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During the Late Jurassic, important palaeogeographic events occurred in Eurasia, North America and Gondwana. Continental rift, subduction and orogeny produced different levels of marine inundation of terrestrial systems, with rising sea... more
During the Late Jurassic, important palaeogeographic events occurred in Eurasia, North America and Gondwana. Continental rift, subduction and orogeny produced different levels of marine inundation of terrestrial systems, with rising sea level. Shallow epicontinental seaways started to separate North America from Eurasia, Gondwana, and also between segments of Gondwana itself. Tethys, the east-west seaway, expanded and at times covered large parts of the continental interior of Eurasia. The aperture of new seaways such as the Greenland-Norwegian seaway and the Mezen-Pechora strait system in the northern hemisphere; the Hispanic Corridor, between North and South America; and the Trans-Erythrean seaway (or South Africa/Rocas Verdes seaway) in the southern hemisphere allowed for intermittent interchange of invertebrate and marine vertebrate faunas.
During the past five years, the ichthyosaur fossil record has provided a way to describe new species so as to complement diagnoses of species that for a long time had been either synonymised or considered invalid. These taxonomic studies allow us now to understand the paleo-distribution of the ichthyosaurs around the world better as the relationships between the realms of the northern-southern hemisphere and boreal regions. The present report is a generic-level analysis of the dispersal routes of ichthyosaurs during the Late Jurassic compared with one of its top predators, Pliosaurus, and the palaeogeographic significance of high-latitude species such as Arthropterygius spp., Undorosaurs spp., Cryopterygius spp, Janusaurus and non-ubiquitous ichthyosaurs.
During the past five years, the ichthyosaur fossil record has provided a way to describe new species so as to complement diagnoses of species that for a long time had been either synonymised or considered invalid. These taxonomic studies allow us now to understand the paleo-distribution of the ichthyosaurs around the world better as the relationships between the realms of the northern-southern hemisphere and boreal regions. The present report is a generic-level analysis of the dispersal routes of ichthyosaurs during the Late Jurassic compared with one of its top predators, Pliosaurus, and the palaeogeographic significance of high-latitude species such as Arthropterygius spp., Undorosaurs spp., Cryopterygius spp, Janusaurus and non-ubiquitous ichthyosaurs.
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“Rauisuchia” is a non‐monophyletic group of quadrupedal and carnivorous pseudosuchians that inhabited the entire world during the Middle–Upper Triassic period (Anisian/Ladinian–Rhaetian). In South America, “rauisuchians” reached the... more
“Rauisuchia” is a non‐monophyletic group of quadrupedal and carnivorous pseudosuchians that inhabited the entire world during the Middle–Upper Triassic period (Anisian/Ladinian–Rhaetian). In South America, “rauisuchians” reached the largest sizes among continental carnivores. Despite their important ecological role, some aspects of their palaeobiology have been poorly examined. Here, we study appendicular bones, dorsal ribs and osteoderms of two genera, the Argentinean Fasolasuchus tenax (PVL 3850, holotype) and the Brazilian Prestosuchus chiniquensis (SNSB‐BSPG AS XXV) respectively. The femur of F. tenax is formed by laminar fibrolamellar bone, which is composed of non‐fully monorefringent woven‐fibred matrix and primary osteons; the dorsal rib has a Haversian bone composition with an external fundamental system recorded and the osteoderm is formed by well‐organised parallel‐fibred bone. The femur, humerus and fibula of P. chiniquensis are mostly composed of strongly arranged parallel‐fibred bone and a laminar vascularisation. The minimal ages obtained correspond to 9 years for F. tenax (based on the maximum number of growth marks in the osteoderm) and 4 years for P. chiniquensis (obtained from the highest count of growth marks in the femur and in the humerus). F. tenax attained somatic and skeletal maturity, while P. chiniquensis was near to reaching skeletal and sexual maturity, but it was somatically immature. The overall rapid growth rate and the high and uniform vascularisation seems to imply that these features are common in most of “rauisuchians”, except in P. chiniquensis.
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Category affiliation of the sampled extinct testudinatans.
