Gianechini, F. A., Codorniú, L., Arcucci, A. B., Elías, G. C., and D. Rivarola. 2015. Archosauriform remains from the Late Triassic of San Luis province, Argentina, Quebrada del Barro Formation, Marayes–El Carrizal Basin. Journal of South American Earth Sciences. DOI:10.1016/j.jsames.2015.12.012
http://www.sciencedirect.com/science/article/pii/S0895981115301073
Abstract- Here we present archosauriform remains from ‘Abra de los Colorados’, a fossiliferous locality at Sierra de Guayaguas, NW San Luis Province. Two fossiliferous levels were identified in outcrops of the Quebrada del Barro Formation (Norian), which represent the southernmost outcrops of the Marayes–El Carrizal Basin. These levels are composed by massive muddy lithofacies, interpreted as floodplain deposits. The specimens consist of one incomplete maxilla (MIC-V718), one caudal vertebra (MIC-V719), one metatarsal (MIC-V720) and one indeterminate appendicular bone (MIC-V721). The materials can be assigned to Archosauriformes but the fragmentary nature and lack of unambiguous synapomorphies preclude a more precise taxomic assignment. The maxilla is remarkably large and robust and represents the posterior process. It preserved one partially erupted tooth with ziphodont morphology. This bone shows some anatomical traits and size match with ‘rauisuchians’ and theropods. MIC-V719 corresponds to a proximal caudal vertebra. It has a high centrum, a ventral longitudinal furrow, expanded articular processes for the chevrons, a posteriorly displaced diapophysis located below the level of the prezygapophyses, and short prezygapophyses. This vertebra would be from an indeterminate archosauriform. MIC-V720 presents a cylindrical diaphysis, with a well-developed distal trochlea, which present resemblances with metatarsals of theropods, pseudosuchians, and silesaurids, although the size matches better with theropods. MIC-V721 has a slender diaphysis and a convex triangular articular surface, and corresponds to an indeterminate archosauriform. Despite being fragmentary, these materials indicate the presence of a diverse archosauriforms association from Late Triassic beds of San Luis. Thus, they add to the faunal assemblage recently reported from this basin at San Juan Province, which is much rich and diverse than the coeval paleofauna well known from Los Colorados Formation in the Ischigualasto–Villa Union Basin.
Showing posts with label Argentina. Show all posts
Showing posts with label Argentina. Show all posts
A New Lagerpetid Dinosauromorph from the Late Triassic of Argentina
Martínez, R. N., Apaldetti, C., Correa, G. A., and D. Abelín. 2015. A Norian lagerpetid dinosauromorph from the Quebrada del Barro Formation, northwestern Argentina. Ameghiniana (future issue) doi:10.5710/AMGH.21.06.2015.2894
Abstract: The early evolution of Ornithodira, the clade that includes pterosaurs and dinosaurs, is poorly known. Until a decade ago, the basal radiation of Dinosauromorpha, the clade including dinosaurs and birds, was poorly understood because of a scarce of fossil record, which was restricted to specimens known of the Ladinian Chañares Formation from Argentina. In the last years the discovery of several non-dinosaurian dinosauromorphs dramatically expanded this record and also demonstrated that this group—previously restricted to the Middle Triassic—persisted at least well into the Norian. Although Norian non-dinosaurian dinosauromorphs have been reported from several places around the world, the only known Norian non-dinosauriform dinosauromorphs—Dromomeron romeri and Dromomeron gregorii—come from North America. We report here the first record from the Southern Hemisphere of a non-dinosauriform dinosauromorph, Dromomeron gigas sp. nov., from the Norian Quebrada del Barro Formation, northwestern Argentina. A phylogenetic analysis recovers Dromomeron gigas nested into the monophyletic group Lagerpetidae, and as the sister taxon to Dromomeron romeri. The inclusion of D. gigas within Lagerpetidae suggests that body size increased in this lineage over time, as was previously demonstrated for Dinosauriformes as a whole, and that lagerpetids reached a larger size than previously thought. Finally, the new finding provides novel information on the basal radiation of Dinosauromorpha constituting the first record of a Norian association of dinosaurs with non-dinosauriform dinosauromorphs outside North America.
Abstract: The early evolution of Ornithodira, the clade that includes pterosaurs and dinosaurs, is poorly known. Until a decade ago, the basal radiation of Dinosauromorpha, the clade including dinosaurs and birds, was poorly understood because of a scarce of fossil record, which was restricted to specimens known of the Ladinian Chañares Formation from Argentina. In the last years the discovery of several non-dinosaurian dinosauromorphs dramatically expanded this record and also demonstrated that this group—previously restricted to the Middle Triassic—persisted at least well into the Norian. Although Norian non-dinosaurian dinosauromorphs have been reported from several places around the world, the only known Norian non-dinosauriform dinosauromorphs—Dromomeron romeri and Dromomeron gregorii—come from North America. We report here the first record from the Southern Hemisphere of a non-dinosauriform dinosauromorph, Dromomeron gigas sp. nov., from the Norian Quebrada del Barro Formation, northwestern Argentina. A phylogenetic analysis recovers Dromomeron gigas nested into the monophyletic group Lagerpetidae, and as the sister taxon to Dromomeron romeri. The inclusion of D. gigas within Lagerpetidae suggests that body size increased in this lineage over time, as was previously demonstrated for Dinosauriformes as a whole, and that lagerpetids reached a larger size than previously thought. Finally, the new finding provides novel information on the basal radiation of Dinosauromorpha constituting the first record of a Norian association of dinosaurs with non-dinosauriform dinosauromorphs outside North America.
Description of the Ornithosuchid Archosaurian Venaticosuchus rusconii from the Late Triassic of Argentina and the Phylogeny of the Ornithosuchidae
Von Baczko, M. B., Desojo, J. B., and D. Pol. 2014. Anatomy and phylogenetic position of Venaticosuchus rusconii Bonaparte, 1970 (Archosauria, Pseudosuchia), from the Ischigualasto Formation (Late Triassic), La Rioja, Argentina. Journal of Vertebrate Paleontology 34:1342-1356 DOI:10.1080/02724634.2014.860150
Abstract - Ornithosuchidae is a group of Late Triassic pseudosuchian archosaurs of controversial phylogenetic affinities. This clade currently comprises three taxa: Venaticosuchus rusconii and Riojasuchus tenuisceps, both from Argentina, and Ornithosuchus longidens, from Scotland. V. rusconii was erected on the basis of an incomplete skull with articulated lower jaws and some elements of the postcranium that are currently lost. Venaticosuchus rusconii is redescribed here and included for the first time in a phylogenetic analysis to test its affinities with ornithosuchids. The bizarre morphology of V. rusconii has a unique combination of traits that distinguishes it from the other ornithosuchids, such as basipterygoid processes directed ventrally, dentary with the dorsal margin of the anterior end dorsally expanded, articular without a foramen on its medial side, and the absence of a surangular foramen, corroborating the validity of this taxon. V. rusconii is recovered as an ornithosuchid more closely related to R. tenuisceps than to O. longidens, based on the presence of a nearly pointed anterior margin of the antorbital fenestra, and a vertical bony strut of the jugal that separates the antorbital fenestra from the infratemporal fenestra.
Abstract - Ornithosuchidae is a group of Late Triassic pseudosuchian archosaurs of controversial phylogenetic affinities. This clade currently comprises three taxa: Venaticosuchus rusconii and Riojasuchus tenuisceps, both from Argentina, and Ornithosuchus longidens, from Scotland. V. rusconii was erected on the basis of an incomplete skull with articulated lower jaws and some elements of the postcranium that are currently lost. Venaticosuchus rusconii is redescribed here and included for the first time in a phylogenetic analysis to test its affinities with ornithosuchids. The bizarre morphology of V. rusconii has a unique combination of traits that distinguishes it from the other ornithosuchids, such as basipterygoid processes directed ventrally, dentary with the dorsal margin of the anterior end dorsally expanded, articular without a foramen on its medial side, and the absence of a surangular foramen, corroborating the validity of this taxon. V. rusconii is recovered as an ornithosuchid more closely related to R. tenuisceps than to O. longidens, based on the presence of a nearly pointed anterior margin of the antorbital fenestra, and a vertical bony strut of the jugal that separates the antorbital fenestra from the infratemporal fenestra.
