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– Carcharocles megalodon is considered a macropredatory shark that inhabited the seas around the world from middle Miocene to late Pliocene. In Argentina, it has only been formally recorded at two localities. Here, we report the first record for this taxon in the Buenos Aires Province. This occurrence is based on an isolated tooth recovered on the beach at the Punta Médanos locality, which lacks clear stratigraphic context. Based on the regional geology, the specimen probably came from Pliocene beds. Its size indicates that it probably belongs to a juvenile individual. Carcharocles megalodon é considerado um tubarão macropredador que habitou os mares ao redor do mundo desde o Mesomioceno até o Neoplioceno. Na Argentina, a espécie só foi formalmente registrada em duas localidades. Aqui, relatamos o primeiro registro desse táxon na Província de Buenos Aires. Essa ocorrência é baseada em um dente isolado recuperado na praia da localidade de Punta Médanos, que carece de contexto estratigráfico claro. Com base na geologia da região, o espécime provavelmente veio de camadas do Plioceno. Seu tamanho indica que provavelmente pertence a um indivíduo jovem. Fil: De Pasqua, Julieta. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Agnolin, Federico. Universidad Maimónides; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina. Fundación de Historia Natural Félix de Azara; Argentina Fil: Aranciaga Rolando, Alexis Mauro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Bogan, Sergio. Universidad Maimónides; Argentina. Fundación de Historia Natural Félix de Azara; Argentina Fil: Gambetta, Diego. Museo Mar de Ajó; Argentina

We describe the basal mesoeucrocodylian Burkesuchus mallingrandensis nov. gen. et sp., from the Upper Jurassic (Tithonian) Toqui Formation of southern Chile. The new taxon constitutes one of the few records of non-pelagic Jurassic crocodyliforms for the entire South American continent. Burkesuchus was found on the same levels that yielded titanosauriform and diplodocoid sauropods and the herbivore theropod Chilesaurus diegosuarezi, thus expanding the taxonomic composition of currently poorly known Jurassic reptilian faunas from Patagonia. Burkesuchus was a small-sized crocodyliform (estimated length 70 cm), with a cranium that is dorsoventrally depressed and transversely wide posteriorly and distinguished by a posteroventrally flexed wing-like squamosal. A well-defined longitudinal groove runs along the lateral edge of the postorbital and squamosal, indicative of a anteroposteriorly extensive upper earlid. Phylogenetic analysis supports Burkesuchus as a basal member of Mesoeucrocodylia. This new discovery expands the meagre record of non-pelagic representatives of this clade for the Jurassic Period, and together with Batrachomimus, from Upper Jurassic beds of Brazil, supports the idea that South America represented a cradle for the evolution of derived crocodyliforms during the Late Jurassic. We are grateful to C. Alsina, M. Milani, N. Chimento, M. Aranciaga, F. Brissón-Egli, G. Muñoz, and S. Miner for field assistance and technical preparation of Burkesuchus specimens. Special thanks to D. Pol for his comments on an early version of the manuscript. We are indebted to the Agencia Nacional de Promoción Científica y Tecnológica (PICT 2010-066 to F.E.N.), Fondo Nacional de Desarrollo Científico y Tecnológico (no. 1121140 to M.S. the Proyect FIC N° 40000501 to M. S., Conselho Nacional de Desenvolvimento Científico e Tecnológico), National Geographic (NGS Grant CP-075ER-17 to S.R.) and Mr. Coleman Burke for financial support. Special thanks to the editor J. O´Connor and two anonymous reviewers for their enlightening comments which greatly improved the quality of the present contribution.

Alvarezsaurs were a group of theropod dinosaurs found in Asia, North America, South America and Europe during Jurassic and Cretaceous periods. In spite of being known by several specimens, diverse ...

Unenlagia comahuensis was originally described as a phylogenetic link between nonavian dinosaurs and birds. Later it was interpreted by some authors as belonging to the deinonychosaurian clade Dromaeosauridae, and more recently as phylogenetically closer to birds than to dromaeosaurids. The only known specimen is represented by an incomplete skeleton, including vertebrae, incomplete scapular girdle, pelvis, and limbs, coming from Upper Cretaceous beds of Neuquén province, Patagonia, Argentina. The aim of the present paper is to include a detailed anatomical description of Unenlagia (currently only known by preliminary descriptions). Detailed analysis of Unenlagia anatomy resulted in the recognition of one possible additional Unenlagiidae synapomorphy (i.e., the presence of cup-like iliac articulation on ischium). We recognize derived anatomical traits that Unenlagia and kin share with birds, lending support to the interpretation that unenlagiids are stem-Avialae. Particularly, some appendicular features (e.g., scapula with subtriangular and relatively reduced acromion, poor outward projection of the glenoid and glenoidal lips on the scapula, lateral orientation of scapular glenoid, craniolaterally oriented deltopectoral crest of humerus) may be related to the acquisition of anatomical novelties that in birds are associated with flight. The present contribution on Unenlagia provides new data regarding the early evolution of avian features.