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... De esta manera se realizó un análisis del potencial cinético en diversos representantes de arcosauriformes actuales (eg, Alligator mississippienssis Daudin, Caiman latirostris Daudin y Caiman yacare Daudin) y fósiles (Proterochampsa... more
... De esta manera se realizó un análisis del potencial cinético en diversos representantes de arcosauriformes actuales (eg, Alligator mississippienssis Daudin, Caiman latirostris Daudin y Caiman yacare Daudin) y fósiles (Proterochampsa barrionuevoi Reig, Saurosuchus galilei ...
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ABSTRACT
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Simposio III: Ecosistemas triasicos, su paleobiologia y el contexto de recuperacion de la gran extincion
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Binarized cross sections of the sampled specimens
Background: Dakosaurus and Plesiosuchus are characteristic genera of aquatic, large-bodied, macrophagous metriorhynchid crocodylomorphs. Recent studies show that these genera were apex predators in marine ecosystems during the latter part... more
Background: Dakosaurus and Plesiosuchus are characteristic genera of aquatic, large-bodied, macrophagous metriorhynchid crocodylomorphs. Recent studies show that these genera were apex predators in marine ecosystems during the latter part of the Late Jurassic, with robust skulls and strong bite forces optimized for feeding on large prey. Methodology/Principal Findings: Here we present comprehensive osteological descriptions and systematic revisions of the type species of both genera, and in doing so we resurrect the genus Plesiosuchus for the species Dakosaurus manselii. Both species are diagnosed with numerous autapomorphies. Dakosaurus maximus has premaxillary ‘lateral plates’; strongly ornamented maxillae; macroziphodont dentition; tightly fitting tooth-to-tooth occlusion; and extensive macrowear on the mesial and distal margins. Plesiosuchus manselii is distinct in having: non-amblygnathous rostrum; long mandibular
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Gracilisuchus stipanicicorum Romer, 1972 is a basal suchian from the Late Triassic Chañares Formation (Argentina), nested in the recently erected Gracilisuchidae, along with Turfanosuchus dabanensis Young, 1973 and Yonghesuchus... more
Gracilisuchus stipanicicorum Romer, 1972 is a basal suchian from the Late Triassic Chañares Formation (Argentina), nested in the recently erected Gracilisuchidae, along with Turfanosuchus dabanensis Young, 1973 and Yonghesuchus sangbiensis Wu et al., 2001 from China. The six known specimens of Gracilisuchus Romer, 1972 preserve most of the skeleton, lacking only most of the shoulder girdle and forelimb. Our latest fieldwork has recovered two specimens that preserve previously unknown elements, including the humerus, radius, and ulna, as well as the femur, presacral vertebrae, and paramedian osteoderms. The femur and osteoderms were histologically sectioned, which has never been done for Gracilisuchidae. The anatomical analysis revealed characters in the new elements that improve our understanding of the anatomy of Gracilisuchus. Bone histology revealed that the specimen CRILAR PV 490 died before reaching somatic maturity and that growth was relatively slow compared to other pseudosu...
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Figure 13. Paramedian osteoderms of Archeopelta. A, articulated left row and right row in B, dorsal and F, lateral views. Both rows in E, anterior and G, ventral views. C–D, close up of the first osteoderm of the left row in dorsal view.... more
Figure 13. Paramedian osteoderms of Archeopelta. A, articulated left row and right row in B, dorsal and F, lateral views. Both rows in E, anterior and G, ventral views. C–D, close up of the first osteoderm of the left row in dorsal view. Abbreviations: aaf, anterior articular facet; ns, neural spine; p, pit; se, collateral serrations. Scale bar = 2 cm.
Figure 9. First primordial sacral vertebra of Archeopelta in A, anterior; B, dorsal; and C, posterior views; and second primordial sacral in D, dorsal view. Abbreviations: hyp, hyposphene; nc, neural canal; ns, neural spine; os,... more
Figure 9. First primordial sacral vertebra of Archeopelta in A, anterior; B, dorsal; and C, posterior views; and second primordial sacral in D, dorsal view. Abbreviations: hyp, hyposphene; nc, neural canal; ns, neural spine; os, osteoderm; poz, postzygapophysis; prz, prezygapophysis; sr, sacral rib; tp, transverse process; vc, vertebral centrum. Scale bar = 2 cm.