Ignotosaurus fragilis, a New Silesaurid Dinosauriform from the Late Triassic of Argentina and the Vertebrate Succession of the Ischigualasto Formation
Martínez, R. N., Apaldetti, C., Alcober, O. A., Colombi, C. E., Sereno, P. C., Fernandez, E., Santi Malnis, P., Correa, G. A., and D. Abelin. 2013. Vertebrate succession in the Ischigualasto
Formation, Journal of Vertebrate Paleontology, 32:sup1, 10-30, DOI: 10.1080/02724634.2013.818546
Abstract - The Upper Triassic (Carnian–Norian) Ischigualasto Formation has yielded a diverse vertebrate fauna that records the initial phase of dinosaur evolution. Radioisotopic dates from ash layers within the formation provide a chronostratigraphic framework, and stratigraphic and sedimetological studies have subdivided the formation into four members and three abundance-based biozones. We describe two new basal dinosauromorphs, an unnamed lagerpetid and a new silesaurid, Ignotosaurus fragilis, gen. et sp. nov., which increase to 29 the number of vertebrates in the Ischigualasto fauna. We provide a census of 848 fossil specimens representing 26 vertebrate taxa logged to stratigraphic intervals of 50 m. This temporally calibrated census shows that abundance and taxonomic diversity within the Ischigualasto Formation does not change suddenly but rather appears to gradually decline in response to climatic deterioration. The only abrupt shift in faunal composition occurs at the end of the second of three biozones, when the abundant cynodont Exaeretodon is replaced by the rare dicynodont Jachaleria.
Formation, Journal of Vertebrate Paleontology, 32:sup1, 10-30, DOI: 10.1080/02724634.2013.818546
Abstract - The Upper Triassic (Carnian–Norian) Ischigualasto Formation has yielded a diverse vertebrate fauna that records the initial phase of dinosaur evolution. Radioisotopic dates from ash layers within the formation provide a chronostratigraphic framework, and stratigraphic and sedimetological studies have subdivided the formation into four members and three abundance-based biozones. We describe two new basal dinosauromorphs, an unnamed lagerpetid and a new silesaurid, Ignotosaurus fragilis, gen. et sp. nov., which increase to 29 the number of vertebrates in the Ischigualasto fauna. We provide a census of 848 fossil specimens representing 26 vertebrate taxa logged to stratigraphic intervals of 50 m. This temporally calibrated census shows that abundance and taxonomic diversity within the Ischigualasto Formation does not change suddenly but rather appears to gradually decline in response to climatic deterioration. The only abrupt shift in faunal composition occurs at the end of the second of three biozones, when the abundant cynodont Exaeretodon is replaced by the rare dicynodont Jachaleria.
Osteology of Eoraptor lunensis
Finally this is published. Now if I can just get the Revueltosaurus monograph out all will be right in the Triassic world, right?
Sereno, P. C., Martínez, R. N., and O. A. Alcober. 2013. Osteology of Eoraptor lunensis (Dinosauria, Sauropodomorpha). Journal of Vertebrate Paleontology Memoir 12:83-179.
Abstract - We describe the basal sauropodomorph Eoraptor lunensis, based on the nearly complete holotypic skeleton and referred specimens, all of which were discovered in the Cancha de Bochas Member of the Ischigualasto Formation in northwestern Argentina. The lightly built skull has a slightly enlarged external naris and a spacious antorbital fossa with a prominent, everted dorsal margin and internal wall lacking any pneumatic extensions into surrounding bones. The tall quadrate is lapped along its anterior margin by the long, slender ventral process of the squamosal, and the lower jaw has a mid-mandibular joint between a tongue-shaped splenial process and a trough in the angular. All but the posterior-most maxillary and dentary crowns have a basal constriction, and the marginal denticles are larger and oriented more vertically than in typical theropod serrations. Rows of rudimentary palatal teeth are present on the pterygoid. Vertebral centra are hollow, although not demonstrably pneumatized,and all long bones have hollow shafts. The radius and ulna are more robust, the manus proportionately shorter, and the manual unguals less recurved than in the contemporaneous basal theropod Eodromaeus murphi. An outstanding feature of the manus of Eoraptor is the twisted shaft of the first phalanx of the pollex, which deflects medially the tip of the ungual as in basal sauropodomorphs. The long bones of the hind limb have more robust shafts than those of Eodromaeus, although in both genera the tibia remains slightly longer than the femur.
Resumen - Describimos el sauropodomorfo basal Eoraptor lunensis basados en el esqueleto prácticamente completo del holotipo y especímenes referidos, todos ellos descubiertos en el Miembro Cancha de Bochas de la Formaci ón Ischigualasto, en el noroeste de Argentina. El grácil cráneo tiene las narinas externas ligeramente agrandadas, una amplia fosa antorbital con un margen dorsal prominente y evertido, y ausencia de extensiones neumáticas en los huesos circundantes. El alto cuadrado presenta todo su margen anterior solapado por el delgado proceso ventral del escamoso y la mandíbula tiene una junta medial entre un proceso linguoide del esplenial y un canal en el angular. Todas las coronas dentarias y maxilares, menos las más posteriores, tienen una constricci ón basal y los dentículos marginales son largos y orientados más verticalmente que en el aserrado típico de los terópodos. El pterigoideo tiene filas de dientes palatales rudimentarios. Los centros de las vértebras son huecos, aunque no demostrablemente neumatizados, y todos los huesos largos tienen las di íafisis huecas. El radio y la ulna son más robustos, la mano proporcionalmente corta y los ungueales manuales menos recurvados que en el contemporáneo terópodo basal Eodromaeus murphi. Una característica sobresaliente de la mano de Eoraptor es la rotaci ón de la primera falange del pulgar, que desvía medialmente la punta del ungueal como en los sauropodomorfos basales. Los huesos largos de las piernas tienen di áfisis más robustas que aquellas de Eodromaeus, aunque en ambos géneros la tibia es ligeramente más larga que el fémur.
Sereno, P. C., Martínez, R. N., and O. A. Alcober. 2013. Osteology of Eoraptor lunensis (Dinosauria, Sauropodomorpha). Journal of Vertebrate Paleontology Memoir 12:83-179.
Abstract - We describe the basal sauropodomorph Eoraptor lunensis, based on the nearly complete holotypic skeleton and referred specimens, all of which were discovered in the Cancha de Bochas Member of the Ischigualasto Formation in northwestern Argentina. The lightly built skull has a slightly enlarged external naris and a spacious antorbital fossa with a prominent, everted dorsal margin and internal wall lacking any pneumatic extensions into surrounding bones. The tall quadrate is lapped along its anterior margin by the long, slender ventral process of the squamosal, and the lower jaw has a mid-mandibular joint between a tongue-shaped splenial process and a trough in the angular. All but the posterior-most maxillary and dentary crowns have a basal constriction, and the marginal denticles are larger and oriented more vertically than in typical theropod serrations. Rows of rudimentary palatal teeth are present on the pterygoid. Vertebral centra are hollow, although not demonstrably pneumatized,and all long bones have hollow shafts. The radius and ulna are more robust, the manus proportionately shorter, and the manual unguals less recurved than in the contemporaneous basal theropod Eodromaeus murphi. An outstanding feature of the manus of Eoraptor is the twisted shaft of the first phalanx of the pollex, which deflects medially the tip of the ungual as in basal sauropodomorphs. The long bones of the hind limb have more robust shafts than those of Eodromaeus, although in both genera the tibia remains slightly longer than the femur.
Resumen - Describimos el sauropodomorfo basal Eoraptor lunensis basados en el esqueleto prácticamente completo del holotipo y especímenes referidos, todos ellos descubiertos en el Miembro Cancha de Bochas de la Formaci ón Ischigualasto, en el noroeste de Argentina. El grácil cráneo tiene las narinas externas ligeramente agrandadas, una amplia fosa antorbital con un margen dorsal prominente y evertido, y ausencia de extensiones neumáticas en los huesos circundantes. El alto cuadrado presenta todo su margen anterior solapado por el delgado proceso ventral del escamoso y la mandíbula tiene una junta medial entre un proceso linguoide del esplenial y un canal en el angular. Todas las coronas dentarias y maxilares, menos las más posteriores, tienen una constricci ón basal y los dentículos marginales son largos y orientados más verticalmente que en el aserrado típico de los terópodos. El pterigoideo tiene filas de dientes palatales rudimentarios. Los centros de las vértebras son huecos, aunque no demostrablemente neumatizados, y todos los huesos largos tienen las di íafisis huecas. El radio y la ulna son más robustos, la mano proporcionalmente corta y los ungueales manuales menos recurvados que en el contemporáneo terópodo basal Eodromaeus murphi. Una característica sobresaliente de la mano de Eoraptor es la rotaci ón de la primera falange del pulgar, que desvía medialmente la punta del ungueal como en los sauropodomorfos basales. Los huesos largos de las piernas tienen di áfisis más robustas que aquellas de Eodromaeus, aunque en ambos géneros la tibia es ligeramente más larga que el fémur.
Bone Diagenesis Study of Early Triassic Cynodonts from Argentina
Previtera, E., D'Angelo, J. A., and A. C. Mancuso. 2013. Preliminary chemometric study of bone diagenesis in Early Triassic cynodonts from Mendoza, Argentina. Ameghiniana 50:460-468.
