This review is based on all publications with information on T. venustus, including journal articles, books, book chapters, guides and online sources. Some of these sources contain dot maps (Formas et al. 2001; Caro-Lagos and Charrier 2020; Díaz-Páez and Alveal 2021; González-Véliz et al. 2022), surface maps (Charrier 2019; IUCN 2022) or less precise or incomplete information on the geographic range and/or altitudinal limits (e.g. Formas 1995; Veloso 2006; Rabanal and Nuñez 2008; Stuart et al. 2008; Lobos et al. 2013). Presence points were downloaded from GBIF and iNaturalist; both sites were accessed on March 30, 2023. In addition to the coordinates and altitude, for each point some clarifications on its location were added (Table 1, column Remarks).

A map with all the localities collected was made in ArcMap v10.8, using satellite imagery as a base. We used the exact coordinates provided in each publication, except in the case of the localities of the Altos de Lircay National Reserve and surroundings (Araya and Cisternas 2008), which were extracted directly from their satellite map. The two original localities, Hacienda San Ignacio de Pemehue and Cordillera de Chillán (Philippi 1899, 1902), where the species has not been recorded again, were published without coordinates. Therefore, we resorted to literature and other documents from the late 19^th and early 20^th centuries to pin down their location more precisely. One of these sources (Germain 1894) was used to trace the possible route of the trip where that author supposedly collected one of the type specimens. Areas within the altitudinal limits specified in the description of the species, between 914 and 1219 meters (3000–4000 feet), were mapped using ArcMap to restrict the location of possible collection places for this specimen. Moreover, a layer was added with the areas protected by the Sistema Nacional de Áreas Silvestres Protegidas del Estado of Chile (SNASPE) to determine which localities are state protected. Finally, a similar map was produced for the GBIF and iNaturalist points.

The new locality of T. venustus was discovered by chance by one of the authors (J.I. Osses). The coordinates and altitude were recorded in situ with a cell phone and verified on Google Earth. The size of the adult individuals (snout-vent length, SVL) was estimated with the lid of a camera (diameter 52 mm) placed next to them. None of the observed individuals was captured.

We compiled 14 localities of Telmatobufo venustus, including the new one described by us (Table 1). We did not include the locality of Niblinto (Ibarra et al. 1999) in Table 1, cited as an imprecise record by González-Véliz et al. (2022). The original source does not specify if it is in the National Reserve or in the Nature Sanctuary called Los Huemules del Niblinto, it was mentioned without coordinates, and it is not supported by collected or photographed material. Therefore, we consider that the presence of the species in that area requires confirmation. We mapped only 13 localities (Fig. 1), since Alto de Vilches (Formas and Veloso 1982) was replaced with more precise sites subsequently reported within and around the reserve (Araya and Cisternas 2008). Five of the mapped locations are within state-protected areas (SNASPE): one in the Radal Siete Tazas National Park, which constitutes the northern end of the distribution of the species, and four in the Altos de Lircay National Reserve (Fig. 1). Eighteen points were downloaded from iNaturalist and nine from GBIF (Suppl. material 1), but six of the latter (the only ones with coordinates) come from iNaturalist and have the same associated coordinates. Most of the iNaturalist points fall in low-lying anthropized areas, along roads or in difficult-to-access mountainous areas, but all around the Altos de Lircay National Reserve (Suppl. material 2). Therefore, we assume that the observations were made in that reserve, but the coordinates have been obscured by default (with an accuracy of ~ 28.7 km) because it is a threatened species (taxon geoprivacy). Thus, we do not include these points in the collection of localities (Table 1, Fig. 1) because we consider them redundant with the published geographic information of the species.

Figure 1. 

Geographic distribution of Telmatobufo venustus. Orange circles: literature localities; yellow octagram: possible location of Cordillera de Chillán according to this study; red diamond: new locality described here; blue circles: possible locations of Ralco. The insets to the right show enlargements of the northern (A) and southern (B) ends of its distribution. Inset B shows the possible routes (greenish solid and yellow dashed lines) that Philibert Germain followed, from west to east, on his journey inside the Hacienda San Ignacio de Pemehue in 1893 (see details in Results). The red segments of the solid and dashed lines represent the sectors of Germain’s routes that lie between 914 and 1219 meters (gray areas of inset B). The semi-transparent green areas represent the areas protected by the state of Chile (SNASPE). The thin white lines within Chile correspond to the boundaries of the administrative regions (named with white letters).

