the skull, passing through the height of the posterior end of the narial fossa, where it sharpens posteriorly. Posteromedially, the posterodorsal process of the premaxilla overlaps the nasal bone, excluding the maxilla from the margin of both the narial fossae and the posterior margin of the external nares. A few thin and curved longitudinal ridges are present in the dorsolateral surfaces of the premaxillae, as well as some subtle bosses in their anterolateral sides. The premaxillae do not display any nodular ornamentation in their dorsal surfaces, differing from Proterochampsa barrionuevoi. The palatal rami of the premaxillae contact the anterior and lateral surfaces of the vomers. There is no sign of interdental plates in the premaxilla. Maxilla (Figs 3–5): The maxilla is large and comprises most of the lateral surface of the snout, extending from its contact with the premaxilla, level with the midportion of the nasal openings, until beyond the centre of the antorbital fenestra. The maxilla forms the anterior-third part of the border of the antorbital fenestra; however, it slightly differs in the left antorbital fenestra, as the anteromedial process of the left jugal forms most of its lateral border. Medially to the antorbital fenestra, in dorsal view, the maxilla of Proterochampsa nodosa has a sharp posterodorsal process that extends between the nasal and prefrontal but fails to reach the frontal. There is no maxillary antorbital fossa in the specimen. A shallow depression extending forwards from the anterior rim of the antorbital fenestra can be seen in the dorsal surface of the right maxilla, though it is not suggestive of a marked fossa, as seen in Pr. barrionuevoi (Dilkes & Arcucci, 2012). Furthermore, the anterior margin of the antorbital fenestra of Pr. nodosa is rounded and gently curved, differing from the sharp and angular condition in most Pr. barrionuevoi (e.g. PVL-2063 and PVSJ- 77). The dorsal contact between the maxilla and the jugal, in lateral view, is posteroventrally curved and goes from the anterior rim of the antorbital fenestra, across the lateral side of the skull and down until the end of the alveolar margin of the maxilla. The palatal process of the maxilla can be seen through the anterior half of the antorbital fenestra, in dorsal view (Fig. 4) and contacts the palatine posteriorly and medially, forming an interdigitated suture, parallel to the anterior margin of the choana (Fig. 3). Nasal (Figs 3–5): The nasal forms the posterior border of the external nares and is better observed in the dorsal view. Its internarial process is thin and contacts the premaxilla anteriorly, in the midportion of the anteroposterior span of the external narial openings. There, the nasal and premaxilla form a point contact creating together an internarial bar. Anterolaterally the nasal contacts the premaxilla, excluding it entirely from the narial fossa, which is entirely composed by an excavation on the nasal surface. Laterally, the nasal contacts the dorsal facet of the maxilla for most of its anteroposterior length, extending from the posterior tip of the premaxilla and posteriorly surpassing the level of the posterior border of the antorbital fenestra. Posteriorly, the nasal inserts between the prefrontal and the frontal, and presents a posteromedial serrated suture with the frontal. Though some slices allow part of the nasal cavity to be seen (Fig. 7), this is restricted to a small portion of the specimen. Indeed, most of the inner surface of the nasal cavity was poorly sampled in the tomograms, hampering a complete reconstruction. The nasal presents two longitudinal ridges: one along the medial suture, where either pair contacts each other; and one along the centre of the bone, extending anteriorly from the nares to reach the level of the antorbital fenestra. A few dispersed small nodules can also be seen, mostly concentrated in the posterior part of the left nasal. The posterior contact of the nasals with the prefrontal and frontal