The larynx is a highly complex structure responsible for sound production during vocalization, a key element of anuran biology and evolution. Larynx morphology shows an astounding diversity in anurans; however, its structure has been studied in detail in only a few species. In this study, we describe the structure of the larynx in Scarthyla and most species of Pseudis (Hylidae, Hylinae, Pseudini) and related clades based on dissections and histological techniques. We propose homology hypotheses related to the arytenoid and cricoid cartilages, associated musculature, and vocal cords, which can be used to study laryngeal evolution in other groups of frogs. Character-state reconstruction on available phylogenetic hypotheses enabled us to infer new synapomorphies for the tribe, for each of the two genera, and for species groups within Pseudis. We also comment on advertisement call characteristics in relation to laryngeal morphology in the tribe.

Abstract Despite the strong conservatism of vertebrate eyes, many amphibians have supplementary structures in their irises. These have been referred to with the terms umbracula, menisci, or pupillary nodules, although often inconsistently. Moreover, widespread yet previously undescribed projections of the iris substantially modify pupil shape. This study clarifies the terminology of iris structures, describes new ones, discusses their homology and reviewes their distribution across Lissamphibia. We examined 214 representatives of 58 families through dissections and histology, and expanded observations with literature and public image repositories to a dataset of 784 species. Six main categories of supplementary iris structures were identified, most being unique among vertebrates: pupillary nodules (including umbracula), menisci, ciliary processes, marginal outgrowths, ventral notches, and median dark spots. We defined character states, and ancestral character reconstruction on most recent phylogenetic hypotheses revealed synapomorphies for Anura, Caudata, and several internal clades. We further investigated links between these structures, ontogeny, and pupil shape—a trait of taxonomic and ecological importance—and analysed correlations with microhabitat and diel activity to discuss the impact on visual ecology. Lastly, we revise all features that make amphibian eyes unique among vertebrates surveying all known synapomorphies and noteworthy features of the visual systems of Lissamphibia, Batrachia, Anura, Caudata, and Gymnophiona.

We describe a new species of the Isthmohyla tica group that occurs along the montane regions of the central Pacific of Costa Rica, between 1,400 and 2,000 masl. Although the new species is the sister taxon of a clade including an unde-scribed species and I. rivularis, it is more similar to I. tica. However, the new species can be distinguished because the flanks have scattered, distinct, round and irregular dark blotches or spots and because the advertisement call is comprised by a single, tonal note, typically emitted singly or in series, at dominant frequencies of 4,048–4,909 Hz, with a duration of 10–50 ms. The new species exhibits a broad acoustic repertoire composed of advertisement, release, and courtship calls, with the latter being emitted underwater. We discuss our findings with respect to adult and larval morphology, reproductive biology, and bioacoustics of the I. tica group.

We describe the tadpole of Charadrahyla esperancensis, which is characterized by having a ventral umbelliform oral disc that they use to feed on suspended particles on the water surface while swimming upside down and forming schools. So far, these characters are only reported for this species among the eight species of the genus with known tadpoles. The occurrence of a ventral umbelliform oral disc represents another instance of evolution of this peculiar oral disc among hylids. We also increase the known distribution of this species to a locality 25 km NW (air line) away from the type locality and correct a previous report of C. esperancensis tadpoles that confused them with those of Duellmanohyla ignicolor.

Abstract We describe a system of long and well-defined ligaments associated with the metacarpals of anurans. We observed differences in the presence, nature, and points of origin and insertion of each ligament by studying the diversity of all major clades of Anura. We produced a data matrix composed of 414 species (representing 56 of the 60 currently recognized families) and 29 characters. We identified seven different ligaments along metacarpals II–V, with individual species presenting from none to five. The medial ligament of metacarpal IV is the most widespread, occurring in 68% of species, whereas the remaining ligaments are more sparsely distributed. The ancestral character state reconstructions provided several synapomorphies at different taxonomic levels. We observed more ligaments and structural diversity in clades such as Pipidae and Phyllomedusinae, suggesting a relationship with the manual dexterity that characterize these clades. These results highlight previously undocumented variation in the ligament system of the anuran hand and its potential functional relevance. We discuss possible explanations for the abundant homoplasy observed in this character system, such as functional constraints, alternative hand musculoskeletal morphologies in arboreal anurans, and notable asymmetries in the pattern of losses and gains.

