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We studied the external and oral cavity morphology of the tadpoles of eight species of Hypsiboas in the H. albopunctatus, H. faber, H. punctatus and H. pulchellus species groups. After a review of the available information about larval external and oral cavity morphology, no character state seems to be synapomorphic for Hypsiboas. The presence of a fleshy projection in the inner margin of the nostrils and rounded vacuities of the anteromedial surface of the choanae (pending the confirmation of the latter in Hyloscirtus and Myersiohyla) seems to be synapomorphic for the tribe Cophomantini, as previously noticed by other authors. Some putative synapomorphies are suggested for some species groups of Hypsiboas, but a denser sampling is needed to study the taxonomic distribution of these character states, in order to determine which clades they may support. The presence of lateral flaps with labial teeth in the oral disc is a variable feature of many species in the H. faber and H. pulchellus groups. A spiracular tube free from the body wall is present in some species, mostly in the H. albopunctatus group, but also in the H. rufitelus, H. faber and H. pulchellus groups. Unique ventrolateral cumules of neuromasts are present in H. faber, and also in some species of other groups of Hypsiboas and of the sister genus Aplastodiscus. Our results highlight the importance of studying the taxonomic distribution of many character states that were sometimes overlooked in tadpole descriptions but seem relevant to test phylogenetic hypothesis.

Pleurodema bibroni and P. kriegi are poorly known species with a troublesome taxonomic history. They are cryptic taxa, currently considered as valid species on the grounds of biogeographic and ecological differences. The first is known from much of southern Uruguay and from the northeastern region of the State of Rio Grande do Sul, Brazil (from sea level to 900 m a.s.l.); the latter is restricted to high grasslands of the Sierras Grandes in central Argentina, between 800–2000 m a.s.l. Herein, we compare their tadpoles and advertisement call and provide some notes on their conservation status and natural history. The tadpoles of both species are very similar, belonging to the benthic ecomorphological guild, and are characterized by: total length about 35 mm at stages 33–36; globose body; short lateral sinister spiracle posterodorsally directed; pineal end organ visible between the eyes; medial vent tube, with its opening aligned with the ventral fin, directed to the left or to the right; vent tube enclosed in a transparent saccular structure underlying the limb buds; tail length about 60% of the total length, with bluntly rounded tip; oral disc anteroventral, laterally emarginated, with very robust jaw sheaths and marginal papillae arranged in a single or double row with a large dorsal gap; labial tooth row formula 2(2)/3(1); gap in A2 wide with the upper jaw sheath partially placed within it; P3 about half the length of the other rows. The advertisement call exhibits the same temporal and spectral structure in both species. It consists of long trills (up to about 45–70 s) that are emitted sporadically; notes are about 0.044–0.062 s, separated by gaps of 0.024–0.058 s (note repetition rate 8.9–13.2/s) and have three pulses. Dominant frequency ranges between 1729 and 2162 Hz. Reproductive season of both species differed, autumn and winter for Uruguayan populations of P. bibroni and spring and summer for P. kriegi. Defensive encounter behavior (deimatic behavior) consisting in exhibition of the eye-like lumbar glands was documented in P. bibroni and P. kriegi (along with exposure of reddish flash coloration), and also in P. borellii, P. bufoninum and P. thaul. Similar behavior previously unreported for a Pleurodema species lacking noticeable lumbar glands was observed in P. tucumanum. The analysis of the literature, material in collections and fieldwork done by the authors over the last decade in Uruguay suggests that P. bibroni is undergoing severe decline. It was a common species up to the early 1970’s, but few populations close to each other in southeastern Uruguay are the only ones currently known. The conservation status of P. bibroni is of major concern as most known remnant populations are located in coastal areas with an increasing impact of urbanization. In contrast, P. kriegi seem to have stable populations, many of them within protected areas.

The oral apparatus of anuran tadpoles is a unique structure composed of soft and keratinized parts surrounding the mouth. Among the many variations, a common oral apparatus involves a dorsal gap in the marginal papillae, keratinized jaw sheaths, and two upper and three lower rows of labial teeth. In Leiuperidae, besides this generalized morphology, four configurations are distinguished by the arrangement of the lower marginal papillae and the number of lower tooth rows. Study of the early oral ontogeny in 12 species representing these five configurations shows variations in the development of the lower marginal papillae and the third lower labial tooth row. Similar configurations may result from similar pathways (e.g. Physalaemus cuvieri group and Pseudopaludicola falcipes) or different pathways (e.g. generalized oral discs of Pleurodema and Physalaemus). Different oral configurations may result from overlapping trajectories ending at different stages (e.g. Physalaemus riograndensis and Ph. biligonigerus) or different trajectories (e.g. Ph. henselii and Ph. gracilis). Further studies are needed to interpret the role that heterochrony has played in evolutionary change within this family. The unsuspected variation occurring in this transient structure highlights its evolutionary potential and might be insightful in studies of anuran phylogenies that are largely based on adult characters.

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...

We studied the oral apparatus, buccal cavity and musculoskeletal features in tadpoles of five species of the genus Scinax (S. acuminatus, S. uruguayus, S. aff. pinima, S. aromothyella, and S. berthae). Observed variation is mainly related to intrageneric grouping. Scinax acuminatus (S. ruber clade, sister taxon of S. rostratus group) has a distinctive combination of a mental gap in the margin of oral papillae, straight labial teeth with few or absent cusps, processus muscularis acute and posteriorly directed, and m. subarcualis rectus I with two slips. Scinax uruguayus and S. aff. pinima (S. uruguayus group) have keratinized sheets ventrolateral to the lower jaw sheath, well-developed infralabial and lateral ridge papillae, robust jaw cartilages, cornua trabeculae with short and widely divergent free portions, processus articularis short and wide, processus muscularis thin and directed anteriorly. Scinax aromothyella and S. berthae (S. catharinae group) have poorly developed, non-colored spurs behind the lower jaw sheath, long and thin processus articularis, wide and rounded processus muscularis, and tripartite cartilago suprarostralis. Anatomical features described are congruent with current phylogenetic arrangements based on molecular, chromosomal, and morphological data, and provide a source of information that can be useful to solve interspecific relationships within Scinax.

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