Diverse hypotheses have been proposed with the aim to explain the extinction of Late Pleistocene/Holocene mammals, including the Megafauna from America. Some authors support that human being was the direct responsible of extinction by means of intensive hunting, as proposed by the “blitzkrieg” or overkilling hypothesis. However, evidence is not conclusive. As is well known by biologists, exotic diseases may play an important role in local extinction of diverse vertebrates. On this basis, some speculated that the arrival of man may also have introduced new diseases that may have played an important role on native mammals, especially megafaunal populations, probably constituting a key factor on their extinction. Recent findings of the parasite Fasciola hepatica in endemic deer from Holocene sites in Patagonia (and also probably from camelids in Peru) previous to Hispanic colonization constitute indirect evidence that may sustain this hypothesis. Because one of the main definite host of this parasite are humans, this potential disease may have been introduced by human populations as hosts and then disperse through the entire continent, as evidenced by the finding of Fasciola hepatica in Patagonia. Its presence in endemic deer and camelids previous to Hispanic colonization, reinforces the proposal that human-related diseases may have played some role in Late Pleistocene extinction of large native mammals.

The fossil record of Pleistocene Proterotheriidae is scarce. It is restricted to the species Neolicaphrium recens known from Brazil, Uruguay, and Argentina, and to Uruguayodon alius, from Uruguay. Up to the date, proterotheriids are absent from the Pleistocene record of the Pampean Region. The aim of the present contribution is to report isolated remains of proterotheriids coming from Punta Indio and Punta Médanos localities, at the coast of Buenos Aires Province, Argentina. The specimens were found in the coastline and lack precise stratigraphical position. These findings indicate that Pleistocene proterotheriids were probably more diversified and geographically widespread than previously thought. O registro fóssil pleistocênico de Proterotheriidae é escasso. Se restringe às espécies Neolicaphrium recens, conhecida para o Brasil, Uruguai e Argentina, e Uruguayodon alius do Uruguai. Até o presente momento, os proteroterídeos estão ausentes no Pleistoceno da Região Pampeana da Argentina. A presente contribuição tem por objetivo reportar restos isolados de proteroterídeos provenientes das localidades de Punta Indio e Punta Médanos, região costeira da Província de Buenos Aires, Argentina. Os espécimes foram encontrados na linha de costa e carecem de contexto estratigráfico preciso. Estes achados sugerem que os proteroterídeos pleistocênicos eram possivelmente mais diversificados e mais amplamente distribuídos geograficamente do que se supunha anteriormente. Fil: Agnolin, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina. Universidad Maimónides; Argentina. Fundación de Historia Natural Félix de Azara; Argentina Fil: Chimento, Nicolás Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Bruyere, Marcelo R.. No especifíca

The Litopterna is an extinct clade of endemic South American ungulates that range from Paleocene up to late Pleistocene times. Because of their unique anatomy, litopterns are of uncertain phylogenetic affinities. However, some nineteenth century authors, considered litopterns as related to perissodactyl ungulates, a hypothesis recently sustained by molecular data. The aim of the present contribution is to include litopterns and other South American related taxa in a comprehensive phylogenetic analysis together with several extant and extinct basal perissodactyl ungulates. The analysis resulted in the nesting of litopterns and kin as successive stem-clades of crown Perissodactyla. Further, litopterns are not phylogenetically grouped with any North American basal ungulate, in agreement with some previous proposals. Presence of pan-perissodactyls in South America and India indicates that southern continents probably played an important role in the early evolution of hoofed mammals. Fil: Chimento, Nicolás Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Agnolin, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina. Fundación de Historia Natural Félix de Azara; Argentina

The fossil history of Neogene chelonioid sea turtles from South America is very incomplete. To date, only the isolated remains of dermochelyids and stem-cheloniids have been reported from the Mioce...