We describe a new species of the Ololygon catharinae group from the Cerrado biome, in the state of Minas Gerais, Brazil. Ololygon paracatu sp. nov. is morphologically similar to O. goya and O. skaios, although in phylogenetic analyses, it is recovered as the poorly supported sister taxon of O. pombali. It is distinguished from other species of the O. catharinae group by having a canthus rostralis marked and curved; subovoid snout in dorsal view and protruding in profile; inverted triangle shaped interocular blotch, exceeding the posterior margin of the eyes; inguinal region and hidden areas of thighs with dark brown irregular blotches on a pale yellow background in life; and advertisement call composed of 3-5 pulsed notes and dominant frequency of 2.5-3.5 kHz. Ololygon paracatu sp. nov. inhabits gallery forests associated with streams in the Cerrado biome.

The hylid genus Bokermannohyla comprises 31 species distributed across the Atlantic Forest, Caatinga and Cerrado domains, and their transition zones in Brazil. These species are currently included in three species groups (the B. circumdata, B. martinsi and B. pseudopseudis groups). In this paper, we present the results of a molecular phylogenetic analysis that includes 30 of the 31 species of the genus. Our results indicate that the currently recognized species groups are polyphyletic. To remedy this, we recognize four well-supported species groups-the B. astartea, B. izecksohni, B. nanuzae and B. oxente groups-and leave B. alvarengai, B. saxicola, B. ibitiguara and B. sazimai unassigned to any group. The new phylogenetic hypothesis allowed us to examine the evolution of oviposition sites, revealing that oviposition in water retained in restricted aquatic spaces (rock crevices, natural or male-modified basins or male-excavated tunnels) evolved from oviposition in streams during the evolutionary history of Bokermannohyla. Finally, our results support the hypothesis that this genus initially diversified in the Campos Rupestres (highland rocky fields) of the Serra do Espinhaço, with a subsequent, major diversification in the Atlantic Forest.

Of the many features that make frogs and toads unique, vocal sacs are among the most remarkable. Vocal sacs are inflatable, elastic chambers present in adult males of most anurans and are key elements in their social interactions. Traditionally vocal sacs have been associated primarily with acoustic communication, but their functions are currently being reinterpreted, and there is increasing evidence that they play a wider role in anuran biology. We surveyed the anatomical and histological structure of vocal sacs in all major clades of frogs by examining 777 specimens representing 605 species. Herein we characterize the morphological diversity of the three elements that compose the vocal sac: the gular skin, the superficial submandibular musculature, and the internal mucosa. We describe major anatomical patterns and define characters that we optimize on a comprehensive phylogenetic hypothesis of Anura. Integrating this anatomical information with images and videos of vocalizing frogs, we produce an updated morphological classification that includes 20 patterns of vocal sac morphology, each of which can be diagnosed by internal and external structures. Applying this classification to 4358 species, we discuss major evolutionary trends, taking ontogeny, homology, and multimodal communication into consideration. A single, spherical vocal sac is the most widely distributed vocal sac shape (present in 63% of known species), but some degree of lateralization (bilobate or paired sacs) has evolved in almost all anuran families. Some groups, such as Hylidae and Ranidae, are particularly diverse and contain more than 10 different vocal sac morphologies. Vocal sacs are absent in 18% of anurans and have been lost between 146 and 196 times, an astounding number considering their biological importance. Lastly, we review the morphological diversity and taxonomic relevance of vocal sac structures for each of the 58 families of recent anurans.

