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Representative skeletal elements of ornithosuchid archosaur Dynamosuchus collisensis gen. et sp. nov. (CAPPA/UFSM 0248) from Janner outcrop, Carnian, Late Triassic. A. Selected skull bones in left lateral view. B. Reconstruction of the skull. C. Skull in ventral view. D. Left quadrate and quadratojugal in posterodorsal view. E. Parabasisphenoid in left lateral view. F. Neural arch of an anterior cervical vertebra in anterior view. G. Centrum of a cervical vertebra in left lateral view. H. Right osteoderm in dorsal view. I. Neural arch of an anterior dorsal vertebra in left lateral view. J. Left ilium in lateral view. L. Right humerus in anterior view. M. Right forearm in medial view. N. Left manus in dorsal view. O. Right (reversed) pubis in lateral view. P. Left femur in anterior view. Q. Left fibula in lateral view. Some unpreserved portions are modified from Baczko et al. in press, for the reconstruction of the skeleton of CAPPA/UFSM 0248 (preserved elements indicated in orange) (K). Scale bars 20 mm.
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Ornithosuchidae is one of the most enigmatic clades of Triassic pseudosuchians. The group is composed by three carnivorous species that were excavated from Upper Triassic beds of Scotland and Argentina. We describe the first ornithosuchid from the Upper Triassic sediments of Brazil and explore its phylogenetic affinities and implications for the ev...
Citations
... The inclusion of Parvosuchus aurelioi in the phylogenetic analysis did not affect the placement of Gracilisuchidae within the phylogenetic tree of Pseudosuchia, reinforcing the hypothesis that gracilisuchids are an early diverging clade of suchians. This same arrangement has been recovered in previous iterations of the present data matrix 2,4,16,18,27 , including through Bayesian phylogenetic analysis 2,4 . The present analysis also corroborates that gracilisuchids are more closely related to paracrocodylomorphs than to Ornithosuchidae, Erpetosuchidae, or Aetosauriforms. ...
... The clade is represented by Archeopelta arborensis 45 , Pagosvenator candelariensis 41 , Schultzsuchus loricarus 34 , Prestosuchus chiniquensis 6,7 , and Decuriasuchus quartacolonia 33 . Archeopelta arborensis and Pagosvenator candelariensis were carnivorous members of Erpetosuchidae 18,27,41 , both reached more than 2 m in length. Schultzsuchus loricarus was a large carnivorous from the clade Poposauroidea 34 . ...
Before the rise of dinosaurs and pterosaurs, pseudosuchians—reptiles from the crocodilian lineage—dominated the Triassic land ecosystems. This lineage diversified into several less inclusive clades, resulting in a wide ecomorphological diversity during the Middle and Late Triassic. Some giant pseudosuchians occupied the top of the trophic webs, while others developed extensive bony armor as a defense mechanism, which later evolved as a convergence in the avemetatarsalian lineage. On the other hand, there were groups like the Gracilisuchidae, which was composed of carnivorous forms with lightweight build and less than 1 m in length. The fossil record of gracilisuchids is geographically restricted to China and Argentina, with one ambiguous record from Brazil. In the present study, the first unambiguous gracilisuchid from Brazil is described. Parvosuchus aurelioi gen. et sp. nov. comes from the Dinodontosaurus Assemblage Zone of the Santa Maria Formation, which is associated with the Ladinian-Carnian boundary. Composed of a complete cranium, vertebrae, pelvic girdle and hindlimbs, the new species nests with Gracilisuchus stipanicicorum and Maehary bonapartei in a phylogenetic analysis. Its discovery fills a taxonomic gap in Brazilian pseudosuchian fauna and reveals the smallest known member of this clade from the Dinodontosaurus Assemblage Zone, highlighting the diversity of pseudosuchians during the moment that preceded the dawn of dinosaurs.
... F is the total pressure force of the jaws, F' is the force compressing a held prey item, F '' is the force pushing a prey item out of the mouth (Yudin, 1970 with additions). (Müller et al., 2020); (c) Venaticosuchus rusconii (Baczko, 2018); (d) Ornithosuchus longidens (Walker, 1964). ...