FIGURE 17. Right pedal phalanx IV-1 of Aetobarbakinoides brasiliensis in medial (A), lateral (B), dorsal (C), ventral (D), proximal (E), and distal (F) views. Abbreviations: clf, collateral fossa; pdl, proximodorsal lip; pvl,... more
FIGURE 17. Right pedal phalanx IV-1 of Aetobarbakinoides brasiliensis in medial (A), lateral (B), dorsal (C), ventral (D), proximal (E), and distal (F) views. Abbreviations: clf, collateral fossa; pdl, proximodorsal lip; pvl, proximoventral lip. Scale bar equals 1 cm.
FIGURE 16. Right pes of Aetobarbakinoides brasiliensis in proximal (A), dorsal (B), ventral (C), lateral (D), medial (E), and distal (F) views. Abbreviations: I-V, metatarsal I-V; clf, collateral fossa. Scale bar equals 2 cm.
FIGURE 15. Right distal tarsal IV of Aetobarbakinoides brasiliensis in dorsal (A), ventral (B), lateral (C), medial (D), proximal (E), and distal (F) views. Scale bar equals 1 cm.
FIGURE 14. Right pes of Aetobarbakinoides brasiliensis in dorsal view. Abbreviations: IV-1, first pedal phalanx of the fourth digit; dtIV, disal tarsal IV; mttI-V, metatarsal I-V. Scale bar equals 2 cm.
FIGURE 12. Right humerus of Aetobarbakinoides brasiliensis in ventral (A), dorsal (B), lateral (C), medial (D), proximal (E), and distal (F) views. Abbreviations: dpc, deltopectoral crest; dr, dorsal ridge; dt, dorsal tuberosity; enc,... more
FIGURE 12. Right humerus of Aetobarbakinoides brasiliensis in ventral (A), dorsal (B), lateral (C), medial (D), proximal (E), and distal (F) views. Abbreviations: dpc, deltopectoral crest; dr, dorsal ridge; dt, dorsal tuberosity; enc, entepicondyle; gt, greater trochanter; lg, lateral groove; lvt, lateroventral tuberosity; mg, median ventral groove. Scale bar equals 2 cm.
FIGURE 5. Last cervical and three first dorsal vertebrae of Aetobarbakinoides brasiliensis in left lateral (A), ventral (B), right lateral (C), and posterior (D) views; and last cervical rib of Aetobarbakinoides brasiliensis in posterior... more
FIGURE 5. Last cervical and three first dorsal vertebrae of Aetobarbakinoides brasiliensis in left lateral (A), ventral (B), right lateral (C), and posterior (D) views; and last cervical rib of Aetobarbakinoides brasiliensis in posterior view (E). Abbreviations: cn, centrum; cp, capitulum; dp, diapophysis; hy, hyposphene; os, osteoderms; poz, postzygapophysis; pp, parapophysis; tb, tuberculum. Scale bar equals 2 cm.
In the present contribution we revise, figure, and redescribe several isolated braincases of the iconic aetosaur Desmatosuchus from the Placerias Quarry locality, Chinle Formation, Arizona, United States. The detailed study of the... more
In the present contribution we revise, figure, and redescribe several isolated braincases of the iconic aetosaur Desmatosuchus from the Placerias Quarry locality, Chinle Formation, Arizona, United States. The detailed study of the isolated braincases from the UCMP collection allowed us to assign them at the species‐level and recognize two species of Desmatosuchus for the Placerias Quarry: D. spurensis and D. smalli. The former can be distinguished from the latter by the presence of a transverse sulcus on the parietals, deep median pharyngeal recess on the basisphenoid, almost no gap between the basal tubera and the basipterygoid processes, and the exoccipitals meeting at the midline. The presence of D. smalli at the Placerias Quarry has not been previously reported. Based on the braincases UCMP 27408, 27410, 27407, three new brain endocasts were developed through CT scan images, reconstructing the most complete endocranial casts known for an aetosaur, including the encephalon, crani...
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We report 27 cases of delayed-onset dystonia in patients with antecendents of perinatal asphyxia after excluding other possible causes of dystonia. The patients were 16 males and 11 females (mean +/- SD age at onset of dystonia = 13.0 +/-... more
We report 27 cases of delayed-onset dystonia in patients with antecendents of perinatal asphyxia after excluding other possible causes of dystonia. The patients were 16 males and 11 females (mean +/- SD age at onset of dystonia = 13.0 +/- 9.4 yr). Adverse obstetric and/or perinatal events were presented by 20 patients, and other neurological symptoms or signs were present prior to dystonia in 15 patients. The pattern of dystonia was: generalized (eight cases), segmental (six), multifocal (three), hemidystonia (two), and focal (eight). Cranial CT or MRI were normal in 21 cases, and showed brain hemiatrophy in three cases, and periventricular demyelination, subcortical atrophy and increased ventricular size in one case each. The possible cause-effect relationship is discussed.