Neoprocoela edentata is a fossil anuran collected in Scarritt Pocket, Patagonia, Argentina. This locality provided the first described pre-Neogene batrachofauna of South America, which is also one of the few known to include representatives of extant taxa. Neoprocoela edentata shows an unusual combination of characters, and it has alternatively been related to Bufonidae or to a polyphyletic assemblage including Calyptocephalellidae and Telmatobiidae. In this article, we redescribe the single specimen of N. edentata, complementing the examination with micro-CT scan reconstructions, and expanding its original description. This results in a combination of character states unique to Bufonidae, allowing us to confidently assign N. edentata to this family. Then, we performed a total evidence phylogenetic analysis, including molecular and osteological data, to evaluate the phylogenetic relationships of N. edentata within Bufonidae. This species was recovered in a strongly supported clade with the extant genus Nannophryne; thus, Neoprocoela is considered a junior synonym of this genus, retaining edentata as a valid species. Finally, considering the geographic and stratigraphic provenance of the fossil remains, we discuss its value as evidence of the early evolution of South American toads and as an absolute-age calibration point, something relatively unusual for neobatrachian fossil species of that age.

We describe a new species, the fourth of the Scinax eurydice species group and the first one of this group found in Peru. The other three species, S. castroviejoi, S. sateremawe, and S. eurydice, are distributed across the Andes in Bolivia, the western Amazon basin of Brazil, and northeastern and southeastern Brazil, respectively. We describe the new species and use external morphological traits, such as the color pattern of flanks and inguinal region and vocal sac structure, to differentiate it from related species in the group. A phylogenetic analysis placed the new species as the sister taxon of S. sateremawe & thorn; S. castroviejoi. Uncorrected pairwise distances in the 16S ribosomal gene fragment between the new species and the other three in the group vary from 12.6 to 15.5% and greatly exceed the thresholds commonly used to distinguish Neotropical treefrog species. Additionally, the weakly bilobate vocal sac in the new species, shared with S. castroviejoi and S. sateremawe, may represent a synapomorphy of this clade of the S. eurydice group.

Dendropsophus is one of the most species-rich genera of hylid treefrogs. Recent studies integrating Sanger-generated mitochondrial and nuclear loci with phenomic characters (SP) have advanced understanding of this clade, but questions about its internal relationships and biogeographic history persist. To address these questions, we used anchored hybrid enrichment (AHE) to combine 432 nuclear loci for 78 taxa (72 % of species) with published data. Quantitatively, the impact of the AHE data was modest, with compositional differences in only three recognized clades and more than 80 % of the clades in the AHE + SP analyses also supported in the SP-only analyses. Nevertheless, the impact of AHE was crucial for resolving and increasing support for multiple nodes. We transferred one species of the former D. ruschii group to the D. decipiens group and redefined the D. leucophyllatus group to avoid paraphyly. We estimated divergence times to reconstruct the clade's biogeographic history. We also examined evolution of oviposition sites and assessed its effect on lineage accumulation. Dendropsophus likely originated similar to 57 mya, predating the Andean uplift, with some taxa showing dispersal patterns less constrained by ecological changes than previously thought.

Sphaenorhynchini comprises 15 species of small, greenish treefrogs from cis ‐Andean South America. Araujo‐Vieira et al. (2019, A total evidence analysis of the phylogeny of hatch‐faced treefrogs [Anura: Hylidae: Sphaenorhynchus ], Cladistics 35, 469–486) conducted a total evidence parsimony analysis of DNA sequences and phenotypic data, corroborating the monophyly of Sphaenorhynchus , identifying three species groups, and placing the unusual species S . pauloalvini as sister to all other species. On this basis and numerous phenotypic differences, Araujo‐Vieira et al. (2020, A new genus of lime treefrogs [Anura: Hylidae: Sphaenorhynchini], Zool. Anz. 286, 81–89) erected the genus Gabohyla for S . pauloalvini . Subsequently, Pereira et al. (2022, The dispersal between Amazonia and Atlantic Forest during the Early Neogene revealed by the biogeography of the treefrog tribe Sphaenorhynchini [Anura, Hylidae], Ecol. Evol. 12, e8754) performed a Bayesian analysis of a subset of Araujo‐Vieira et al.'s (2019) molecular data and found G . pauloalvini to be nested within Sphaenorhynchus , which they attributed exclusively to choice of analytical method. To test this claim, we performed parsimony and Bayesian analyses of the total evidence dataset and the complete and partial molecular datasets with either the entire outgroup sample or a single terminal. The topology from the Bayesian analysis of the complete dataset is almost identical to that of Araujo‐Vieira et al. (2019), with G. pauloalvini sister to Sphaenorhynchus , thereby refuting Pereira et al.'s claim. Moreover, the monophyly of Sphaenorhynchus sensu stricto was remarkably robust, being recovered in all analyses except the Bayesian analysis of the partial molecular dataset with a single outgroup terminal (i.e., the analysis performed by Pereira et al.). In addition to supporting the continued recognition of Gabohyla , our results underscore the importance of considering not only the choice of analytical method, but also character and taxon sampling—including outgroup sampling—before rejecting prior findings.

