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(Reptilia, Archosauria) De La Formación Los Chañares

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(Reptilia, Archosauria) De La Formación Los Chañares ESTUDIO DE LOS DINOSAUROMORPHA (REPTILIA, ARCHOSAURIA) DE LA FORMACIÓN CHAÑARES (TRIÁSICO SUPERIOR), PROVINCIA DE LA RIOJA, ARGENTINA. SUS IMPLICANCIAS EN EL ORIGEN DE LOS DINOSAURIOS FEDERICO LISANDRO AGNOLÍN Directores: Dr. Fernando E. Novas Dr. Leopoldo Soibelzon Lugar de trabajo: Laboratorio de Anatomía Comparada y Evolución de los Vertebrados, Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”. Buenos Aires, Argentina. Institución: Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata. 2017 F. Agnolin - Dinosauriformes del Triásico Superior de La Rioja, Argentina RESUMEN En la presente tesis se lleva adelante un estudio descriptivo, comparativo y filogenético de los dinosauromorfos basales hallados en niveles de la Formación Chañares, Triásico Superior (Carniano temprano), aflorantes en el Parque Nacional Talampaya, provincia de La Rioja, Argentina. Los taxones analizados incluyen a Lagerpeton chanarensis, Lagosuchus lilloensis, Marasuchus talampayensis, Lewisuchus admixtus y Pseudolagosuchus major. Una revisión de los caracteres anatómicos de Lagerpeton chanarensis (unánimente interpretado como un Dinosauromorpha basal por autores previos) resulta en el reconocimiento de una numerosas similitudes con arcosauriformes basales del clado Proterochampsia. Adicionalmente, la estructura de la cadera y del miembro posterior indican que Lagerpeton poseía un andar más esparrancado que el linaje de los dinosauriformes. Se revalida a Lagosuchus talampayensis (previamente considerado como un nomen dubium) y se lo considera como sinónimo más antiguo de Marasuchus lilloensis. Se describe un nuevo ejemplar de Lewisuchus admixtus, cuyos caracteres permiten confirmar que Pseudolagosuchus admixtus es un sinónimo menor de Lewisuchus. Se describe un nuevo género y especie de Dinosauriformes de la Formación Chañares, con numerosos rasgos derivados que permiten reconocerlo como un representante del clado Saurischia. El análisis filogenético aquí elaborado deriva también en una serie de implicancias con respecto a la filogenia de Dinosauria basales. En primer lugar, una revisión de Pisanosaurus mertii, Formación Ischigualasto (Carniano Superior), permite reubicarlo como grupo hermano de Dinosauria, rechazando así la hipótesis de que se trataba de un ornitisquio basal. 2 F. Agnolin - Dinosauriformes del Triásico Superior de La Rioja, Argentina De este modo, no existen registros concretos de dinosaurios Ornithischia para el Período Triásico. Herrerasauridae y Guaibasauridae resultan dentro de Saurischia, pero por fuera del clado que incluye a Theropoda y Sauropodomorpha (=Eusaurischia). Herrerasauria incluye además de Herrerasauridae al taxón norteamericano Chindesaurus bryansmalli (Formación Chinle, Hayden Quarry, Nuevo México). Sobre la base de observación del material disponible, Tawa hallae descripto como el Neotheropoda más basal y antiguo conocido constituye un sinónimo de Chindesaurus bryansmalli. Por otro lado, Guaibasauridae se compone de formas problemáticas, previamente asociadas con los Sauropodomorpha, como ser Guaibasaurus, Eoraptor, Eodromaeus, Panphagia, Saturnalia, y Pampadromaeus. Bajo este nuevo arreglo taxonómico, los supuesto ornitisquios, sauropodomorfos y terópodos pre-Carnianos no resultan más que linajes tempranos que sufren una extinción hacia el límite Carniano-Noriano. Posteriormente, durante el Noriano, Theropoda y Sauropodomorpha sensu stricto se constituyen en los clados dominantes de los ecosistemas terrestres. El reconocimiento de Silesauridae y Pisanosaurus como grupos hermano sucesivos de Dinosauria, fortalece la hipótesis que sustenta que la condición herbívora era ancestral para Dinosauria. Sobre la base del presente análisis, es posible inferir una condición monofilética para la herbivoría en Silesauridae, Pisanosaurus, Ornithischia, Sauropodomorpha y Guaibasauridae, mientras que los caracteres relacionados con la carnivoría presentes en Herrerasauria y Theropoda habrían sido adquiridos convergentemente. 