La fauna de planarias terrestres (Tricladida, Geoplanoidea), babosas (Mollusca, Gas tropoda), diplópodos (Myriapoda, Diplopoda), sínfilos (Myriapoda, Symphylla) y arácnidos (Chelicerata) de la Ciudad Autónoma de Buenos Aires (CABA, Argentina) permanece pobremente conocida. En la presente contribución se dan a conocer nuevos registros de especies de estos grupos, naturalizadas en el ámbito urbano de CABA y alrededores. Las colectas y observaciones fueron realizadas sin un método sistemático. Se reportan: Rhynchodemus sylvaticus (Tricladida, Geoplanidas; primer registro para la provincia de Buenos Aires y segundo para Argentina), Obama nungara Tricladida, Geoplanidae; primera cita para CABA), Imbira flavonigra (Tricladida, Geoplanidae; primer registro para Argentina), Milax gagates (Mollusca, Milacidae; primer registro para CABA), Cylindroiulus latestriatus (Diplopoda, Julidae; primer registro para Argentina), Ophyiulus pilosus (Diplopoda, Julidae; primer registro para Argentina), Brachydesmus superus (Diplopoda, Paradoxomatidae; primer registro para CABA y segundo para Argentina), Symphylella vulgaris (Symphyla, Scolopendrellidae; primer registro para Argentina), Cylisticus convexus (Oniscidea, Cylisticidae; segunda cita para Argentina, luego de 90 años), Uloborus plumipes (Arachnida, Uloboridae; segunda cita para CABA y para Argentina) y Leucauge argyra (Arachnida, Tetragnathidae; primera cita para la provincia de Buenos Aires y segunda cita para Argentina). Diversos autores indican para Europa un rápido incremento en el número de especies invertebradas introducidas, un patrón extrapolable a Argentina. Lamentablemente,hasta la fecha, no se cuenta con datos certeros acerca de los patrones de distribución o abundancia de estas especies. En este sentido es necesario priorizar su conocimiento, incluso de aquellas potencialmente perjudiciales para ambientes nativos.

The fossil record of owls of the families Strigidae and Tytonidae in South America is poor. The aim of the present contribution is to report for the first time fossil Strigiformes from Riobamba Canton, at Chimborazo province, in Ecuador. The specimens come from a large owl burrow from Late Pleistocene beds of the Cangagua Formation. We report the finding of fossil record of Athene cunicularia and Tyto aff. T. furcata and the first fossil record of Glaucidium from Ecuador. Further, a giant species of the genus Asio is described. The specimen constitutes the largest known asionine owl, being approximately of the size of a big female of Bubo virginianus. Based on prey content at the fossil burrow, it is possible that the new Asio species predated on the other owls. If this inference is correct, it may represent the first evidence indicating intra-ordinal predation in the fossil record. Fil: Lo Coco, Gastón Ernesto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Agnolin, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina. Fundación de Historia Natural Félix de Azara; Argentina Fil: Román Carrión, José Luis. Escuela Politécnica Nacional; Ecuador

We report the first record of the genus Xiphactinus from southern South America. The recovered fossil material consists of an associated maxilla and abdominal vertebra, probably derived from latest...

We report the first record of the Porto Alegre Golden-eyed Treefrog, Trachycephalus mesophaeus (Hensel, 1867), from Argentina based on a single specimen collected in the 1980s at Las Lomitas, province of Formosa, northeastern Argentina. This new record, within the Chacoan Biogeographical Region, is separated by more than 1300 km from its main range in the Atlantic Forest. Fil: García Marsa, Jordi Alexis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Agnolin, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina. Universidad Maimónides; Argentina Fil: D'angelo, Julia Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina

The fossil record of the genus Bothrops is still sparse in South America. Most records belong to extant species recovered in strata not older than the late Pleistocene. The genus was also tentatively reported from the early Pliocene and early–middle Pleistocene of Buenos Aires province, Argentina, based on fragmentary specimens. The aim of the present contribution is to report the partial vertebral column of a viperid snake discovered in the lower Pliocene layers of Farola de Monte Hermoso locality, southern Buenos Aires province. The specimen can be referred to the extant genus Bothrops, representing the oldest occurrence for this taxon. This finding supports the hypothesis sustained by previous authors that indicate a “stasis” in the evolution of the South American herpetofauna since the late Neogene, at least.