The description of the tadpole of Isthmohyla debilis by Duellman (1970) revealed a distinctive morphology that deviated from closely related stream-breeding species within the I. tica group in several important aspects, including the size of the oral disc, configuration of submarginal papillae on both labia, body shape, and jaw sheath morphology. These character states complicated the identification of phenotypic synapomorphies for the clade composed by I. debilis, I. rivularis, I. tica, and tentatively, I. pictipes and I. xanthosticta. We collected adults and tadpoles of I. debilis in the Reserva Forestal Fortuna, western Panama. Our findings indicate that the previously described tadpoles assigned to I. debilis were misidentified and likely correspond to the Panamanian lineage associated with I. lancasteri. We show that the larvae of I. debilis indeed share all the character states present in their closely related species, including a depressed body with a sloping snout and an enlarged oral disc that is nearly as wide as the body, deep angular folds, complete marginal papillae, three or more rows of submarginal papillae in the upper and lower labia, an M-shaped upper jaw sheath and LTRF 2/3, with complete tooth rows. Moreover, we provide information on vocalizations, natural history, and adult coloration patterns across the known geographic range of I. debilis. Additionally, we report a currently extant population of I. debilis from Boquete, western Panama, complementing a previous, tentative record of the species from the same area.

The most generalized reproductive mode in anurans is the deposition of egg clutches in water that develop into exotrophic aquatic tadpoles. Yet, despite this extended distribution, cases of parental care on submerged egg clutches are poorly documented. Because of its high diversity, its aquatic habits, and reports on males of two species standing next to the clutch, the Andean genus Telmatobius Wiegmann, 1834 offers an excellent model to examine the evolution of such behavior and the factors influencing it. Here, we combine field and laboratory studies to describe the breeding biology and parental care behavior in Telmatobius culeus (Garman, 1876), Telmatobius hintoni Parker, 1940, Telmatobius intermedius Vellard, 1951, Telmatobius jelskii (Peters, 1873), and Telmatobius oxycephalus Vellard, 1946. Our findings indicate that these five species have prolonged breeding season, and use concealed underwater shelters between rocks or macrophytes for mating and egg deposition. We showed that clutches of 35-560 eggs are deposited in these shelters. Males were observed next to the egg clutch and defending it aggressively against intruders, including conspecifics. Females were, on average, larger than males supporting the hypothesis that competition among males does not drive sexual size dimorphism in the genus. Our findings provide meaningful data to use in conservation programs, given that most species of Telmatobius are considered endangered and fill a significant information gap in understanding parental care's origin in Nobleobatrachia.

Keratinized labial teeth of the oral apparatus are a conspicuous evolutionary novelty of anuran tadpoles. Although several comparative studies have investigated their diversity in shape, arrangement, and function, no attempts have been made so far to explore taxonomic distribution and relationship with ontogenetic patterns at a global level. In this paper, we survey the variation in labial tooth row numbers in tadpoles in a phylogenetic context and discuss the developmental patterns probably involved in interspecific disparity. A configuration of two upper and three lower tooth rows occurs in almost half of free-living tadpoles but mostly concentrates in Notogaeanura; in Indianura, three rows are frequent in the lower lip but combined usually with increased numbers in the upper lip. While the homology between individual rows in this 2/3 and lower configurations seems straightforward to assess, the diversity of addition pattern of tooth rows in the upper and lower lips of tadpoles belonging to different clades merits the development of alternative terminology and refined coding systems for future phylogenetic analyses.