Abstract - The non-mammalian therapsids dominated the terrestrial ecosystems during the Late Paleozoic–Early Mesozoic. The cynodonts have been studied from a taxonomic, osteologic and morphological perspective. However, taphonomy using chemometrics has been barely explored. This report includes a rib and an appendicular bone of cynodonts from the Puesto Viejo Group (Mendoza, Argentina). These fossils are studied for the first time using SEM-EDX. Semi-quantitative data derived from SEM-EDX spectra is evaluated by principal component analysis to gain new insights regarding the different diagenetic pathways of bone microstructure. The multivariate model supports the distinction of different sampled areas (bone, transition zone and rock matrix), in terms of chemical parameters. Differentiation is based mainly on varying contents of Ca, P, F, Si, Al, K, O, Mn and Fe. Variable concentrations of Fe and Mn could be related to different facies (floodplain and crevasse splay). These results along with thin section petrographical analysis confirm –in one of the cases– the substitution of hydroxyapatite by fluorapatite in the bone microstructure. Fossil-diagenetic processes observed herein include substitution, fracturing, brittle deformation and different permineralization events. Permineralization stages during burial history include infilling of vascular canals, trabeculae and fractures with hematite, manganite and calcite. The presence of calcite and iron enrichment indicates local reducing conditions below water-table during precipitation. This chemometric approach to the study of Triassic cynodont remains proved useful for assessing the chemical changes in bone microstructure.
Resumen - Los terápsidos no-mamaliformes dominaron los ecosistemas terrestres durante el Paleozoico Tardío–Mesozoico Temprano. Los cinodontes han sido estudiados desde una perspectiva taxonómica, osteológica y morfológica. Sin embargo, análisis tafonómicos usando quimiometría son escasos. Esta contribución incluye una costilla y un hueso apendicular de cinodontes del Grupo Puesto Viejo (Mendoza, Argentina). Estos fósiles se analizaron por primera vez usando SEM-EDX. Los datos semi-cuantitativos derivados de SEM-EDX se evaluaron mediante análisis de componentes principales para obtener nuevos conocimientos sobre las diferentes vías diagenéticas de la microestructura ósea. El modelo multivariado apoya la distinción de las diferentes áreas de la muestra (hueso, zona de transición y matriz rocosa), en términos de parámetros químicos. La diferenciación se basa principalmente en diferentes contenidos de Ca, P, F, Si, Al, K, O, Mn y Fe. Concentraciones variables de Fe y Mn pueden asociarse a las diferentes facies (planicie de inundación y depósitos de desbordamiento). Estos resultados, junto con los análisis petrográficos de secciones delgadas confirman en uno de los casos la sustitución de la hidroxiapatita por fluorapatita en la microestructura ósea. Los procesos fósildiageneticos observados incluyen sustitución, fracturación, deformación frágil y diferentes eventos de permineralización. Las etapas de permineralización incluyen rellenos de hematita, manganita y calcita, en canales vasculares, trabéculas y fracturas, durante el enterramiento. La presencia de calcita y de hierro indica condiciones reductoras locales bajo el nivel freático durante la precipitación. Este enfoque quimiométrico para el estudio de cinodontes triásicos demostró ser útil para evaluar los cambios químicos de la microestructura ósea.
Abstract - The non-mammalian therapsids dominated the terrestrial ecosystems during the Late Paleozoic–Early Mesozoic. The cynodonts have been studied from a taxonomic, osteologic and morphological perspective. However, taphonomy using chemometrics has been barely explored. This report includes a rib and an appendicular bone of cynodonts from the Puesto Viejo Group (Mendoza, Argentina). These fossils are studied for the first time using SEM-EDX. Semi-quantitative data derived from SEM-EDX spectra is evaluated by principal component analysis to gain new insights regarding the different diagenetic pathways of bone microstructure. The multivariate model supports the distinction of different sampled areas (bone, transition zone and rock matrix), in terms of chemical parameters. Differentiation is based mainly on varying contents of Ca, P, F, Si, Al, K, O, Mn and Fe. Variable concentrations of Fe and Mn could be related to different facies (floodplain and crevasse splay). These results along with thin section petrographical analysis confirm –in one of the cases– the substitution of hydroxyapatite by fluorapatite in the bone microstructure. Fossil-diagenetic processes observed herein include substitution, fracturing, brittle deformation and different permineralization events. Permineralization stages during burial history include infilling of vascular canals, trabeculae and fractures with hematite, manganite and calcite. The presence of calcite and iron enrichment indicates local reducing conditions below water-table during precipitation. This chemometric approach to the study of Triassic cynodont remains proved useful for assessing the chemical changes in bone microstructure.
Resumen - Los terápsidos no-mamaliformes dominaron los ecosistemas terrestres durante el Paleozoico Tardío–Mesozoico Temprano. Los cinodontes han sido estudiados desde una perspectiva taxonómica, osteológica y morfológica. Sin embargo, análisis tafonómicos usando quimiometría son escasos. Esta contribución incluye una costilla y un hueso apendicular de cinodontes del Grupo Puesto Viejo (Mendoza, Argentina). Estos fósiles se analizaron por primera vez usando SEM-EDX. Los datos semi-cuantitativos derivados de SEM-EDX se evaluaron mediante análisis de componentes principales para obtener nuevos conocimientos sobre las diferentes vías diagenéticas de la microestructura ósea. El modelo multivariado apoya la distinción de las diferentes áreas de la muestra (hueso, zona de transición y matriz rocosa), en términos de parámetros químicos. La diferenciación se basa principalmente en diferentes contenidos de Ca, P, F, Si, Al, K, O, Mn y Fe. Concentraciones variables de Fe y Mn pueden asociarse a las diferentes facies (planicie de inundación y depósitos de desbordamiento). Estos resultados, junto con los análisis petrográficos de secciones delgadas confirman en uno de los casos la sustitución de la hidroxiapatita por fluorapatita en la microestructura ósea. Los procesos fósildiageneticos observados incluyen sustitución, fracturación, deformación frágil y diferentes eventos de permineralización. Las etapas de permineralización incluyen rellenos de hematita, manganita y calcita, en canales vasculares, trabéculas y fracturas, durante el enterramiento. La presencia de calcita y de hierro indica condiciones reductoras locales bajo el nivel freático durante la precipitación. Este enfoque quimiométrico para el estudio de cinodontes triásicos demostró ser útil para evaluar los cambios químicos de la microestructura ósea.
A New Non-mammaliaform Eucynodont from the Ischigualasto Formation of Argentina
Martínez, R. N., Fernandez, E., and O. A. Alcober. 2013. A new non-mammaliaform eucynodont from the Carnian-Norian Ischigualasto Formation, Northwestern Argentina. Revista Brasileira de Paleontologia 16: 61-76. doi:10.4072/rbp.2013.1.05
Abstract - The record of non-mammaliaformes eucynodonts from the Carnian-Norian Ischigualasto Formation is diverse and abundant, including a medium to large size herbivore and small carnivores. Here is described a new small eucynodont from the Ischigualasto Formation, on the basis of a partial skull. The new taxon is characterized by palatal process of the premaxilla extending posterior to the level of the first postcanine; deep and large maxillary laterodorsal fossa that opens at the level of the root of the upper canine; and postorbital bar diverging posterolaterally at very low angle (35.6°) from the anteroposterior axis of the skull. Results from a phylogenetic analysis supports the new genus placement as a probainognathian eucynodont, more derived than Probainognathus Romer, and more closely related to Ecteninion Martinez, May & Forster and Trucidocynodon Oliveira, Soares & Schultz than to any other eucynodont. Ecteniniidae is proposed as a new clade including the new genus, Ecteninion and Trucidocynodon, and in the phylogenetic hypothesis represents the sister-group of Prozostrodontia (Prozostrodon Bonaparte & Barberena, Tritylodontidae and Mammaliaformes). Additionally, the new taxon from the Ischigualasto Formation shows that the Scaphonyx-Exaeretodon-Herrerasaurus biozone has similar cynodont diversity than the supposedly contemporaneous Hyperodapedon Assemblage Zone of Santa Maria 2 Sequence, in Southern Brazil.
Abstract - The record of non-mammaliaformes eucynodonts from the Carnian-Norian Ischigualasto Formation is diverse and abundant, including a medium to large size herbivore and small carnivores. Here is described a new small eucynodont from the Ischigualasto Formation, on the basis of a partial skull. The new taxon is characterized by palatal process of the premaxilla extending posterior to the level of the first postcanine; deep and large maxillary laterodorsal fossa that opens at the level of the root of the upper canine; and postorbital bar diverging posterolaterally at very low angle (35.6°) from the anteroposterior axis of the skull. Results from a phylogenetic analysis supports the new genus placement as a probainognathian eucynodont, more derived than Probainognathus Romer, and more closely related to Ecteninion Martinez, May & Forster and Trucidocynodon Oliveira, Soares & Schultz than to any other eucynodont. Ecteniniidae is proposed as a new clade including the new genus, Ecteninion and Trucidocynodon, and in the phylogenetic hypothesis represents the sister-group of Prozostrodontia (Prozostrodon Bonaparte & Barberena, Tritylodontidae and Mammaliaformes). Additionally, the new taxon from the Ischigualasto Formation shows that the Scaphonyx-Exaeretodon-Herrerasaurus biozone has similar cynodont diversity than the supposedly contemporaneous Hyperodapedon Assemblage Zone of Santa Maria 2 Sequence, in Southern Brazil.