The aim of the present contribution is to describe a new genus and species of Pipoidea from the Huitrera Formation (Eocene) from Patagonia, Argentina. The new genus shows a unique combination of characters indicating that it is a valid taxon different from other pipimorphs, including the coeval Llankibatrachus truebae. The phylogenetic analysis resulted in the nesting of the new taxon within a previously unrecognized endemic clade of South American aglossans. This new clade turns out to be the sister-group of crown-group Pipidae. This phylogenetic proposal reinforces the hypothesis sustaining the dispersal of pipids between Africa and South America through an island chain or a continental bridge across the Atlantic Ocean by Early Tertiary times. Le but de cet article est de décrire de nouveaux genre et espèce de Pipioidea de la formation Huitrera (Éocène) de Patagonie, Argentine. Le nouveau genre montre une combinaison unique de caractères indiquant que c’est un taxon valide, différent des autres pipimorphes incluant Llankibatrachus truebae, contemporain. L’analyse phylogénétique résulte en la nidification du nouveau taxon au sein d’un clade endémique, auparavant non reconnu, d’aglosses d’Amérique du Sud. Il en résulte que le nouveau clade est le groupe frère du groupe couronne des Pipidae. Cette proposition phylogénétique renforce l’hypothèse en faveur d’une dispersion des pipidés entre l’Afrique et l’Amérique du Sud au moyen d’une chaîne insulaire ou d’un pont continental à travers l’Océan atlantique au Tertiaire inférieur. Fil: Aranciaga Rolando, Alexis Mauro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Agnolin, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina. Fundación de Historia Natural Félix de Azara; Argentina Fil: Corsolini, Julián. Museo de Geología y Paleontología del Lago Gutierrez “Dr. Rosendo Pascual”; Argentina

Phylogenetic relationships of megaraptorid theropods are under intense debate. Some authors interpret them as archaic allosauroids that survived up to Late Cretaceous, whereas others consider megaraptorids as basal tyrannosauroids. The recently described Patagonian taxon Murusraptor barrosaensis offers novel information on skull, axial and hind limb anatomy, all of which may help in elucidating the phylogenetic affinities of megaraptorids as a whole. Murusraptor is particularly similar to juvenile specimens of tyrannosaurids; both share: 1) lacrimal with a long anterior process; 2) corneal process and; 3) lateral pneumatic fenestra; 4) square and dorsoventrally low frontals; 5) parietals with well-developed sagittal and nuchal crests, among other features. The current study lends further support to the hypothesis that megaraptorans are basal members of Coelurosauria (supported by 20 synapomophies), with strongest affiliation with Tyrannosauroidea (supported by >20 synapomorphies). Fil: Aranciaga Rolando, Alexis Mauro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Novas, Fernando Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Agnolin, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina

The saber-toothed cat Smilodon is a characteristic genus of the Pleistocene faunas of the American continent. Smilodon belongs to an extinct clade of felids that had hypertrophied blade-like upper canines. Because the length of the canines is so extreme, the killing bite of Smilodon is a hotly debated topic in vertebrate paleontology. Some authors have proposed that saber-toothed cats had a weak bite and their canines were fragile, not useful for attacking prey or penetrating bones. The aim of the present contribution is to describe two new specimens of Smilodon populator that have injuries on their skulls. Although it cannot be ruled out that the injuries were caused by a potential prey kicking the skull, the size, shape and general features of the injuries suggest that they were inflicted by the upper canines of another Smilodon individual during agonistic interactions. Le chat à dents de sabre Smilodon est un genre caractéristique du continent Américain. Smilodon appartient à un clade éteint de félidés ayant des canines supérieures hypertrophiées en forme de lame. En raison de l’extrême longueur de ses canines, la morsure mortelle de Smilodon fait l’objet d’un vif débat en paléontologie des vertébrés. Certains auteurs ont suggéré que les chats à dents de sabre avaient une morsure faible et que leurs canines étaient fragiles et n’avaient pas d’utilité dans l’attaque des proies ou la pénétration de ces dents dans les os. Le but du présent article est de décrire deux nouveaux spécimens de Smilodon populator qui ont des blessures sur leur crâne. Bien qu’on ne puisse exclure le fait que les blessures aient été causées par une proie potentielle ayant donné des coups sur le crâne, la taille, la forme et les caractéristiques générales des blessures suggèrent que celles-ci ont été causées par les canines supérieures d’un autre individu Smilodon pendant des interactions agonistiques. Fil: Chimento, Nicolás Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Agnolin, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina. Fundación de Historia Natural Félix de Azara; Argentina Fil: Soibelzon, Leopoldo Héctor. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Departamento Científico de Paleontología de Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina Fil: Ochoa, Javier G.. Museo Regional “Florentino Ameghino”; Argentina Fil: Buide, Viviana. Museo de Ciencias Naturales “Carlos Ameghino”; Argentina

