Ophthalmosaurids (Ichthyosauria: Thunnosauria) : Alpha taxonomy, clades and names

Fil: Fernández, Marta Susana. División Paleontología Vertebrados. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; ArgentinaFil: Campos, Lisandro. División Paleontología Vertebrados. Facultad de Ciencias Naturales y Museo. Universidad Nacional de La Plata; Argentin

Unexpected skeletal histology of an ichthyosaur from the middle jurassic of patagonia: Implications for evolution of bone microstructure among secondary aquatic tetrapods

During the Mesozoic, one of the most significant evolutionary processes was the secondary adaptation of tetrapods to life in water. Several non-related lineages invaded from the terrestrial realms and from the oceans of the entire world. Among these lineages, ichthyosaurs were particularly successful. Advance parvipelvian ichthyosaurs were the first tetrapods to evolve a fish-shaped body profile. The deep skeletal modifications of their bodies, as well as their biology, depict advance ichthyosaurs as the paradigm of secondary adaptation of reptiles tomarine life. Functional inferences point to themas off-shore cruising forms, similar to a living tuna, and some of them were capable of deep diving. Bone histology of some genera such as Temnodontosaurus, Stenopterygius, Ichthyosaurus, and Caypullisaurus, characterized by overall cancellous bone, is consistent with the idea of a fish-shaped ichthyosaurs as fast and far cruisers. Here, we provide histological examination of the ribs of the Middle Jurassic parvipelvian Mollesaurus. Contrasting with the bone histology of other parvipelvian, Mollesaurus ribs are characterized by a compact and thick cortex. Our data indicate that the rib cage was heavy and suggest that not all advanced ichthyosaurs were fast cruisers. The compact and dense ribs in these parvipelvian show that advance ichthyosaurs were ecologically more diverse than previously thought and that the lightening of the skeleton reversed, as also occurred in the evolution of cetacean, at least once along the evolutionary history of ichthyosaurs.Fil: Talevi, Marianella. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación en Paleobiología y Geología; ArgentinaFil: Fernández, Marta Susana. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentin

OftalmosÁUridos (Ichthyosauria: Thunnosauria): taxonomía Alfa, clados y nombres

Thunnosaurian ichthyosaurs represent the paradigm of reptilian body designed for a pelagic life style. Most derived thunnosaurian, the ophthalmosaurids, have been traditionally considered as members of a declining lineage. New findings and the re-examination of histori- cal collections radically changed our conceptions about them. Opthalmosaurids were ecologically more diverse than previously thought. The past few decades have seen an increase of nominal species spurred by new findings and analyses. A still unresolved problem is that many species are only known by their holotypes. Nevertheless, morphological disparity is a compelling argument for considering them as valid. All recent cladistic analyses of ichthyosaurs recover ophthalmosaurids as a clade. Neither the addition of new information nor the addition of new entities resulted in its collapse. On this basis, the assignment of Linnaean rank to this clade (Ophtalmosauridae) is reasonable as it satisfied the primary recommended criteria for taxa naming: monophyly and stability. As the lists of species and genus names are used as input in major data bases for interpreting major turnover and/or extinction patterns, efforts must be focused on clarifying as much as possible the alpha taxonomy. Two major pending issues are the delimitation of Ophthalmosaurus-Baptanodon, and Platypterygius. The case of Platypterygius is complex because the type species is poorly known, its holotype is lost, and there is no consensus among specialist about the species that should be included in this genus. On the other hand, we advocate for the use of the name Baptanodon natans instead of Ophthalmosaurus natans.. Los ictiosaurios tunosaurios representan, entre los reptiles, el paradigma de la adaptación secundaria a la vida pelágica. Los tunosaurios más derivados, los oftalmosáuridos, han sido considerados tradicionalmente como miembros de un linaje en declive. Nuevos hallazgos, y la revisión de las colecciones histó- ricas, cambiaron radicalmente nuestras concepciones acerca de ellos indicando que eran ecológicamente muy diversos. En las últimas décadas se ha producido un aumento de las especies nominales de oftalmosáuridos. Un problema aún no resuelto es que muchas especies solo son conocidas por sus holotipos. No obstante, la disparidad morfológica es un argumento de peso para considerarlas como válidas. Todos los análisis cladísticos recuperan a los oftalmosáuridos como un grupo monofilético. La adición de nueva información no provoca su colapso. Sobre esta base la asignación de rango linneano a este clado (Ophthalmosauridae) es razonable ya que cumple con los criterios recomendados para nombrar taxones: monofilia y estabilidad. Dado que las listas de especies y géneros se utilizan frecuentemente como datos básicos para interpretar patrones faunísticos y de extinción, los esfuerzos deben centrarse en aclarar lo más posible las listas taxonómicas. Dos temas pendientes son la delimitación de Ophthalmosaurus-Baptanodon y de Platypterygius. El caso de Platypterygius es complejo debido a que la especie tipo es poco conocida, su holotipo está perdido, y no hay consenso entre los especialistas sobre las especies que deben ser incluidas en él. Por otra parte, proponemos mantener el uso del nombre Baptanodon natans en lugar de Ophthalmosaurus natans.Fil: Fernández, Marta Susana. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Campos, Lisandro. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. División Paleontología Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentin

A social and emotional model for obtaining believable emergent behaviors

Proceeding of: 13th International Conference, AIMSA 2008, Varna, Bulgaria, September 4-6, 2008This paper attempts to define an emotional model for virtual agents that behave autonomously in social worlds. We adopt shallow modeling based on the decomposition of the emotional state in two qualities: valence (pleasantness or hedonic value) and arousal (bodily activation) and, also, for the agent personality based on the five factors model (openness, conscientiousness, extroversion, agreeableness and neuroticism). The proposed model aims to endow agents with a satisfactory emotional state achieved through the social actions, i.e. the development of social abilities. Psychology characterizes these social abilities for: using the language as a tool (verbal and nonverbal communication), being learned, producing reciprocal reward among the individuals involved in the communication and for depending on the individual features. We have implemented our model in the framework of a computer game, AI-live, to show its validity.Publicad

Braincase and endocranial anatomy of two thalattosuchian crocodylomorphs and their relevance in understanding their adaptations to the marine environment

Thalattosuchians are a group of Mesozoic crocodylomorphs known from aquatic deposits of the Early Jurassic-Early Cretaceous that comprises two main lineages of almost exclusively marine forms, Teleosauridae and Metriorhynchoidea. Teleosaurids were found in shallow marine, brackish and freshwater deposits, and have been characterized as semiaquatic near-shore forms, whereas metriorhynchids are a lineage of fully pelagic forms, supported by a large set of morphological characters of the skull and postcranial anatomy. Recent contributions on Thalattosuchia have been focused on the study of the endocranial anatomy. This newly available information provides novel evidence to suggest adaptations on the neuroanatomy, senses organs, vasculature, and behavioral evolution of these crocodylomorphs. However, is still not clear if the major morphological differences between teleosaurids and metriorhynchids were also mirrored by changes in the braincase and endocranial anatomy. Based on X-ray CT scanning and digital endocast reconstructions we describe the braincase and endocranial anatomy of two well-preserved specimens of Thalattosuchia, the semiaquatic teleosaurid Steneosaurus bollensis and the pelagic metriorhynchid Cricosaurus araucanensis. We propose that some morphological traits, such as: an enlarged foramen for the internal carotid artery, a carotid foramen ventral to the occipital condyle, a single CN XII foramen, absence of brain flexures, well-developed cephalic vascular system, lack ofsubtympanic foramina and the reduction of the paratympanic sinus system, are distinctive features of Thalattosuchia. It has been previously suggested that the enlarged foramen for the internal carotid artery, the absence of brain flexures, and the hypertrophied cephalic vascular system were synapomorphies of Metriorhynchidae; however, new information revealed that all of these features were already established at the base of Thalattosuchia and might have been exapted later on their evolutionary history. Also, we recognized some differences within Thalattosuchia that previously have not been received attention or even were overlooked (e.g., circular/bilobate trigeminal foramen, single/double CN XII foramen, separation of the cranioquadrate canal from the external otic apertureFacultad de Ciencias Naturales y Muse

First report of Leptonectes (Ichthyosauria: Leptonectidae) from the Lower Jurassic (Pliensbachian) of Asturias, northern Spain

Early Jurassic ichthyosaurs are well-known based on the abundant and exquisitely preserved European records of the Western Tethys. For example, faunas from Southern England and the Toarcian Posidonia shales of Holzmaden and surrounding areas (Germany) are known worldwide. However, between these areas there are still gaps and/or under-sampled localities from the northern coast of Europe. In recent years as a result of systematic palaeontological and geological explorations of Pliensbachian fossiliferous localities along the coast of Asturias (northern Spain), ichthyosaur specimens have been collected. One of them can be identified at lower taxonomic levels and it is referred to Leptonectes sp. These new findings highlight the richness of the fossil record of the northern coast of Spain and suggest that the abundance of Pliensbachian ichthyosaurs worldwide may have been underestimated.Facultad de Ciencias Naturales y Muse

First report of Leptonectes (Ichthyosauria: Leptonectidae) from the Lower Jurassic (Pliensbachian) of Asturias, northern Spain

Early Jurassic ichthyosaurs are well-known based on the abundant and exquisitely preserved European records of the Western Tethys. For example, faunas from Southern England and the Toarcian Posidonia shales of Holzmaden and surrounding areas (Germany) are known worldwide. However, between these areas there are still gaps and/or under-sampled localities from the northern coast of Europe. In recent years as a result of systematic palaeontological and geological explorations of Pliensbachian fossiliferous localities along the coast of Asturias (northern Spain), ichthyosaur specimens have been collected. One of them can be identified at lower taxonomic levels and it is referred to Leptonectes sp. These new findings highlight the richness of the fossil record of the northern coast of Spain and suggest that the abundance of Pliensbachian ichthyosaurs worldwide may have been underestimated.Facultad de Ciencias Naturales y Muse

