Most anurans possess a tympanic middle ear (TME) that transmits sound waves to the inner ear; however, numerous species lack some or all TME components. To understand the evolution of these structures, we undertook a comprehensive assessment of their occurrence across anurans and performed ancestral character state reconstructions. Our analysis indicates that the TME was completely lost at least 38 independent times in Anura. The inferred evolutionary history of the TME is exceptionally complex in true toads (Bufonidae), where it was lost in the most recent common ancestor, preceding a radiation of >150 earless species. Following that initial loss, independent regains of some or all TME structures were inferred within two minor clades and in a radiation of >400 species. The reappearance of the TME in the latter clade was followed by at least 10 losses of the entire TME. The many losses and gains of the TME in anurans is unparalleled among tetrapods. Our results show that anurans, and especially bufonid toads, are an excellent model to study the behavioural correlates of earlessness, extratympanic sound pathways, and the genetic and developmental mechanisms that underlie the morphogenesis of TME structures.

True toads of the genus Rhinella are among the most common and diverse group of Neotropical anurans. These toads are widely distributed throughout South America, inhabiting a great diversity of environments and ecoregions. Currently, however, the genus is defined solely on the basis of molecular characters, and it lacks a proper diagnosis. Although some phenetic species groups have traditionally been recognized within Rhinella, the monophyly of some of them have been rejected in previous phylogenetic analyses, and many species remain unassigned to these poorly defined groups. Additionally, the identity and taxonomy of several species are problematic and hinder the specific recognition and description of undescribed taxa. In this work, we first perform phylogenetic analyses of separate mitochondrial and nuclear datasets to test the possible occurrence of hybridization and/or genetic introgression in the genus. The comparative analysis of both datasets revealed unidirectional mitochondrial introgressions of an unknown parental species into R . horribilis ("ghost introgression") and of R . dorbignyi into R . bernardoi; therefore, the mitochondrial and nuclear datasets of these species were considered separately in subsequent analyses. We performed total-evidence phylogenetic analyses that included revised molecular (four mitochondrial and five nuclear genes) and phenotypic (90 characters) datasets for 83 nominal species of Rhinella, plus several undescribed and problematic species and multiple outgroups. Results demonstrate that Rhinella was nonmonophyletic due to the position of R . ceratophrys, which was recovered as the sister taxon of Rhaebo nasicus with strong support. Among our outgroups, the strongly supported Anaxyrus + Incilius is the sister clade of all other species of Rhinella. Once R . ceratophrys is excluded, the genus Rhinella is monophyletic, well supported, and composed of two major clades. One of these is moderately supported and includes species of the former R . spinulosa Group (including R . gallardoi); the monophyletic R . granulosa, R . crucifer, and R . marina Groups; and a clade composed of the mitochondrial sequences of R . horribilis. The other major clade is strongly supported and composed of all the species from the non-monophyletic R . veraguensis and R . margaritifera Groups, the former R . acrolopha Group, and R . sternosignata. Consistent with these results, we define eight species groups of Rhinella that are mostly diagnosed by phenotypic synapomorphies in addition to a combination of morphological character states. Rhinella sternosignata is the only species that remains unassigned to any group. We also synonymize nine species, treat three former subspecies as full species, and suggest that 15 lineages represent putative undescribed species. Lastly, we discuss the apparently frequent occurrence of hybridization, deep mitochondrial divergence, and "ghost introgression"; the incomplete phenotypic evidence (including putative character systems that could be used for future phylogenetic...

ResumenEste estudio presenta la revisión actualizada de la riqueza, composición y distribución de los anfibios y reptiles del departamento del Casanare. Se revisaron 1.012 ejemplares depositados en las principales colecciones biológicas del país y se recolectaron 658 ejemplares en cuatro municipios de Casanare. Se obtuvo el registro de 46 especies de anfibios y 65 especies de reptiles, de las cuales, seis corresponden a nuevos registros y dos amplían la distribución conocida en el país. Los municipios de Sácama, Támara y Recetor presentaron los mayores vacíos de información.Palabras clave: Orinoquía colombiana, herpeto fauna, llanos, piedemonte, distribución.Current knowledge of the amphibian and reptile fauna in the department of Casanare, Colombia AbstractThe present study is an updated revision of the richness, composition and distribution of amphibians and reptiles in Casanare. A total of 1,012 specimens from the main Colombian biological collections were examined and 658 specimens were collected in four Casanare municipalities. As a result, we reported 46 species of amphibians and 65 species of reptiles of which six are new records and two extend their known distribution in Colombia. Additionally, we identified Sácama, Támara and Recetor as the municipalities with the poorest knowledge of their amphibians and reptiles.Key words: Orinoquia, herpeto fauna, distribution, savanna, foothill. Ciencias naturales IntroducciónDurante la última década, tanto el gobierno nacional, como la empresa privada, las organizaciones no gubernamentales, las universidades y los centros de investigación han volcado su atención sobre los diferentes ecosistemas de Casanare motivados por el acelerado crecimiento económico de la región y las radicales transformaciones de los paisajes naturales de las llanuras y el piedemonte. Esto ha generado un creciente número de investigaciones que han significado avances en el conocimiento de los anfibios y reptiles del departamento.A pesar de su vasta extensión y de la importancia que ha tomado esta región para el país, en términos biológicos los esfuerzos han sido insuficientes, ya que el desconocimiento de su fauna sigue siendo evidente, sobre todo en lo concerniente a la fauna de anfibios y reptiles, cuya composición se conoce de manera aceptable en la zona del piedemonte llanero, pero no así en la zona de las sabanas o llanuras del Orinoco.Los primeros registros sobre la herpeto fauna del departamento se deben a Amaral (1931) y Medem (1965, 1981) en lo concerniente a los reptiles y a Cochran & Goin (1970) en cuanto a los anfibios. Tuvieron que pasar tres décadas para que figuraran nuevos registros del departamento, cuando Ruiz, et al., (1996) actualizaron la lista de especies de anfibios del país, con cuyos registros, y los de otras publicaciones, Acosta-Galvis (2000) realizó una nueva revisión de los anfibios de Colombia en la que reportó 22 especies en Casanare. Recientemente, Acosta-Galvis & Alfaro-Bejarano (2011) actualizaron la información sobre los anfibios de este departamento ...

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