ABSTRACT Notosuchians are a crocodyliform clade with a rich Gondwanan fossil record, especially i... more ABSTRACT Notosuchians are a crocodyliform clade with a rich Gondwanan fossil record, especially in Cretaceous South American deposits. More than half of all described species come from South America and, around one quarter, have been discovered in the Adamantina Formation (Bauru Group, Brazil). The large amount of notosuchian remains from this formation, along with its chronostratigraphic uncertainty, may be distorting notosuchian palaeodiversity estimates. In order to analyse how these factors could be biasing our interpretations, palaeodiversity estimates were performed excluding and including the Adamantina Formation occurrence data, as well as assigning them to the main age ranges that have been proposed for the formation (Turonian-Santonian and Campanian-Maastrichtian). Furthermore, as other factors might be influencing palaeodiversity fluctuations, a modelling approach was performed to assess which abiotic factors, sampling artefacts, or a combination of them, could be driving these palaeodiversity dynamics. The results showed that the Adamantina Formation is causing a Lagerstätte effect that is distorting palaeodiversity estimates and, depending on the age assigned to that formation, the tempo and magnitude of the maximum palaeodiversity reached during the Late Cretaceous substantially changes. The results also suggest that the temporal bias might affect palaeobiological reconstructions not only in notosuchians but also in other groups.
Teorías de la evolución Notas desde el sur Teorías de la evolución : Notas desde el sur / Leonard... more Teorías de la evolución Notas desde el sur Teorías de la evolución : Notas desde el sur / Leonardo Salgado y Andrea Arcucci. 1a ed.-Viedma : Universidad Nacional de Río Negro, 2016. 264 p.; 15x23 cm Lecturas de Cátedra isbn 978-987-3667-37-4 1. Evolución humana. 2. Teoría de la evolución. 3. Biología evolutiva. i. Arcucci, Andrea ii. Título. cdd 576.8 Este libro se utiliza en las licenciaturas en Geología y Paleontología y en el Profesorado de nivel medio y superior en Biología en las asignaturas de Evolución y Genética, Biología i y ii, Paleontología y Pensamiento y Actividad Científica.
A new lithostrotian sauropod, the small-sized Overosaurus paradasorum n. gen et sp. from the Anac... more A new lithostrotian sauropod, the small-sized Overosaurus paradasorum n. gen et sp. from the Anacleto Formation (Campanian, Late Cretaceous, Neuquén Group, Patagonia, Argentina) is here described. The specimen (MAU-Pv-CO-439) consists of a fully articulated vertebral series from the 10 th cervical to the 20 th caudal vertebra, the last cervical ribs, several dorsal ribs in articulation with their respective vertebrae, the complete right ilium and fragments of the left ilium. Overosaurus paradasorum is diagnosed by a unique combination of characters that includes (1) posterior cervical vertebrae with long pre-and postzygapophyses that project beyond the anterior and posterior borders of the centrum, respectively, (2) postspinal lamina absent in all dorsal neural spines, (3) wide and massive 9 th and 10 th caudal centra that are slightly excavated laterally and have relatively flat ventral surfaces, (4) laminar projection on the posterior border of the second and third dorsal rib, (5) ilium proportionally shorter anteroposteriorly and taller dorsoventrally than in other lithostrotians, and (6) the preacetabular process of the ilium strongly deflected laterally and with a ventrolaterally tapering end. Analysis of the phylogenetic relationships of Overosaurus places it within the Aeolosaurini, as the sister taxon of a monophyletic group formed by Aeolosaurus rionegrinus, A. maximus, Gondwanatitan faustoi and Pitekunsaurus macayai. Overosaurus is a new representative of a highly diversified assemblage of Campanian lithostrotians from Patagonia that includes both Aeolosaurini and saltasaurids (e.g. Saltasaurus, Neuquensaurus)-this small new taxon falls within the low end of the size spectrum represented by these Late Cretaceous sauropods.
