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In the present contribution, we aim to present the osteology of ‘ULBRA-PVT-281’, which comprises the best-preserved skeleton of Prestosuchus chiniquensis ever found. ULBRA-PVT-281 combines the morp...

A review of the type and referred material of von Huene shows that Prestosuchus is a valid taxon represented by, at least, three different species: the lectotype and para-lectotype of Prestosuchus chiniquensis, an unnamed species from Brazil (UFRGS-PV-0152-T), and the new combination Prestosuchus nyassicus (=Stagonosuchus nyassi-cus). Several more recently referred specimens are also included within the genus Prestosuchus based on the absence of a vertical crest dorsal to the supracetabular rim; dorsal margin of postacetabular part of ilium concave; marked angle between pubic peduncle/obturator plate and ischial shaft; and elongate posteromedial depression on the distal fibula, making it one of the best known rauisuchian taxa. The phylogenetic analysis recovered a monophyletic Prestosuchidae including Saurosuchus galilei, Luperosuchus fractus, Prestosuchus chiniquensis, Prestosuchus nyassicus, and several specimens referred to the genus Prestosuchus. This clade is supported by the presence of a ridge on the ventral process of the squamosal; anteroventral process of the squamosal perforates the lower temporal fenestra; palpebral bones extensively sutured to each other and to the lateral margin of the frontals; robust, knob-shaped attachment for the musculus iliofibularis on the fibula; and anterior portion of nasals elevated above the skull roof. The identification of this natural group evidenced a remarkable diversity and abundance of basal loricatans in the Middle-Late Triassic continental ecosystems of southern Gondwana. Fil: Desojo, Julia Brenda. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Von Baczko, Belen. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Rauhut, Oliver Walter Mischa. Bayerische Staatssammlung für Paläontologie und Geologie; Alemania. Ludwig Maximilians Universitat; Alemania

In this contribution we analyze and discuss the microanatomy and histology of postcranial osteoderms of a number of "rauisuchians" from different localities of South America (Argentina and Brazil). The studied sample includes osteoderms of Fasolasuchus tenax, Prestosuchus chiniquensis, Saurosuchus galilei and an undetermined rauisuchian from Brazil. The bone microanatomy of the osteoderms is variable: whereas some specimens have a rather compact structure, others show a diploe architecture with a central cancellous core bordered by two compact cortices. Both external and basal cortices are mainly composed of poorly vascularized, fine and coarse parallel-fibred bone and networks of interwoven and mineralized fiber bundles. The internal region of the non-remodeled specimens consists of a well- vascularized core in which the intrinsic fibers exhibit important variations (even in the same specimen), ranging from coarse, parallel-fibred to woven-fibred bone tissues. Lines of arrested growth (LAGs) are well recorded in both basal and external cortices. Differences in the bone microstructure (compact vs. diploe) could be related to the age, sex and reproductive status of the sampled individuals. Hence, age estimation based on the count of LAGs in rauisuchian osteoderms appears to be reliable only in the early stages of ontogeny. The bone microstructure suggests that rauisuchian osteoderms were originated through a mechanism that involves both intramembranous and metaplastic ossifications. Fil: Cerda, Ignacio Alejandro. Universidad Nacional de Rio Negro. Sede Alto Valle. Instituto de Investigaciones en Paleobiologia y Geologia; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Desojo, Julia Brenda. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales; Argentina Fil: Scheyer,Torsten M. . Universität Zürich. Paläontologisches Institut und Museum; Suiza Fil: Schultze, Cesar Leandro . Universidade Federal do Rio Grande do Sul; Brasil

Unlike most rauisuchians, which are known based on partially preserved specimens, fossils attributed to Decuriasuchus quartacolonia include a monotaxonomic assemblage com- posed of nine associated individuals (MCN-PV10.105a-i), three with almost complete skulls (MCN-PV10.105a,c,d), and a partial disarticulated skull (MCN-PV10.004) collected in the Mid- dle Triassic (Ladinian, Dinodontosaurus Biozone) beds of the Santa Maria Formation, in south Brazil. Because of its completeness and possible phylogenetic position, as one of the most basal loricatans, D. quartacolonia is a key taxon for anatomic, evolutionary and biomechanical stud- ies of rauisuchians. The comparative description of its osteology reveals that the skull and mandi- ble of D. quartacolonia are very similar to those of cf. Prestosuchus chiniquensis and Saurosuchus galilei, sharing a drop-shaped subnarial fenestra, a subtriangular antorbital fenestra with an elon- gated and narrow anterior point, a 'roman nosed' nasal, and a posteroventrally oriented ridge on the lateral surface of the ventral ramus of the squamosal. Among the differences are the autapomor- phies of D. quartacolonia: numerous maxillary teeth (17), lateral expansion of the nasal/lacrimal covering the antorbital fenestra dorsally, and squamosal and quadratojugal forming a subtriangular projection that invades the lower temporal fenestra. The study of rauisuchians began in the middle of the 20th century, when the German palaeontolo- gist Friedrich von Huene discovered archosaur fossils in Brazil. Huene (1938b, 1942) described four new taxa currently considered as rauisuchians: Prestosuchus chiniquensis, Prestosuchus loricatus, Procerosuchus celer and Rauisuchus tiradentes. The generic name of the latter taxon, in honour of Guilherme Rau, a Brazilian-German dentist who collaborated with Huene, achieved family and class status in later works (e.g. Huene 1956; Krebs 1976; Bonaparte 1984; Parrish 1993; Brusatte et al. 2010; Nesbitt 2011). Since then, several fur- ther rauisuchian remains have been discovered in Brazil, including rather complete specimens such as that of cf. Prestosuchus chiniquensis (UFRGS-PV0156T; Barberena 1978). However, more recently, about 70 years after Huene's discov- eries, a new taxon was proposed (Franca et al. 2011a). Named Decuriasuchus quartacolonia, the taxon was based on a monotaxonomic assemblage

The ‘rauisuchians’ are a group of Triassic pseudosuchian archosaurs that displayed a near global distribution. Their problematic taxonomic resolution comes from the fact that most taxa are represented only by a few and/or mostly incomplete specimens. In the last few decades, renewed interest in early archosaur evolution has helped to clarify some of these problems, but further studies on the taxonomic and paleobiological aspects are still needed. In the present work, we describe new material attributed to the ‘rauisuchian’ taxonPrestosuchus chiniquensis, of theDinodontosaurusAssemblage Zone, Middle Triassic (Ladinian) of the Santa Maria Supersequence of southern Brazil, based on a comparative osteologic analysis. Additionally, we present well supported evidence that these represent juvenile forms, due to differences in osteological features (i.e., a subnarial fenestra) that when compared to previously described specimens can be attributed to ontogeny and indicate variation within a single taxon of a problematic but important osteological structure in the study of ‘rauisuchians.’

Yarasuchus deccanensis gen. and sp. nov. is a new addition to the poorly known Middle Triassic terrestrial vertebrates. It is described on the basis of the fossil material of at least two incompletely preserved individuals and several isolated bones. It was a long-necked, gracile animal and might have had a facultatively bipedal gait. Apart from its characteristic elongate cervical vertebrae, other osteological features of Y. deccanensis resemble those of Prestosuchus, Saurosuchus, Ticinosuchus and ‘Mandasuchus’. It is therefore referred to the Rauisuchian family Prestosuchidae despite the debated validity of this taxon.