Formas and Veloso (1982) were the first to indicate that the type locality of T. venustus is Cordillera de Chillán (Andean foothills, east of the city of Chillán), which has been included in some maps despite being an indeterminate place (Formas et al. 2001; Díaz-Páez and Alveal 2021). The mention of Cordillera de Chillán as the type locality is based on a specimen from the collection of the Museo de Zoología de Concepción (MUZUC or MZUC 205051) labeled as the holotype (as it appears in the photograph of the same source), and recognized as such in subsequent publications (e.g. Formas 1995; Formas et al. 2001). The problem with this type locality is that Philippi (1899) described the species from four specimens from Hacienda San Ignacio de Pemehue and Cordillera de Chillán, without defining a holotype, and the only remaining specimen of the type series (MZUC 205051) apparently has a wrong collection number and is currently missing. The only specimen from the Hacienda San Ignacio de Pemehue had already been lost at the time of the description (Philippi 1899). In the 1970s, only one of the three specimens from Cordillera de Chillán could be in the collection of the Museo Nacional de Historia Natural of Santiago (MNHN). Apparently, this specimen is one of the two that existed in the MNHN collection at the beginning of the 20^th century, whose localities of origin were Chillán and El Recinto (Quijada 1914). This specimen appears photographed in Donoso-Barros (1972) and is the same one identified as MZUC 205051 by Formas and Veloso (1982). There is no published information on the specimen MZUC 205051 before 1982, so we speculate that it was entered into the collection and identified as the holotype by Roberto Donoso Barros in the early 70’s, but without a nomenclatural act formally published in the peer-reviewed literature. Furthermore, since Philippi (1899) did not select a specimen from the type series as the holotype, this only remaining syntype should have been designated as the lectotype (International Code of Zoological Nomenclature, ICZN 1999), thereby also automatically defining the type locality (Cordillera de Chillán). Unfortunately, we could neither find any specimen accurately identifiable as T. venustus in the MZUC collection nor a record with the number 205051, since the number of the collection does not reach 50,000 specimens yet. The apparent loss of the only remaining specimen of the type series and confusion about its collection number prevent us from amending its typification (designating it the lectotype), and from recognizing the currently accepted type locality of the species. Consequently, following the rules of the ICZN (1999), in the absence of a holotype or lectotype, the type locality of T. venustus corresponds to the two localities of origin of the type series: Hacienda San Ignacio de Pemehue and Cordillera de Chillán.

The only specimen of T. venustus from Hacienda San Ignacio de Pemehue known to date (Philippi 1899) was collected by the entomologist Philibert Germain. At the time, that estate (“hacienda”) covered more than 240,000 hectares (Flores 2013), from near the city of Mulchén to the town of Lonquimay in the south, and eastward to the border with Argentina. We reconstructed the possible route that Germain followed during his exploration of the estate in December 1893 (Germain 1911), which is described in Germain (1894). The trip can be divided into two parts. In the first stage, Germain started from a place called El Cisne, following the right bank of the Renaico River, then, crossed a small mountain range, Pichinitrun (also known as Pichinitro, Pichinitron or Pichi-Nitron), to reach the Vilucura River basin (also known as Vilicura or Villucura), and followed the right bank of this river to reach a place called Lolco. We used the map of the Comisión Chilena de Límites (1908) to plot this part of the journey as there is a road that exactly matches the description of Germain (1894) (Fig. 1B, greenish solid line). The second part of the trip was not described in detail by Germain (1894). He apparently set out from Lolco up the right bank of the river almost to its source (the Headwaters of Lolco), crossed a bare alpine area of the Cordillera de Toluaca (Tolhuaca Range) to reach the basin of the Lonquimay River, and finally followed a tributary of this river (not named) until reaching the Lonquimay “pampa”, where the administrator’s house of this sector of the estate was located. This part of the trip (Fig. 1B, dashed yellow line) was traced partly following current paths (Google Earth); the location of the administrator’s house was located according to the map by Soza (1891). We identified four areas along the reconstructed tracks, one of which could correspond to the southern limit of the range of the species (red segments of the paths in Fig. 1B), considering the elevation range specified (3000–4000 ft) in the species description (Philippi 1899). Regarding the accepted type locality until now, Cordillera de Chillán (Formas and Veloso 1982), González-Véliz et al. (2022) highlighted that the new locality near San Fabián de Alico described by them would be close to it. In fact, the new locality is in the Andean foothills, approximately 66 km east of Chillán, but there is no direct way to get there from this city. Instead, we propose a more precise place for the locality of Cordillera de Chillán, in the vicinity of the town of Recinto, located about 47 km southeast of the city of Chillán, on the road that ends at Termas de Chillán. This is based on a specimen of Bufo venustus that appears in the catalog of amphibians housed in the MNHN at the beginning of the last century published by Quijada (1914), labeled “El Recinto, 1897”. According to Philippi (1899), Germain brought to the Museum the specimens from the Cordillera de Chillán that were used to describe the species in January 1897. Germain described numerous insects in Chile, including some beetles from Termas de Chillán (Germain 1911). Thus, it is possible that he collected the individuals of T. venustus from Cordillera de Chillán at an intermediate point of the way such as Recinto. Finally, we also propose possible locations for the locality of Ralco (Díaz et al. 1983). The only specimen observed there, until now, was collected supposedly in the Biobío River, but this type of river is different from the typical environment where the species is known up to now (Fenolio et al. 2011). In addition, the imprecise coordinates that appear in Díaz et al. (1983) fall about 8 km east of the Biobío River, on the side of a mountain at ~ 1885 m elevation and far from currently recognizable roads. Therefore, we tentatively locate “Ralco” in the upper part of the two tributaries (Malla and Quepuca rivers; points 12 of Fig. 1B) of the Biobío River closest to the coordinates given by Díaz et al. (1983). We also emphasize that there is no additional data or information published about the locality reported by Díaz et al. (1983) to affirm that it was flooded after 1983 as it appears in the literature (Fenolio et al. 2011; Díaz-Páez and Alveal 2021).