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Protocol of the data acquisition
The lower jaw of early tetrapods is composed of several intramembranous ossifications. However, a tendency toward the independent reduction of the number of bones has been observed in the mandible of mammals, lepidosaurs, turtles,... more
The lower jaw of early tetrapods is composed of several intramembranous ossifications. However, a tendency toward the independent reduction of the number of bones has been observed in the mandible of mammals, lepidosaurs, turtles, crocodiles, and birds. Regarding archosaurs, the coronoid and prearticular bones are interpreted to be lost during the evolution of stem-birds and stem-crocodiles, respectively, but the homology of the post-dentary bones retained in living pseudosuchians remains unclear. Here, we combine paleontological and embryological evidence to explore in detail the homology of the crocodylian post-dentary bones. We study the mandible embryogenesis on a sample of 71 embryos of Caiman and compare this pattern with the mandibular transformations observed across pseudosuchian evolution. In the pre-hatching ontogeny of caimans, at least five intramembranous ossification centers are formed along the margins of the internal mandibular fenestra (perifenestral centers) and, subsequently, merge to form the coronoid (three intramembranous centers), angular (one intramembranous center), and articular (one intramembranous and one chondral center). In the fossil record, an independent prearticular is lost around the base of Mesoeucrocodylia (optimized as reappearing in Thalattosuchia if they are placed within Neosuchia), and the coronoid is apomorphically lost in notosuchians. The integration of embryological and paleontological data indicates that most perifenestral centers are involved in the origin of the prearticular of non-mesoeucrocodylian pseudosuchians. These centers are rearranged during the evolution to contribute to different post-dentary bones in mesoeucrocodylians bolstering the idea that the coronoid and the articular of Crocodylia are not completely homologous to those of other diapsids.
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El presente catálogo lista los materiales de mamíferos marinos depositados en la colección de Mastozoología del Museo de La Plata. Esta contribución es una actualización del catálogo inédito realizado por R. Bastida, J.B. Desojo y L.H.... more
El presente catálogo lista los materiales de mamíferos marinos depositados en la colección de Mastozoología del Museo de La Plata. Esta contribución es una actualización del catálogo inédito realizado por R. Bastida, J.B. Desojo y L.H. Soibelzon en 1997. Se incluyen todos los materiales del superorden Cetartilodactyla, orden Cetacea, subórdenes Mysticeti y Odontoceti, orden Carnivora, suborden Caniformia y orden Sirenia. La colección de Mastozoología de la División Zoología Vertebrados del Museo de La Plata cuenta con 185 especímenes referidos a 37 especies de mamíferos marinos.
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Aetosauria is a clade of obligately quadrupedal, heavily armoured pseudosuchians known from Upper Triassic (late Carnian–Rhaetian) strata on every modern continent except Australia and Antarctica. As many as 22 genera and 26 species... more
Aetosauria is a clade of obligately quadrupedal, heavily armoured pseudosuchians known from Upper Triassic (late Carnian–Rhaetian) strata on every modern continent except Australia and Antarctica. As many as 22 genera and 26 species ranging from 1 to 6 m in length, and with a body mass ranging from less than 10 to more than 500 kg, are known. Aetosauroides scagliai was recently recovered as the most basal aetosaur, placed outside of Stagonolepididae (the last common ancestor of Desmatosuchus and Aetosaurus). Interrelationships among the basal aetosaurs are not well understood but two clades with relatively apomorphic armour – the spinose Desmatosuchinae and the generally wide-bodied Typothoracisinae – are consistently recognized. Paramedian and lateral osteoderms are often distinctive at the generic level but variation within the carapace is not well understood in many taxa, warranting caution in assigning isolated osteoderms to specific taxa. The aetosaur skull and dentition varies...