Abstract. In South America, tetrapod footprints of Middle Triassic age were only described from t... more Abstract. In South America, tetrapod footprints of Middle Triassic age were only described from the Cuyana (Cerro de las Cabras Formation) and Ischigualasto-Villa Union (Los Rastros Formation) basins in west-central Argentina. They are scarce and remain mostly undescribed. Their significance and the putative trackmakers are identified and discussed within a phylogenetic context in the present contribution. Several groups of tetrapods are suggested to be represented, as non-mammalian therapsids, crurotarsal archosaurs and putative dinosaurs. The presence of crurotarsal archosaurs and non-mammalian therapsids in Cerro de las Cabras Formation suggests a tetrapod fauna more diverse than that documented by the known body fossil record. The ichnites described from the Los Rastros Formation are, until now, the only evidence of amniotes in the Ischigualasto-Villa Union Basin during the deposition of these levels. They indicate the presence of putative dinosaurs, crurotarsal archosaurs and non-mammalian therapsids, which are already well represented in the rest of the sequence by skeletal remains. Resumen. HUELLAS DE TETRAPODOS DEL TRIASICO MEDIO DEL EXTREMO SUR DE AMERICA DEL SUR. En America del Sur, huellas de tetrapodos del Triasico Medio solo se conocen en niveles de las cuencas Cuyana (Formacion Cerro de las Cabras) e Ischigualasto-Villa Union (Formacion Los Rastros), en el centro-oeste de Argentina. Las huellas son escasas y la mayoria de los especimenes no estan descriptos. En el presente trabajo el significado de estas huellas y sus supuestos generadores son discutidos en un contexto filogenetico. Asi, varios grupos de tetrapodos han sido identificados como terapsidos no mamalianos, arcosaurios crurotarsales y probables dinosaurios. La presencia de arcosaurios crurotarsales y terapsidos no mamalianos en niveles de la Formacion Cerro de las Cabras sugiere una fauna mas diversa que lo que indica el registro de restos fosiles esqueletarios conocidos para los mismos niveles. Las icnitas de la Formacion Los Rastros son hasta el momento la unica evidencia de amniotas en la Cuenca de Ischigualasto-Villa Union durante la depositacion de dichos niveles. Ellas indican la existencia de probables dinosaurios, arcosaurios crurotarsales y terapsidos no mamalianos, bien representados en el resto de la sequencia por restos esqueletarios.
Significant paleobiological data has emerged from the San Luis Basin (Early Cretaceous, Aptian-Al... more Significant paleobiological data has emerged from the San Luis Basin (Early Cretaceous, Aptian-Albian in Central Argentina) during the last decades. Two units in this basin include lake paleo-environments with important fossil contents in an excellent state of preservation that could be considered as Konservat Lagerstätten deposits. The association of fossil leaves and pollen grains from the La Cantera Formation is one of the most ancient and complete angiosperm records in South America and the bryophyte association of the same unit constitutes one the most complete records of its type in Argentina. Insects from five different orders have been identified in this association, and three endemic species of aquatic insects from the La Cantera Formation have been described as belonging to the Notonectidae and Corixidae families, including the oldest member of the Anisopinae subfamily. The Pterodaustro guinazui association from the Lagarcito Formation is one of the few fossil associations...
