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Calyptocephalella gayi is one of over 6,000 neobatrachians arranged into two main groups, Hyloides and Ranoides. Phylogenetically, C. gayi is placed in Australobatrachia, a Gondwanan clade that is either the most basal clade of Hyloides or the sister group of Hyloidea, depending on the cladistic hypothesis; as such, this species is a key taxon in the study of the early evolution of Neobatrachia. The ontogeny of the postcranial skeleton of C. gayi is described in this article. The description is based on pattern of chondrification and ossification of skeletal elements in a growth series of tadpoles, on juveniles and adult individuals. Particular attention was devoted to some developmental aspects and morphological traits of the adult skeleton. The body of Presacral Vertebra VIII is formed from three centers of ossification, in contrast to the usual two dorsolateral centers observed in the remaining vertebrae of C. gayi, as well as in most anuran taxa for which the development of the axial skeleton is known. Each half of the pelvic girdle arises from a single cartilaginous element. The early development of the autopodia of both the forelimb and hindlimb includes the presence of an additional chondral element, which occurs during the formation of Distal Carpal 5 and the transient formation of Distal Tarsal 4 before the latter is incorporated in the cartilaginous distal end of the fibular. Some osteological aspects of other australobatrachian anurans also are reviewed (e.g., presence of intervertebral discs) based on reports in the literature, as well as first hand observations. In the course of this study, it became evident that further osteological studies are needed to formulate a clear picture of the evolution of skeletal characters not only within Australobatrachia, but also within Neobatrachia. Fil: Muzzopappa, Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina Fil: Pugener, Lourdes Analia. Universidad Nacional de La Pampa; Argentina Fil: Baez, Ana Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Ciencias Geológicas; Argentina

El género de neobatracios Calyptocephalella Strand, cercanamente relacionado con los miobatracoideos australianos en recientes análisis moleculares, está actualmente restringido a los cuerpos de agua del bosque Austral en Chile aunque tuvo una distribución más amplia de acuerdo a la información paleontológica. Se describe aquí material nuevo y muy bien preservado proveniente del Mioceno temprano de la localidad Estancia Baibián, provincia de Chubut, Argentina, el cual es asignado a Calyptocephalella canqueli Schaeffer, especie erigida a partir de restos deseadenses (Oligoceno tardío), pero que fuera subsecuentemente sinonimizada con laúnica especie viviente del género: Calyptocephalella gayi Duméril y Bibron. Sin embargo, en base a comparaciones detalladas, se concluye en el presente trabajo que C. canqueli es un taxón válido que habitó Patagonia al este de los Andes durante el Oligoceno tardío-Mioceno temprano, y se provee una diagnosis revisada. La evidencia palinológica sumada a la presencia de C. canqueli documenta que los bosques húmedos, dominados por la angiosperma Nothofagus, persistieron cerca de la costa atlántica durante el Mioceno. La desaparición de ambientes propicios debido a una marcada tendencia a la aridez que se inició en el Mioceno medio probablemente haya sido responsable de la extinción de este género de anuros al este de los Andes. Abstract. The neobatrachian genus Calyptocephalella Strand, closely allied to the Australian myobatrachoids in recent molecular analyses, is now restricted to lowland water bodies of the Austral forests of Chile but had a broader distribution according to paleontological data. New, well-preserved material from the early Miocene locality Estancia Baibián, Chubut Province, Argentina, is described herein and assigned to Calyptocephalella canqueli Schaeffer, a species erected on the basis of Deseadan (late Oligocene) specimens, but subsequently synonymized with the only living species, Calyptocephalella gayi Duméril and Bibron. Detailed comparisons suggest that Calyptocephalella canqueli is a valid taxon representing frogs that inhabited Patagonia east of the Andes in the late Oligocene-early Miocene; a revised diagnosis is provided for the species. Palynological evidence coupled with the presence of C. canqueli document that humid forests, dominated by the angiosperm Nothofagus, persisted near the Atlantic coast in the Miocene. Disappearance of suitable habitats owing to a marked drying trend that started in the middle Miocene may have been responsible for the demise of this anuran genus east of the Andes. Fil: Muzzopappa, Paula. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología. Laboratorio de Paleontología Evolutiva de Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Baez, Ana Maria. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología. Laboratorio de Paleontología Evolutiva de Vertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina