Morphological characterization and taxonomic key for tadpoles of Brazilian Cerrado

Abstract Currently, amphibians are recognized as the most threatened vertebrate group worldwide. In this context, studies that offer tools for amphibian conservation are strategic to reduce the threats to this group. The absence of detailed descriptions and morphological variation of the anuran larval stage and the lack of identification tools increase the difficulty of anuran larval stage identification by non-specialists. Here we present the morphological characterization of tadpoles of 49 anuran species that occur in the Cerrado biome and transitional areas. Also, we compared our characterization with available descriptions of the tadpole and provided comments about the morphological variation found in our samples. Finally, we produced a taxonomic key as a tool for species identification using the anuran larval stage.


Introduction
Amphibian populations are declining worldwide (Blaustein 2002), with almost 41% of the known species at risk of extinction (Pimm et al. 2014).Public agencies for environment management have proposed conservation programs for several species in different countries in an effort to revert the threatened status of amphibians (Mushet et al. 2012; see also the Brazilian Ministry of Environment resolutions n° 25/2012 and n° 293/2018 for example of conservation action plans for amphibians).However, the lack of basic information about species' natural history or distribution adds an extra layer of difficulty to planning conservation strategies (see a review in Brito 2010).For example, the correct identification of specimens used in several types of scientific research, from surveys to ecological experiments, is an activity that has its importance underestimated (Bortolus 2008).Errors in species identification can have unpredictable consequences for research outcomes, and the correct use of taxonomy is necessary for the estimation of species richness (e.g., Gotelli 2004, Bortolus 2008, Trindade-Filho et al. 2012, Melo et al. 2013, Rossa-Feres et al. 2015).
The negative effect of the knowledge gap in taxonomy for anuran conservation is a concern for regions such as the Brazilian savannah, due to the high rate of degradation and environmental modification, associated with high levels of endemism and diversity of amphibians (Myers et al. 2000, Bini et al. 2006, Trindade-Filho et al. 2012, Melo et al. 2014).The Brazilian Savanna, also known as "Cerrado", is the second largest Brazilian biome, being considered the largest savanna region in South America and the most diversified savanna in the world (Ab'Saber 1977, Silva & Bates 2002).Currently, about 220 species are known to this biome, with ~52% of these species considered endemic (Valdujo et al. 2012, Azevedo et al. 2016).However, this richness is probably underestimated since many new species have been described each year (e.g., Andrade et al. 2018, Pinheiro et al. 2018, Vaz Silva et al. 2018).
For most anuran species, the larval stage, denominated tadpoles, are the easiest developmental stage to encounter and to collect, since they remain in the aquatic environment for a longer period than adults, which makes them a fundamental component for biodiversity surveys (Lips & Savage 1996, Altig & McDiarmid 1999, Rossa-Feres & Nomura 2006, Andrade et al. 2007, Alves-Ferreira et al. 2021).Also, the importance of the larval traits for reconstruction of the phylogenetic relationships (e.g., Haas 2003, Frost et al. 2006) and ecological processes modelling has been increasingly recognized (see a discussion in Rossa-Feres et al. 2015).For example, morphological variation has been used for taxonomy (e.g., Rossa-Feres & Nomura 2006, Channing et al. 2016, Arifin et al. 2018, Dubeux et al. 2020, Montilla et al. 2023), ecotoxicology (e.g., Costa & Nomura 2016, Costa et al. 2017), and investigating ecological process at the community level (e.g., Marques & Nomura 2015;Marques et al. 2018;Annibale et al. 2020).However, we need to better understand the natural morphological variation of tadpoles, resulted from interaction with predators and competitors or from inter-and intrapopulation variation, to differentiate it from the impact on anurans of changes in land use, land cover, climate change, or other man-induced environmental modifications (Rossa-Feres et al. 2015).Without knowing the normal variation in each population, the association of morphological changes to anthropogenic disturbance is more challenging (Costa & Nomura 2016, Costa et al. 2017, Annibale et al. 2020).This is particularly important when we consider the actual conservation status of the Cerrado biome and its rate of habitat modification and land-use conversion, and the threats to the herpetofauna (Klink & Machado 2005, Colli et al. 2020).
Despite the growing importance of tadpoles in different branches of science, the difficulties in the correct identification of species still represents a major obstacle to include anuran larvae in management and conservation studies, mainly due to the high intraspecific morphological variation in tadpoles (Andrade et al. 2007).Also, the misleading identification of tadpoles could result in an artificial morphological variation, as variation in tadpole morphology could be a consequence of the difficulty in identifying cryptic species (Santos et al. 2018).Without an understanding of the species morphological variation throughout its area of occurrence, the interpretation of the variation among populations will remain unclear (Gehara et al. 2014).Thus, investment in the training of taxonomists, incentives for collaboration between researchers, for example, in addition to tools to increase accuracy in species identification are important actions to reduce this knowledge gap (Bortolus 2008).
One valuable tool for accessing correct species identification of anuran larvae is the use of taxonomic keys, while not the sole, taxonomic keys are highly useful and easily accessible (Gotelli 2004).Additionally, they offer a more cost-effective solution compared to other techniques (Stein et al. 2014).Despite the importance of this tool and the high anuran diversity in Brazil, only seven identification keys for tadpoles are known up-to-date: one for the region of Central Amazonia (Hero 1990), one for species occurring in the northwestern region of São Paulo state (Rossa Feres & Nomura 2006), one for the Rio Grande do Sul state (Machado & Maltchik 2007), one for species with occurrence in municipalities of Alvorada de Minas, Conceição do Mato Dentro and Dom Joaquim, Minas Gerais state (Pimenta et al. 2014), one for the southward portion of Ilha Grande, municipality of Angra dos Reis, Rio de Janeiro state (Fatorelli et al. 2018), and more recently one key for tadpoles of the northern region of the Atlantic Forest (Dubeux et al. 2020) and another for the Iron Quadrangle, Southeastern Brazil (Pezzuti et al. 2021).Here we present a characterization of the external morphology and an identification key for tadpoles of 49 species with occurrence in areas of Brazilian Cerrado (following the species inventories for the Biome presented in Valdujo et al. 2012 andAzevedo et al. 2016).

Study area
Geographically, the Cerrado biome occupies a central position in South America and shares contact zones with the two largest rainforest blocks of the Neotropics (Amazonia and Atlantic Forest biomes) as well as with two dry regions (Caatinga and Chaco biomes) (Ab 'Saber 1977, Silva & Bates 2002).The Cerrado is characterized by a complex landscape with high horizontal heterogeneity along its distribution, from open and savanic vegetation to forested habitats (Ribeiro & Walter 1998).The savanna formations include the "campo rupestre" (sensu Silveira et al. 2016) and "cerrado sensu stricto" vegetational types, also known as the typical cerrado (Ribeiro & Walter 1998).The forest formations are constituted of "cerradão" (i.e., transition between semideciduous forests and typical cerrado areas), semi-deciduous forests, "veredas", riparian and gallery forests (Ribeiro & Walter 1998).The grasslands formations are made up of wet grasslands, dry grasslands and "rupestre" fields (Campos & Lage 2013).The Cerrado biome has a strongly seasonal climate, with a wet and warm season that lasts from October to April, and a dry and cold season that lasts from May to September (Klink & Machado 2005).In this study, we used the official limits of Cerrado biome defined by the Instituto Brasileiro de Geografia e Estatística (IBGE) (available in https://www.ibge.gov.br/geociencias/informacoes-ambientais). Valdujo et al. (2012) found that the diversity of anuran species in the Cerrado was influenced by the proximity to the surrounding domains, like the Caatinga or the Amazon.For example, they state that shared species between the Cerrado and the Amazon are less likely to co-occur with species from the Cerrado-Atlantic Forest border (Valdujo et al. 2012).The same occur for the dry diagonal (Chaco-Cerrado-Caatinga, Valdujo et al. 2012).More important, Valdujo et al. (2012) highlight the importance of transitional areas to the composition of anuran species pool in the Cerrado, especially in the transition of the Cerrado and Atlantic Forest.Thus, we included five species that occurs in transitional areas between Cerrado and Atlantic Forest, which are Rhinella ornata x Rhinella crucifer Thomé, Zamudio, Haddad & Alexandrino 2012, Thoropa miliaris (Spix 1824), Scinax longilineus (Lutz 1968), Proceratophrys boiei (Wied 1825), and Odontophrynus cf.juquinha (Baldissera et al. 2004, Valdujo et al. 2012, Pimenta et al. 2014, Matavelli et al. 2018, Eterovick et al. 2020).We are following Thomé et al. (2012) and citing the previous known populations of R. pombali Baldissera, Caramaschi & Haddad 2004 included in our samples as Rhinella ornata x Rhinella crucifer, once R. pombali is currently considered a hybrid formed by R. crucifer and R. ornata parents (Thomé et al. 2012; but see also the discussion in Pereyra et al. 2021).
All tadpoles were obtained from the Coleção Zoológica da Universidade Federal de Goiás (ZUFG), municipality of Goiânia, Goiás state, Brazil (Appendix 1), collected from different localities from the Brazilian Cerrado (Figure 1).To be more concise, we present information about the collection locations along with the description of external morphology in the "Results" section.We defined the tadpole's identity using known morphological diagnostic traits with the help of ZUFG collection curators (NM Maciel, RP Bastos, and FN -one of the authors) or by consulting external experts at the time of the tadpole's collection and inclusion in the ZUFG collection (DC Rossa-Feres, W Vaz-Silva, NYN Dias -particularly for tadpoles from Scinax, NM Maciel -for Rhinella).When necessary, we also compared the morphology of tadpoles in our samples with available descriptions (indicated in the "Results" section -Comments) or by using taxonomic keys (Rossa-Feres and Nomura 2006).Following the best practices proposed by Vink et al. (2012), when we were not confident to attribute a nominal taxon for a given tadpole morphotype, but we found a consistently morphological variation that differentiates it from other species in our sample, we used "aff.","cf.", "gr.", or "sp." as appropriate.
For the morphological characterization and elaboration of the taxonomic key, we examined two to 15 individuals between stages 30 to 40 (sensu Gosner 1960).For the genus Bokermannohyla Faivovich, Haddad, Garcia, Frost, Campbell & Wheeler, 2005, with species reproducing in lotic environments and that have longer larval period (Patterson & McLachlan 1989), we used individuals at Gosner's stage 25.Whenever possible, we included individuals from more than one population to evaluate inter-populational variation in the morphological traits.Nomenclature of morphological characteristics (Figures 2-4) followed Altig & Johnston (1986;1989), andMcDiarmid &Altig (1999).When, in the description, we were referring to the oral disc, we use "A" to describe the teeth rows that were positioned anterior to the oral aperture, and "P" to describe the teeth rows that were positioned posterior to the oral aperture.Each letter was followed by a number that represents the position of a given row of ones in relation to the oral disc, and the "A" rows follow a distal-proximal ascending order, while the "P" rows follow a proximal-distal ascending order, in relation to the oral opening, as shown in Figure 3.6 in McDiarmid & Altig (1999).
The size classes of body shape in lateral view, nares, eye, spiracle, tail muscle, and fin height were determined by the following ratios, respectively: body width/body height (compressed ≤ 1 < depressed), nares size/eye diameter (small ≤ 0.14 < medium < 0.38 ≤ large ≤ 0.50 < very large), eye diameter/body height (small ≤ 0.17 < medium < 0.29 ≤ large), tail muscle width/body width (narrow ≤ 0.29 < medium < 0.49 ≤ wide), dorsal fin height/tail muscle height (low ≤ 0.49 < medium < 1.01 ≤ high), ventral fin height/tail muscle height (low ≤ 0.43 < medium < 0.97 ≤ high), spiracle length/body length (short ≤ 0.06 < medium < 0.19 ≤ long), and spiracle width/body height (narrow ≤ 0.09 < medium < 0.25 ≤ wide).The size classes of the above-mentioned measurements were defining as "small ≤ -1 SD < mean < +1 SD ≤ large" for all measurements, except for nares diameter, that was defined as "small ≤ -1 SD < mean < +1 SD ≤ large ≤ +2 SD < very large", and body shape.The standard deviations for the definition of size classes were calculated considering a sample of 322 anuran Brazilian species, collected during the project "SISBIOTA Girinos do Brasil" (DC Rossa-Feres, unpublished data).For body shape, we considered the body compressed when body height is higher than body width, and depressed when body width is higher than body height.Morphometric traits were reported in the characterization of each tadpole as mean ± standard deviation for total length and (range) for all other measurements.The complete morphometric information can be seen in Table 1.We considered lateral lines evident when the lateral lines were easily observed at stereomicroscopic.All morphometric traits were measured from digital photographs, obtained with a M205A Leica ® stereomicroscopic with a DFC550 camera, using the software ImageJ (1.51i).Each tadpole was placed in a petri dish and positioned in lateral or dorsal view using a water-based gel for image capture.To illustrate the external morphology, once tadpoles were larger than the visual field of the stereomicroscopic, we had taken from three to six digital images from one tadpole and combined they in an image editor software.To illustrate the oral disc, one tadpole in our series was dissected and mounted on a paraffin block, positioned with entomological pins to keep the mouth open, and submerged in distilled water for image capturing.We used a commercial 1% methylene blue solution to highlight oral disc parts, spiracle, or vent tube of tadpoles, as necessary.Table 1.Measurements (mm) of the tadpoles characterized in this study and on which the descriptions are based on.Character abbreviations: total length (TL), body length (BL), tail muscle height (TMW), tail muscle width (TMW); body height (BH), body width (BW), eye diameter (ED), nare diameter (ND), nare-eye distance (NED); dorsal fin height (DFH), ventral fin height (VFH), spiracle length (SL), spiracle width (SW), and dorsal fin insertion angle (DFA).

Results
In this study, we present the morphological characterization for tadpoles of 49 anuran species, with about 600 specimens analyzed, from the families Bufonidae (Rhinella cerradensis, R. diptycha, R. ornata x R. crucifer), Cycloramphidae (Thoropa megatympanum, T. miliaris), Dendrobatidae (Adelphobates galactonotus, Ameerega flavopicta), Hylidae (Boana albopunctata, Boa. lundii, Boa. raniceps, Boa. cf. crepitans, Bokermannohyla alvarengai, Bok. pseudopseudis, Bok. sapiranga, Dendropsophus minutus, D. soaresi 1, Figure 5).The body shape is ovoid in dorsal view and globular-depressed in lateral view (BW/BH = 1.24-1.34).The snout is sloped in lateral view.The oral disc is ventral, laterally emarginate, with a uniseriate row of elongated marginal papillae, interrupted by dorsal and ventral gaps; few submarginal papillae scattered laterally, smaller than the marginal papillae.Labial teeth row formula (LTRF) is 2(2)/3(1), with row A1 = A2, P1 = P2 and P3 slightly smaller than P2 in length.The upper jaw sheath is narrow, arc-shaped, and the lower jaw sheath is narrow, U-shaped; the upper jaw sheath is slightly wider than the lower jaw sheath.Nares medium (ND/ED = 0.30-0.37),elliptical, with a small projection on the marginal rim, dorsally positioned.Eyes small (ED/ BH = 0.15-0.16),dorsally positioned.Spiracle sinistral, short (SL/ BL = 0.03-0.04),narrow (SW/BH = 0.08-0.09),with opening at the middle third of the body, directed posterodorsally, with the centripetal wall fused to the body wall.Vent tube medial, fused with the ventral fin.The caudal musculature width is narrow (TMW/BW = 0.18-0.19).The dorsal fin is high (DFH/TMH = 1.27-1.38), originating at the bodytail junction with acute slope, and convex margin; ventral fin is high (VFH/TMH = 1.04-1.09)with convex margin; the tail tip is rounded.Lateral lines are evident.Comments.According to Maciel et al. (2007) the tadpoles of R. cerradensis can be differentiated from tadpoles of other Rhinella species by body proportions (in relation to tail and total length), spiracle position, and the "absence of an external spiracular tube'', with the opening in the body wall.Rhinella cerradensis tadpoles analyzed in this study closely resemble the individual described by Maciel et al. (2007), but presented an external spiracular tube, like other Rhinella species.We examined the tadpoles used in the description of R. cerradensis (CHUNB 49574) and the absence of an external spiracular tube (Maciel et al. 2007) represents a difference in the interpretation of the authors and not a morphological variation.