<div><p><i>Lewisuchus admixtus</i> is an enigmatic early dinosauriform fr... more <div><p><i>Lewisuchus admixtus</i> is an enigmatic early dinosauriform from the Chañares Formation, Ladinian of Argentina, which has been recently considered a member of Silesauridae. Yet, it differs markedly from Late Triassic silesaurids in dental and vertebral anatomy. Indeed, a detailed redescription of its holotype allowed the identification of several features of the skeleton previously unrecognized amongst silesaurids. These include pterygoid teeth, a dorsomedial posttemporal opening on the otoccipital, foramina associated with cranial nerves X–XII on the caudal region of the prootic–otoccipital, and postaxial neck/trunk vertebrae with craniocaudally expanded neural spines. The presence of a single row of presacral scutes was also confirmed. Some elements previously referred to, or found associated with, the holotype, including a lower jaw, pedal elements and an astragalus, more probably correspond to proterochampsid remains. The anatomical information available for the holotype of <i>L. admixtus</i> was rescored into a new phylogenetic dataset for dinosauromorphs, mostly based on previous works. <i>Lewisuchus admixtus</i> and <i>Pseudolagosuchus major</i> are treated as distinct OTUs because their preserved skeletons mostly lack overlapping parts. The parsimony analysis supports the basal position of <i>L</i>. <i>admixtus</i> within dinosauriforms, prior to the silesaurid–dinosaur split, rather than at the base of Silesauridae. This suggests that a higher number of early dinosauriform clades branched in the Middle and Late Triassic than previously suggested.</p></div
Fil: Arcucci, Andrea Beatriz. Universidad Nacional de San Luis. Facultad de Quimica, Bioquimica y... more Fil: Arcucci, Andrea Beatriz. Universidad Nacional de San Luis. Facultad de Quimica, Bioquimica y Farmacia. Departamento de Bioquimica y Ciencias Biologicas. Area de Zoologia; Argentina
The present note brings to light a new form of thecodont, pertaining to the Suborder Pseudosuchia... more The present note brings to light a new form of thecodont, pertaining to the Suborder Pseudosuchia (sensu Bonaparte, 1982), which adds to the genera known from the Los Chañares fauna, of Chañarian age (Middle Triassic), from Provincia de La Rioja (Romer, 1971, 1972; Bonaparte, 1975, 1982b). This local Los Chañares fauna, described in general terms by Romer, is very important for our knowledge of thecodonts, as much from a systematic as an evolutionary point of view. This association includes eight genera of thecodonts, in addition to that described here, pertaining to at least six different families. Due to this diversity, this combination is the largest known for the Middle Triassic worldwide, since the records from Europe, East Africa and Brazil are considerably poorer. The recovery of this new lagosuchid brings new anatomical information about the development of the advanced mesotarsal-type tarsus. whose origin is under discussion (Brinkman, 1981; Chatterjee, 1982) and whose more ...
Lagerpeton chanarensis forms part of an important Triassic fauna, produced by the lower part of t... more Lagerpeton chanarensis forms part of an important Triassic fauna, produced by the lower part of the Ischichuca Formation (Chañares Formation of Romer and Jensen, 1966), Los Chañares locality, La Rioja, Argentina, which corresponds to the Chañarian Reptile Age, correlated with the European Anisian (Bonaparte, 1978, 1982b). This faunistic association includes therapsids, both cynodonts and dicynodonts (Romer, 1972c; Bonaparte op. cit.), and thecodonts pertaining to two suborders (Erythrosuchia and Pseudosuchia, sensu Bonaparte, 1982a) and five families: Cerritosauridae, Rauisuchidae, Lagosuchidae, Ornithosuchidae and Sphenosuchidae, represented by several genera (Bonaparte, 1978). The importance of studying this fauna rests in the fact that Middle Triassic thecodonts, particularly from the lower part of this period, represent an important evolutionary moment in the history of archosaurs, since they attempted a great adaptive radiation that was the basis of later evolution of the group...
A NEW CRETACEOUS MESOEUCROCODYLIA FROM THE NORTH OF THE NEUQUÉN BASIN, ARGENTINA. In this contrib... more A NEW CRETACEOUS MESOEUCROCODYLIA FROM THE NORTH OF THE NEUQUÉN BASIN, ARGENTINA. In this contribution, a new specimen of Mesoeucrocodylia from levels attributed to the Plottier Formation (Cretaceous, Upper Coniacian) is described in the locality Yacimiento Narambuena, Rincón de los Sauces, in the north section of the Neuquén Province. The material includes an incomplete subadult specimen with mostly articulated postcranium of an approximate length of 60 cm. The study and comparisons to allow distinguish the specimen from other Mesoeucrocodylia previously known from this same basin and suggest the presence of a new taxon, increasing the diversity of this clade in this period in the Neuquén Basin. The specimen from Rincon de los Sauces presents postcraneal characters previously attributed to Notosuchia and Neosuchia, both clades mainly defined by cranial characters. This set of primitive and derived characters prevents the location of its precise phylogenetic position among the Mesoeucrocodylia.
