A SMALL BODY SIZED NON-ARISTONECTINE ELASMOSAURID (SAUROPTERYGIA, PLESIOSAURIA) FROM THE LATE CRETACEOUS OF PATAGONIA WITH COMMENTS ON THE RELATIONSHIPS OF THE PATAGONIAN AND ANTARCTIC ELASMOSAURIDS
Keywords:
Elasmosauridae. Cretácico Superior, Patagonia, Península AntárticaAbstract
The systematics of the Late Cretaceous non-aristonectine elasmosaurids from Argentinean Patagonia are poorly known as there is no valid species currently recognized. Here a new non-aristonectine elasmosaurid: Kawanectes lafquenianum nov. comb. from the late Campanian–early Maastrichtian Allen Formation is diagnosed. K. lafquenianum is a distinctively small-body sized non-aristonectine elasmosaurid characterized by caudal vertebrae with marked laterally projected parapophyses, presence of pelvic bar, high ratio (~1.2) between humerus/femur length and a large posterodistal projection of the humerus which bears a posterior accessory articular facet. A phylogenetic analysis recovered K. lafquenianum closely related with Morenosaurus stocki, Vegasaurus molyi, and Aristonectinae, showing the relationships between the elasmosaurids from Patagonia, Western Antarctic, and the Pacific coast of the USA. K. lafquenianum is part of the fauna of the coeval Allen and La Colonia formations that also comprises indeterminate aristonectines and polycotylids. This relatively high diversity plesiosaur fauna includes the three main morphotypes (aristonectines, non-aristonectine elasmosaurids and polycotylids), which is remarkable because the depositational environments of the Allen Formation have been inferred as marginal marine to non-marine environments. Resumen. UN PEQUEÑO ELASMOSÁURIDO NO ARISTONECTINO (SAUROPTERYGIA, PLESIOSAURIA) DEL CRETÁCICO SUPERIOR DE PATAGONIA CON COMENTARIOS SOBRE LA RELACIÓN ENTRE LOS ELASMOSÁURIDOS DE ANTÁRTIDA Y PATAGONIA. La sistemática de los elasmosáuridos no aristonectinos del Cretácico de la Patagonia Argentina es poco conocida, no habiendo ninguna especie válida reconocida actualmente. En esta contribución un nuevo elasmosáurido no aristonectino: Kawanectes lafquenianum nov. comb. proveniente de la Formación Allen (Campaniano superior–Maastrichtiano inferior) es diagnosticado. K. lafquenianum es un elasmosáurido no aristonectino de pequeño tamaño corporal que se caracteriza por la presencia de vértebras caudales con parapófisis fuertemente proyectadas lateralmente, presencia de barra pélvica, elevada proporción longitud del húmero / longitud del fémur (~1,2) y una marcada proyección posterodistal del húmero que lleva una carilla articular accesoria. El análisis filogenético recupera a K. lafquenianum, estrechamente relacionado con Morenosaurus stocki, Vegasaurus molyi y los aristonectinos que muestran las relaciones entre los elasmosáuridos del norte de Patagonia, Antártida Occidental y la costa pacífica de USA. K. lafquenianum es parte de la fauna de las formaciones coetáneas Allen y La Colonia, que comprende aristonectinos indeterminados y policotílidos. Esta diversidad relativamente alta, con los tres morfotipos principales presentes (elasmosáuridos aristonectinos, elasmosáuridos no aristonectinos y policotílidos), es notable ya que el ambiente de depositación de la Formación Allen se ha inferido como marino marginal con intercalaciones de ambientes no marinos.Downloads
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