Postcranial Anatomy of a Late Triassic Sauropodomorph from Argentina
Apaldetti, C., Diego Pol, D., and A. Yates. 2012. The postcranial anatomy of Coloradisaurus brevis (Dinosauria: Sauropodomorpha) from the Late Triassic of Argentina and its phylogenetic implications. Palaeontology (Early View) DOI: 10.1111/j.1475-4983.2012.
Abstract - Basal sauropodomorphs from the Upper Triassic Los Colorados Formation
of north-western Argentina have been known for several decades but
most of them are only briefly described. New postrcanial remains of
Coloradisaurus brevis, the most gracile sauropodomorph from this unit,
are described here and evaluated within a phylogenetic context. These
materials belong to a single individual and include elements of the
vertebral column, pectoral girdle, incomplete forelimb, pelvis and
hindlimb. These elements share an autapomorphic feature with the type
specimen of Coloradisaurus brevis and provide novel and unique
features that diagnose this taxon, such as pubic apron with
semicircular cross-section and with a depression on its anterior
surface, distal surface of the tibia deflected and facing
posterodistally and well-developed pyramidal dorsal process of the
posteromedial corner of the astragalus. Several postcranial characters
of Coloradisaurus are exclusively shared with Lufengosaurus, from the
Lower Jurassic of China. The inclusion of this information in two
recent phylogenetic data sets depicts Coloradisaurus as closely
related to Lufengosaurus and well nested within Plateosauria. Both
data sets used indicate strong character support for the inclusion of
Coloradisaurus and Lufengosaurus within Massospondylidae.
Abstract - Basal sauropodomorphs from the Upper Triassic Los Colorados Formation
of north-western Argentina have been known for several decades but
most of them are only briefly described. New postrcanial remains of
Coloradisaurus brevis, the most gracile sauropodomorph from this unit,
are described here and evaluated within a phylogenetic context. These
materials belong to a single individual and include elements of the
vertebral column, pectoral girdle, incomplete forelimb, pelvis and
hindlimb. These elements share an autapomorphic feature with the type
specimen of Coloradisaurus brevis and provide novel and unique
features that diagnose this taxon, such as pubic apron with
semicircular cross-section and with a depression on its anterior
surface, distal surface of the tibia deflected and facing
posterodistally and well-developed pyramidal dorsal process of the
posteromedial corner of the astragalus. Several postcranial characters
of Coloradisaurus are exclusively shared with Lufengosaurus, from the
Lower Jurassic of China. The inclusion of this information in two
recent phylogenetic data sets depicts Coloradisaurus as closely
related to Lufengosaurus and well nested within Plateosauria. Both
data sets used indicate strong character support for the inclusion of
Coloradisaurus and Lufengosaurus within Massospondylidae.
Reanalysis of the Archosauriform Proterochampsa from the Late Triassic of Argentina
Dilkes,
D., and A. Arcucci. 2012. Proterochampsa
barrionuevoi (Archosauriformes: Proterochampsia) from The Late Triassic
(Carnian) of Argentina and a phylogenetic analysis of Proterochampsia.
Palaeontology early online. doi: 10.1111/j.1475-4983.2012.01170.x http://onlinelibrary.wiley.com/doi/10.1111/j.1475-4983.2012.01170.x/abstract
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.
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.
Hind limb osteology of Gracilisuchus stipanicicorum
Lecuona, A., and J. B. Desojo 2011. Hind limb osteology of Gracilisuchus
stipanicicorum (Archosauria: Pseudosuchia). Earth and Environmental Science Transactions of the Royal Society of Edinburgh, 102, 105–128.
Abstract - Gracilisuchus stipanicicorum Romer, 1972, from the Middle-Late Triassic of the Ischigualasto–Villa Unio´n Basin of Argentina, is an extinct pseudosuchian archosaur on the stem to Crocodylomorpha. The pelvic girdle and hind limb anatomy of a referred specimen of Gracilisuchus stipanicicorum is described and compared with that from a broad range of archosauriform taxa, including basal members such as crurotarsans and basal ornithodirans. The description of this specimen reveals new information on the anatomy of the pelvic girdle and hind limb of Gracilisuchus, through a detailed examination of some anatomical regions barely or not previously described, as well as reinterpretations of previous features. The phylogenetic affinities of Gracilisuchus within the Archosauria remain to be tested, but Gracilisuchus shares two putative synapomorphies with some non-crocodyliform crocodylomorphs, providing tentative support for the monophyly of Sphenosuchia (e.g., Sereno & Wild 1992; Wu & Chatterjee 1993) and the close relationship of Gracilisuchus to that clade. These characteristics are: (i) the morphology and poor development of the femoral fourth trochanter, closely resembling the condition of Pseudhesperosuchus and Trialestes; and (ii) a poor anterior development of the femoral head, shared with Pseudhesperosuchus. On the other hand there are characters that reject the inclusion of Gracilisuchus within Crocodylomorpha (Nesbitt 2011), such as the absence of an imperforated acetabulum, and that rather suggests a sister-taxon position to Crocodylomorpha.
New Postcranial material of Proterochampsa barrionuevoi from the Upper Triassic of Argentina
Trotteyn, M. J. 2011. Material postcraneano de Proterochampsa barrionuevoi Reig, 1959 (Diapsida: Archosauriformes) del Triásico Superior del centro-oeste de Argentina. Ameghiniana 48:424-446.
Resumen - Los proterochámpsidos son miembros del clado Archosauriformes y se distinguen del resto por presentar cráneo predominantemente deprimido, transversalmente expandido en el extremo posterior, hocico angosto y alargado longitudinalmente, y narinas ubicadas sobre la línea media, ausencia de postfrontal y presencia de pie asimétrico. La familia Proterochampsidae se compone de cinco géneros presentes en las formaciones triásicas de Argentina y Brasil. En esta familia se incluye la especie argentina Proterochampsa barrionuevoi Reig, proveniente de la Formación Ischigualasto (Triásico Superior). Este taxón era conocido por el cráneo y algunas vértebras cervicales, pero el resto del material poscraneano era totalmente desconocido hasta el presente. En esta contribución se describe detalladamente un ejemplar de Proterochampsa barrionuevoi (PVSJ 606), incluyendo el cráneo, toda la serie vertebral, escápulas, coracoides, cintura pélvica, húmero derecho, radio y ulna del mismo lado, ambos fémures y miembro posterior derecho casi completo. Asimismo se presenta una diagnosis enmendada para la especie, constando de los siguientes caracteres neurocraneales diagnósticos: depresión semilunar expuesta ventrolateralmente, fosa basiesfenoidea rodeada rostrolateralmente por un reborde con forma de “V” con sus ramas convexas. Entre los caracteres que diferencian a P. barrionuevoi de la especie brasilera P. nodosa se citan: angostamiento anterior del hocico menos gradual que el de P. nodosa, occiput más deprimido, narinas lanceoladas con ambos extremos aguzados y frontal menos irregular que el de P. nodosa.
POSTCRANIAL MATERIAL OF PROTEROCHAMPSA BARRIONUEVOI REIG, 1959 (DIAPSIDA: ARCHOSAURIFORMES) FROM THE UPPER TRIASSIC OF CENTRAL-WESTERN ARGENTINA.
POSTCRANIAL MATERIAL OF PROTEROCHAMPSA BARRIONUEVOI REIG, 1959 (DIAPSIDA: ARCHOSAURIFORMES) FROM THE UPPER TRIASSIC OF CENTRAL-WESTERN ARGENTINA.
Abstract - Proterochampsids are members of the clade Archosauriformes, a group distinguished from others because of its depressed skulls transversely expanded at the posterior end, narrow and longitudinally long snout, nares located close to the midline, absence of postfrontals, and presence of an assymmetric pes. The family Proterochampsidae includes five genera recorded in Triassic formations of Argentina and Brazil. In this family is included the Argentinean species Proterochampsa barrionuevoi Reig, from the Late Triassic Ischigualasto Formation. This taxon was known from skulls and cervical vertebrae, but the rest of the postcranium remained unknown until now. Herein, a new and almost complete specimen of Proterochampsa barrionuevoi is described in detail (PVSJ 606). The specimen includes skull, complete vertebral series, scapulae, coracoids, pelvic girdle, right humerus, right radius and ulna, both femora, and complete right hindlimb. An emended diagnosis considering neurocranial features –semilunar depression ventrolaterally exposed, basisphenoidal fossa surround by a rostrolateraly V-shaped ridge with convex branches– is provided. The features distinguishing P. barrionuevoi from the Brazilian species P. nodosa are: snout becoming narrow anteriorly in a less gradual manner than in P. nodosa, lower occiput, nares lanceolate with narrow anterior and posterior ends, and frontal less irregular that in P. nodosa.