Abstract: Restudy of skulls and available postcrania of the proterochampsian archosauriform Prot... more Abstract: Restudy of skulls and available postcrania of the proterochampsian archosauriform Proterochampsa barrionuevoi from the Ischigualasto Formation (Upper Triassic, Carnian) in the San Juan Province, Argentina, confirms that the genus is diagnosed by autapomorphies that include dermal sculpturing consisting of prominent ridges and nodular protuberances, a large hook‐like lateral projection on the quadratojugal, an antorbital fossa restricted to a depression along the maxilla, lateral expansion of the premaxilla anterior to the premaxilla–maxilla contact, absence of a supratemporal fossa, exclusion of jugal from suborbital fenestra, basal tubera of parabasisphenoid facing ventrally and reaching laterally beyond the basipterygoid process, and a ventral lamina on the angular. Proterochampsa nodosa is a valid species distinguished from P. barrionuevoi by fewer cranial ridges with larger protuberances, relatively smaller supratemporal fenestrae and width of frontals between orbits less than that of the nasals. A phylogenetic analysis supports the monophyly of Proterochampsia consisting of Proterochampsa, Chanaresuchus bonapartei, Gualosuchus reigi, Tropidosuchus romeri and Cerritosaurus binsfeldi. A temporal separation between the two basal proterochampsians with earliest records in the Late Triassic (Proterochampsa and Cerritosaurus) and Chanaresuchus, Gualosuchus and Tropidosuchus in the Middle Triassic indicates hidden proterochampsian diversity in the Middle Triassic.
Geological Society, London, Special Publications, 2013
Proterochampsia is a monophyletic group of crocodile-like archosauriforms currently endemic to th... more Proterochampsia is a monophyletic group of crocodile-like archosauriforms currently endemic to the late Middle and early Late Triassic of South America considered as one of the potential successive sister-taxa of the crown group Archosauria. The proterochampsians come from the Ischigualasto-Villa Unión Basin in the west of Argentina and the Parana Basin in the south of Brazil. The traditional composition of the group includes the genera Cerritosaurus Price 1946, Proterochampsa Reig 1959 (with two species: P. barrionuevoi in Argentina and P. nodosa Barberena 1982 in Brazil), Chanaresuchus Romer (with two species from Argentina: C. bonapartei Romer and C. ischigualastensis Trotteyn et al. 2012), Gualosuchus reigi Romer 1971 and Tropidosuchus romeri Arcucci 1990. After a precladistic history of confusion about their relationships with crocodilians, in the last 20 years new discoveries of taxa, and more systematic and phylogenetic studies, have clarified their position as non-archosauri...
Lewisuchus admixtus is an enigmatic early dinosauriform from the Chañares Formation, Ladinian of ... more Lewisuchus admixtus is an enigmatic early dinosauriform from the Chañares Formation, Ladinian of Argentina, which has been recently considered a member of Silesauridae. Yet, it differs markedly from Late Triassic silesaurids in dental and vertebral anatomy. Indeed, a detailed redescription of its holotype allowed the identification of several features of the skeleton previously unrecognized amongst silesaurids. These include pterygoid teeth, a dorsomedial posttemporal opening on the otoccipital, foramina associated with cranial nerves X-XII on the caudal region of the prootic-otoccipital, and postaxial neck/trunk vertebrae with craniocaudally expanded neural spines. The presence of a single row of presacral scutes was also confirmed. Some elements previously referred to, or found associated with, the holotype, including a lower jaw, pedal elements and an astragalus, more probably correspond to proterochampsid remains. The anatomical information available for the holotype of L. admixtus was rescored into a new phylogenetic dataset for dinosauromorphs, mostly based on previous works. Lewisuchus admixtus and Pseudolagosuchus major are treated as distinct OTUs because their preserved skeletons mostly lack overlapping parts. The parsimony analysis supports the basal position of L. admixtus within dinosauriforms, prior to the silesaurid-dinosaur split, rather than at the base of Silesauridae. This suggests that a higher number of early dinosauriform clades branched in the Middle and Late Triassic than previously suggested.