Rhynchocephalians are a lepidosaur clade with a single living species. Here we report the first record of an eilenodontine sphenodontian from Turonian beds in South America. The new Turonian basal eilenodontine sphenodontian, Patagosphenos watuku gen. et sp. nov, is described. The specimen is represented by partial cranial and postcranial remains, being very similar to other eilenodontines such as Kaikaifilusaurus and Eilenodon. Moreover, the genus Kaikaifilusaurus is reported for the first time from Turonian beds. Furthermore, this genus is revalidated, being previously considered as a nomen dubium. Paleohistological analysis of Patagosphenos gen. nov reveals a similar bone microstructure to that of the living Sphenodon. We infer that physiological adaptations to survive in cold (freezing conditions) environments may constitute the key pre-adaptation that allowed Sphenodon to survive the Cretaceous-Palaeogene boundary.

The fossil record of Early Cretaceous birds in South America has been restricted to members of Enantiornithes from the Crato Formation (Aptian) of Brazil. Here we describe a new genus and species o...

Lewisuchus admixtus is an early dinosauriform described by Alfred Romer in 1972 on the basis of a single, incomplete skeleton, collected in lower Upper Triassic rocks of the renowned Chanares Formation, at the Los Chanares type-locality, La Rioja Province, north-western Argentina. Recent field explorations to the type-locality resulted in the discovery of two partial articulated skeletons, which provide significant novel information. The cranial bones, presacral series, femur, tibia, and proximal tarsals of the new specimens match the preserved overlapping anatomy of the holotype and previously referred specimens of L. admixtus, including the presence of unique combination of character states among dinosauriforms (anterior presacral column with additional ossification on the top of neural spines, dorsal neural spines fan-shaped, anterior surface of the astragalus with a dorsally curved groove, and an inflated area on the anterior portion of the medial surface of this bone). This new information improves our understanding of the anatomy and taxonomy of early dinosauriforms and reinforces the role of Argentinean beds on the study of the origin of dinosaurs.

The fossil record of fishes from the Farola de Monte Hermoso locality (lower Pliocene) in the southern Buenos Aires province, Argentina, shows an unusual composition. The locality at the southern boundary of the Brazilian Ichthyogeographic Realm. However, its fossil record is composed of fossil fishes that are not necessarily related to Brazilian lineages, namely indeterminate siluriforms, trichomycterid catfishes, and percomorphaceans. The aim of the present contribution is to describe and report for the first time isolated specimens belonging to Characidae fishes. In the Pampean region the fossil record of characids is restricted to Oligosarcus Günther, 1864 sp. from the late-middle Pleistocene. The present finding fills a temporal gap between the Paleogene and Quaternary reports and indicates that Brazilian fish lineages were present in the area by early Pliocene times, and may constitute an indirect evidence of the evolution of the basins in the southern Pampean Area. Le registre fossile de poissons de la localité de Farola de Monte Hermoso (Pliocène inférieur) dans la province méridionale de Buenos Aires, Argentine, est encore biaisé. Il est situé à la limite méri- dionale du domaine ichthyogéographique brésilien. Cependant, son registre fossile est composé de poissons fossiles qui ne sont pas nécessairement reliés aux lignées brésiliennes, en particulier siluri- formes indéterminés, poissons-chats trichomyctéridés et percomorphacéens. Le but de la présente contribution est de décrire et mentionner des spécimens isolés appartenant aux poissons Characidés. Dans la région de la Pampa, le registre fossile des Characidés est restreint à Oligosarcus Günther, 1864 sp. du Pléistocène moyen tardif. Les présentes découvertes comblent un vide temporel entre les registres au Paléogène et au Quaternaire et indiquent que des lignées de poissons brésiliens étaient présents dans la zone au Pliocène inférieur et peuvent constituer une preuve indirecte de l’évolution des bassins dans le domaine méridional de la Pampa. Fil: Bogan, Sergio. Fundación de Historia Natural Félix de Azara; Argentina Fil: Agnolin, Federico. Fundación de Historia Natural Félix de Azara; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Mirande, Juan Marcos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - Tucumán. Unidad Ejecutora Lillo; Argentina. Fundación Miguel Lillo; Argentina