3 F. Agnolin - Dinosauriformes del Triásico Superior de La Rioja, Argentina ABSTRACT Present PhD thesis includes a descriptive, comparative, and phylogenetical analysis of basal dinosauriforms found in levels of the Chañares Formation, Upper Triassic (early Carnian), that outcrop at the Parque Nacional Talampaya, La Rioja province, Argentina. The analyzed taxa include Lagerpeton chanarensis, Lagosuchus lilloensis, Marasuchus talampayensis, Lewisuchus admixtus, and Pseudolagosuchus major. The reanalysis of several anatomical features of Lagerpeton chanarensis (unanimously interpreted as a basal dinosauromorph by previous authors) results in the recognition of several similarities with basal archosariforms of the Proterochampsia clade. Additionally, the morphology of the pelvic girdle and hindlimb, indicates that Lagerpeton has a sprawling locomotion, different from dinosauriform taxa. On the other side, after a detailed analysis Lagosuchus talampayensis (previously considered as a nomen dubium) is revalidated, and is considered as the senior synonym of Marasuchus lilloensis. A new specimen of Lewisuchus admixtus is described. Its features allow to confirm the hypothesis sustaining that Pseudolagosuchus admixtus is a junior synonym of Lewisuchus. A new genus and species of Dinosauriformes from the Chañares Formation is described. It shows several derived features that allow recognizing it as a new representative of the Saurischia clade. The phylogenetic analysis here performed results in several implicances regarding the phylogenetic relationships among basal dinosaurs. On the first hand, an overview of Pisanosaurus mertii (Ischigualasto Formation; Upper Carnian), allows reinterpreting it as the sister group of Dinosauria, contrasting with previous hypotheses that included it among 4 F. Agnolin - Dinosauriformes del Triásico Superior de La Rioja, Argentina basal ornithischians. In this way, there are no single records of Ornithischia in the Triassic Period. Herrerasauridae and Guaibasauridae are nested within Saurischia, but as sister to the clade including Theropoda and Sauropodomorpha (=Eusaurischia). Herrerasauria includes Herrerasauridae and the North American taxon Chindesaurus bryansmalli (Chinle Formation, Hayden Quarry, New Mexico). On the basis of the observation of available material, Tawa hallae, described as the most ancient and basal neotheropod constitutes a junior synonym of Chindesaurus bryansmalli. On the other side, Guaibasauridae is composed by problematic taxa, previously referred to Sauropodomorpha, including Guaibasaurus, Eoraptor, Eodromaeus, Panphagia, Saturnalia, y Pampadromaeus. Under this new arrangement, the possible pre-Carnian ornithischians, sauropodomorphs, and theropods are reinterpreted as early lineages that become extinct by the Carnian-Norian limit. Posteriorly, during the Norian, Theropoda and Sauropodomorpha sensu stricto become the dominant clades of terrestrial ecosystems. The recognition of Silesauridae and Pisanosaurus as successive stem taxa to Dinosauria, strengthen the hypothesis that sustain that herbivory was ancestral for Dinosauria. On the basis of present analysis, it is possible to infer a monophyletic condition for the herbivorous condition in Silesauridae, Pisanosaurus, Ornithischia, Sauropodomorpha and Guaibasauridae, whereas features related to carnivory in Herrerasauria and Theropoda were acquired by convergent phenomena. 5 F. Agnolin - Dinosauriformes del Triásico Superior de La Rioja, Argentina ÍNDICE CAPÍTULO 1- INTRODUCCIÓN………………………………………………...10 CAPÍTULO 2- OBJETIVOS E HIPÓTESIS A PONER A PRUEBA…………..14 CAPÍTULO 3- MATERIALES Y MÉTODOS……………………………………17 Especímenes y figuras……………………………………………………………….17 Análisis filogenético………………………………………………………………….18 Muestreo de caracteres………………………………………………………............19 Análisis de la matriz de datos………………………………………………………..20 CAPÍTULO 4- POSICIÓN GEOGRÁFICA Y ESTRATIGRÁFICA……...........21 CAPÍTULO 5- UNIDADES TAXONÓMICAS OPERACIONALES……............26 Taxones incluidos en el presente análisis……………………………………...........27 Taxones no incluídos en el presente análisis………………………………………..42 CAPÍTULO 6- RECONSIDERACIÓN DE LA POSICIÓN FILOGENÉTICA DE LAGERPETON CHANARENSIS……………………………………………………57 Introducción………………………………………………………………………..…57 Materiales estudiados de Lagerpeton chanarensis……………………………….....59 Resultados…………………………………………………………………….............60 Notas anatómicas……………………………………………………………..............62 6 F. Agnolin - Dinosauriformes del Triásico Superior de La Rioja, Argentina Codificaciones modificadas del set de datos de Nesbitt (2011)…………………...66 Caracteres plesiomórficos compartidos entre Lagerpeton y Proterochampsidae que están ausentes en Dinosauriformes……..…………………………………………..76 Características derivadas compartidas entre Lagerpeton y Proterochampsia…..78 Reevaluación sobre la postura y reconstrucción anatómica de Lagerpeton……...89 Cambios en la taxonomía de Ornithodira………………………………………….95 CAPÍTULO 7- REVALUACIÓN DE LAGOSUCHUS TALAMPAYENSIS……..97 PARTE 1- DESCRIPCIÓN Y VALIDEZ TAXONÓMICA DE LAGOSUCHUS TALAMPAYENSIS…………………………………………………………………..97 Introducción………………………………………………………………………….97 Resultados……………………………………………………………………………98 Comentarios finales…………………………………………………………………112 Conclusiones…………………………………………………………………………112 PARTE 2- NOTAS DESCRIPTIVAS SOBRE “MARASUCHUS LILLOENSIS” Introducción…………………………………………………………………………113 Notas descriptivas…………………………………………………………………...114 Comentarios sobre la morfología del neurocráneo Lagosuchus talampayensis…122 Conclusiones………………………………………………………………………....126
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