ABSTRACT Notosuchians are a crocodyliform clade with a rich Gondwanan fossil record, especially i... more ABSTRACT Notosuchians are a crocodyliform clade with a rich Gondwanan fossil record, especially in Cretaceous South American deposits. More than half of all described species come from South America and, around one quarter, have been discovered in the Adamantina Formation (Bauru Group, Brazil). The large amount of notosuchian remains from this formation, along with its chronostratigraphic uncertainty, may be distorting notosuchian palaeodiversity estimates. In order to analyse how these factors could be biasing our interpretations, palaeodiversity estimates were performed excluding and including the Adamantina Formation occurrence data, as well as assigning them to the main age ranges that have been proposed for the formation (Turonian-Santonian and Campanian-Maastrichtian). Furthermore, as other factors might be influencing palaeodiversity fluctuations, a modelling approach was performed to assess which abiotic factors, sampling artefacts, or a combination of them, could be driving these palaeodiversity dynamics. The results showed that the Adamantina Formation is causing a Lagerstätte effect that is distorting palaeodiversity estimates and, depending on the age assigned to that formation, the tempo and magnitude of the maximum palaeodiversity reached during the Late Cretaceous substantially changes. The results also suggest that the temporal bias might affect palaeobiological reconstructions not only in notosuchians but also in other groups.
Teorías de la evolución Notas desde el sur Teorías de la evolución : Notas desde el sur / Leonard... more Teorías de la evolución Notas desde el sur Teorías de la evolución : Notas desde el sur / Leonardo Salgado y Andrea Arcucci. 1a ed.-Viedma : Universidad Nacional de Río Negro, 2016. 264 p.; 15x23 cm Lecturas de Cátedra isbn 978-987-3667-37-4 1. Evolución humana. 2. Teoría de la evolución. 3. Biología evolutiva. i. Arcucci, Andrea ii. Título. cdd 576.8 Este libro se utiliza en las licenciaturas en Geología y Paleontología y en el Profesorado de nivel medio y superior en Biología en las asignaturas de Evolución y Genética, Biología i y ii, Paleontología y Pensamiento y Actividad Científica.
A new lithostrotian sauropod, the small-sized Overosaurus paradasorum n. gen et sp. from the Anac... more A new lithostrotian sauropod, the small-sized Overosaurus paradasorum n. gen et sp. from the Anacleto Formation (Campanian, Late Cretaceous, Neuquén Group, Patagonia, Argentina) is here described. The specimen (MAU-Pv-CO-439) consists of a fully articulated vertebral series from the 10 th cervical to the 20 th caudal vertebra, the last cervical ribs, several dorsal ribs in articulation with their respective vertebrae, the complete right ilium and fragments of the left ilium. Overosaurus paradasorum is diagnosed by a unique combination of characters that includes (1) posterior cervical vertebrae with long pre-and postzygapophyses that project beyond the anterior and posterior borders of the centrum, respectively, (2) postspinal lamina absent in all dorsal neural spines, (3) wide and massive 9 th and 10 th caudal centra that are slightly excavated laterally and have relatively flat ventral surfaces, (4) laminar projection on the posterior border of the second and third dorsal rib, (5) ilium proportionally shorter anteroposteriorly and taller dorsoventrally than in other lithostrotians, and (6) the preacetabular process of the ilium strongly deflected laterally and with a ventrolaterally tapering end. Analysis of the phylogenetic relationships of Overosaurus places it within the Aeolosaurini, as the sister taxon of a monophyletic group formed by Aeolosaurus rionegrinus, A. maximus, Gondwanatitan faustoi and Pitekunsaurus macayai. Overosaurus is a new representative of a highly diversified assemblage of Campanian lithostrotians from Patagonia that includes both Aeolosaurini and saltasaurids (e.g. Saltasaurus, Neuquensaurus)-this small new taxon falls within the low end of the size spectrum represented by these Late Cretaceous sauropods.