Abelisaurid theropods are well known in Cretaceous beds along South America, particularly Patagonia. However, the record of latest Cretaceous abelisauroids is still far from satisfactory. Until recently, few taxa were described from Maastrichtian beds: Carnotaurus sastrei and Quilmesaurus curriei, but also perhaps Abelisaurus comahuensis. In this contribution, we describe a new genus and species (Niebla antiqua gen. et sp. nov.), of medium-sized abelisaurid coming from Late Cretaceous (Maastrichtian) beds from Río Negro province, northern Patagonia, Argentina. The paleohistological analysis shows that this individual has reached the somatical maturity and that it represents an adult of a mid-sized abelisaurid. The specimen is represented by a nearly complete braincase, fragmentary jaw and teeth, relatively complete scapulocoracoid, dorsal ribs and incomplete vertebrae. The new taxon is relatively small, much smaller than other coeval abelisaurids such as Carnotaurus and Abelisaurus. The braincase shows autapomorphic features such a dorsoventrally tall basal tuber and postemporal foramen enclosed by parietal and exoccipitals. The scapulocoracoid is notably similar to that of Carnotaurus in having a posterodorsally oriented glenoid, a dorsoventrally expanded and wide coraco-scapular plate, and a very narrow and straight scapular blade. These features are very different from those of other abelisaurids, which may indicate a unique conformation of the pectoral girdle among these South American theropods. Fil: Aranciaga Rolando, Alexis Mauro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Cerroni, Mauricio Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: García Marsa, Jordi Alexis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Agnolin, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Motta, Matias Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Rozadilla, Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Brissón Egli, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Novas, Fernando Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina

Gondwanatheria is an enigmatic mammaliaform clade distributed in the Cretaceous and Paleogene of South America, Africa, Madagascar, India and Antarctica. The Mesozoic record in South America is restricted to the Latest Cretaceous of Río Negro and Chubut provinces, Argentina and Magallanes Region of southern Chile. The aim of the present contribution is to describe a new specimen of gondwanatherian mammaliaforms from beds belonging to the Maastrichtian Chorrillo Formation, cropping out 30 km SW of El Calafate, Santa Cruz Province, Argentina. It is represented by a single molariform referable to the species Magallanodon baikashkenke with which it shares a unique combination of characters. Analysis of the unique combination of characters exhibited by Magallanodon shed doubts on the monophyly of Ferugliotheriidae and suggest that South American taxa may be closely related to each other. The wide geographical distribution and occurrence of gondwanatherians on geological units of diverse origins suggest that they were capable of facing disparate environmental conditions.

Pterosaurs were the first vertebrates to evolve powered flight1 and comprised one of the main evolutionary radiations in terrestrial ecosystems of the Mesozoic era (approximately 252–66 million years ago), but their origin has remained an unresolved enigma in palaeontology since the nineteenth century2–4. These flying reptiles have been hypothesized to be the close relatives of a wide variety of reptilian clades, including dinosaur relatives2–8, and there is still a major morphological gap between those forms and the oldest, unambiguous pterosaurs from the Upper Triassic series. Here, using recent discoveries of well-preserved cranial remains, microcomputed tomography scans of fragile skull bones (jaws, skull roofs and braincases) and reliably associated postcrania, we demonstrate that lagerpetids—a group of cursorial, non-volant dinosaur precursors—are the sister group of pterosaurs, sharing numerous synapomorphies across the entire skeleton. This finding substantially shortens the temporal and morphological gap between the oldest pterosaurs and their closest relatives and simultaneously strengthens the evidence that pterosaurs belong to the avian line of archosaurs. Neuroanatomical features related to the enhanced sensory abilities of pterosaurs9 are already present in lagerpetids, which indicates that these features evolved before flight. Our evidence illuminates the first steps of the assembly of the pterosaur body plan, whose conquest of aerial space represents a remarkable morphofunctional innovation in vertebrate evolution. Lagerpetids, bipedal archosaurs that are thought to be related to dinosaurs, are instead a sister group to pterosaurs, and although they have no obvious flight adaptations they share numerous synapomorphies with pterosaurs across the entire skeleton.