Rhinella diptycha (Werner 1894)
First Description of the tadpole: Jaboticabal -SP, Brazil (Rosa, 1965).Other characterizations: São José do Rio Preto -SP, Brazil (Vizotto 1967); Argentina (Cei 1980);Nova Itapirema -SP, Brazil (Rossa-Feres & Nomura 2006); Eastern Region of the Meridional Espinhaço Range -MG, Brazil (Pimenta et al. 2014); Bahia State, Brazil (Mercês et al. 2009); Fernando de Noronha -PE, Brazil (Tolledo & Toledo 2010); northern region of the Atlantic Forest (Dubeux et al. 2020) 6).The body shape is elliptical in dorsal view and globular-depressed in lateral view (BW/BH = 1.21-1.23).The snout is rounded in lateral view.The oral disc is ventral, laterally emarginate, with a uniseriate row of conical marginal papillae, interrupted by dorsal and ventral gap; few submarginal papillae scattered laterally, smaller than the marginal papillae.LTRF is 2(2)/3, with row A1 = A2, P1 = P2 and P3 slightly smaller than P2.The upper jaw sheath is narrow, arc-shaped, and the lower jaw sheath is narrow, U-shaped; the upper jaw sheath is slightly wider than the lower jaw sheath.Nares medium to large (ND/ ED = 0.34-0.38),elliptical, with a small projection on the marginal rim, dorsally positioned.Eyes medium (ED/BH = 0.18-0.18),dorsally positioned.Spiracle sinistral, with medium length (SL/BL = 0.06-0.10),narrow (SW/BW = 0.09-0.09),opening at the middle third of the body, directed posterodorsally, with the centripetal wall completely fused to the body wall.Vent tube medial, fused with the ventral fin.The caudal musculature width is narrow (TMH/BW = 0.20-0.21).The dorsal fin has medium height (DFH/TMH = 0.73-0.99),originating at the anterior third of the tail with an acute slope, and with convex margin; ventral fin has medium height (VFH/TMH = 0.59-0.86)with convex margin; the tail tip is rounded.Lateral line not evident.Comments.Tadpoles from populations currently associated with Rhinella diptycha were described by Rosa (1965), Vizotto (1967), Cei (1980) (as Bufo paracnemis), Mercês et al. (2009), Tolledo & Toledo (2010) and Dubeux et al. (2020) (as Rhinella jimi).Tadpoles described by Cei (1980) were larger than those used in our description.In Stage 37 the Argentinean populations presented total length of 35 mm, while the analyzed in this study at the same stage presented total length of 23.87 mm, like those described by Vizotto (1967) -Feres & Nomura (2006), Mercês et al. (2009), Tolledo & Toledo (2010) and Dubeux et al. (2020), differing from the LTRF 2(2)/3(1) described by Rosa (1965), Vizotto (1967) and Cei (1980).Both Rosa (1965) and Rossa-Feres & Nomura (2006) suggests that the interrupted P1 could be caused by manipulation of the tadpoles, but this seems instead morphological variation.From the eleven tadpoles analyzed, two presented the P2 slightly wider than P1, two individuals from different locations presented the LTRF 2(2)/3(1) and the submarginal papillae with the same size of the marginal papillae.Rhinella diptycha seems to have variable spiracle position among the different populations studied.In Rossa-Feres & Nomura (2006), the position of the spiracle is in the posterior third of the body, while in Cei (1980) and Tolledo & Toledo (2010) the spiracle is described as positioned at the midbody, while Mercês et al. (2009) described it as positioned in the anterior half of the body.Dubeux et al. (2020) do not provide a description for R. diptycha but informs its general aspects together with other Rhinella tadpoles included in their study.In our samples, five individuals in both lots analyzed had the spiracle positioned at the posterior third of the body.Tadpoles of R. diptycha can be distinguished from R. cerradensis by having the body elliptical in dorsal view, depressed body, dorsal fin originating at the anterior third of the tail, LTRF 2(2)/3, mainly by snout rounded in lateral view, and by the presence of unpigmented longitudinal stripe along the ventral edge of the tail musculature.7).The body shape is ovoid in dorsal view and globular-depressed in lateral view (BW/BH = 1.19-1.27).The snout is rounded in lateral view.The oral disc is ventral, laterally emarginate, with a uniseriate row of conical marginal papillae, interrupted by dorsal and ventral gap; few submarginal papillae laterally, forming a row on the inner side of the lateral emargination, with the same size as the marginal papillae.LTRF is 2(2)/3, A1 = A2, P1 = P2 and P3 slightly smaller than P-2; the upper jaw sheath is narrow, arc-shaped, and the lower jaw sheath is narrow, U-shaped; the upper jaw sheath slightly wider than the lower jaw sheath.Nares medium (ND/ED = 0.22-0.36),elliptical, with a small projection on marginal rim, dorsally positioned.Eyes small (ED/BH = 0.14-0.15),dorsally positioned.Spiracle sinistral, with medium length (SL/BL = 0.09-0.10)and medium width (SW/BH = 0.11-0.12),opening at the middle third of the body, directed posterodorsally, with the centripetal wall completely fused to the body wall.Vent tube medial, fused with the ventral fin.The caudal musculature width is narrow (TMW/BW = 0.20-0.21).The dorsal fin has medium to high height (DFH/TMH = 0.63-1.02),originating at the body-tail junction with acute slope, and convex margin; ventral fin has medium height (VFH/TMH = 0.55-0.82)with convex margin; the tail tip is rounded.Lateral line not evident.

Rhinella ornata x Rhinella crucifer
Comments.Rhinella pombali, treated as a species by Baldissera et al. (2004), is currently considered a hybrid formed by R. crucifer and R. ornata parents (Thomé et al. 2012; but see also the discussion in Pereyra et al. 2021).Thus, we used previous descriptions of tadpoles treated as R. pombali to compare with our description.The populations analyzed by Pimenta et al. (2014), treated as Rhinella crucifer were compared to our description.The populations described by Lourenço et al. (2010) were smaller (total length = 21.50 mm) than the populations that we studied, but this difference could be explained by the difference in the developmental stages of the tadpoles analyzed [stages 35-38 in Lourenço et al. (2010), stage 40 in our sampled population].In addition, the tadpoles describe by Lourenço et al. (2010) have the oral disc not emarginate, but the figure shows that the oral disc is emarginate laterally.We found intrapopulation variation in teeth row formula, with one individual with LTRF 2(2)/3(1), and in submarginal papillae, with one individual without submarginal papillae.Tadpoles of (formerly known as) R. pombali can be distinguished from tadpoles of R. cerradensis by the rounded snout, and LTRF 2(2)/3, and from tadpoles of R. diptycha by the ovoid body shape, larger body proportions, eyes dorsolaterally directed, and spiracle opening at the posterior third of the body.
Characterization.Total length 24.09 ± 0.71 mm (Table 1, Figure 9).The body shape is elliptical in dorsal view and oval-depressed in lateral view (BW/BH = 1.30-1.60).The snout is rounded in lateral view.The oral disc is ventral, ventrally emarginate, with a uniseriate row of marginal papillae, elongated laterally and short ventrally, interrupted by dorsal gap; The upper jaw sheath is wide, arc-shaped, and the lower jaw sheath is wide, U-shaped; the upper and lower jaw sheath of the same width.Nares medium (ND/ED = 0.15-0.17),elliptical, laterally positioned.Eyes large (ED/BH = 0.32-0.34),dorsally positioned.Spiracle lateroventral, with medium length (SL/BL = 0.10-0.14)and width (SW/BH = 0.24-0.24),with opening at the middle third of the body, directed posterodorsally, with the centripetal wall completely fused to the body wall.Vent tube medial, with free distal edge.The caudal musculature width is medium (TMW/BW = 0.31-0.31).The dorsal fin is low (DFH/TMH = 0.05-0.12),originating at the posterior third of the tail with acute slope, and margin parallel to the caudal musculature; ventral fin is low (VFH/TMH = 0.11-0.16)with margin parallel to the caudal musculature; the tail tip is rounded.Lateral line not evident.
Comments.Tadpoles analyzed in this study are like the description of Bokermann (1965) and Pezzuti et al. (2021), and just one individual in our sample had a different LTRF of 2(1,2)/3(1).Pezzuti et al. ( 2021) described the tadpoles with the oral disc lateroventrally emarginate, while we considered the emargination ventral, with a small nostril, while we considered the nares medium sized, and with a short spiracle, while we considered it medium sized.Tadpoles of T. miliaris can be distinguished from tadpoles of T. megatympanum by the elliptical body in dorsal view, lower dorsal fin, and larger vent tube (LT/LMC = 1.72 mm in T. miliaris, and LT/LMC = 1.27 mm in T. megatympanum).However, regarding this last trait, we suspected that the vent tube in our T. miliaris sample were damaged during collecting and the validity of this difference should be evaluated in future studies.
Comments.A discussion about the importance of larval morphology for systematic of the Dendrobatoidea and their relatives was provided by Santos et al. (2018).
The body shape is elliptical in dorsal view and globular-depressed in lateral view (BW/BH = 1.08-1.17   1, Figure 14).ventral gap in the marginal papillae, but in one specimen, and a short P4 row in another one.Disregarding these variations, the tadpoles are similar when compared to our sample.The populations analyzed by  1, Figure 15).The body shape is ovoid in dorsal view and globular-depressed in lateral view (BW/BH = 1.13-1.17   1, Figure 16).2021) also were larger (56.1 mm) than the tadpoles that we described, and had medium sized nares, while we considered it larger.The oral disc of the tadpoles from the Iron Quadrangle also had lateroventrally emargination and marginal papillae with alternate disposition (Pezzuti et al. 2021).Although the illustration presented by Sazima & Bokermann (1977) show the LTRF 2(1,2)/5(1), the authors describe it as 2(2)/5(1), the same observed by Pimenta et al. (2014) 1, Figure 17).   1, Figure 18).The body shape is elliptical in dorsal view and globular-depressed in lateral view (BW/BH = 1.14-1.19).The snout is rounded in lateral view.The oral disc is ventral, emarginate ventrally, with a uniseriate row of elongated marginal papillae, biseriate laterally, interrupted by a dorsal gap; submarginal papillae scattered laterally, smaller than the marginal papillae; accessory teeth row present laterally in the oral disc.LTRF is 2(2)/5(1), A1 = A2; P1 = P2 = P3 = P4 > P5.The upper jaw sheath is narrow, arc-shaped, and the lower jaw sheath is narrow, V-shaped; the upper jaw sheath is wider than the lower jaw sheath.Nares medium to large (ND/ED = 0.35-0.43),elliptical, with a projection on marginal rim, dorsally positioned.Eyes small (ED/BH = 0.14-0.18),dorsally positioned.Spiracle sinistral, with medium length (SL/BL = 0.09-0.10)and medium width (SW/BH = 0.14-0.17),opening at the middle third of the body, directed posterodorsally, with the centripetal wall fused to the body wall and with a free distal edge.Vent tube dextral, fused to the ventral fin.The caudal musculature width is medium to wide  (TMW/BW = 0.45-0.69).The dorsal fin has low to medium height (DFH/TMH = 0.41-0.64),originating at the body with an acute slope, and margin convex to the caudal musculature; ventral fin has low to medium height (DFH/TMH = 0.30-0.53)with parallel margin; the tail tip is pointed.Lateral line evident.
Comments.From the total of analyzed individuals, four presented alternated marginal papillae, three had accessory teeth rows laterally, one presented marginal papilla in the upper labium, and three presented P1<P2.Tadpoles analyzed by Lins et al. (2018) closely resemble those presented herein, with the exception that the accessory teeth rows were absent in their populations and described as a variation presented in only one individual.
The body shape is elliptical in dorsal view and triangular-depressed in lateral view (BW/BH = 1.09-1.17The dorsal fin has medium height (DFH/TMH = 0.86-0.94),originating at the body with median slope, and convex margin; ventral fin has medium height (VFH/TMH = 0.76-0.77)with a convex margin; the tail tip end in a flagellum.Lateral line not evident.
Comments.Tadpoles described by Vizotto (1967) differ from our sample by the LTRF 2(2)/3, however the author reports that the LTRF 2(2)/3(1) was also observed.Tadpoles described by Vizotto (1967)  Characterization.Total length 42.14 ± 3.76 mm (Table 1, Figure 22).Comments.Our tadpoles are like those described by Vizotto (1967) and Cei (1980), differing only by the disposition of submarginal papillae, with 4 to 6 rows laterally in the oral disc in these tadpoles.1, Figure 23).     1, Figure 24).The body shape is rounded in dorsal view and globular-depressed in lateral view (BW/BH = 1.12-1.17).The snout is rounded in lateral view.The oral disc is ventral, folded ventrally and ventrolaterally, with a biseriate row of mixed conical and elongated marginal papillae, without dorsal gap; presence of submarginal papillae aggregated lateroventrally, mixing small and large submarginal papillae, also mixing submarginal papillae that were smaller and larger than marginal papillae; submarginal papillae when larger than marginal papillae could have lateral projection, forming a T-shape.LTRF is 2( 2 Comments.Tadpoles described by Lourenço et al. (2013) present snout sloped or truncated in lateral view (rounded in our samples).
The large oral disc, continuous row of marginal papillae, without a dorsal gap, and the amount and shape of the submarginal papillae are useful traits that help to distinguish the tadpoles of Scinax pombali from the tadpoles of other species of Scinax included in our study.In our sample, one individual presented the marginal papillae uniseriate in alternate disposition and biseriate laterally, and another individual had A2 slightly smaller than A1.  1, Figure 25).The body shape is elliptical in dorsal view and globular-depressed in lateral view (BW/BH = 1.01-1.06).The snout is rounded in lateral view.