Abstract. In South America, tetrapod footprints of Middle Triassic age were only described from t... more Abstract. In South America, tetrapod footprints of Middle Triassic age were only described from the Cuyana (Cerro de las Cabras Formation) and Ischigualasto-Villa Union (Los Rastros Formation) basins in west-central Argentina. They are scarce and remain mostly undescribed. Their significance and the putative trackmakers are identified and discussed within a phylogenetic context in the present contribution. Several groups of tetrapods are suggested to be represented, as non-mammalian therapsids, crurotarsal archosaurs and putative dinosaurs. The presence of crurotarsal archosaurs and non-mammalian therapsids in Cerro de las Cabras Formation suggests a tetrapod fauna more diverse than that documented by the known body fossil record. The ichnites described from the Los Rastros Formation are, until now, the only evidence of amniotes in the Ischigualasto-Villa Union Basin during the deposition of these levels. They indicate the presence of putative dinosaurs, crurotarsal archosaurs and non-mammalian therapsids, which are already well represented in the rest of the sequence by skeletal remains. Resumen. HUELLAS DE TETRAPODOS DEL TRIASICO MEDIO DEL EXTREMO SUR DE AMERICA DEL SUR. En America del Sur, huellas de tetrapodos del Triasico Medio solo se conocen en niveles de las cuencas Cuyana (Formacion Cerro de las Cabras) e Ischigualasto-Villa Union (Formacion Los Rastros), en el centro-oeste de Argentina. Las huellas son escasas y la mayoria de los especimenes no estan descriptos. En el presente trabajo el significado de estas huellas y sus supuestos generadores son discutidos en un contexto filogenetico. Asi, varios grupos de tetrapodos han sido identificados como terapsidos no mamalianos, arcosaurios crurotarsales y probables dinosaurios. La presencia de arcosaurios crurotarsales y terapsidos no mamalianos en niveles de la Formacion Cerro de las Cabras sugiere una fauna mas diversa que lo que indica el registro de restos fosiles esqueletarios conocidos para los mismos niveles. Las icnitas de la Formacion Los Rastros son hasta el momento la unica evidencia de amniotas en la Cuenca de Ischigualasto-Villa Union durante la depositacion de dichos niveles. Ellas indican la existencia de probables dinosaurios, arcosaurios crurotarsales y terapsidos no mamalianos, bien representados en el resto de la sequencia por restos esqueletarios.
Significant paleobiological data has emerged from the San Luis Basin (Early Cretaceous, Aptian-Al... more Significant paleobiological data has emerged from the San Luis Basin (Early Cretaceous, Aptian-Albian in Central Argentina) during the last decades. Two units in this basin include lake paleo-environments with important fossil contents in an excellent state of preservation that could be considered as Konservat Lagerstätten deposits. The association of fossil leaves and pollen grains from the La Cantera Formation is one of the most ancient and complete angiosperm records in South America and the bryophyte association of the same unit constitutes one the most complete records of its type in Argentina. Insects from five different orders have been identified in this association, and three endemic species of aquatic insects from the La Cantera Formation have been described as belonging to the Notonectidae and Corixidae families, including the oldest member of the Anisopinae subfamily. The Pterodaustro guinazui association from the Lagarcito Formation is one of the few fossil associations...