differs from most Pr. barrionuevoi specimens. While in Pr. barrionuevoi the nasal–frontal suture is almost transversally straight (Reig, 1959; Dilkes & Arcucci, 2012), in Pr. nodosa both nasals form an anterior embayment and the frontals extend anteriorly between them. Another distinctive feature between both species is that, in the Brazilian form, the nasal pair is wider than the minimum interorbital space, while in Pr. barrionuevoi, the space between the orbits is virtually the same width as that of the nasal pair (Dilkes & Arcucci, 2012). Prefrontal (Figs 4–6): In dorsal view, the prefrontal has an overall trapezoid shape, from the anteromedial border of the antorbital fenestra until the posteromedial border of the orbit. Its lateral contact with the lacrimal is anteroposteriorly straight, levelled roughly at the lateromedial midpoint both of the antorbital fenestra and the orbit. The prefrontal forms most of the posteromedial border of the antorbital fenestra. Anteriorly, it has a small and orthogonal contact with the posteromedial end of the maxilla. The posterior region of the prefrontal, by its turn, forms the anteromedial border of the orbit. Medially and posteromedially, the prefrontal contacts the frontal, and this suture is marked by a small, longitudinal ridge. There is a small medial contact between the prefrontal and the nasal, which prevents the posterior tip of maxilla from reaching the frontal. Together with the frontal, the prefrontal forms a tall and well-developed interorbital ridge, which extends bordering the medial and anteromedial rim of the orbits, forming a deep and marked U-shaped depression, with its concavity facing anteriorly. This feature is markedly distinct from Pr. barrionuevoi, where the interorbital region is comparatively smoother and less elevated. Barberena (1982) also mentions that the prefrontal part of this ridge branches out into approximately three smaller ridges in Pr. nodosa, while Dilkes & Arcucci (2012) indicate the presence of only two branches. The left prefrontal counterpart could be interpreted as having a ridge branching into three smaller ridges, but only two of these branches can be pointed out with certainty. Frontal (Figs 3–5): In dorsal view, the frontal is an elongate bone that extends from level with the posterior border of the antorbital fenestra until the posterior border of the orbit. The medial suture between the two frontals can be seen along most of its extent. In dorsal view, the frontal can be divided into an anterior and a posterior ramus, which are separated by an interorbital ridge, with the posterior ramus standing significantly higher than the anterior one (Fig. 4) The anterior ramus is narrower and elongated, comprising nearly two-thirds of the total anteroposterior length of the frontal. While in Pr. barrionuevoi the anterior portion of the frontal contributes to the medial rim of the orbit, in Pr. nodosa the anterior ramus of the frontal is isolated in the middle of the skull by the prefrontal and only its posterior ramus contributes to the orbit, forming its posteromedial rim. Barberena (1982) highlights the frontal morphology and the frontal–nasal suture as important features in distinguishing Pr. nodosa from Pr. barrionuevoi. Dilkes & Arcucci (2012) noted that the discovery of new specimens of Pr.barrionuevoi diminishes this difference between the two species, given the intraspecific variability in the Argentinean species. However, its anterior and lateral sutures are still sufficiently distinct to be denoted as species-specific features. While the frontal in specimens of Pr. barrionuevoi is nearly rectangular, forming lateromedially straight sutures with the nasal and parietal, the sutures in Pr. nodosa are more complex, displaying mainly oblique frontal–nasal and frontal–parietal contacts, with its anterolateral border delimited by a posterior process of the nasal bone. Lacrimal (Figs 3–5): The lacrimal is a small element with an irregular shape. In dorsal