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FIGURE 11. Right scapula of Aetobarbakinoides brasiliensis in lateral (A), medial (B), anterior (C), posterior (D), distal (E), and proximal (F) views. Abbreviations: afc, articular facet for coracoid; ap, acromial process; gf, glenoid... more
FIGURE 11. Right scapula of Aetobarbakinoides brasiliensis in lateral (A), medial (B), anterior (C), posterior (D), distal (E), and proximal (F) views. Abbreviations: afc, articular facet for coracoid; ap, acromial process; gf, glenoid fossa; sad, sub-acromial depression; sat, sub-acromial tuberosity; sb, scapular blade; sgl, supraglenoid lip. Scale bar equals 2 cm.
FIGURE 7. Dorsal vertebra 8 of Aetobarbakinoides brasiliensis in left lateral (A), anterior (B), ventral (C), and posterior (D) views. Abbreviations: dp, diapophysis; dr, dorsal rib; hy, hyposphene; os, osteoderm; poz, postzygapophysis;... more
FIGURE 7. Dorsal vertebra 8 of Aetobarbakinoides brasiliensis in left lateral (A), anterior (B), ventral (C), and posterior (D) views. Abbreviations: dp, diapophysis; dr, dorsal rib; hy, hyposphene; os, osteoderm; poz, postzygapophysis; prf, prespinal fossa; prz, prezygapophysis; psf, postspinal fossa. Scale bar equals 2 cm.
FIGURE 3. Middle cervical vertebra (C5–6) of Aetobarbakinoides brasiliensis in anterior (A), posterior (B), right lateral (C), dorsal (D), left lateral (E), and ventral (F) views. Abbreviations: cr, cervical rib; dp, diapophysis; hy,... more
FIGURE 3. Middle cervical vertebra (C5–6) of Aetobarbakinoides brasiliensis in anterior (A), posterior (B), right lateral (C), dorsal (D), left lateral (E), and ventral (F) views. Abbreviations: cr, cervical rib; dp, diapophysis; hy, hyposphene; leprz, laterally extended prezygapophysis; nc, neural canal; ns, neural spine; poz, postzygapophysis; pp, parapophysis; prz, prezygapophysis; psf, post-spinal fossa. Scale bar equals 1 cm.
FIGURE 2. Chronostratigraphical column of the Santa Maria Supersequence showing the Aetobarbakinoides-bearing level. Modified from Zerfass et al. (2003) and Desojo et al. (2011). The ages indicated with an asterisk within the Carnian and... more
FIGURE 2. Chronostratigraphical column of the Santa Maria Supersequence showing the Aetobarbakinoides-bearing level. Modified from Zerfass et al. (2003) and Desojo et al. (2011). The ages indicated with an asterisk within the Carnian and Norian stages are the radioisotopic datings of the Ischigualasto Formation reported by Rogers et al. (1993: close to the base of the unit; dating re-calculated by Furin et al. [2006]) and Martinez et al. (2011: close to the top of the unit). Norian-Rhaetian and Triassic-Jurassic boundaries after Muttoni et al. (2010).
The postcranial skeleton of Neoaetosauroides (Archosauria: Aetosauria) from the Upper Triassic of west-central Argentina . The postcranial skeleton of the aetosaur Neoaetosauroides Bonaparte, based on previously studied specimens and... more
The postcranial skeleton of Neoaetosauroides (Archosauria: Aetosauria) from the Upper Triassic of west-central Argentina . The postcranial skeleton of the aetosaur Neoaetosauroides Bonaparte, based on previously studied specimens and additional material, is described herein. The new material consists of proatlas, cervical vertebrae, and appendicular dermal scutes collected in the Los Colorados Formation, Ischigualasto-Villa Unión Basin. All these materials are compared with those of other aetosaur taxa and functionally significant characters of the pelvic girdle and hindlimbs are in particular discussed. This study reveals a great anatomical diversity (e.g. , differences in degree of pelvic expansion, femoral flexure, and crural and tarsal morphology) and suggests that Aetosauria might have included semi-erect and erect forms. This possible spectrum of locomotor postures, together with their wide size range, support previous propositions of more varied lifestyles among aetosaurs tha...