Visiting Triassic Park - Ischigualasto Parque Triasico in Argentina
Last month I was fortunate to be able to travel to Argentina for some research time and to attend and present at the Fourth Latin American Vertebrate Paleontology Conference in San Juan. Part of the meeting involved a field trip to the nearby Ischigualasto National Park which is famous for its exposures of Triassic rocks and for fossils of some of the earliest dinosaurs including Eoraptor and Herrerasaurus. As I work at the other Triassic Park, Petrified Forest National Park in Arizona, I was really looking forward to this visit and it did not dissappoint. Below I've posted some photos highlighting my visit.
The visitors center includes mounts (below) and life reconstructions (above) of many of the animals found in Triassic strata in the park. There are also exhibits of actual bones.
Outcrops of the Upper Triassic Ischigualasto Formation. The expanse of the exposures is incredible.
Bones, the Ischigualasto is full of bones.
Christian Sidor and Zhe-Xi Luo getting excited about a cynodont skull that Chris found.
Another in-situ cynodont skull. They are extremely (and amazingly) common here.
Rhynchosaur bones weathering out. Again, the amount of fossil material in the exposures is staggering. Amazingly rhynchosaurs and cynodonts are so common, they are usually not collected. Working in a formation (the Chinle) where these types of animals are relatively unknown, it was very difficult to leave this material behind.
The younger Los Colorados Formation above the Ischigualsto.
Ischigualsto Park and the Ischigualsto Formation are absolutely incredible and I hope to be able to return someday to make new discoveries.
Ischigualsto Park and the Ischigualsto Formation are absolutely incredible and I hope to be able to return someday to make new discoveries.
Day 1 - Buenos Aires - Museo Argentino de Ciencias
I'm now in Buenos Aires having arrived yesterday. I was fortunate to have the same flight as Casey Holliday (although he was bumped up to first class!) so we travelled together the first day here. Our first day was spent at the Museo Argentino de Ciencias Naturales (MACN) with me looking at aetosaur skulls (courtesy of Dra. Julia Desojo) and Casey looking at some crocodylian skulls. Had an energetic lunch with Julia and Oliver Rauhut (who was also visiting). Here is a photo of Julia and Oliver in Julia's office trying to work on some research despite our repeated intrusions and partaking of the local beverage of choice.
Here is a photo of the Museo Argentina de Ciencias Naturales.
Day 2: Intense aetosaur discussion with Julia Desojo and examination of a new taxon she is proposing.
Here is a photo of the Museo Argentina de Ciencias Naturales.
Beautiful skull of the aetosaur Neoaetosauroides engaeus.
Day 2: Intense aetosaur discussion with Julia Desojo and examination of a new taxon she is proposing.
IV Congresso Latino-Americano de Paleontologia de Vertebrados
I'm off to San Juan Argentina to attend and present two talks at the IV Congresso Latino-Americano de Paleontologia de Vertebrados. I'm also planning to do some aetosaur research in Buenos Aires and San Miguel de Tucuman. An added bonus is a field trip to Ischigualasto National Park. This years meeting promises to be well attended with lots of great talks. In addition there are two symposia (Triassic and Jurassic theropods and basal archosaurs) heavy on Triassic research. You can read more about the meeting here:
http://www.congresopaleo.com.ar/bin-debug/congreso.html
Hopefully I'll see many of you there!
http://www.congresopaleo.com.ar/bin-debug/congreso.html
Hopefully I'll see many of you there!
New Sauropodomorph from the Upper Triassic Los Colorados Formation of Argentina
Ezcurra, M. D., and C. Apaldetti. In Press. A robust sauropodomorph specimen from the Upper Triassic of Argentina and insights on the diversity of the Los Colorados Formation. Proceedings of the Geologists' Association. doi:10.1016/j.pgeola.2011.05.002
Abstract - The Late Triassic rocks document the first steps of the early dinosaur evolutionary radiation. Although the oldest dinosaurs were not abundant in their assemblages, sauropodomorphs achieved a wide taxonomic diversity and high abundance towards the Triassic–Jurassic boundary. In South America, this pattern is documented in the Ischigualasto-Villa Unión Basin of northwestern Argentina, in which dinosaurs achieved a numerical dominance over other tetrapods during the deposition of the upper levels of the late Norian-Rhaetian Los Colorados Formation. In this contribution we enrich the faunal list of this assemblage with the description of a new medium-sized basal sauropod specimen with a very robust tibial morphology. This new specimen differs from the other known sauropodomorphs described for the Los Colorados Formation and increases the alpha-diversity recorded for this group. A phylogenetic analysis recovered the new specimen at the base of Sauropoda and closely related to Lessemsaurus, Antetonitrus, and other basal sauropods. These results match with the high degree of robustness observed in the tibia of the specimen reported here, which closely approaches the morphology documented for other basal sauropods and departs from the morphospace occupied by non-sauropod sauropodomorphs. A two step pattern of tibia robustness increase is observed in the sauropodomorph phylogeny, a pattern that coincides and could be related with the acquisition of more habitual quadrupedal gait achieved by basal sauropods.
Abstract - The Late Triassic rocks document the first steps of the early dinosaur evolutionary radiation. Although the oldest dinosaurs were not abundant in their assemblages, sauropodomorphs achieved a wide taxonomic diversity and high abundance towards the Triassic–Jurassic boundary. In South America, this pattern is documented in the Ischigualasto-Villa Unión Basin of northwestern Argentina, in which dinosaurs achieved a numerical dominance over other tetrapods during the deposition of the upper levels of the late Norian-Rhaetian Los Colorados Formation. In this contribution we enrich the faunal list of this assemblage with the description of a new medium-sized basal sauropod specimen with a very robust tibial morphology. This new specimen differs from the other known sauropodomorphs described for the Los Colorados Formation and increases the alpha-diversity recorded for this group. A phylogenetic analysis recovered the new specimen at the base of Sauropoda and closely related to Lessemsaurus, Antetonitrus, and other basal sauropods. These results match with the high degree of robustness observed in the tibia of the specimen reported here, which closely approaches the morphology documented for other basal sauropods and departs from the morphospace occupied by non-sauropod sauropodomorphs. A two step pattern of tibia robustness increase is observed in the sauropodomorph phylogeny, a pattern that coincides and could be related with the acquisition of more habitual quadrupedal gait achieved by basal sauropods.
New Postcranial Material of the Rauisuchian Saurosuchus galilei from the Late Triassic of Argentina
Trotteyn, M. J., Desojo, J. B., y O. A. Alcober. 2011. Nuevo material postcraneo de Saurosuchus galilei Reig (Archosauria: Crurotarsi) del Triasico Superior del centrooeste de Argentina. Ameghiniana 48:605 - 620.
Resumen - Saurosuchus galilei Reig es un “rauisúquido” proveniente de la Formación Ischigualasto (Triásico Superior, Carniano), del centrooeste Argentino. En esta contribución se presenta la primera descripción detallada del complejo proatlas-atlas-axis; columna vertebral completa y articulada; y ambas escápulas de este taxón. La morfología general del complejo proatlas-atlas-axis es similar a la de otros “rauisúquidos”. Las vértebras cervicales son comprimidas axialmente y elongadas dorsoventralmente. El complejo atlas-axis y las cervicales, presentan los rasgos típicos de un animal con cuello corto y robusto. En las cervicales y en las dorsales puede observarse una serie de láminas, depresiones interlaminares y depresiones en el cuerpo vertebral que también se han descrito en otros “rauisúquidos”. En las vértebras presacras se observa una quilla ventral y una marcada expansión del extremo dorsal de la espina neural. La serie caudal presenta centros comprimidos axialmente, con un surco ventral orientado anteroposteriormente. La escápula es robusta, la hoja escapular es moderadamente expandida y levemente curvada. La notable diversidad que presentan los “rauisúquidos” en general, hace que sea necesario un análisis profundo para abordar problemáticas morfofuncionales y filogenéticas, con las cuales se espera que contribuya este nuevo material.