<div><p><i>Lewisuchus admixtus</i> is an enigmatic early dinosauriform fr... more <div><p><i>Lewisuchus admixtus</i> is an enigmatic early dinosauriform from the Chañares Formation, Ladinian of Argentina, which has been recently considered a member of Silesauridae. Yet, it differs markedly from Late Triassic silesaurids in dental and vertebral anatomy. Indeed, a detailed redescription of its holotype allowed the identification of several features of the skeleton previously unrecognized amongst silesaurids. These include pterygoid teeth, a dorsomedial posttemporal opening on the otoccipital, foramina associated with cranial nerves X–XII on the caudal region of the prootic–otoccipital, and postaxial neck/trunk vertebrae with craniocaudally expanded neural spines. The presence of a single row of presacral scutes was also confirmed. Some elements previously referred to, or found associated with, the holotype, including a lower jaw, pedal elements and an astragalus, more probably correspond to proterochampsid remains. The anatomical information available for the holotype of <i>L. admixtus</i> was rescored into a new phylogenetic dataset for dinosauromorphs, mostly based on previous works. <i>Lewisuchus admixtus</i> and <i>Pseudolagosuchus major</i> are treated as distinct OTUs because their preserved skeletons mostly lack overlapping parts. The parsimony analysis supports the basal position of <i>L</i>. <i>admixtus</i> within dinosauriforms, prior to the silesaurid–dinosaur split, rather than at the base of Silesauridae. This suggests that a higher number of early dinosauriform clades branched in the Middle and Late Triassic than previously suggested.</p></div
Fil: Arcucci, Andrea Beatriz. Universidad Nacional de San Luis. Facultad de Quimica, Bioquimica y... more Fil: Arcucci, Andrea Beatriz. Universidad Nacional de San Luis. Facultad de Quimica, Bioquimica y Farmacia. Departamento de Bioquimica y Ciencias Biologicas. Area de Zoologia; Argentina
The present note brings to light a new form of thecodont, pertaining to the Suborder Pseudosuchia... more The present note brings to light a new form of thecodont, pertaining to the Suborder Pseudosuchia (sensu Bonaparte, 1982), which adds to the genera known from the Los Chañares fauna, of Chañarian age (Middle Triassic), from Provincia de La Rioja (Romer, 1971, 1972; Bonaparte, 1975, 1982b). This local Los Chañares fauna, described in general terms by Romer, is very important for our knowledge of thecodonts, as much from a systematic as an evolutionary point of view. This association includes eight genera of thecodonts, in addition to that described here, pertaining to at least six different families. Due to this diversity, this combination is the largest known for the Middle Triassic worldwide, since the records from Europe, East Africa and Brazil are considerably poorer. The recovery of this new lagosuchid brings new anatomical information about the development of the advanced mesotarsal-type tarsus. whose origin is under discussion (Brinkman, 1981; Chatterjee, 1982) and whose more ...
Lagerpeton chanarensis forms part of an important Triassic fauna, produced by the lower part of t... more Lagerpeton chanarensis forms part of an important Triassic fauna, produced by the lower part of the Ischichuca Formation (Chañares Formation of Romer and Jensen, 1966), Los Chañares locality, La Rioja, Argentina, which corresponds to the Chañarian Reptile Age, correlated with the European Anisian (Bonaparte, 1978, 1982b). This faunistic association includes therapsids, both cynodonts and dicynodonts (Romer, 1972c; Bonaparte op. cit.), and thecodonts pertaining to two suborders (Erythrosuchia and Pseudosuchia, sensu Bonaparte, 1982a) and five families: Cerritosauridae, Rauisuchidae, Lagosuchidae, Ornithosuchidae and Sphenosuchidae, represented by several genera (Bonaparte, 1978). The importance of studying this fauna rests in the fact that Middle Triassic thecodonts, particularly from the lower part of this period, represent an important evolutionary moment in the history of archosaurs, since they attempted a great adaptive radiation that was the basis of later evolution of the group...
A NEW CRETACEOUS MESOEUCROCODYLIA FROM THE NORTH OF THE NEUQUÉN BASIN, ARGENTINA. In this contrib... more A NEW CRETACEOUS MESOEUCROCODYLIA FROM THE NORTH OF THE NEUQUÉN BASIN, ARGENTINA. In this contribution, a new specimen of Mesoeucrocodylia from levels attributed to the Plottier Formation (Cretaceous, Upper Coniacian) is described in the locality Yacimiento Narambuena, Rincón de los Sauces, in the north section of the Neuquén Province. The material includes an incomplete subadult specimen with mostly articulated postcranium of an approximate length of 60 cm. The study and comparisons to allow distinguish the specimen from other Mesoeucrocodylia previously known from this same basin and suggest the presence of a new taxon, increasing the diversity of this clade in this period in the Neuquén Basin. The specimen from Rincon de los Sauces presents postcraneal characters previously attributed to Notosuchia and Neosuchia, both clades mainly defined by cranial characters. This set of primitive and derived characters prevents the location of its precise phylogenetic position among the Mesoeucrocodylia.