Abstract. Aetosaurs are quadrupedal archosaurs that had a worldwide distribution during the Late Triassic. They had small heads relative to their body size and a long tail, and they are characterized by a dorsal and ventral carapace... more
Abstract. Aetosaurs are quadrupedal archosaurs that had a worldwide distribution during the Late Triassic. They had small heads relative to their body size and a long tail, and they are characterized by a dorsal and ventral carapace formed by ornamented and articulated osteoderms. Although aetosaurs historically have been considered the only herbivorous among the early pseudosuchian archosaurs, few analyses quantitatively assess their feeding habits, and some authors have proposed omnivorous and/or scavenging habits for the group. Neoaetosauroides engaeus is an aetosaur from the Late Triassic of the Los Colorados Formation, La Rioja, Argentina. N. engaeus is known from three relatively well-preserved skulls, making it an excellent taxon to study the feeding ecology. We applied the Finite Element Method to estimate bite force and to evaluate the structural response of the skull at different positions during food processing. Our results show that the skull of N. engaeus generated a bite force of 3.6 kN, a magnitude comparable with the measurement made in Alligator mississippiensis, and could resist lateral and longitudinal forces during feeding. This indicates that N. engaeus was capable of hunting of small living prey (e.g., cynodonts) with its jaws, and/or dragging carcasses of larger sizes (e.g., dicynodonts). These results bring new evidence that supports possible zoophagy or omnivory for N. engaeus, thus expanding the potential ecological roles of aetosaurs.
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Rhynchosaurs were quadrupedal, bulky herbivorous archosauromorph diapsids with a highly specialized dental apparatus. This group is restricted to the Triassic Period and became extremely abundant worldwide during the late Carnian,... more
Rhynchosaurs were quadrupedal, bulky herbivorous archosauromorph diapsids with a highly specialized dental apparatus. This group is restricted to the Triassic Period and became extremely abundant worldwide during the late Carnian, numerically dominating some of the first dinosaur-bearing assemblages. Despite their high abundance in upper Carnian beds of South America, rhynchosaurs are restricted to a handful of specimens in the latest Ladinian–early Carnian tetrapod assemblages of this continent. Here, we improve the record of one of the oldest rhynchosaur assemblages of South America with the detailed description of all the rhynchosaur specimens currently known from the Tarjadia Assemblage Zone (AZ) (late Ladinian–?earliest Carnian) of the Chañares Formation (Ischigualasto-Villa Unión Basin, La Rioja Province). Most of these specimens were only preliminarily reported before, and as part of this revision we name the new taxon Elorhynchus carrolli gen. et sp. nov. based on one of these specimens, which represents the first new taxon for the Chañares Formation in 22 years. Elorhynchus carrolli and three more rhynchosaur specimens from the Chañares Formation are identified as stenaulorhynchine rhynchosaurs based on the presence of a crowded field of numerous lingual teeth in the dentary and the presence of small occlusal teeth in the maxillary tooth plate. Although their morphology is congruent, we did not refer the other stenaulorhynchine specimens to Elorhynchus carrolli because they lack diagnostic overlapping character states between them. Nevertheless, there is no current evidence for the presence of more than one rhynchosaur species in the Chañares Formation. The description of Elorhynchus carrolli and the other stenaulorhynchines from the Chañares Formation reinforces biostratigraphical links with the Dinodontosaurus AZ (Santa Maria Supersequence) of southern Brazil and the Lifua Member of the Manda Beds of Tanzania. http://zoobank.org/urn:lsid:zoobank.org:pub:E2662419-8AD5-4C1E-9900-BD1380BE65A4
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Prestosuchus chiniquensis is the most famous "rauisuchian" described by Friedrich von Huene, eight decades ago, and several specimens have been assigned to this taxon since then. In the present contribution, we provide the first... more
Prestosuchus chiniquensis is the most famous "rauisuchian" described by Friedrich von Huene, eight decades ago, and several specimens have been assigned to this taxon since then. In the present contribution, we provide the first detailed description of a complete and very well preserved skull (including the braincase) assigned to Prestosuchus chiniquensis from the Dinodontosaurus Assemblage Zone of the Santa Maria Supersequence of southern Brazil. The detailed description of the skull of Prestosuchus chiniquensis, besides increasing the knowledge about this taxon, may help elucidate the taxonomic relationships of pseudosuchians even further, since most of the characters used in phylogenetic analyzes are cranial. The presence of the subnarial fenestra, a controvertial extra opening on the skull of "rauisuchians", is thoroughly discussed considering the evidence provided by this new specimen. We consider that the small slit-opening between the premaxilla and the ma...