Loricariidae is a very diverse lineage of Neotropical fishes, being the most speciose family of the order Siluriformes. However, the loricariid fossil record is still very sparse. The aim of the present contribution is to describe in detail several bones belonging to the loricariid genus Acanthicus coming from late Miocene beds located at the Paraná River cliffs, Entre Ríos province, Argentina. Fishes of the Acanthicus clade are currently restricted to the northern half of South America, being mainly distributed in the Orinoco and Amazonas basins, with a single genus reaching the Paraná-Plata basin. Acanthicus adds to the list of several taxa that are shared by the Miocene of Paraná, Amazonas and Orinoco basins, but that nowadays are absent in the former (e.g., Colossoma, Phractocephalus, and Brachyplatystoma), and are typical of large river channels. This report of Acanthicus supports a close affinity between freshwater faunas of the Paraná, Orinoco, and Amazonas basins. Miocene fossils of freshwater fishes recorded in Paraná beds shed light on the connections between ancient basins of South America and also indicate that several fish clades suffered regional extinctions during the late Neogene or the beginning of the Quaternary.

The fossil record of basal paravians in Gondwana is still poorly known, being limited to the Cretaceous unenlagiids from South America and the problematic Rahonavis from Madagascar. Here we report on a new paravian from the Cenomanian-Turonian (Late Cretaceous) of Río Negro province, NW Patagonia, Argentina. The new taxon exhibits a derived bird-like morphology of the forelimbs (e.g., robust ulna with prominent, anteriorly oriented, and proximally saddle-shaped radial cotyle and wide medial flange on metacarpal I) and a plesiomorphic foot with a raptorial pedal digit II. Phylogenetic analysis recovers the new taxon in a monophyletic clade with Rahonavis, being the sister group of the remaining Avialae and more derived than other non-avian dinosaurs. Both exhibit derived forelimb traits in opposition with their plesiomorphic hind limbs. The position of the new taxon and Rahonavis as stem avialans indicates that Gondwanan basal paravians are represented by two different clades, at least. The new taxon probably constitutes a previously unknown grade in the avian-line theropods in which some flight-related adaptations of the forelimbs are present in cursorial taxa. The present discovery sheds light on the acquisition of flight-related traits in non-avian dinosaurs and on the still poorly known paravian radiation in Gondwana. Fil: Motta, Matias Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Agnolin, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina. Fundación de Historia Natural Félix de Azara; Argentina Fil: Brissón Egli, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Novas, Fernando Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina

The deposits of the Chorrillo Formation (Maastrichtian) were accumulated during a ‘continental window’ that occurred during the Late Cretaceous in the Austral-Magallanes foreland basin, southern Patagonia, Argentina. The aim of the present contribution is to describe the depositional conditions as well as new vertebrate and plant fossils from this unit. The analysis of these deposits resulted in the definition of five architectural elements: Complex sandy narrow sheets channels (SS), Complex gravelly narrow sheets channels (GS), Sandstone lobes (SL), Thick fine-grained deposits (GF) and Thin dark fine-grained deposits (DF). These were separated into channelized and non-channelized units and represent the accumulation in a fine-grained dominated, fossil rich fluvial depositional system. Vertebrates fossil records include two species of frogs of the genus Calypteocephalella (representing the southernmost record of Pipoidea), snakes belonging to Madtsoiidae and Anilioidea (the latter ones being the first records for the basin), chelid turtles similar to Yaminuechelys-Hydromedusa, meiolaniiform turtles, titanosaur sauropods, megaraptoran theropods, new remains of the elasmarian Isasicursor santacrucensis (including the first cranial remains available for this species), hadrosaur ornithischians, enantiornithine birds. Sharks and elasmosaurs are also recorded and may possibly derive from the overlying marine Calafate Formation. These new taxa, together with previous findings from the Chorrillo Formation, are included into a stratigraphic column, thus providing valuable information that sheds new light on faunistic composition and paleobiogeography of high-latitude biotas of Gondwana.