view, this bone is limited to the space between the posterior border of the antorbital fenestra and the anterolateral border of the orbit, but the morphology of both lacrimals in Pr. nodosa is inconsistent. While the right lacrimal is restricted in-between the antorbital fenestra and the orbit, its left counterpart seems to extend posteriorly, nearly contacting the anterolateral edge of the postorbital. While in Pr. barrionuevoi the lacrimal is restricted between the posterior margin of the antorbital fenestra and the anteromedial margin of the orbit, in Pr. nodosa the lacrimal is comparatively expanded and forms a greater portion of the anterior and anterolateral rim of the orbit. Its overall shape is semicircular. Laterally, the contact with the jugal bone is rounded, while its medial contact with the prefrontal is anteroposteriorly straight. A subtle longitudinal ridge is present at the anterolateral end of both lacrimals. Jugal (Figs 3–5): The jugal is triradiate and formed by an anterior, a dorsal and a posterior ramus. While the left jugal element is completely preserved, the right counterpart has a fractured posterior ramus. The jugal would be best described in lateral view as an upside-down ‘T’ (Fig. 5), sprawling anteroposteriorly and, to a lesser extent, dorsally. This bone comprises a large part of the lateral side of the skull, forming most of the lateral rim of the antorbital fenestra, a small portion of the lateral border of the orbit, and most of the anterior and lateral rim of the infratemporal fenestra. Anteriorly, it forms a dorsoventrally oblique contact with the maxilla, roughly at the middle to anterolateral point of the antorbital fenestra. Its left counterpart contacts the lacrimal in a near U-shaped suture when seen dorsally, while the same contact in its right counterpart appears to be nearly longitudinally straight. The posterior ramus of the jugal, in lateral view, extends forming an oblique contact that overlaps the anterior ramus of the quadratojugal. The dorsal ramus of the jugal contacts the postorbital bone, with the former element composing most of the anterior margin of the infratemporal fenestra. In dorsal view, the anterior ramus of the left jugal forms the lateral margin of the antorbital fenestra, up to its anterior margin. However, the suture of the anterior contact between the right jugal and right maxilla is not as clear, and the anterior ramus of the jugal seems to form only the posterolateral margin of the antorbital fenestra. In ventral view, the contact between the jugal and the ectopterygoid can be observed (Fig. 3). It is similar to the condition depicted in Pr. barrionuevoi, in which the lateral margin of the ectopterygoid overlaps the medial margin of the jugal., Published as part of Simão-Oliveira, Daniel De, Pinheiro, Felipe Lima, Andrade, Marco Brandalise De & Pretto, Flávio Augusto, 2022, Redescription, taxonomic revaluation and phylogenetic affinities of Proterochampsa nodosa (Archosauriformes: Proterochampsidae) from the early Late Triassic of the Candelaria Sequence (Santa Maria Supersequence), pp. 1310-1332 in Zoological Journal of the Linnean Society 196 (4) on pages 1314-1326, DOI: 10.1093/zoolinnean/zlac048, http://zenodo.org/record/7390673, {"references":["Barberena MC. 1982. Uma nova especie de Proterochampsa (Proterochampsa nodosa sp. nov.) do Triassico do Brasil. Anais da Academia Brasileira de Ciencias 54: 127 - 141.","Abdala F, Barberena M, Dornelles J. 2002. A new species of the traversodontid cynodont Exaeretodon from the Santa Maria Formation (Middle / Late Triassic) of southern Brazil. Journal of Vertebrate Paleontology 22: 313 - 325.","Rogers RR, Swisher CC III, Sereno PC, Forster CA, Monetta AM. 1993. The Ischigualasto tetrapod assemblage (Late Triassic, Argentina) and 40 Ar / 39 Ar dating of dinosaur origins. Science 260: 794 - 797.","Langer MC. 2005. Studies on continental Late Triassic tetrapod biochronology II. The Ischigualastian and a Carnian global correlation. Journal