Abstract - New postcranial material of Saurosuchus galilei Reig (Archosauria : Crurotarsi) from the Late Triassic of Central-Western Argentina . Saurosuchus galilei Reig is a “rauisuchid” from the Ischigualasto Formation (late Carnian, Late Triassic) located in central-western Argentina. This paper is the first detailed description of the proatlas-atlas-axis complex of this taxon, of a complete and articulated vertebral column, and of both scapulae. Overall morphology of the proatlas-atlas-axis complex is similar to that of other “rauisuchids”. This complex and the post-axial cervical vertebrae show the typical traits of an animal with a short and strong neck. The cervical vertebrae are anteroposteriorly compressed and dorsoventrally elongated. Vertebral laminae, interlaminar depressions, and lateral depressions on the centra are present in the cervical and dorsal vertebrae, as in other “rauisuchids”. The presacral series bears ventrally keeled centra and large transversal expansions of the distal ends of the neural spines. The caudal series shows axially compressed centra with a longitudinal ventral groove. The scapulae are very robust and have a brief expansion and a slightly curved scapular blade. The remarkable diversity of “rauisuchids” in general, makes a detailed analysis necessary in order to approach morphofunctional and phylogenetic problems; this new material is expected to contribute towards the solution of these problems.
Resumen - Saurosuchus galilei Reig es un “rauisúquido” proveniente de la Formación Ischigualasto (Triásico Superior, Carniano), del centrooeste Argentino. En esta contribución se presenta la primera descripción detallada del complejo proatlas-atlas-axis; columna vertebral completa y articulada; y ambas escápulas de este taxón. La morfología general del complejo proatlas-atlas-axis es similar a la de otros “rauisúquidos”. Las vértebras cervicales son comprimidas axialmente y elongadas dorsoventralmente. El complejo atlas-axis y las cervicales, presentan los rasgos típicos de un animal con cuello corto y robusto. En las cervicales y en las dorsales puede observarse una serie de láminas, depresiones interlaminares y depresiones en el cuerpo vertebral que también se han descrito en otros “rauisúquidos”. En las vértebras presacras se observa una quilla ventral y una marcada expansión del extremo dorsal de la espina neural. La serie caudal presenta centros comprimidos axialmente, con un surco ventral orientado anteroposteriormente. La escápula es robusta, la hoja escapular es moderadamente expandida y levemente curvada. La notable diversidad que presentan los “rauisúquidos” en general, hace que sea necesario un análisis profundo para abordar problemáticas morfofuncionales y filogenéticas, con las cuales se espera que contribuya este nuevo material.
Abstract - New postcranial material of Saurosuchus galilei Reig (Archosauria : Crurotarsi) from the Late Triassic of Central-Western Argentina . Saurosuchus galilei Reig is a “rauisuchid” from the Ischigualasto Formation (late Carnian, Late Triassic) located in central-western Argentina. This paper is the first detailed description of the proatlas-atlas-axis complex of this taxon, of a complete and articulated vertebral column, and of both scapulae. Overall morphology of the proatlas-atlas-axis complex is similar to that of other “rauisuchids”. This complex and the post-axial cervical vertebrae show the typical traits of an animal with a short and strong neck. The cervical vertebrae are anteroposteriorly compressed and dorsoventrally elongated. Vertebral laminae, interlaminar depressions, and lateral depressions on the centra are present in the cervical and dorsal vertebrae, as in other “rauisuchids”. The presacral series bears ventrally keeled centra and large transversal expansions of the distal ends of the neural spines. The caudal series shows axially compressed centra with a longitudinal ventral groove. The scapulae are very robust and have a brief expansion and a slightly curved scapular blade. The remarkable diversity of “rauisuchids” in general, makes a detailed analysis necessary in order to approach morphofunctional and phylogenetic problems; this new material is expected to contribute towards the solution of these problems.
First Well-Preserved Heterodontosaurid Material from South America: Manidens condorensis from the Middle Jurassic of Argentina
Pol, D., Rauhut, O. W. M., and M. Becerra. 2011. A Middle Jurassic heterodontosaurid dinosaur from Patagonia and the evolution of heterodontosaurids. Naturwissenschaften (online first) DOI 10.1007/s00114-011-0780-5
Abstract - Heterodontosauridae is a morphologically divergent group of dinosaurs that has recently been interpreted as one of the most basal clades of Ornithischia. Heterodontosaurid remains were previously known from the Early Jurassic of southern Africa, but recent discoveries and studies have significantly increased the geographical and temporal range for this clade. Here, we report a new ornithischian dinosaur from the Middle Jurassic Cañadón Asfalto Formation in central Patagonia, Argentina. This new taxon, Manidens condorensis gen. et sp. nov., includes well-preserved craniomandibular and postcranial remains and represents the only diagnostic ornithischian specimen yet discovered in the Jurassic of South America so far. Derived features of its anatomy indicate that Manidens belongs to Heterodontosauridae, as the sister taxon of Heterodontosaurus and other South African heterodontosaurids. The presence of posterior dentary teeth with high crowns but lacking extensive wear facets in Manidens suggests that this form represents an intermediate stage in the development of the remarkable adaptations to herbivory described for Heterodontosaurus. The dentition of Manidens condorensis also has autapomorphies, such as asymmetrically arranged denticles in posterior teeth and a mesially projected denticle in the posteriormost teeth. At an estimated total length of 60–75 cm, Manidens furthermore confirms the small size of basal heterodontosaurids.
Abstract - Heterodontosauridae is a morphologically divergent group of dinosaurs that has recently been interpreted as one of the most basal clades of Ornithischia. Heterodontosaurid remains were previously known from the Early Jurassic of southern Africa, but recent discoveries and studies have significantly increased the geographical and temporal range for this clade. Here, we report a new ornithischian dinosaur from the Middle Jurassic Cañadón Asfalto Formation in central Patagonia, Argentina. This new taxon, Manidens condorensis gen. et sp. nov., includes well-preserved craniomandibular and postcranial remains and represents the only diagnostic ornithischian specimen yet discovered in the Jurassic of South America so far. Derived features of its anatomy indicate that Manidens belongs to Heterodontosauridae, as the sister taxon of Heterodontosaurus and other South African heterodontosaurids. The presence of posterior dentary teeth with high crowns but lacking extensive wear facets in Manidens suggests that this form represents an intermediate stage in the development of the remarkable adaptations to herbivory described for Heterodontosaurus. The dentition of Manidens condorensis also has autapomorphies, such as asymmetrically arranged denticles in posterior teeth and a mesially projected denticle in the posteriormost teeth. At an estimated total length of 60–75 cm, Manidens furthermore confirms the small size of basal heterodontosaurids.
Leonerasaurus taquetrensis, a New Derived Sauropodomorph from the Early Jurassic (or Late Triassic?) of Argentina
I'm not even going to attempt to delve into this new paper here because Adam Yates is back and has the detailed write-up at Dracovenator!
All of these recent sauropodomorph finds have me totally fired up to find one in the Chinle Formation this summer! (but I'll settle for the skull of Chindesaurus).
Pol, D., Garrido, A., and I. A. Cerda. 2011. A New Sauropodomorph Dinosaur from the Early Jurassic of Patagonia and the Origin and Evolution of the Sauropod-type Sacrum. PLoS ONE 6(1): e14572. doi:10.1371/journal.pone.0014572
ABSTRACT
Background
The origin of sauropod dinosaurs is one of the major landmarks of dinosaur evolution but is still poorly understood. This drastic transformation involved major skeletal modifications, including a shift from the small and gracile condition of primitive sauropodomorphs to the gigantic and quadrupedal condition of sauropods. Recent findings in the Late Triassic–Early Jurassic of Gondwana provide critical evidence to understand the origin and early evolution of sauropods.
Methodology/Principal Findings
A new sauropodomorph dinosaur, Leonerasaurus taquetrensis gen. et sp. nov., is described from the Las Leoneras Formation of Central Patagonia (Argentina). The new taxon is diagnosed by the presence of anterior unserrated teeth with a low spoon-shaped crown, amphicoelous and acamerate vertebral centra, four sacral vertebrae, and humeral deltopectoral crest low and medially deflected along its distal half. The phylogenetic analysis depicts Leonerasaurus as one of the closest outgroups of Sauropoda, being the sister taxon of a clade of large bodied taxa composed of Melanorosaurus and Sauropoda.
Conclusions/Significance
The dental and postcranial anatomy of Leonerasaurus supports its close affinities with basal sauropods. Despite the small size and plesiomorphic skeletal anatomy of Leonerasaurus, the four vertebrae that compose its sacrum resemble that of the large-bodied primitive sauropods. This shows that the appearance of the sauropod-type of sacrum predated the marked increase in body size that characterizes the origins of sauropods, rejecting a causal explanation and evolutionary linkage between this sacral configuration and body size. Alternative phylogenetic placements of Leonerasaurus as a basal anchisaurian imply a convergent acquisition of the sauropod-type sacrum in the new small-bodied taxon, also rejecting an evolutionary dependence of sacral configuration and body size in sauropodomorphs. This and other recent discoveries are showing that the characteristic sauropod body plan evolved gradually, with a step-wise pattern of character appearance.
All of these recent sauropodomorph finds have me totally fired up to find one in the Chinle Formation this summer! (but I'll settle for the skull of Chindesaurus).