... The crowns of the teeth are extremely high, serrated, strongly compressed laterally, and short in the anteroposterior direction, weakly widening towards the base and only slightly bent backward (Fig. 8). The edge of the enamel on the crowns of the teeth in ornithosuchids originates near the edge of the alveoli (Walker, 1964;Bonaparte, 1971;Baczko and Ezcurra, 2013;Baczko et al., 2014;Baczko and Desojo, 2016;Müller et al., 2020). The postcranial skeleton of ornithosuchids is very strong and massive for these relatively small thecodonts; in particular, this concerns limb bones. ...
... The joint with this structure is encountered only in this family. The caudal orientation of the calcaneal tuber also indicates a parasagittal or close-to-parasagittal posture of their limbs (Newton, 1894;Walker, 1964;Bonaparte, 1971Bonaparte, , 1975Baczko and Ezcurra, 2013;Baczko and Desojo, 2016;Baczko et al., 2019;Müller et al., 2020). ...
... Euparkeria capensis served as the F I G U R E 1 Location and geological context of the Pivetta site (Restinga Sêca, Rio Grande do Sul, Brazil). Surface distribution of the geologic units in the area (modified from Müller et al., 2020). Red arrow points to the layer where CAPPA/UFSM 0373 was collected. ...
The Carnian (Upper Triassic) rocks of the Candelária Sequence present a rich record of dinosaurs, including some of the oldest known dinosaurs worldwide. In this contribution we describe the first unequivocal dinosaur from the Pivetta site, located in the Restinga Sêca municipality, Southern Brazil. The specimen CAPPA/UFSM 0373 is an isolated but well-preserved left ilium. A thorough examination of the specimen's anatomy and a phylogenetic analysis provides evidence that CAPPA/UFSM 0373 belongs to the Herrerasauria. We were able to identify several similarities with potential non-herrerasaurid herrerasaurians (e.g., Tawa hallae, "Caseosaurus crosbyensis"), which were previously only known from North American deposits. In contrast, herrerasaurids (e.g., Herrerasaurus ischigualastensis) are almost exclusively known from South America. Our results support the nesting of CAPPA/UFSM 0373 as an early-diverging herrerasaurian. Furthermore, this is potentially the first record of a non-herrerasaurid herrerasaurian in unambiguous Carnian beds, suggesting a hidden diversity of dinosaurs in the Carnian rocks of the Candelária Sequence, which can be revealed even by fragmentary specimens.
... Posteriorly, Bonaparte (1997) presumed a carnivorous diet for R. tenuisceps based on its dental morphology and snout specialized for sectioning its prey. More recently, Baczko (2018), followed by Müller et al. (2020), proposed once again a scavenger habit for ornithosuchids, in these cases for V. rusconii (from the Ischigualasto Formation, Argentina) and D. collisensis (from the Santa Maria Formation, Candelária Sequence, Brazil) based on a geometric biomechanical study and on taphonomical observations respectively. ...
... Aun así, la colección PVL sigue teniendo una enorme relevancia para investigaciones del universo paleoherpetológico mesozoico argentino, lo cual se hace evidente en la actividad científica más reciente que sigue produciendo importantes contribuciones a partir de los fósiles representados en sus colecciones (e.g., Desojo et al., 2016Desojo et al., , 2020 Cruzado-Caballero y Powell, 2017;Ezcurra, 2017;von Baczko et al., 2020;Müller et al., 2020;ver Material Suplementario). ...
PALEOHERPETOLOGY IN THE MIGUEL LILLO INSTITUTE OF THE NATIONAL UNIVERSITY OF TUCUMAN, ARGENTINA. The Vertebrate Fossil Laboratory (LVF) of the Miguel Lillo Institute at the National University of Tucuman started in 1957 with the initial drive of Osvaldo Reig, who was its first Director and Curator of the Lillo Vertebrate Paleontology (PVL) collection. José Bonaparte, initially incorporated as technician, was the Director of the LVF from 1960 to 1978, after Reig. These researchers, together with Rodolfo Casamiquela (then at the La Plata Museum), dramatically altered the knowledge of argentinean Mesozoic amphibians and reptiles during the decades of 1960s and 1970s, representing the onset of a new chapter for the argentinean paleontology. During that time, these researchers described 34 new species and collected several fossil specimens from Mesozoic outcrops of different regions of Argentina. This activity enriched the PVL, resulting in a key collection for the study of Triassic paleoherpetology, a relevance that continues today. Jaime Powell took over the LVF after Bonaparte and conducted intensive research, mostly on sauropod dinosaurs from Argentina. Paleoherpetological research was complemented by an important team of technicians and artists who, in addition to fieldwork and fossil preparation, mounted fossil skeletons, made sculptures and life reconstructions of the Mesozoic fauna. Nowadays, the Lillo community has an important and dynamic group of researchers, mostly focused on the study of Cenozoic mammals.
... The alveolar line is slightly concave in lateral view; however, the caudal portion of the dentary lacks a dorsal expansion (= coronoid process). The mandibular symphysis is limited to the rostralmost tip of the dentary, differing from the longer symphysis of ornithosuchids (Nesbitt, 2011;Von Baczko & Ezcurra, 2013;Müller et al., 2020). Caudal to the symphysis, there is a wide Meckelian groove, which almost reaches the ventral margin of the element, as in Ixalerpeton polesinensis (Ezcurra et al., 2020). ...
Faxinalipterus minimus was originally described as a purported pterosaur from the Late Triassic (early Norian) Caturrita Formation of southern Brazil. Its holotype comprises fragmentary postcranial elements, whereas a partial maxilla was referred to the species. The assignment of Faxinalipterus minimus to Pterosauria has been questioned by some studies, but the specimen has never been accessed in detail after its original description. Here we provide a reassessment of Faxinalipterus minimus after additional mechanical preparation of the holotype. Our interpretations on the identity of several bones differ from those of the original description, and we found no support favoring pterosaur affinities for the taxon. The maxilla previously referred to Faxinalipterus minimus is disassociated from this taxon and referred to a new putative pterosauromorph described here from a partial skull and fragmentary postcranial elements. Maehary bonapartei gen. et sp. nov. comes from the same fossiliferous site that yielded Faxinalipterus minimus, but the lack of overlapping bones hampers comparisons between the two taxa. Our phylogenetic analysis places Faxinalipterus minimus within Lagerpetidae and Maehary bonapartei gen. et sp. nov. as the earliest-diverging member of Pterosauromorpha. Furthermore, the peculiar morphology of the new taxon reveals a new dental morphotype for archosaurs, characterized by conical, unserrated crowns, with a pair of apicobasally oriented grooves. These two enigmatic archosaurs expand our knowledge on the Caturrita Formation fauna and reinforce the importance of its beds on the understanding of Late Triassic ecosystems.
... Location and geological context of the ''Posto" site (Dona Francisca, Rio Grande do Sul, Brazil) and specimen CAPPA/UFSM 0282. A: Surface distribution of the geologic units in the area (modified fromMüller et al., 2020). B: hypothetical reconstruction of the skeleton of CAPPA/UFSM 0282 depicting the preserved femur. ...
Whereas the oldest dinosaur skeletons have been excavated from mid to late Carnian beds of South America, its close relatives occur in Anisian to early Carnian deposits from Argentina, Tanzania and Zambia. These close relative forms are key taxa regarding the investigation of macroevolution of dinosauromorphs. Early dinosaurs are well-documented from Carnian strata of Brazil, whereas the Ladinian deposits lack any unambiguous evidence of dinosauromorphs. Here, we present the first dinosauromorph from the Middle Triassic sediments (Pinheiros-Chiniquá Sequence) of Brazil. The new specimen is a right femur and is from the Dinodontosaurus Assemblage Zone (AZ). This AZ is usually correlated with the Tarjadia AZ from Argentina, which is ascribed to the Ladinian-Carnian boundary and currently lacks any evidence of dinosauromorphs. Therefore, the new specimen is potentially the oldest dinosauromorph from South America, narrowing the biogeographical gap between Africa and Argentina during the early radiation of dinosauromorphs. In addition, the new specimen establishes that dinosauromorphs lived in South America earlier than previously expected, extending the record into the Ladinian.
... Regarding cynodonts, the most abundant taxon is the traversodontid Exaeretodon riograndensis (Oliveira et al., 2007;Liparini et al., 2013;Müller et al., 2020a), whereas specimens of the ecteniniid Trucidocynodon riograndensis were rare (Oliveira et al., 2010;Stefanello et al., 2018). On the other hand, archosauromorphs are represented by dinosaurs (e.g., Pampadromaeus barberenai and Bagualosaurus agudoensis; Cabreira et al., 2011;Pretto et al., 2018), as well as the ornithosuchid Dynamosuchus collisensis (Müller et al., 2020b). Furthermore, rhynchosaur remains attributed to Hyperodapedon sp. were collected (Langer et al., 2007a), however, with the discovery of the taxon Teyumbaita sulcognathus (Montefeltro et al., 2010) occurring in stratigraphic levels above Hyperodapedon in several sites from both Brazil and Argentina (Desojo et al., 2020), the assignment of these remains to Hyperodapedon should be considered carefully until they are properly reviewed. ...