A new anablepid (Cyprinodontiformes) from the Late Miocene of Puchuzum locality, San Juan Province, Argentina is described here. The collected specimens include male and female individuals showing marked sexual dimorphism and represented different ontogenetic stages. The fossils show a unique combination of characters reveals a new genus and species, Sanjuanableps calingasta. The phylogenetic analysis allowed to identify a monophyletic clade including Anableps, Tucmanableps and Sanjuanableps, which constitutes the sister group of other anablepids. During the Late Miocene, Sanjuanableps possibly formed monospecific shoals in shallow ponds of salty water in semiarid environments. Fil: Bogan, Sergio. Universidad Maimónides. Departamento de Ciencias naturales y Antropología. Fundación de Historia Natural "Félix de Azara"; Argentina Fil: Contreras, Victor Hugo. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Geología "Dr. Emiliano Aparicio"; Argentina Fil: Agnolin, Federico. Fundación de Historia Natural Félix de Azara; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina Fil: Tomassini, Rodrigo Leandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Geológico del Sur. Universidad Nacional del Sur. Departamento de Geología. Instituto Geológico del Sur; Argentina Fil: Peralta, Silvio Heriberto. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Geología "Dr. Emiliano Aparicio"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Marsh rats of the species Holochilus vulpinus inhabit mesic and humid environments. For this reason, it is frequently used in paleoenviromental studies to infer past humid conditions. Holocene archeological record indicates that H. vulpinus had a wider geographical distribution than today. Its regional extinction in north Patagonia at the XIX century was attributed to the dry and cold Little Ice Age (LIA). Here we present the finding of a specimen of H. vulpinus from northeastern Patagonia (Valcheta stream, Río Negro province, Argentina), just at the end of LIA. Implications of this novel historical record are discussed. Fil: Agnolin, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina Fil: Lucero, Sergio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”; Argentina Fil: Torres Monges, Julio Cesar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto de Diversidad y Evolución Austral; Argentina

The record of sauropods in the Upper Cretaceous of Patagonia is rich. However, there are still several blanks on this record. Here it is described a new sauropod assemblage coming from the Salitral Ojo de Agua Area, Rio Negro province, northern Patagonia, Argentina (Allen Formation; Maastrichtian). Remains of indeterminate saltasaurines, aeolosaurines, as well as new specimens of the small saltasaurine Rocasaurus muniozi and the new eutitanosaur Menucocelsior arriagadai gen. et sp. nov., are described. The new eutitanosaur is represented by an incomplete caudal series and some appendicular bones that indicate that it does not belong to any previously recognized eutitanosaur clade (e.g, Colossosauria, Saltasaurinae, Aeolosaurini). The co-occurrence of several roughly coeval titanosaurs in a restricted area (as occur in Bajo de Santa Rosa, Salitral Moreno and Salitral Ojo de Agua sites) with different body plans, indicates that they probably occupied particular ecological niches and that probably competition for resources was limited, allowing the connivance of several taxa in a single locality and age. This pattern is not observed in other sites of the world. Based on these records and on the high diversity of osteoderm morphotypes recovered, it appears to be certain that palaeoecological conditions in the area were able to sustain and promote the flourishing of many species of titanosaurs.

The fossil record of gondwanatherian mammaliaforms from Patagonia is represented by several species known on the basis of isolated teeth, with the single exception of a partial dentary with two molariforms of the Paleocene species Sudamerica ameghinoi. The aim of the present contribution is to describe both a fragmentary dentary (with the base of the lower incisive) and a partial upper incisor coming from the Campanian–Maastrichtian Chorrillo Formation, at the La Anita Farm, SW Santa Cruz province, Argentina. The specimens are referred to Magallanodon baikashkenke, a species previously known by isolated teeth from the Dorotea (Chile) and Chorrillo (Argentina) beds. The present discovery expands our knowledge of this mammaliaform clade.

Triassic beds from Argentina and Brazil provide the most relevant fossil record of early dinosauriforms in terms of numerical abundance and taxonomic diversity. This record currently represents the best source to understand the origin and early evolutionary radiation of dinosaurs. In the present paper we offer an updated review focused on the available evidence of Carnian dinosaurs from this continent, but we also discuss the record of Triassic dinosaur precursors and the evolution of Triassic dinosaurs in other continents. It is clear that, aside the agreed taxonomic composition of some particular dinosaurian subclades (e.g., Herrerasauridae, Neotheropoda), there is no consensus about early dinosaur phylogeny, and our paper is not the exception. Recent years witnessed the discovery of several new early dinosaurian taxa, as well as reviews of the taxonomic allocation of several renowned forms such as Lagerpeton, Lewisuchus, Pisanosaurus, and Eoraptor. New analyses demonstrate that evidence supporting the taxonomic referrals of pre-Norian dinosaurs to Theropoda, Sauropodomorpha and Ornithischia are tenuous, at best. Here we present new anatomical observations and comparisons for each of these South American early dinosauriforms with the aim to test previous phylogenetic interpretations. Evidence from South America allows reviewing the phylogenetic relationships of taxa from other continents, including Tawa, Chindesaurus, and Daemonosaurus, which are here suggested to nest within Herrerasauria. Evidence at hand indicates that herrerasaurs were a successful clade of archaic predatory saurischians that inhabited both South and North America, and probably also India and Europe.