Abstract: Restudy of skulls and available postcrania of the proterochampsian archosauriform Prot... more Abstract: Restudy of skulls and available postcrania of the proterochampsian archosauriform Proterochampsa barrionuevoi from the Ischigualasto Formation (Upper Triassic, Carnian) in the San Juan Province, Argentina, confirms that the genus is diagnosed by autapomorphies that include dermal sculpturing consisting of prominent ridges and nodular protuberances, a large hook‐like lateral projection on the quadratojugal, an antorbital fossa restricted to a depression along the maxilla, lateral expansion of the premaxilla anterior to the premaxilla–maxilla contact, absence of a supratemporal fossa, exclusion of jugal from suborbital fenestra, basal tubera of parabasisphenoid facing ventrally and reaching laterally beyond the basipterygoid process, and a ventral lamina on the angular. Proterochampsa nodosa is a valid species distinguished from P. barrionuevoi by fewer cranial ridges with larger protuberances, relatively smaller supratemporal fenestrae and width of frontals between orbits less than that of the nasals. A phylogenetic analysis supports the monophyly of Proterochampsia consisting of Proterochampsa, Chanaresuchus bonapartei, Gualosuchus reigi, Tropidosuchus romeri and Cerritosaurus binsfeldi. A temporal separation between the two basal proterochampsians with earliest records in the Late Triassic (Proterochampsa and Cerritosaurus) and Chanaresuchus, Gualosuchus and Tropidosuchus in the Middle Triassic indicates hidden proterochampsian diversity in the Middle Triassic.
Geological Society, London, Special Publications, 2013
Proterochampsia is a monophyletic group of crocodile-like archosauriforms currently endemic to th... more Proterochampsia is a monophyletic group of crocodile-like archosauriforms currently endemic to the late Middle and early Late Triassic of South America considered as one of the potential successive sister-taxa of the crown group Archosauria. The proterochampsians come from the Ischigualasto-Villa Unión Basin in the west of Argentina and the Parana Basin in the south of Brazil. The traditional composition of the group includes the genera Cerritosaurus Price 1946, Proterochampsa Reig 1959 (with two species: P. barrionuevoi in Argentina and P. nodosa Barberena 1982 in Brazil), Chanaresuchus Romer (with two species from Argentina: C. bonapartei Romer and C. ischigualastensis Trotteyn et al. 2012), Gualosuchus reigi Romer 1971 and Tropidosuchus romeri Arcucci 1990. After a precladistic history of confusion about their relationships with crocodilians, in the last 20 years new discoveries of taxa, and more systematic and phylogenetic studies, have clarified their position as non-archosauri...
Lewisuchus admixtus is an enigmatic early dinosauriform from the Chañares Formation, Ladinian of ... more Lewisuchus admixtus is an enigmatic early dinosauriform from the Chañares Formation, Ladinian of Argentina, which has been recently considered a member of Silesauridae. Yet, it differs markedly from Late Triassic silesaurids in dental and vertebral anatomy. Indeed, a detailed redescription of its holotype allowed the identification of several features of the skeleton previously unrecognized amongst silesaurids. These include pterygoid teeth, a dorsomedial posttemporal opening on the otoccipital, foramina associated with cranial nerves X-XII on the caudal region of the prootic-otoccipital, and postaxial neck/trunk vertebrae with craniocaudally expanded neural spines. The presence of a single row of presacral scutes was also confirmed. Some elements previously referred to, or found associated with, the holotype, including a lower jaw, pedal elements and an astragalus, more probably correspond to proterochampsid remains. The anatomical information available for the holotype of L. admixtus was rescored into a new phylogenetic dataset for dinosauromorphs, mostly based on previous works. Lewisuchus admixtus and Pseudolagosuchus major are treated as distinct OTUs because their preserved skeletons mostly lack overlapping parts. The parsimony analysis supports the basal position of L. admixtus within dinosauriforms, prior to the silesaurid-dinosaur split, rather than at the base of Silesauridae. This suggests that a higher number of early dinosauriform clades branched in the Middle and Late Triassic than previously suggested.
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