Pol, D., Garrido, A., and I. A. Cerda. 2011. A New Sauropodomorph Dinosaur from the Early Jurassic of Patagonia and the Origin and Evolution of the Sauropod-type Sacrum. PLoS ONE 6(1): e14572. doi:10.1371/journal.pone.0014572
ABSTRACT
Background
The origin of sauropod dinosaurs is one of the major landmarks of dinosaur evolution but is still poorly understood. This drastic transformation involved major skeletal modifications, including a shift from the small and gracile condition of primitive sauropodomorphs to the gigantic and quadrupedal condition of sauropods. Recent findings in the Late Triassic–Early Jurassic of Gondwana provide critical evidence to understand the origin and early evolution of sauropods.
Methodology/Principal Findings
A new sauropodomorph dinosaur, Leonerasaurus taquetrensis gen. et sp. nov., is described from the Las Leoneras Formation of Central Patagonia (Argentina). The new taxon is diagnosed by the presence of anterior unserrated teeth with a low spoon-shaped crown, amphicoelous and acamerate vertebral centra, four sacral vertebrae, and humeral deltopectoral crest low and medially deflected along its distal half. The phylogenetic analysis depicts Leonerasaurus as one of the closest outgroups of Sauropoda, being the sister taxon of a clade of large bodied taxa composed of Melanorosaurus and Sauropoda.
Conclusions/Significance
The dental and postcranial anatomy of Leonerasaurus supports its close affinities with basal sauropods. Despite the small size and plesiomorphic skeletal anatomy of Leonerasaurus, the four vertebrae that compose its sacrum resemble that of the large-bodied primitive sauropods. This shows that the appearance of the sauropod-type of sacrum predated the marked increase in body size that characterizes the origins of sauropods, rejecting a causal explanation and evolutionary linkage between this sacral configuration and body size. Alternative phylogenetic placements of Leonerasaurus as a basal anchisaurian imply a convergent acquisition of the sauropod-type sacrum in the new small-bodied taxon, also rejecting an evolutionary dependence of sacral configuration and body size in sauropodomorphs. This and other recent discoveries are showing that the characteristic sauropod body plan evolved gradually, with a step-wise pattern of character appearance.
Koilamasuchus gonzalezdiazi, a New Basal Archosauriform from the Lower Triassic of Argentina
Ezcurra, M. D. , Lecuona, A., and A. Martinelii. 2010. A new basal archosauriform diapsid from the Lower Triassic of Argentina, Journal of Vertebrate Paleontology 30:1433-1450, doi: 10.1080/02724634.2010.501446
Abstract - The best-known South American Early Triassic archosauriform belongs to a putative proterosuchid briefly reported by Jose Bonaparte in 1981, collected from the Quebrada de los Fosiles Formation (Puesto Viejo Group, Argentina). This specimen consists of well-preserved natural external molds of a partial postcranium that preserve dorsal vertebrae, osteoderms, a dorsal rib, a possible gastralium, a chevron, a humerus, an ilium, two metapodials, and an ungual. We re-describe this specimen and identify autapomorphies that allow us to recognize Koilamasuchus gonzalezdiazi, gen. et sp. nov. The presence of an iliac blade with a slightly convex dorsal margin and with a maximum length more than 3 times its maximum height places Koilamasuchus within Archosauriformes. A cladistic analysis of basal Archosauriformes positions Koilamasuchus more crownwards than Proterosuchus, Sarmatosuchus, Fugusuchus, and Osmolskina, as the sister taxon of the clade that includes Erythrosuchidae and Archosauria. Proterosuchidae is found to be paraphyletic. The presence of an iliac preacetabular process, a pubic peduncle that forms an angle lower than 45◦ to the longitudinal axis of the ilium, and dorsal body osteoderms positions Koilamasuchus in Archosauriformes more crownwards than proterosuchids. Koilamasuchus is more basal than erythrosuchids within Archosauriformes because of the presence of dorsal ribs with a poorly developed proximal end. Koilamasuchus importantly increases the diversity of Archosauriformes during the biotic recovery following the Permo-Triassic mass extinction.
This is an interesting paper from the new issue of the Journal of Vertebrate Paleontology describing a new archosauriform from the Early Triassic of South America. Along with recent descriptions of the enigmatic form Vancleavea (Parker and Barton 2008; Nesbitt et al. 2009) as well as a modern description of Doswellia (Dilkes and Sues 2009), this new taxon helps flesh out relationships in this part of the tree. I've only briefly skimmed the paper so far, but noticed some interesting conclusions from the study:
1) Proterosuchidae is paraphyletic - the monophyly of the group is rarely tested as most recent studies just use Proterosuchus as a terminal taxon in phylogenetic analyses.
2) Vancleavea and Doswellia form a clade which is closer to Archosauria than Euparkeria and Chanaresuchus are - as stated in the paper this is closer to the results that I obtained in my 2008 paper on Vancleavea (Parker and Barton 2008); however, the results of our phylogenetic analysis weren't very robust.
3) Turfanosuchus is a pseudosuchian - I've always hypothesized this as the calcaneum of Turfanosuchus is extremely similar to that of aetosaurs and the femur is almost identical to that of Revueltosaurus in overall morphology and in possessing a massive fourth trochanter (Parker et al. 2005).
One unfortunate preservational aspect of this material is the lack of the femur, which I feel is a key element in determining whether the taxon would be closer to Proterosuchus and Erythrosuchus with their primitive morphology, or to the more derived forms Vancleavea and Euparkeria (see the discussion in Parker and Barton 2008). Another key aspect that could affect the phylogenetic analysis (and possibly did in this paper) is the coding of osteoderms as present in Erythrosuchus, which could potentially place erythrosuchids in a more crownward position. Despite the recovery of a couple of possible osteoderms with material of Erythrosuchus (Gower 2003) their actual presence in this taxon is ambiguous and should not be coded as present (Parker and Barton 2008; Nesbitt et al. 2009). This coding may explain why Koilamasuchus is recovered as more basal to erythrosuchids in this analysis.
REFERENCES
Dilkes, D.W., and H.-D. Sues. 2009. Redescription and phylogenetic relationships of Doswellia kaltenbachi (Diapsida: Archosauriformes) from the Upper Triassic of Virginia. Journal of Vertebrate Paleontology 29:58–79.
Gower, D. J. 2003. Osteology of the early archosaurian reptile Erythrosuchus africanus Broom. Annals of the South African Museum 110:1–84.
Nesbitt, S. J., Stocker, M. R., Small, B. J., and Downs, A. 2009. The osteology and relationships of Vancleavea campi (Reptilia: Archosauriformes). Zoological Journal of the Linnean Society 157:814–864.
Parker, W. G., and B. J. Barton. 2008. New information on the Upper Triassic archosauriform Vancleavea campi based on new material from the Chinle Formation of Arizona. Paleontologia Electronica 11.3.14A:1–20.
Parker, W. G., R. B. Irmis, S. J. Nesbitt, J. W. Martz, and L. S. Browne. 2005. The Late Triassic pseudosuchian Revueltosaurus callenderi and its implications for the diversity of early ornithischian dinosaurs. Proceedings of the Royal Society of London, Series B: Biological Sciences 272:963–969.
Abstract - The best-known South American Early Triassic archosauriform belongs to a putative proterosuchid briefly reported by Jose Bonaparte in 1981, collected from the Quebrada de los Fosiles Formation (Puesto Viejo Group, Argentina). This specimen consists of well-preserved natural external molds of a partial postcranium that preserve dorsal vertebrae, osteoderms, a dorsal rib, a possible gastralium, a chevron, a humerus, an ilium, two metapodials, and an ungual. We re-describe this specimen and identify autapomorphies that allow us to recognize Koilamasuchus gonzalezdiazi, gen. et sp. nov. The presence of an iliac blade with a slightly convex dorsal margin and with a maximum length more than 3 times its maximum height places Koilamasuchus within Archosauriformes. A cladistic analysis of basal Archosauriformes positions Koilamasuchus more crownwards than Proterosuchus, Sarmatosuchus, Fugusuchus, and Osmolskina, as the sister taxon of the clade that includes Erythrosuchidae and Archosauria. Proterosuchidae is found to be paraphyletic. The presence of an iliac preacetabular process, a pubic peduncle that forms an angle lower than 45◦ to the longitudinal axis of the ilium, and dorsal body osteoderms positions Koilamasuchus in Archosauriformes more crownwards than proterosuchids. Koilamasuchus is more basal than erythrosuchids within Archosauriformes because of the presence of dorsal ribs with a poorly developed proximal end. Koilamasuchus importantly increases the diversity of Archosauriformes during the biotic recovery following the Permo-Triassic mass extinction.