There is no current consensus in the literature about the altitudinal limits of T. venustus. For example, Formas et al. (2001) defined the range between 600 and 1280 m, while an earlier source (Formas 1995) specified higher limits (1500–1700 m), which appear in most of the subsequent publications and sources of information about the species (e.g. Díaz-Páez and Ortiz 2003; Rabanal and Nuñez 2008; Stuart et al. 2008; Fenolio et al. 2011; Díaz-Páez and Alveal 2021), and even in the species summary information file of the Ministry of the Environment of Chile (https://clasificacionespecies.mma.gob.cl/wp-content/uploads/2019/10/Telmatobufo_venustus.pdf). Considering the records with precise altitudes collected here (Table 1), the highest point is Arroyo puente del tronco, at 1638 m, inside the Altos de Lircay National Reserve (Araya and Cisternas 2008). Regarding the lower limit, we discard that of Formas et al. (2001) (600 m) because there is no reliable precedent that allows to locate any population at that altitude. On the other hand, Cuevas and Formas (2001) reported the presence of T. venustus at the type locality of Alsodes hugoi Cuevas & Formas, 2001, Altos de Lircay National Reserve, at 900 m, specifically on the banks of the Lircay River. In the extreme northwest of the Reserve, there are sectors on the south bank of the Lircay River at around 900 m, which could be the area where the type series of A. hugoi was collected. Furthermore, this limit would be close to the originally minimum altitude (3000 ft = 914 m) reported by Philippi (1899). Therefore, we define the altitudinal limits of T. venustus as between ~ 900 and 1638 m.

The new locality, Estero Pichipangue (Fig. 2A), corresponds to a melt stream with crystalline waters located on the northwest slope of the Callaqui volcano and that flows into the Pangue river, which in turn flows into the Biobío River, in a sector called Pitrilon (southeast of the Biobío Region). On February 16, 2022, eight T. venustus adults (Fig. 2B) were observed at night on the banks of Estero Pichipangue, at an approximate height of 1150 m. The individuals were easily recognized as members of the genus Telmatobufo by the presence of parotid glands, the numerous and prominent glands on the back, highly developed interdigital webbing on the hindlegs and the vertical pupil, and at the species level by their orange-reddish spots on a dark background. An average SVL of 65 mm was estimated for the eight observed adults (range, ~ 60–70 mm). The stream where the adults were observed presents a gentle slope, with a maximum depth of 30 cm, and a rocky and sandy bottom. Inside the stream, three T. venustus larvae were observed clinging to the bottom rocks (Fig. 2C). The tadpoles were identified as Telmatobufo by their dorsoventrally flattened bodies, the presence of a suctorial oral disk, and by its thick tail, particularly at the base (Díaz et al. 1983; Fenolio et al. 2011). The habitat where the adults and larvae of T. venustus were found corresponds to mountain mixed forest dominated by Nothofagus dombeyi, and, to a lesser extent, by N. alpina; the understory is dominated by Chusquea quila, Fuchsia magellanica and abundant Gunnera tinctoria. About 3.2 km upstream from the site where the T. venustus individuals were observed, close to the tree line, an adult of Nannophryne variegata Günther, 1870 (SVL = ~ 50 mm) was observed on the bank of the stream, among the riparian vegetation (Fig. 2D). This new record of N. variegata is located about 50 km south from the northernmost known point of the species (Cisternas-Medina et al. 2019). The Estero Pichipangue is far from human settlements and shows very few signs of human intervention. No salmonids were observed in the stream, a potential threat to T. venustus larvae and other amphibians (Fenolio et al. 2011), but the area around the stream could be threatened by livestock, since it is used for “veranadas” (summer pastures).

Figure 2. 

Stream and anurans observed at the new locality of Telmatobufo venustus, Estero Pichipangue, Biobío Region, Chile. A. Stream near the site where the adults and larvae of T. venustus were found; B. Adult male of T. venustus from Estero Pichipangue; SVL ~ 6.5 cm; C. Tadpole of T. venustus; D. Adult of Nannophryne variegata.