Whereas sauropod dinosaurs from the Jurassic and Cretaceous Periods were the largest land animals that ever lived, some of their early relatives evolved relatively large bodies during the Triassic Period. The evolutionary pathways followed by the earliest sauropodomorphs towards the acquisition of massive bodies are poorly understood. However, new finds from South America and Africa are reshaping our knowledge of this issue. Here, we describe a new early and relatively large sauropodomorph represented by a partial postcranial skeleton excavated from Carnian-aged beds (Upper Triassic) of southern Brazil. The new specimen is recovered as a sauropodomorph more closely related to bagualosaurians
than saturnaliids or other early-diverging forms in two phylogenetic analyses. The new specimen is generically indeterminate but provides important evidence of an early increase in body size in Sauropodomorpha, being significantly larger than that of coeval or older forms (except Bagualosaurus agudoensis). Furthermore, the specimen is about 3.2 times heavier than Buriolestes schultzi, the earliest-branching Sauropodomorph. The slender hind limbs and typical cursorial proportions present in the earliest sauropodomorphs are mostly maintained in the new specimen despite its larger body size.
... Despite this excellent fossil record, the relationships of early-diverging suchians remain incompletely understood (e.g., Brusatte, Benton, Desojo, & Langer, 2010;Butler et al., 2014;Ezcurra et al., 2017;Gower & Wilkinson, 1996;Nesbitt, 2011;von Baczko & Ezcurra, 2013). Renewed interest in those early-diverging pseudosuchians, along with new discoveries, has greatly improved our understanding of their diversity, disparity, and phylogenetic relationships (e.g., Butler et al., 2014;Butler, Nesbitt, Charig, Gower, & Barrett, 2018;Desojo et al., 2013;Desojo, Von Baczko, & Rauhut, 2020;Ezcurra et al., 2017;Marsh, Smith, Parker, Irmis, & Kligman, 2020;Müller, von Baczko, Desojo, & Nesbitt, 2020;Nesbitt et al., , 2014Nesbitt, Desojo, & Irmis, 2013;Nesbitt, Stocker, et al., 2018;von Baczko, Desojo, & Ponce, 2020;von Baczko & Ezcurra, 2013). The discovery of early-diverging pseudosuchian taxa with a combination of plesiomorphic and apomorphic character states help clarify some of the in-group relationships within Pseudosuchia, but at the same time has also shown homoplasy in certain character states (e.g., Ezcurra et al., 2017;Nesbitt, 2005aNesbitt, , 2005bNesbitt, 2011;Nesbitt & Butler, 2013;Nesbitt, Liu, & Li, 2011;Nesbitt & Norell, 2006;. ...
... That study recovered R. callenderi as the sister taxon to the early-diverging suchian clade Ornithosuchidae. Another broad-scale analysis of archosaur relationships by Nesbitt et al. (2011) recovered R. callenderi in a well-supported position as the sister taxon to aetosaurs, a result supported by more recent studies (e.g., Nesbitt and Butler, 2013;Nesbitt et al., 2014;Nesbitt, Stocker, et al., 2018Butler et al., 2014;Müller et al., 2020). ...
... We tested the phylogenetic position of R. callenderi in the most comprehensive global early-diverging archosaur study to date (Nesbitt, 2011) including modifications by Butler et al. (2014), Nesbitt et al. (2017); Nesbitt, Stocker, et al. (2018), and. This dataset has the broadest sampling of pseudosuchians thus far, but does not have the more complete sampling of taxa and characters associated with ornithosuchids (Müller et al., 2020), erpetosuchids (Lacerda et al., 2018) present in the Ezcurra et al. (2020) dataset, or the larger sampling of paracrocodylomorphs in Desojo et al. (2020) or Nesbitt, Zawiskie, and Dawley (2020); these data will be included elsewhere. Characters 1-412 are from Nesbitt et al. (2011) with some modifications noted below, Character 413 is from Butler et al. (2014), Characters 414-419 are from Nesbitt et al. (2017), 420-434 are from Parker (2016a) modified by , and 435-444 are from . ...