of South American Earth Sciences 19: 219 - 239.","Furin S, Preto N, Rigo M, Roghi G, Gianolla P, Crowley JL, Bowring SA. 2006. Highprecision U-Pb zircon age from the Triassic of Italy: implications for the Triassic time scale and the Carnian origin of calcareous nannoplankton and dinosaurs. Geology 34: 1009 - 1012.","Martinez RN, Sereno PC, Alcober OA, Colombi CE, Renne PR, Montanez IP, Currie BS. 2011. A basal dinosaur from the dawn of the dinosaur era in southwestern Pangaea. Science 331: 206 - 210.","Langer MC, Ribeiro AM, Schultz CL, Ferigolo J. 2007. The continental tetrapod-bearing Triassic of south Brazil. In: Lucas SG, Spielmann JA, eds. The Global Triassic.. New Mexico Museum of Natural History and Science Bulletin 41: 201 - 218.","Horn BLD, Melo TM, Schultz CL, Philipp RP, Kloss HP, Goldberg K. 2014. A new third-order sequence stratigraphic framework applied to the Triassic of the Parana Basin, Rio Grande do Sul, Brazil, based on structural, stratigraphic and paleontological data. Journal of South American Earth Sciences 55: 123 - 132.","Reig OA. 1959. Primeros datos descriptivos sobre nuevos reptiles arcosaurios del Triasico de Ischigualasto (San Juan, Argentina). Revista de la Asociacion Argentina de Geologia 13: 257 - 270.","Dilkes DQ, Arcucci A. 2012. Proterochampsa barrionuevoi (Archosauriformes: Proterochampsia) from the Late Triassic (Carnian) of Argentina and a phylogenetic analysis of Proterochampsia. Palaeontology 55: 1 - 33.","Trotteyn MJ, Arcucci AB, Raugust T. 2013. Proterochampsia: an endemic archosauriform clade from South America. In: Nesbitt SJ, Desojo JB, Irmis RB, eds. Anatomy, phylogeny and palaeobiology of early archosaurs and their kin, Vol. 379. London: Geological Society, Special Publication, 59 - 90.","Sill WD. 1967. Proterochampsa barrionuevoi and the early evolution of the Crocodilia. Bulletin of the Museum of Comparative Zoology, Harvard University 135: 415 - 446.","Bonaparte JF. 1971. Cerritosaurus binsfeldi Price, tipo de una nueva familia de tecodontes (Pseudosuchia: Proterochampsia). Anais da Academia Brasileira de Ciencias 43: 417 - 422.","Kischlat EE. 2000. Tecodoncios: a aurora dos arcossaurios no Triassico, 273 - 316. In: Holtz M, De Ros LF, eds. Paleontologia do Rio Grande do Sul. Porto Alegre: CIGO ⁄ UFRGS, 398.","Romer AS. 1971. The Chanares (Argentina) Triassic reptile fauna. XI: two new long-snouted thecodonts, Chanaresuchus and Gualosuchus. Breviora 379: 1 - 22.","Trotteyn MJ, Martinez RN, Alcober OA. 2012. A new proterochampsid Chanaresuchus ischigualastensis (Diapsida, Archosauriformes) in the Early Late Triassic Ischigualasto Formation, Argentina. Journal of Vertebrate Paleontology 32: 485 - 489.","Trotteyn MJ, Ezcurra MD. 2020. Redescription of the holotype of Chanaresuchus bonapartei Romer, 1971 (Archosauriformes: Proterochampsidae) from the Upper Triassic rocks of the Chanares Formation of north-western Argentina. Journal of Systematic Palaeontology 18 (17): 1415 - 1443. doi: 10.1080 / 14772019.2020.1768167","Wynd BM, Nesbitt SJ, Stocker MR, Heckert AB. 2020. A detailed description of Rugarhynchos sixmilensis, gen. et comb. nov. (Archosauriformes, Proterochampsia) and cranial convergence in snout elongation across stem and crown archosaurs. Journal of Vertebrate Palaeontology 39: e 1748042.","Trotteyn MJ, Ezcurra MD. 2014. Osteology of Pseudochampsa ischigualastensis gen. et comb. nov. (Archosauriformes: Proterochampsidae) from the early Late Triassic Ischigualasto Formation of northwestern Argentina. PLoS One 9: e 111388.","Ezcurra MD. 2016. The phylogenetic relationships of basal archosauromorphs, with an emphasis on the systematics of proterosuchian archosauriforms. PeerJ 4: e 1778.","Butler RJ, Ezcurra MD, Liu J, Sookias RB, Sullivan C. 2019. The anatomy and phylogenetic position of the erythrosuchid archosauriform Guchengosuchus shiguaiensis from the earliest Middle Triassic of China. PeerJ 7: e 6435."]}

Dataset taken from Baron et al. (2017) with properly ordered characters.