Scinax rupestris
The oral disc is anteroventral, not emarginate, with a uniseriate row of conical marginal papillae, interrupted by a dorsal gap; submarginal papillae aggregated laterally, and smaller than the marginal papillae.
The LTRF 2(2)/3(1), the most common in our sample, is described as a variation in the original description (Araujo-Vieira et al. 2015).We also observed a variation in the density of pigmentation in the body coloration, as reported by Araujo-Vieira et al. (2015).Two individuals from our sample had the body ovoid in dorsal view, two showed an evident lateral line, two had the LTRF 2(2)/3, three had fewer submarginal papillae, scattered lateroventrally, and three had the A1 teeth row of the same length than the A2.Characterization.Total length 30.12 ± 2.01 mm (Table 1, Figure 26).The body shape is elliptical in dorsal view and triangular-compressed in lateral view (BW/BH = 0.90-0.94).The snout is rounded in lateral view.
The oral disc is anteroventral, ventrally emarginate, with a uniseriate row of conical marginal papillae, in alternate disposition, interrupted by a dorsal gap; submarginal papillae aggregate laterally, of the same size as the marginal papillae.LTRF is 2(2)/3(1), A1 = A2, P1 > P2 > P3.The upper jaw sheath is narrow, M-shaped, and the lower jaw sheath is narrow, V-shaped; the lower jaw sheath is slightly wider than the upper jaw sheath.
Comments.Tadpoles described by Alves & Carvalho-e-Silva (1999)    due to the snout sloped in lateral view, nares with opening laterally directed (anterolaterally directed in S. similis), and to S. fuscomarginatus due to the position of fin origin, away from the eyes position, and deeper fins.They also are distinguished from S. rupestris by the oral disc ventrally emarginated.
Other characterizations: Jaboticatubas -MG, Brazil (Cei 1980) 1, Figure 28).Comments.Tadpoles analyzed in our study closely resemble those described by Cei (1980) and Pimenta et al. (2014), differing only by the elliptical body shape in dorsal view from those tadpoles described by Cei (1980), which was described as ovoid, but this difference represents a difference in terminology use.Tadpoles described by Bokermann (1967) had a different LTRF [2(1,2)/3(1)].In our sample, one of the tadpoles had the A2 teeth row longer than the A1.Tadpoles of S. squalirostris were distinguished from tadpoles of S. fuscovarius because they were slender, had a rounded snout, and the origin of the dorsal fin is closer to the eyes.In addition, S. squalirostris could be distinguished from the tadpoles of S. fuscomarginatus by higher body and deeper dorsal and ventral fins.The snout rounded in lateral view differ S. squalirostris from S. rupestris and Scinax sp., and the oral disc ventrally emarginated differ S. squalirostris from S. rupestris.Tadpoles of S. squalirostris are smaller and had the P3 smaller when compared to S. similis.
Characterization.Total length 36.46 ± 4.02 mm (Table 1, Figure 29).Comments.Tadpoles described by Schiesari et al. (1996) were larger (TL = 59.9 mm, Stages 39) than those in our sample.Tadpoles described by Duellman (2005) do not have submarginal papillae, but the author report the presence of small papillae positioned in the lateral folder, which could be a reference to the accessory teeth rows or o the  submarginal papillae.Cei (1980) reports for the tadpoles of Argentina a LTRF 2(2)/5(1), eventually with an additional P6, but generally, the P5 and P6 were highly fragmented whenever present.For Duellman (1970) and Rossa-Feres & Nomura (2006), the P6 teeth row was more common and the interruptions in the teeth rows had a different pattern, resulting in a LTRF of 4(1,2,4)/6(1,6).Schiesari et al. (1996) already described the variation in the number of teeth rows, suggesting that this variation could be related to the developmental stages, finding until nine posterior labial teeth rows in tadpoles of T. typhonius.In our sample, the LTRF showed large variation, with LTRF 4(1,3)/5(1) found in eight of the tadpoles, followed by the LTRF 3(1,3)/6(1), found in five of the tadpoles, and the LTRF 3(1)/5(1), found in one of the tadpoles.Whenever present, the row P6 was shorter than the other rows of labial teeth and fragmented and, as seen by Schiesari et al. (1996) 1, Figure 30).The body shape is ovoid in dorsal view and globular-depressed in lateral view (BW/BH = 1.27-1.09).The snout is rounded in lateral view.The oral disc is anteroventral, not emarginate, with a uniseriate row of elongate marginal papillae, in alternate disposition, interrupted by a dorsal gap; submarginal papillae absent.LTRF is 2(2)/3, A1 slightly smaller than A2, P1 = P2 and P3 slightly smaller than P2.The upper jaw sheath is narrow to medium, arc-shaped, and the lower jaw sheath is narrow, V-shaped; the upper jaw sheath is wider than the lower jaw sheath.Nares medium to large (ND/ED = 0.36-0.39),elliptical, dorsally positioned.Eyes medium (ED/BH = 0.17-0.17),dorsally positioned.Spiracle sinistral, with medium length (SL/BL = 0.10-0.18)and medium width (SW/BH = 0.13-0.17),opening on the middle third of the body, posterodorsally directed, with centripetal wall fused to the body wall.Vent tube medial, fused to the ventral fin.The caudal musculature width is medium (TMW/BW = 0.27-0.41).The dorsal fin is low (DFH/TMH = 0.43-0.48),originating at the tail-body junction with acute slope, and convex margin; ventral fin is low (DFH/TMH = 0.41-0.43)with convex margin to the caudal musculature; the tail tip is pointed.Lateral line not evident.
Comments.Tadpoles described by Lescure (1973) 1, Figure 31).The body shape is ovoid in dorsal view and globular-depressed in lateral view (BW/BH = 1.15-1.18).The snout is rounded in lateral view.The oral disc is anteroventral, not emarginate, with a uniseriate row of short and rounded marginal papillae, alternated ventrally, interrupted by a dorsal gap; submarginal papillae absent.LTRF is 1/2(1), P1 slightly smaller than P2; the upper jaw sheath is narrow to medium, arc-shaped, and the lower jaw sheath is narrow, V-shaped; the upper and lower jaw sheath have the same width.Nares medium to large (ND/ED = 0.35-0.38),elliptical, dorsally positioned.Eyes small to medium (ED/ BH = 0.14-0.171921).
The caudal musculature width is medium (TMW/BW = 0.32-0.36).The dorsal fin has medium height (DFH/TMH = 0.67-0.71),originating on the posterior third of the body with a median slope, with convex margin; ventral fin has medium height (VFH/TMH = 0.61-0.61)with convex margin; the tail tip is rounded.Lateral line not evident.

Physalaemus cuvieri Fitzinger, 1826
First Description of the tadpole: São Paulo, Brazil (Bokermann, 1962).Other characterizations: Argentina (Cei, 1980); Boracéia -SP, Brazil (Heyer et al. 1990) 1, Figure 36).The body shape is ovoid in dorsal view and globular-depressed in lateral view (BW/BH = 1.06-1.27).The snout is rounded in lateral view.The oral disc is ventral, laterally emarginate, with a uniseriate row of elongated marginal papillae, interrupted by one dorsal, one ventral and two lateroventral ventral gaps (C4 type sensu Vera Candioti et al. 2011), submarginal papillae absent.LTRF is 2(2)/3(1), with the A1 slightly smaller than the A2, P1˃P2 and P3 with a third the length of the P2.The upper jaw sheath is narrow to medium, arc-shaped, and the lower jaw sheath is narrow, U-shaped; the lower jaw sheath is wider than the upper jaw sheath.Nares very large (ND/ED = 0.80-0.85),elliptical, with a small projection on marginal rim, dorsally positioned.Eyes small From the total of analyzed individuals, three had the LTRF 2/3(1), four had the A1 with the same length than the A2, five had one or two submarginal papillae laterally (from which one had accessory teeth row), and six individuals had the upper jaw sheath M-shaped.The presence of marginal rim also varies, with three tadpoles with a small projection on the marginal rim, and three tadpoles presented the marginal rim in only one nare.Tadpoles of P. cuvieri are easily differentiated from those of P. centralis by the LTRF 2(2)/3(1), larger nares (average of 1.01 mm in diameter for P. cuvieri, and 0.53 mm for P. centralis), and by the spiracle posterodorsally directed.
Other characterizations: Nova Itapirema -SP, Brazil (Nomura et al. 2003) 1, Figure 38).The body shape is ovoid in dorsal view and globular-depressed in lateral    Comments.Tadpoles analyzed by Schulze et al. (2015) were smaller (TL = 17.7 mm, , and were described as having a rounded snout.In three of six individuals in our sample, the spiracle was not long enough to cover the vent tube and in one of six individuals, the vent tube was dextral.
Other characterizations: Argentina (Cei 1980, Lavilla 1992) Comments.Vizotto (1967) considered the tadpoles to have large eyes while Cei (1980) and Lavilla (1992) described the eyes of the tadpoles as small.Tadpoles in our sample are like those described by Rossa-Feres & Nomura (2006).In two individuals in our sample, the spiracle was not long enough to cover the vent tube.Tadpoles of D. muelleri were easily differentiated from those of C. albopunctatus by the larger total length and the rounded snout in lateral view.Characterization.Total length 26.94 ± 4.27 mm (Table 1, Figure 41).The body shape is rounded in dorsal view and triangular-depressed in lateral view (BW/BH = 1.41-1.72).The snout is truncate in lateral view.Oral disc modified without keratinized mouthparts or papillae; presence of paired dermal flaps suspended in front of oral cavity; dermal flaps with irregular edges.Nares not perforated.Eyes small (ED/BH = 0.16-0.17),laterally positioned.Spiracle ventral, with medium length (SL/BL = 0.14-0.19)and medium width (SW/BH = 0.12-0.17),opening on the posterior to the body, covering the vent tube, posteriorly directed, with the centripetal wall not fused with the body wall.Vent tube medial with sinistral opening, fused to the ventral fin.The caudal musculature    1, Figure 43).     1, Figure 44).Characterization.Total length 32.67 ± 4.61 mm (Table 1, Figure 46).   1, Figure 48).The body shape is elliptical in dorsal view and globular-depressed in lateral view (BW/BH = 1.15-1.18).The snout is rounded in lateral view.The oral disc is ventral, laterally emarginate, with a uniseriate row of elongated marginal papillae, interrupted by a dorsal gap; submarginal papillae absent.LTRF is 2(2)/3(1), A1 ˂ A2, P1 = P2 ˃ P3.The upper jaw sheath is wide, arc-shaped, and the lower jaw sheath is wide, V-shaped; the upper jaw sheath is wider than the lower jaw sheath.Nares medium (ND/ED = 0.17-0.20),rounded, with a small projection on the marginal     1, Figure 51).The body shape is elliptical-elongated in dorsal view and triangularcompressed in lateral view (BW/BH = 0.83-0.92).The snout is truncated in lateral view.Oral disc anteroventral, ventrally emarginate, with a uniseriate row of elongated marginal papillae, in alternated disposition, interrupted by a dorsal gap; submarginal papillae scattered laterally, and smaller than the marginal papillae.LTRF is 2(2)/3(1), A1 slightly smaller than A2, P1 = P2 and P3 with about a third of the P2 length.The upper jaw sheath is narrow to medium, M-shaped, and the lower jaw sheath is narrow, V-shaped; the upper jaw sheath is wider than the lower jaw sheath.Nares small to medium (ND/ED = 0.08-0.21),elliptical, laterally positioned.Eyes medium (ED/BH = 0.26-0.30),laterally positioned.Spiracle ventral, short to medium (SL/BL = 0.06-0.09),with medium width (SW/BH = 0.13-0.16),opening at the middle third of the body, posteriorly directed, with the centripetal wall fused to the body wall.Vent tube medial with dextral opening, fused to the ventral fin.The caudal musculature width is wide (TMW/BW = 0.50-0.51).The dorsal fin is low (DFH/TMH = 0.28-0.43),originating at the tail-body junction with acute slope, with margin parallel to the caudal musculature; ventral fin has medium height (VFH/TMH = 0.57-0.73)with convex margin; the tail tip end with a flagellum.Lateral line evident.
Comments.Tadpoles described by Cei (1980) differed from the tadpoles in our sample by the LTRF 2(2)/2(1) and the dextral vent tube.The populations analyzed by Vera Candioti (2007) had uniseriate marginal papillae.Two morphotypes were presented by Schulze et al. (2015), from Bolivia, the "P.azureus A" and "P.azureus B" (treated as Phyllomedusa azurea).The morphotype B (Schulze et al. 2015) was described with a sloped snout in lateral view, arc-shaped upper jaw sheath, V-shaped lower jaw sheath, marginal papillae biseriate laterally and uniseriate in alternated disposition ventrally, and without submarginal papillae.The morphotype A (Schulze et al. 2015) also had a sloped snout in lateral view, but the marginal papillae were biseriate lateral and ventrally, and the submarginal papillae were absent.The morphotype A presented a narrow ventral gap, variation that we observed in seven tadpoles in our sample.Two individuals had ventral emargination in the oral disc, and one individual had a biseriate marginal papillae.The lateroventrally spiracle described by Schulze et al. (2015) represent a difference in terminology use, but the position is the same.We prefer the use of ventral spiracle, once the spiracle can be only seen in ventral position, although it is not positioned in the sagittal line.
Pithecopus oreades (Brandão, 2002) First Description of the tadpole: Goiás -Brasil (Brandão, 2002).1, Figure 52).The body shape is elliptical-elongated in dorsal view and triangularcompressed in lateral view (BW/BH = 0.98-1.00).The snout is rounded to sloped in lateral view.The oral disc is anteroventral, ventrally emarginate, with a uniseriate row of elongated marginal papillae, in alternated disposition, interrupted by a dorsal and a small ventral gap; submarginal papillae scattered laterally, smaller than the marginal papillae.LTRF is 2( 2  0.25-0.26),laterally positioned.Spiracle ventral, short to medium (SL/ BL = 0.05-0.09),with medium width (SW/BH = 0.11-0.15),opening at the middle third of the body, posteriorly directed, displaced to the left, with the centripetal wall fused to the body wall.Vent tube medial with dextral opening, fused to the ventral fin.The caudal musculature width is medium to wide (TMW/BW = 0.45-0.51).The dorsal fin is low (DFW/TMW = 0.39-0.40),originating at the tail-body junction with acute slope, with margin parallel to the caudal musculature; ventral fin has medium height (VFH/TMH = 0.57-0.70)with convex margin; the tail end with a flagellum.Lateral line evident.Comments.Our tadpoles are like those described by Brandão (2002), but the presence of a narrow ventral gap was not reported in the original description.1, Figure 53).Comments.We were unable to associate this morphotype to the other known species of Pithecopus.Tadpoles of Pithecopus sp.differ from tadpoles of P. azurea and P. oreades by the taller caudal musculature, lower dorsal fin, and smaller total length.In one individual, we observed a narrow ventral gap.

Discussion
Most larval studies in Brazil are related to descriptive studies, like the description of the external morphology (Andrade et al. 2007), which allow the inclusion of larval morphology as functional or ecological traits in hypothesis test (e.g., Arifin et al. 2021).However, we still need to understand the extent of variation in morphological traits to increase the accuracy of taxonomic studies, and its usefulness in ecological studies.In the characterizations that we provided in this article, we found variation in the body or oral features even for species that we do not have a larger sample, which highlight the need to not underestimate the amount of intra-or interpopulation morphological variation and the impact of such variation in defining morphotypes for taxonomic studies (Grosjean 2005) or evaluating the effect of environmental modifications (e.g., Costa & Nomura 2016, Costa et al. 2017), for example.Moreover, tadpoles are known to exhibit phenotypic plasticity and morphological variation in tadpoles is expected throughout its area of occurrence, due to changes in local environmental conditions or the presence of predators and competitors (Marques & Nomura 2018).In general, morphological characterization of the external morphology of tadpoles does not receive much attention from researchers or journals, with several journals indicating that tadpole morphological characterization should be published as Short Notes or Correspondence (e.g., Santos et al. 2018, Tolledo & Toledo 2010, Verdade et al. 2023).Certainly, we can have many arguments for a given report to be published as a summarized version, but this decision ideally should be done case by case, once this type of publication reduces the opportunity for discussion of the results and for comparisons.Also, when a given tadpole morphology is already formally described, the interest to report other characterization of the same tadpole with samples from different localities is reduced, unless the original description is not very detailed, have a low sample of individuals, or is based on individuals in early developmental stages (i.e., below Gosner's Stage 34).Such constraint in reporting morphological variation, despite its result from the interest of researchers for novelty or journal editorial decisions, implies a generalization of the tadpole morphology based on the first description for the entire range of the species distribution and restricts the morphological sampling throughout the geographical range of the species.Although the effect of availability is not restricted to the reports of tadpoles' morphology, it is an issue to be considered, nevertheless.One of the possibilities to overcome this effect is to produce descriptive reports with broader geographical samples and to use more diverse and comparative analytical methods.However, in a continental size country like Brazil, this sampling and analytical decisions can result in greater logistical costs, which could be prohibitive, once financial resource is an important constraint of biodiversity research in developing countries (Young 2005).The increase of independent and geographically restricted reports of tadpoles' morphology would help to reduce several opportunities costs and increase the open collaboration in biodiversity  The ontogenetic variation can lead to erroneous determination of diagnostic traits (see Gosner 1960, Grosjean 2005, andNavarro Acosta & Vera Candioti 2017 for a discussion about morphological variation regarding developmental allometry).To avoid this problem, the use of tadpoles between Stages 32 and 40 was suggested by Grosjean (2005), once it is more likely that any variation in these developmental stages reflect interspecific variation than ontogenetic changes.It would be ideal if all anuran species had a known developmental table for the larval stage, but we are far from this reality.Even if we consider that the ontogenetic changes in the larval stage among anuran species is relatively uniform, and then could be illustrated by the Gosner's (1960) developmental table, we do not have enough information about populational variation to define which are the most reliable traits for taxonomic comparisons.
The shape of the snout, the body or fins or the size of eyes and nares had great variation in tadpoles' descriptions.The use of morphological traits as nominal variables increases the risk of subjective interpretation of such traits.Although the variability in the reports of the external morphology could represent a natural variation in a continuous shape scale, and the use of nominal descriptors in the characterization is also useful to describe tadpole morphology, the use of quantitative morphometric definitions for such shapes would increase reliability in tadpoles' descriptions.An attempt to provide morphological definitions was made by Altig (1970), modified posteriorly by Altig & McDiarmind (1986, 1999).Despite being widely used, in many descriptions several traits are lacking, or the traits are not used as proposed.Together with the terminology problem, the use of ratios to describe tadpole morphology limits the utility of the descriptions.Although ratios are helpful to establish a size proportion of the morphological trait, we cannot access the raw information from ratios.Conversely, the use of new technologies in image capture and processing allowed an increase in the quality of pictures in recent descriptions of tadpoles' external morphology (e.g., Chiasmocleis schubarti, Santos et al. 2015;Crossodactylus aeneus, Silva-Soares et al. 2015;Dendropsophus branneri, Abreu et al. 2015), and the use of quantitative morphometric analytical approaches, as geometric morphometric (e.g., Pezzuti et al. 2016).
We detected large variation in external morphological traits of tadpoles from several anuran species, with no reference in other available descriptions of such variation.Evaluation if these variations represent some level of phenotypic plasticity or a clue for taxonomic use, like a complex of cryptic species, is hard to define once data about morphological traits from populations throughout a geographic gradient is lacking.

How to use this taxonomic key
We think this taxonomic key would be helpful to anyone interested in describing the anuran biodiversity using larval stage information, but the users should be aware of its limitations.First, the distribution of anuran species in the Cerrado Biome is compartmentalized, thus many species that occur in the Cerrado-Atlantic Forest border are not expected to be found in the Cerrado-Amazon border, and vice-versa (Valdujo et al. 2012).The user should know the expected species pool for the sampled area to avoid misidentification.Second, we should expect variation in tadpole morphology; thus, the user should compare the tadpole morphology with the larval description before associating a larval morphology with a species name.This taxonomic key includes about 22% of the species known to occur in the Cerrado biome, and for many anurans' species larval stage is currently unknown.For example, for the 114 anurans species that occur in the Goiás State, central Brazil, 35 does not have their larval stage described (Vaz-Silva et al. 2020).Thus, the user should be aware that this taxonomic key can be useful to indicate which species the larva belongs to or exclude other species to which the larva does not belong.Finally, we invite other researchers with samples of tadpoles' larvae of species not included to modify this taxonomic key to improve its accuracy and species coverage.

Figure 1 .
Figure 1.Map of remaining of Cerrado biome.Red circles represent the localities of the tadpoles used in the present study.Inset map: South America.

Figure 2 .
Figure 2. Morphological characteristics used to larval characterizations and in the taxonomic key.Details of a typical tadpole in lateral view, and body shape in dorsal and lateral view.

Figure 3 .
Figure 3. Morphological characteristics used to larval characterizations and in the taxonomic key.Details of the nares, spiracle, fins, and tail tips.

Figure 4 .
Figure 4. Morphological characteristics used to larval characterizations and in the taxonomic key.Details of the oral disc.
that presented 23.50 mm, and by Rossa-Feres & Nomura (2006) with 24.31 mm.The LTRF 2(2)/3 was the mostly common observed by us and is the same as reported by
The body shape is elliptical in dorsal view and globular-depressed in lateral view (BW/BH = 1.38-1.49).The snout is rounded in lateral view.The oral disc is ventral, laterally emarginate, with a uniseriate row of elongated marginal papillae, interrupted by a dorsal gap; few submarginal papillae scattered laterally, of the same length as the marginal papillae.LTRF is 2(2)/3(1), A1˂A2, P1˂P2˃P3.The upper jaw sheath is narrow, arc-shaped, and the lower jaw sheath is narrow, V-shaped; the upper jaw sheath is wider than the lower jaw sheath.Nares medium (ND/ED = 0.18-0.15),elliptical, with a small projection on marginal rim, dorsolaterally positioned.Eyes medium (ED/BH = 0.20-0.24),dorsally positioned.Spiracle sinistral, with medium length (SL/BL = 0.09-0.11)and wide width (SW/BH = 0.15-0.20),opening at the middle third of the body, directed posterodorsally, with the centripetal wall completely fused to the body wall.Vent tube dextral, fused with the ventral fin.The caudal musculature width is medium (TMW/BW = 0.38-0.39).The dorsal fin has medium height (DFH/ TMH = 0.59-0.61),originating at the body-tail junction with an acute slope, and convex margin; ventral fin has low to medium height (VFH/ TMH = 0.38-0.46)with margin parallel to the caudal musculature; the tail tip is pointed.Lateral line not evident.Comments.Tadpoles analyzed byDias et al. (2018) closely resemble those described herein.Tadpoles described byPezzuti et al. (2021) differ by the spiracle length, that they considered short while we considered it medium sized.One individual in our sample presented marginal and submarginal papillae conical in the upper labium.
The body shape is elliptical in dorsal view and globular-depressed in lateral view (BW/BH = 1.05-1.12).The snout is rounded in lateral view.The oral disc is ventral, emarginate ventrally, with a uniseriate row of elongated marginal papillae, in alternated disposition, interrupted by a dorsal gap; submarginal papillae scattered laterally, smaller than the marginal papillae, accessory teeth rows present laterally in the oral disc.LTRF is 3(1,3)/6(1), A1 slightly smaller than A2 and A3 slightly smaller than A2; P1 = P2 = P3 = P4 = P5 > P6.The upper jaw sheath is narrow, arc-shaped, and the lower jaw sheath is wide, V-shaped; the upper jaw sheath is wider than the lower jaw sheath.Nares large (ND/ ED = 0.38-0.40),elliptical, with a small projection on the marginal rim, dorsally positioned.Eyes medium (ED/BH = 0.18-0.20),dorsally positioned.Spiracle sinistral, with medium length (SL/BL = 0.10-0.13)and medium width (SW/BH = 0.14-0.15),opening at the middle third of the body, directed posterodorsally, with the centripetal wall fused to the body wall, with a free distal edge.Vent tube dextral, fused to the ventral fin.The caudal musculature width is medium to wide (TMW/ BW = 0.47-0.55).The dorsal fin has medium height (DFH/TMH = 0.67-0.70),originating at the body with a median slope, and convex margin; ventral fin has medium height (VFH/TMHW = 0.
Dendropsophus soaresi(Caramaschi & Jim 1983) First Description of the tadpole: Jandaíra -BA, Brazil(Gomes & Peixoto 1991).Other characterization: Not available.Specimens Examined: Brazil, Goiás State, municipalities of Barro Alto(ZUFG 811, ZUFG 862)  and Jataí (ZUFG 773).Description based on ten tadpoles between Gosner Stages 35 and 39.Characterization.Total length 36.88 ± 1.93 mm (Table1, Figure20).The body shape is elliptical elongated in dorsal view and triangularcompressed in lateral view (BW/BH = 1.07-1.07).The snout is sloped in lateral view.The oral disc anteroventral, not emarginate, with a biseriate row of rounded marginal papillae (varying between four to eight marginal papillae laterally), interrupted by a dorsal and lateroventral gap; submarginal papillae absent.LTRF is 0/1, with the P1 teeth row located close to the lower jaw sheath.The upper jaw sheath is narrow to medium, arc-shaped, and the lower jaw sheath is wide, U-shaped; the lower jaw sheath is wider than the upper jaw sheath.Nares medium (ND/ED = 0.17-0.20),rounded, anteriorly positioned.Eyes large (ED/ BH = 0.29-0.31),laterally positioned.Spiracle sinistral, short (SL/BL = 0.04-0.05),with medium width (SW/BH = 0.09-0.11),opening at the middle third of the body, directed posteriorly, with centripetal wall completely fused to the body wall.Vent tube dextral, fused to the ventral fin.The caudal musculature width is wide (TMW/BW = 0.57-0.58).The dorsal fin has medium height (DFH/TMH = 0.58-0.78),originating on the posterior third of the body with a median slope, and convex margin; ventral fin has medium height (VFH/TMH = 0.59-0.80)and with convex margin; the tail tip end in a flagellum.Lateral line not evident.Comments.Our sample of D. soaresi tadpoles closely resemble those described byGomes & Peixoto (1991) but are larger [our sample = 36.88mm of total length,Stages 35-38; Jandaíra = 29.5 mm, Stages  34-38, (Gomes & Peixoto 1991).The population described from Jandaíra, also have longer marginal papillae.From the ten individuals observed in our sample, three presented elliptical nares, and one had a small projection on the nares marginal rim.The spiracle direction also varied, with one specimen presenting spiracle ventrally directed and three posterodorsally directed.Tadpoles of D. minutus are commonly mistaken by tadpoles of D. soaresi, but tadpoles of D. soaresi can be identified by the presence of lateroventral gaps in the row of marginal papillae, the lower jaw sheath wider and straighter than in D. minutus, and the absence of blackish band between the snout and eyes, common in D. minutus.Scinax fuscomarginatus (Lutz 1925) First Description of the tadpole: Nova Itapirema -SP, Brazil (Vizotto 1967).Other characterizations: Nova Itapirema -SP, Brazil (Rossa-Feres & Nomura 2006); Eastern Region of the Meridional Espinhaço Ridge -MG, Brazil (Pimenta et al. 2014).Specimens Examined: Brazil, Goiás State, municipality of Niquelândia (ZUFG 915).Description based on ten tadpoles between Gosner Stages 34 and 39.
view (BW/BH = 1.18-1.21).The snout is sloped in lateral view.The oral disc is anteroventral, laterally emarginate, with uniseriate row of elongated marginal papillae ventrally, in alternated disposition, biseriate lateroventrally, interrupted by a dorsal gap; submarginal papillae absent.LTRF is 2(2)/3(1), with A1 teeth row slightly longer than A2, P1 slightly longer than P2 and P3 slightly shorter than P2.The upper jaw sheath is wide, arc-shaped, and the lower jaw sheath is narrow, V-shaped; the upper and lower jaw sheath had the same width.Nares large (ND/ED = 0.41-0.49),rounded, dorsally positioned.Eyes small to medium (ED/ BH = 0.14-0.18),dorsally positioned.Spiracle sinistral, medium to long (SL/BL = 0.12-0.22),with medium width (SW/BH = 0.15-0.20),opening on the posterior third of the body, posterodorsally directed, with the centripetal wall fused to body wall.Vent tube dextral, fused to the ventral fin.The caudal musculature width is medium (TMW/BW = 0.31-0.36).The dorsal fin has medium height (DFH/TMH = 0.53-0.67),originating on the posterior third of the body with a median slope, with a convex margin; ventral fin has low to medium height (VFH/TMH = 0.29-0.44)with margin parallel to the caudal musculature; the tail tip is pointed.Lateral line not evident.Comments.Tadpoles analyzed by Rossa-Feres & Nomura (2006) differ from those in our sample by the uniseriate marginal papillae and smaller size (TL = 32.64 mm, Stages 35-39, Rossa-Feres & Nomura 2006; TL = 33.84mm, Stages 34-37, our sample).Tadpoles were described by Rossa-Feres & Nomura (2006) as having the P2 teeth row slightly longer than the P1 and the P3, but figure shows the P1 teeth row and the P2 of similar sizes, and both longer than the P3.The populations described by Schulze et al. (2015) were smaller (TL = 31.3mm in Stages 37-41), had a uniseriate marginal papilla, and the P1 teeth row slightly smaller than the P2 and the P3.Three individuals in our sample had the uniseriate marginal papillae in alternated disposition laterally, two individuals had the marginal papillae uniseriate lateroventrally, and one individual had the marginal papillae biseriate laterally.In one individual, the A1 teeth row had the same length than the A-2 and five individuals presented the upper jaw sheath M-shaped.Tadpoles of P. nattereri were easily differentiated from those of P. centralis, P. cuvieri, and P. marmoratus by the absence of a ventral gap.6. Microhylidae Günther 1858 Chiasmocleis albopunctata (Boettger 1885) First Description of the tadpole: Uberlândia -MG, Brazil (Oliveira-Filho & Giaretta 2006).Other characterizations: Bolivia (Schulze et al. 2015).
The body shape is ovoid in dorsal view and globular-depressed in lateral view (BW/BH = 1.06-1.14).The snout is rounded in lateral view.The oral disc is anteroventral, laterally emarginate, with a uniseriate row of conical marginal papillae, interrupted by a dorsal gap; submarginal papillae absent.LTRF is 2(2)/3(1), A1 = A2, P1 = P2>P3; The upper jaw sheath is wide, M-shaped, and the lower jaw sheath is wide, U-shaped; the upper jaw sheath is wider than the lower jaw sheath.Nares small (ND/ED = 0.12-0.14),elliptical, with a small projection on the marginal rim, dorsally positioned.Eyes small (ED/BH = 0.15-0.16),dorsally positioned.Spiracle sinistral, with medium length (SL/BL = 0.09-0.10),narrow to medium (SW/BH = 0.09-0.10),opening on the middle third of the body, posterodorsally directed, with the centripetal wall fused to the body wall and free distal edge.Vent tube medial with dextral opening, fused to the ventral fin.The caudal musculature width is medium (TMW/BW = 0.32-0.32).The dorsal fin has medium height (DFH/TMH = 0.81-0.97),originating at the posterior third of the body with acute slope, with convex margin; ventral fin has medium height (VFH/TMH = 0.68-0.76)with convex margin; the tail tip is rounded.Lateral line not evident.Comments.We are unable to associate this morphotype to other Odontophrynus species.Tadpoles of Odontophrynus sp.differ from the O. cf.juquinha, and O. cultripes by the upper jaw sheath M-shaped and larger total length.One individual presented one submarginal papilla on each side of the oral disc.
The body shape is ovoid in dorsal view and globular-depressed in lateral view (BW/BH = 1.39-1.41).The snout is rounded in lateral view.The oral disc is ventral, laterally and lateroventrally emarginate, with a uniseriate row of conical marginal papillae, interrupted by a dorsal gap; submarginal papillae aggregated laterally, and smaller than the marginal papillae.LTRF is 2/3(1), A1 ˂ A2, P1 = P2 ˃ P3.The upper jaw sheath is narrow, arc-shaped, and the lower jaw sheath is narrow, V-shaped; the upper jaw sheath is wider than the lower.Nares medium (ND/ED = 0.15-0.21),elliptical, with a small projection on the marginal rim, dorsally positioned.Eyes medium (ED/BH = 0.21-0.24),dorsal positioned.Spiracle sinistral, short to medium (SL/BL = 0.05-0.13),narrow to medium (SW/BH = 0.05-0.11),opening on the middle third of the body, posterodorsally directed, with the centripetal wall fused to the body wall and free distal edge.Vent tube medial, fused to the ventral fin.The caudal musculature width is narrow to medium (TMW/BW = 0.25-0.31).The dorsal fin has medium height (DFH/TMH = 0.60-0.66)originating at the posterior third of the body with a median slope, with convex margin; ventral fin is low to medium (VFH/TMH = 0.36-0.70)with margin parallel to the caudal musculature; the tail tip is rounded.Lateral line not evident.Comments.The tadpole presented inEterovick & Sazima (1998) was described with the spiracle dorsally directed and without lateral emargination and folds on the lower labium.The tadpoles in our sample had lateral emargination and two folds in the lower labium, although not as prominent as seems in P. boiei and P. dibernardoi.The presence of lateral emargination and two folds in the lower labium were reported in tadpoles of P. cururu byProvete et al. (2013).Tadpoles of P. cururu differ from tadpoles of P. boiei by larger body proportions, less prominent folds in the lower labium and the greater number of submarginal papillae aggregated in the lateral of the oral disc, and the rounded tail tip.Proceratophrys dibernardoiBrandão, Caramaschi, Vaz-Silva & Campos 2013 First Description of the tadpole: Jataí -GO, Brazil(Santos et al. 2017
research, aligned to the principles and practices of the open science initiative (UNESCO 2021).
Andrade & Cardoso 1991)is study were collected in the type locality of the species and differ from the original description by the body rounded in dorsal view, and nares dorsally positioned (body elliptical and nares dorsolaterally positioned inAndrade & Cardoso 1991).From the 11 analyzed individuals in our sample, one presented body elliptical and the A1 teeth row longer than the A2.Tadpoles of S. longilineus have an oral disc with a concave posterior margin when closed, a shared trait for tadpoles in the S. catharinae group, differing from the other species of Scinax.This trait allows an easy differentiation of S. longilineus tadpoles from S. fuscomarginatus, and S. fuscovarius tadpoles.
http://www.scielo.br/bnhttps://doi.org/10.1590/1676-0611-BN-2023-1486Comments.Scinax pombali Lourenço, Carvalho, Baêta, Pezzuti & Leite 2013 First Description of the tadpole: Capitólio -MG, Brazil (Lourenço et al. 2013).Other characterization: Not available.Specimens Examined: Brazil, Minas Gerais State, Parque Nacional da Serra da Canastra (ZUFG 2493, 2899).Description based on ten tadpoles between Gosner Stages 36 and 40.Characterization.Total length 46.07 ± 3.19 mm (Table had arc-shaped upper jaw sheath and fewer submarginal papillae scattered laterally.Otherwise, our sample closely resemble those tadpoles.In our sample, two individuals had the upper jaw sheath arc-shaped, which indicates that this variation would be common within and among S. similis population.Tadpoles of S. similis are smaller and the dorsal fin origin is closer to the eyes than in S. fuscovarius.Tadpoles of S. similis can also be distinguished from S. fuscovarius by the snout rounded, narrower jaw sheath and smaller total length.Also, S. similis can be distinguished from S. fuscomarginatus by the wider lower jaw sheath and the P3 teeth row being slightly smaller than the P1 and P2 teeth rows.Easily distinguished from S. rupestris due to the oral disc ventrally emarginated.
Scinax gr.ruber First Description of the tadpole: Species uncertain.Other characterizations: Not available.Specimens Examined: Brazil, Goiás State, municipality of Nova Roma (ZUFG: 1881).Description based on four tadpoles between Gosner Stages 31 and 40.Total length 29.92 ± 3.35 mm (Table 1, Figure 27 , Eastern Region of the Meridional Espinhaço Ridge -MG, Brazil (Pimenta et al. 2014).Specimens Examined: Brazil, Minas Gerais State, Parque Nacional da Serra da Canastra (ZUFG 2497, ZUFG 2498).Description based on six tadpoles between Gosner Stages 31 and 36.Characterization.Total length 22.58 ± 1.05 mm (Table Sánchez (2010) et al. (2017) row of marginal papillae.Navarro-Acosta et al. (2017)studied the teeth row development of four tadpoles of anuran species from the Boana pulchella group and B. faber and found that rows were added distally in both labia.The same pattern was reported bySánchez (2010)for Colombian Hiloscirtus species.Thus, despite lack of developmental studies of the oral disc in Trachycephalus, we suggest that is very likely that the formation of supernumerary rows follow the same patterns of development described by Navarro Acosta et al. (2017) andSánchez (2010).The lateral line was evident in six individuals.