Once known solely from dental material and thought to represent an early ornithischian dinosaur, the early‐diverging pseudosuchian Revueltosaurus callenderi is described from a minimum of 12 skeletons from a monodominant bonebed in the upper part of the Chinle Formation of Arizona. This material includes nearly the entire skeleton and possesses a combination of plesiomorphic and derived character states that help clarify ingroup relationships within Pseudosuchia. A phylogenetic analysis recovers R. callenderi in a clade with Aetosauria and Acaenasuchus geoffreyi that is named Aetosauriformes. Key autapomorphies of R. callenderi include a skull that is longer than the femur, a complete carapace of dermal armor including paramedian and lateral rows, as well as ventral osteoderms, and a tail end sheathed in bone. Histology of the femur and associated osteoderms demonstrate that R. callenderi was slow growing and that the individuals from the bonebed were not young juveniles but had not ceased growing. A review of other material assigned to Revueltosaurus concludes that the genus cannot be adequately diagnosed based on the type materials of the three assigned species and that only R. callenderi can be confidently referred to Revueltosaurus.
... The phylogenetic relationships of Pseudosuchia, the crocodileline of Archosauria, have changed dramatically in recent years (e.g., Brusatte et al., 2010;Nesbitt, 2011;Nesbitt and Butler, 2012;Butler et al., 2014;Ezcurra, 2016;Ezcurra et al., 2017;Nesbitt et al., 2017;Lacerda et al., 2018;Desojo et al., 2020a;Foffa et al., 2020;Marsh et al., 2020;Müller et al., 2020). Aetosauria comprises a group of heavily armored quadrupedal pseudosuchians , that is usually found to be an early diverging suchian clade in phylogenetic studies (e.g., Ezcurra, 2016;Lacerda et al., 2018). ...
... Usually, aetosaurs and these groups are also recovered as more closely related to erpetosuchids than to other pseudosuchians (e.g., Nesbitt et al., 2017;Marsh et al., 2020), mainly through the recognition of important shared braincase features (e.g., a lateral ridge of the exoccipitals). In contrast, some studies retrieved Aetosauria as the sister taxon to a clade formed by erpetosuchids and ornithosuchids (e.g., Ezcurra et al., 2017;Müller et al., 2020). The lack of consistency among these studies, aside from the use of different datasets and investigated taxa, can be partially explained by the fact that we still lack a considerable amount of morphological information, particularly regarding the braincase osteology (e.g., Nesbitt et al., 2017). ...
... While in most recent analyses, erpetosuchids are found to be closer relatives of aetosaurs than of other suchian clades (e.g., Ezcurra et al., 2017;Nesbitt et al., 2017;Marsh et al., 2020), in some studies the proximity between the groups is less clear (e.g., Ezcurra et al., 2017;Lacerda et al., 2018;Foffa et al., 2020;Müller et al., 2020;Desojo et al., 2020a). Instead of aetosaurs, in these studies erpetosuchids are found to be more closely related to ornithosuchids, a group that lacks an exoccipital ridge (von Baczko and Desojo, 2016). ...
The phylogenetic relationships of Pseudosuchia, the crocodile-line of Archosauria, are still poorly resolved, in part, due to the lack of crucial braincase information for several key taxa. Recently, erpetosuchids and ornithosuchids have been recovered as close relatives to Aetosauria, sharing several braincase features. Here we provide the description of the first braincase of the basal aetosaur Aetosauroides based on specimens from the Upper Triassic Candelária Sequence of Brazil. Our study revealed the presence of an exoccipital lateral ridge and a medial ridge on the supraoccipital (both shared with all aetosaurs and erpetosuchids, but absent in ornithosuchids) and an anterolateral exit for the internal carotids (shared with all aetosaurs and ornithosuchids, but not with erpetosuchids). Aetosauroides lacks a medial contact between the exoccipitals (shared with the aetosaurs Desmatosuchus smalli and Tecovasuchus) and possesses a single hypoglossal foramen (contrasting with Stagonolepis robertsoni and Desmatosuchus spurensis). It also differs from the putative Argentinian Aetosauroides (PVSJ 326) by the presence of a ridge connecting the basal tubera medially (contrasting also with all stagonolepidoideans) and by a bulbous and ventrolaterally recurved basipterygoid process (contrasting with Paratypothorax). These features show that the braincase of aetosaurs is suitable for providing further phylogenetic information and may contribute to resolving controversies within Pseudosuchia relationships.