Remodelling of skeletal tissues bone and structural specialisations in an elasmosaurid (Sauropterygia: Plesiosauroidea) from the Upper Cretaceous of Patagonia, Argentina

Elasmosauridae were cosmopolitan Late Cretaceous plesiosaurs with conspicuous morphological diversity. Within this group, vertebral morphology is a criterion for estimating relative age in plesiosaur. On the other hand, the microstructure of plesiosaur bone is considered as indicative of ontogenetic stage. However, knowledge about ontogenetic tissue transformation in different elements of the skeleton is poorly known. Resorption and remodelling of skeletal tissues are required for development and growth, mechanical adaptation, repair and mineral homeostasis of the vertebrate skeleton. This contribution analyses different postcranial elements of a Late Cretaceous elasmosaurid from Patagonia. Characterisation of bone microstructure indicates the presence of compact bone inner organisation in an adult derived plesiosaur from the Cretaceous and that the distribution of bone specialisations depicts conspicuous variations within a single skeleton depending on the skeletal element considered. Bone compactness or degree of remodelling in elasmosaurids is not necessarily correlated with the ontogenetic age of the animal or to costal versus pelagic lifestyles. The available data are still scarce, but we propose a topic of discussion: perhaps the degree of remodelling and compactness also may be related to the activity level and increased mechanical load in different skeletal elements.Facultad de Ciencias Naturales y Muse

Oftalmosáuridos (ichthyosauria: thunnosauria): taxonomía alfa, clados y nombres

Thunnosaurian ichthyosaurs represent the paradigm of reptilian body designed for a pelagic life style. Most derived thunnosaurian, the ophthalmosaurids, have been traditionally considered as members of a declining lineage. New findings and the re-examination of historical collections radically changed our conceptions about them. Opthalmosaurids were ecologically more diverse than previously thought. The past few decades have seen an increase of nominal species spurred by new findings and analyses. A still unresolved problem is that many species are only known by their holotypes. Nevertheless, morphological disparity is a compelling argument for considering them as valid. All recent cladistic analyses of ichthyosaurs recover ophthalmosaurids as a clade. Neither the addition of new information nor the addition of new entities resulted in its collapse. On this basis, the assignment of Linnaean rank to this clade (Ophtalmosauridae) is reasonable as it satisfied the primary recommended criteria for taxa naming: monophyly and stability. As the lists of species and genus names are used as input in major data bases for interpreting major turnover and/or extinction patterns, efforts must be focused on clarifying as much as possible the alpha taxonomy. Two major pending issues are the delimitation of Ophthalmosaurus-Baptanodon, and Platypterygius. The case of Platypterygius is complex because the type species is poorly known, its holotype is lost, and there is no consensus among specialist about the species that should be included in this genus. On the other hand, we advocate for the use of the name Baptanodon natans instead of Ophthalmosaurus natans.Los ictiosaurios tunosaurios representan, entre los reptiles, el paradigma de la adaptación secundaria a la vida pelágica. Los tunosaurios más derivados, los oftalmosáuridos, han sido considerados tradicionalmente como miembros de un linaje en declive. Nuevos hallazgos, y la revisión de las colecciones históricas, cambiaron radicalmente nuestras concepciones acerca de ellos indicando que eran ecológicamente muy diversos. En las últimas décadas se ha producido un aumento de las especies nominales de oftalmosáuridos. Un problema aún no resuelto es que muchas especies solo son conocidas por sus holotipos. No obstante, la disparidad morfológica es un argumento de peso para considerarlas como válidas. Todos los análisis cladísticos recuperan a los oftalmosáuridos como un grupo monofilético. La adición de nueva información no provoca su colapso. Sobre esta base la asignación de rango linneano a este clado (Ophthalmosauridae) es razonable ya que cumple con los criterios recomendados para nombrar taxones: monofilia y estabilidad. Dado que las listas de especies y géneros se utilizan frecuentemente como datos básicos para interpretar patrones faunísticos y de extinción, los esfuerzos deben centrarse en aclarar lo más posible las listas taxonómicas. Dos temas pendientes son la delimitación de Ophthalmosaurus-Baptanodon y de Platypterygius. El caso de Platypterygius es complejo debido a que la especie tipo es poco conocida, su holotipo está perdido, y no hay consenso entre los especialistas sobre las especies que deben ser incluidas en él. Por otra parte, proponemos mantener el uso del nombre Baptanodon natans en lugar de Ophthalmosaurus natans.Facultad de Ciencias Naturales y Muse