Table 1 ,
Figure37).The body shape is ovoid in dorsal view and globular-depressed in lateral view (BW/BH = 1.12-1.15).The snout is rounded in lateral view.The oral disc is ventral, laterally emarginate, with a uniseriate row of elongated marginal papillae, interrupted by one dorsal gap (C2 type sensu Vera Candioti et al. 2011); submarginal papillae absent.LTRF is 2(2)/2(1), A1 is slightly smaller than A2, P1 is slightly wider than P2.The upper jaw sheath is narrow to medium, M-shaped, and the lower jaw sheath is narrow, V-shaped; the upper Specimens Examined: Brazil, Goiás State, Parque nacional da Chapada dos Veadeiros National (ZUFG 2294, ZUFG 2948).Description based on six tadpoles between Gosner Stages 35 and 40.Characterization.Total length 20.25 ± 2.65 mm (Table 1, Figure39)., opening on the posterior third of the body, covering the vent tube in three of six tadpoles but anterior to the vent tube in three of six tadpoles, posteriorly directed, with the centripetal wall not fused to the body wall.Vent tube medial, fused to the ventral fin.The caudal musculature width is medium (TMW/BW = 0.27-0.38),with the anterior third of the tail muscle and adjacent fins with a sheath of thick connective tissue.The dorsal fin has medium height (DFH/TMH = 0.51-0.81),originating on the posterior third of the body with median slope, with a convex margin; ventral fin has medium height (VFH/TMH = 0.61-0.91)with a convex margin; the tail tip end with a flagellum.Lateral line evident. http://www.scielo.br/bnhttps://doi.org/10.1590/1676-0611-BN-2023-1486 Fabrezi et al. (2012) 2006)l(Rossa-Feres & Nomura 2006); Bolivia(Schulze et al. 2015).Information about the larval development for populations from Argentina were presented byFabrezi et al. (2012).Specimens Examined: Brazil, Goiás State, municipalities of Britânia(ZUFG 1940), Pontalina (ZUFG 1283, ZUFG 1304), Nova Roma  (ZUFG: 1955), and Mato Grosso do Sul State, municipality of São Gabriel do Oeste(ZUFG 1956).Description based on 15 tadpoles between Gosner Stages 31 and 37. Characterization.Total length 36.45 ± 3.62 mm (Table1, Figure40).The body shape is rounded in dorsal view and triangular-depressed in lateral view (BW/BH = 1.21-1.32).The snout is rounded in lateral view.Oral disc modified without keratinized mouthparts or papillae; presence of a dermal flap suspended in front of oral cavity.Nares not perforated.Eyes medium (ED/BH = 0.16-0.18),laterally positioned.Spiracle ventral, long (SL/BL = 0.22-0.28),narrow to medium (SW/ BH = 0.07-0.10),opening on the posterior third of the body, covering the vent tube, posteriorly directed, with the centripetal wall not fused with the body wall.Vent tube medial, fused to the ventral fin.The caudal musculature width is medium (TMW/BW = 0.28-0.36),with the anterior third of the tail muscle and adjacent fins with a sheath of thick connective tissue.The dorsal fin has medium height (DFH/TMH = 0.64-0.75),originating at the body-tail junction with acute slope, and convex margin; ventral fin has medium height (VFH/TMH = 0.64-0.84)with convex margin; the tail tip is pointed.Lateral line evident.
(Pimenta et al. 2014)ionswere geographically close to the O. juquinha(Rocha et al. 2017), we suspected that this species could have a larger geographical distribution.Our sample is like those described byRocha et al. (2017)but our tadpoles have a larger total length.Other characterizations: Argentina(Cei 1980); Eastern Region of the Meridional Espinhaço Ridge -MG, Brazil(Pimenta et al. 2014).Specimens Examined: Brazil, Goiás State, municipality of Teresópolis (ZUFG 533).Description based on 14 tadpoles between Gosner Stages 35 and 38.Characterization.Total length 34.87 ± 2.23 mm (Table (Savage & Cei 1965)9) medium to high (DFH/TMH = 0.94-1.05),originatingon the posterior third of the body with an acute slope, and convex margin; ventral fin has medium height (VFH/TMH = 0.60-0.65)withmarginparallel to the caudal musculature; the tail tip is rounded.Lateral line evident.Comments.AfterMartino et al. (2019), the O. americanus species was restricted to southern Brazil, but these authors did not define a possible name for populations outside this distribution.Odontophrynus cultripes (Reinhardt & Lütken 1862) First Description of the tadpole: Belo Horizonte -MG, Brazil(Savage & Cei 1965).
Savage & Cei (1965)ing, fused to the ventral fin.The caudal musculature width is medium (TMW/BW = 0.36-0.40).The dorsal fin has medium height (DFH/TMH = 0.61-0.61),originatingat the body with an acute slope, with convex margin; ventral fin has medium height (VFH/TMH = 0.45-0.46)withmarginparallel to the caudal musculature; the tail tip is rounded.Lateral line not evident.Comments.Tadpoles described bySavage & Cei (1965)were smaller (TL = 14 mm, Stage 37) than the tadpoles in our samples (TL = 38.01mm,.Tadpoles of O. cultripes can be distinguished from tadpoles of O. americanus by being smaller and the elliptical body shape in dorsal view.
First Description of the tadpole: not applicable.Other characterizations: not available.Specimens Examined: Brazil, Goiás State, municipality of Pontalina (ZUFG 1294).Description based on two tadpoles at Gosner Stage 34.Characterization.Total length 42.10 ± 0.79 mm (Table