O Período Triássico testemunhou um dos principais eventos na história da vida em nosso planeta, com o surgimento de Dinosauria, que viriam a dominar os ecossistemas do Mesozoico por mais de 150 milhões de anos. Embora o registro fossilífero de dinossauros mesozoicos seja abundante de maneira geral, os primeiros momentos de sua evolução ainda são pobremente amostrados. Os mais antigos registros inequívocos para o grupo provêm de estratos gonduânicos, sobretudo de localidades sul-americanas. Nesse sentido, fósseis provenientes das camadas da base da Sequência Candelária (sul do Brasil) e da Formação Ischigualasto (noroeste da Argentina) têm um papel fundamental no estudo das origens de Dinosauria. Essas camadas situam-se cronologicamente em meados do Carniano (com o datum mais antigo correspondendo a 231,4 Ma), e historicamente têm brindado dezenas de fósseis atribuíveis ao grupo. Com base na paleofauna dessas duas unidades se reconhece, por exemplo, que dinossauros já eram um grupo relativamente diverso durante o Carniano (apesar de esse ser o registro mais antigo do grupo), e pelo menos onze táxons são formalmente aceitos. De maneira geral, contudo, essas formas são bastante similares entre si anatomicamente, e não se reconhece uma grande disparidade morfológica, como a que se estabeleceria a partir do Jurássico. Ainda que o registro destes primeiros dinossauros esteja em crescente expansão, dado o aumento no esforço de coleta, a maioria dos táxons ainda é representada por espécimes fragmentários, o que limita o conhecimento de sua anatomia. A lacuna gerada por essa falta de dados, além de desestabilizar propostas filogenéticas, dificulta o reconhecimento de padrões evolutivos, como a ordem de aquisição de características ao longo de linhagens específicas de Dinosauria. Esta tese se justifica a partir dessa necessidade de aporte de dados, e tem como objetivo relatar novas descobertas realizadas pela equipe do Laboratório de Paleontologia de Vertebrados da UFRGS, em parceria com outras instituições. Entre os resultados diretos deste estudo, foi possível reconhecer um novo táxon referido a Sauropodomorpha, proveniente da base da Sequência Candelária, além de outros registros importantes. Em conjunto, os dados corroboram a ideia de que sauropodomorfos foram a linhagem mais diversa de Dinosauria durante o Carniano. Ainda, sugere-se que, num primeiro estágio da evolução do grupo, as principais modificações anatômicas se concentraram na região do crânio e da dentição e é possível que algumas dessas características tivessem relação com o aprimoramento da herbivoria no grupo. As mudanças mais drásticas no esqueleto pós-craniano só ocorreriam a partir do Noriano, e provavelmente estariam em grande parte relacionadas ao significativo aumento no tamanho corporal apresentado pelos sauropodomorfos da época. Essa tendência, de fato, se seguiria durante o restante do Mesozoico. The Triassic period witnessed one of the major evolutionary events in life history, with the origins of Dinosauria, a group that would dominate Mesozoic ecosystems for more than 150 million years. Although the fossil record of Mesozoic dinosaurs is generally abundant, the earliest moments of their evolution are still poorly sampled. The oldest unequivocal records for the group come from Gondwanic strata, mostly from South American localities. In that sense, fossils collected from the base of the Candelária Sequence (southern Brazil) and from the Ischigualasto Formation (northwestern Argentina) are fundamental to understand the origins of Dinosauria. These units are chronologically situated in the mid-Carnian (with the oldest datum corresponding to 231.4 My), and historically yielded a large sample of fossils attributable to the group. Based on the paleofauna of these two units it is possible to recognize, for example, that Dinosauria were already a relatively diverse group during Carnian times (even though this represents the oldest record for the group), with at least eleven taxa formally accepted. In general, however, those forms are much similar among each other, anatomically speaking, and it is not possible to recognize a great morphological disparity, as would occur starting from the Jurassic. Despite the significant expansion in the known record of early dinosaurs, resultant of an increase in collection efforts, most taxa are still represented by fragmentary specimens, limiting the knowledge of their anatomy. The anatomical gap left by this lack of data not only makes phylogenetic assumptions unstable, but also hampers the recognition of evolutionary patterns, such as the order of character acquisition along specific lineages of Dinosauria. This thesis is justified by the necessity of reporting new data, and has as one of its objectives to communicate new discoveries made by the team of the Laboratory of Vertebrate Paleontology at Universidade Federal do Rio Grande do Sul (UFRGS), in partnership with other institutions. Among the direct results achieved by this study, it was possible to recognize a new taxon referred to Sauropodomorpha, collected from the base of the Candelária Sequence, among other important records. As a whole, the new data reinforce the idea that sauropodomorphs were the most diverse dinosaur lineage during the Carnian. Additionally, it is suggested that, in a first stage of sauropodomorph evolution, the main anatomical transformations were concentrated in the region of the skull and dentition, and it is possible that these acquired features were related with the establishment of hervivorous habits among members of the group. Drastic changes in the post-cranial anatomy would only occur starting from the Norian, and most of them were probably related to the significant increase in body size shown by sauropodomorphs during that time, and along the entire Mesozoic.