This is an interesting paper from the new issue of the Journal of Vertebrate Paleontology describing a new archosauriform from the Early Triassic of South America. Along with recent descriptions of the enigmatic form Vancleavea (Parker and Barton 2008; Nesbitt et al. 2009) as well as a modern description of Doswellia (Dilkes and Sues 2009), this new taxon helps flesh out relationships in this part of the tree. I've only briefly skimmed the paper so far, but noticed some interesting conclusions from the study:
1) Proterosuchidae is paraphyletic - the monophyly of the group is rarely tested as most recent studies just use Proterosuchus as a terminal taxon in phylogenetic analyses.
2) Vancleavea and Doswellia form a clade which is closer to Archosauria than Euparkeria and Chanaresuchus are - as stated in the paper this is closer to the results that I obtained in my 2008 paper on Vancleavea (Parker and Barton 2008); however, the results of our phylogenetic analysis weren't very robust.
3) Turfanosuchus is a pseudosuchian - I've always hypothesized this as the calcaneum of Turfanosuchus is extremely similar to that of aetosaurs and the femur is almost identical to that of Revueltosaurus in overall morphology and in possessing a massive fourth trochanter (Parker et al. 2005).
One unfortunate preservational aspect of this material is the lack of the femur, which I feel is a key element in determining whether the taxon would be closer to Proterosuchus and Erythrosuchus with their primitive morphology, or to the more derived forms Vancleavea and Euparkeria (see the discussion in Parker and Barton 2008). Another key aspect that could affect the phylogenetic analysis (and possibly did in this paper) is the coding of osteoderms as present in Erythrosuchus, which could potentially place erythrosuchids in a more crownward position. Despite the recovery of a couple of possible osteoderms with material of Erythrosuchus (Gower 2003) their actual presence in this taxon is ambiguous and should not be coded as present (Parker and Barton 2008; Nesbitt et al. 2009). This coding may explain why Koilamasuchus is recovered as more basal to erythrosuchids in this analysis.
REFERENCES
Dilkes, D.W., and H.-D. Sues. 2009. Redescription and phylogenetic relationships of Doswellia kaltenbachi (Diapsida: Archosauriformes) from the Upper Triassic of Virginia. Journal of Vertebrate Paleontology 29:58–79.
Gower, D. J. 2003. Osteology of the early archosaurian reptile Erythrosuchus africanus Broom. Annals of the South African Museum 110:1–84.
Nesbitt, S. J., Stocker, M. R., Small, B. J., and Downs, A. 2009. The osteology and relationships of Vancleavea campi (Reptilia: Archosauriformes). Zoological Journal of the Linnean Society 157:814–864.
Parker, W. G., and B. J. Barton. 2008. New information on the Upper Triassic archosauriform Vancleavea campi based on new material from the Chinle Formation of Arizona. Paleontologia Electronica 11.3.14A:1–20.
Parker, W. G., R. B. Irmis, S. J. Nesbitt, J. W. Martz, and L. S. Browne. 2005. The Late Triassic pseudosuchian Revueltosaurus callenderi and its implications for the diversity of early ornithischian dinosaurs. Proceedings of the Royal Society of London, Series B: Biological Sciences 272:963–969.
New Late Triassic Sauropodomorph, Chromogisaurus novasi from Argentina
Ezcurra, M. D. 2010. A new early dinosaur (Saurischia: Sauropodomorpha) from the Late Triassic of Argentina: a reassessment of dinosaur origin and phylogeny. Journal of Systematic Palaeontology 8: 371-425.
Abstract - It was traditionally thought that the oldest known dinosaur assemblages were not diverse, and that their early diversification and numerical dominance over other tetrapods occurred during the latest Triassic. However, new evidence gathered from the lower levels of the Ischigualasto Fm. of Argentina challenges this view. New dinosaur remains are described from this stratigraphical unit, including the new species Chromogisaurus novasi. This taxon is distinguished from other basal dinosauriforms by the presence of proximal caudals without median notch separating the postzygapophyses, femoral lateral surface with deep and large fossa immediately below the trochanteric shelf, and metatarsal II with strongly dorsoventrally asymmetric distal condyles. A phylogenetic analysis found Chromogisaurus to lie at the base of Sauropodomorpha, as a member of Guaibasauridae, an early branch of basal sauropodomorphs composed of Guaibasaurus, Agnosphitys, Panphagia, Saturnalia and Chromogisaurus. Such an affinity is for the first time suggested for Guaibasaurus, whereas Panphagia is not recovered as the most basal sauropodomorph. Furthermore, Chromogisaurus is consistently located as more closely related to Saturnalia than to any other dinosaur. Thus, the Saturnalia + Chromogisaurus clade is named here as the new subfamily Saturnaliinae. In addition, Eoraptor is found to be the sister-taxon of Neotheropoda, and herrerasaurids to be non-eusaurischian saurischians. The new evidence presented here demonstrates that dinosaurs first appeared in the fossil record as a diverse group, although they were a numerically minor component of faunas in which they occur. Accordingly, the early increase of dinosaur diversity and their numerical dominance over other terrestrial tetrapods were diachronous processes, with the latter preceded by a period of low abundance but high diversity.
Besides the information provided in the abstract here are a couple of other tidbits:
1) Diagnosis: the holotype material is very fragmentary, but Chromogisaurus novasi is diagnosed by "the following combination of characteristics (autapomorphies∗): proximal caudals without median notch separating the postzygapophyses; ilium with strongly posteriorly developed postacetabular process; incipiently perforated acetabulum; a femoral lateral surface with deep and large fossa immediately below the trochanteric shelf;∗ and a metatarsal II with strongly dorsoventrally asymmetric distal condyles" (Ezcurra, 2010:374).
2) Etymology: The generic name is a combination of the Greek "chroma" (color) and "gi" (ground or land) for the Painted Valley where the specimen was collected.
3) Clades: This paper provides definitions for the newly recovered clades Guaibasauridae and Saturnaliinae.
4) Chindesaurus: The paper contains discussion on the phylogenetic position of Chindesaurus bryansmalli from the Chinle Formation. This study (378 characters) finds Chindesaurus as eithr a basal theropod or as a non-eusaurischian saurischian.
5) Photos: There is a nice comparative figure (photos) of the skulls of Herrerasaurus, Eoraptor, and Zupaysaurus.
I'm looking forward to reading the rest of this....
Abstract - It was traditionally thought that the oldest known dinosaur assemblages were not diverse, and that their early diversification and numerical dominance over other tetrapods occurred during the latest Triassic. However, new evidence gathered from the lower levels of the Ischigualasto Fm. of Argentina challenges this view. New dinosaur remains are described from this stratigraphical unit, including the new species Chromogisaurus novasi. This taxon is distinguished from other basal dinosauriforms by the presence of proximal caudals without median notch separating the postzygapophyses, femoral lateral surface with deep and large fossa immediately below the trochanteric shelf, and metatarsal II with strongly dorsoventrally asymmetric distal condyles. A phylogenetic analysis found Chromogisaurus to lie at the base of Sauropodomorpha, as a member of Guaibasauridae, an early branch of basal sauropodomorphs composed of Guaibasaurus, Agnosphitys, Panphagia, Saturnalia and Chromogisaurus. Such an affinity is for the first time suggested for Guaibasaurus, whereas Panphagia is not recovered as the most basal sauropodomorph. Furthermore, Chromogisaurus is consistently located as more closely related to Saturnalia than to any other dinosaur. Thus, the Saturnalia + Chromogisaurus clade is named here as the new subfamily Saturnaliinae. In addition, Eoraptor is found to be the sister-taxon of Neotheropoda, and herrerasaurids to be non-eusaurischian saurischians. The new evidence presented here demonstrates that dinosaurs first appeared in the fossil record as a diverse group, although they were a numerically minor component of faunas in which they occur. Accordingly, the early increase of dinosaur diversity and their numerical dominance over other terrestrial tetrapods were diachronous processes, with the latter preceded by a period of low abundance but high diversity.
Besides the information provided in the abstract here are a couple of other tidbits:
1) Diagnosis: the holotype material is very fragmentary, but Chromogisaurus novasi is diagnosed by "the following combination of characteristics (autapomorphies∗): proximal caudals without median notch separating the postzygapophyses; ilium with strongly posteriorly developed postacetabular process; incipiently perforated acetabulum; a femoral lateral surface with deep and large fossa immediately below the trochanteric shelf;∗ and a metatarsal II with strongly dorsoventrally asymmetric distal condyles" (Ezcurra, 2010:374).
2) Etymology: The generic name is a combination of the Greek "chroma" (color) and "gi" (ground or land) for the Painted Valley where the specimen was collected.
3) Clades: This paper provides definitions for the newly recovered clades Guaibasauridae and Saturnaliinae.
4) Chindesaurus: The paper contains discussion on the phylogenetic position of Chindesaurus bryansmalli from the Chinle Formation. This study (378 characters) finds Chindesaurus as eithr a basal theropod or as a non-eusaurischian saurischian.
5) Photos: There is a nice comparative figure (photos) of the skulls of Herrerasaurus, Eoraptor, and Zupaysaurus.
I'm looking forward to reading the rest of this....
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