The sacroiliac articulation in anurans enables locomotion, including burrowing, swimming, jumping, and walking, by facilitating pelvic rotation and sliding. The hylid tribe Scinaxini comprises 134 Neotropical treefrogs divided into three genera: Julianus, Ololygon, and Scinax. The osteological elements of the sacroiliac articulation are well studied within the tribe, with Julianus having distinctive sacral diapophyses and sesamoids. Notably, the species J. camposseabrai has a medially elongated sesamoid, about three times its width in length, along with a short sacral diapophysis-a unique combination among anurans. However, information on the associated musculature in the tribe remains limited, restricting our understanding of this unique morphology. This knowledge gap prompted a detailed investigation of the musculature of the sacroiliac articulation in this clade of treefrogs. We revisited the osteology of the sacroiliac articulation and described its muscles in nine species of Scinaxini, including J. camposseabrai and J. pinimus. Our results showed that the origin and insertion of the muscles are largely conserved across the tribe, but variations exist in the orientation of the m. coccygeosacralis and the degree of separation between slips of the m. iliolumbaris. The species of Julianus have a unique sacroiliac osteo-muscular configuration, particularly J. camposseabrai, which is distinct from any previously described in anurans.

Boana cymbalum has not been collected for the past six decades and is one of the two species of Brazilian frogs formally considered to be extinct. It is also the only species of the B. pulchella group that has never been included in molecular phylogenetic analyses, because no fresh tissue is available. Using specialized historical DNA (hDNA) extraction protocols and high-throughput sequencing, we obtained mitochondrial and nuclear sequences from the 62-yr-old holotype of B. cymbalum. Our results place B. cymbalum as the sister taxon of the clade formed by B. prasina, B. cordobae, and B. pulchella, supporting its inclusion in the B. prasina clade. The scars on the dorsum of adult males suggest male-male combat. Microcomputed tomography revealed the presence of a large postarticular process and a distal prepollex directed laterad to pass ventral to Metacarpal II, two known synapomorphies of the B. pulchella group. On the basis of recordings from 1963, we provide an expanded description of the vocalization of B. cymbalum, consisting of a short, tonal note (Note A) and a longer, multipulsed note (Note B). Finally, we discuss the conservation status of B. cymbalum and the potential application of the newly generated hDNA sequences to screen water bodies near the type locality using environmental DNA in an effort to rediscover this species.

Isthmohyla insolita and Exerodonta catracha are Honduran hylids of uncertain phylogenetic relationships. In this paper we present a phylogenetic analysis of mitochondrial and nuclear genes to study their relationships. Our results show that these species are, respectively, the sister taxon of and nested among the few available species of Plectrohyla, possibly the least studied genus of Hylini in terms of phylogenetic relationships. To solve the polyphyly of Exerodonta and Isthmohyla, both species are provisionally transferred to Plectrohyla, pending a broader phylogenetic study including all species in the genus. Consequently, Isthmohyla is restricted to a group of hylids endemic to the Isthmian highlands of Costa Rica and Panama in lower Central America. The inclusion of I. insolita in Plectrohyla implies another instance of independent evolution of terrestrial egg clutches in Hylini.

We describe a new species in the Scinax granulatus group from the Atlantic Forest of northeastern Brazil and include the new species in an updated phylogenetic hypothesis for the group. The new species differs from all other species in the S. granulatus group by a combination of characters, such as a weakly bilobate vocal sac, moderately developed pre- and postaxial webbing of Toe IV, and advertisement call features. The newly described taxon is more similar with S. tropicalia, a species that is not closely related; both can be distinguished by the red-colored iris in the new species and differences in pulse rate of the call. The new species was recovered as the sister taxon of a clade including all other species of the S. granulatus group. However, the low support of some internal clades suggests that the knowledge about relationships in this group is still incomplete.