There is no officially published etymology for the species epithet “grandisonae”. However, the epithet “grandisonae” is presumably from Alice G. C. Grandison, a colleague of John D. Lynch (Lynch 1975).

Description
Chaltenobatrachus grandisonae is a small to medium sized frog (Basso et al. 2011). From nine male C. grandisonae, the snout-vent length ranges from 32.47 - 38.77 mm, and from seven females examined, the snout-vent length ranges from 26.22 - 38.42 mm (Díaz-Páez et al. 2015). The head is depressed, rounded in dorsal view, and wider than long. It is slightly smaller than one third of its body length. The snout is rounded to slightly square like in the dorsal view. The snout has a noticeable sloping angle at the level of the nostrils in the lateral profile. The upper lip protrudes slightly over the lower lip. The nostrils bulge out in the dorsolateral direction. They are oval in shape and approximately directly located equal distance between the tip of the snout and the eye. The canthus rostral is rounded. The loreal region slopes strongly towards the lip with a weak concave. The eyes are large, prominent and orientated laterally. The pupils are similar in shape to that of a rhombus. The interocular distance is similar to that of the internarial distance. The supratympanic fold is thick and noticeable reaches from the posterior end of the eye to the insertion of the arm (Basso et al. 2011). Chaltenobatrachus grandisonae lacks a tympanum (Díaz-Páez et al. 2015). The skin is thin on the dorsum and covered in mucus. The ventral skin is smooth and loose. Turgid vascularized warts are present on the lower side of the thighs near the vent. The gular fold is faint. Numerous warts of various sizes, shapes, and textures cover the back of the head, dorsum and legs. Chaltenobatrachus grandisonae has thin, average length arms with moderately long fingers. The forearms are relatively stout, compared to the arms. The metacarpal tubercles are large, but low, with the inner metacarpal tubercle being oval and the metacarpal tubercle being slightly bifid. Supernumerary palmar tubercles are absent. The pollex is very wide at the base. The fingers possess noticeable webbing that is more developed between the pollex and second finger and between the second and third fingers. Finger length increases in the order of 1 = 2, 4, 3. The fingertips are rounded. The subarticular tubercles are large and rounded and more protuberant than the metacarpal tubercles. Males display nuptial pads in the form of small growths in the form of harsh pigmentation on the pollex, inner side of the second finger, and the inner edge of the inner metacarpal tubercle. The legs are thin and of average length. The tibiotarsal articulation reaches as far as the eye. When the femurs and tibias are placed at the right angle to the sagittal plane, the tibiotarsal articulations do not touch. A tarsal fold extends along most of the tarsus and continuous to the dermal fringe of the first toe. The plantar skin is swollen, with two little, low, noticeable metatarsal tubercles. The inner metatarsal tubercle is oval and the outer is smaller and circular. Supernumerary plantar tubercles are absent. The toes are depressed, with thick webbing that transitions to deeply incised skin and then to dermal fringes to the rounded tips of the toes. Toe length increases in order of 1, 2, 5, 3, 4. Toe 5 has a less significant degree of dermal fringing. The subarticular tubercles are small and rounded (Basso et al. 2011).

At the time of its description, C. grandisonae was the only member of its genus and was most closely related to frogs of the genus Atelognathus. The placement of C. grandisonae in a new genus is mostly obvious by differences from the defining features of the Atelognathus frogs. Specifically, the genus Atelognathus frogs exhibit large, exposed frontoparietal fontanelle, short palatine bones, and large nasal opening while Chaltenobatrachus has more extensive frontoparietals, long palatines, and small nasal openings. They are further differentiated by C. grandisonae’s extensive alary processes of the premaxillae, maxillary teeth extending up to the middle of the orbit, well ossified sphenethmoid, anteriorly dilated omosternum, webbed fingers, and coloration. Chaltenobatrachus grandisonae has a uniform bright green dorsal coloration with brown to reddish warts and an orange iris with gold spots (Basso et al. 2011).

In life, C. grandisonae exhibits a uniform bright green dorsal coloration with brown to slightly red warts. Dark bands extend across the dorsal side of the legs. Dorsal streaking and warts are more evident in juveniles. Juveniles also exhibit more intense coloring. The belly and lower part of the flanks are greyish with scattered tiny black spots. The throat is white with small dark spots. The ventral skin of the legs is brown and translucent. A dark brown band stretches from the tip of the snout along to axillary region to the supratympanic fold, including the nostril. A dark patch reaches from under the eye to the upper lip. The eyes are circular, with an orange iris that has gold spots and a dark vertical line under the pupil. In some specimens, a small and rounded ventral pupillary nodule is found on the lower border of the iris (Basso et al. 2011).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Argentina, Chile

View distribution map in BerkeleyMapper.

Chaltenobatrachus grandisonae was originally only known to inhabit one locality at Puerto Eden, Wellington Island, Chile (Basso et al. 2011, Veloso and Núñez 2010). It has since been found in three new localities in southern South America along the Chilean-Argentinian border. These locations are Lago Nansen and Lago del Desierto in the province of Santa Cruz in southern Patagonia, Argentina and Laguna Caiquenes from the region of Aysén, Chile (Díaz-Páez et al. 2015). The geography of these locations is very mountainous with strong evidence of glaciation. The summits have permanent snow and glaciers, and exhibit a cold and wet environment, with long winters and abundant snow. The temperate-cold rain forest is rich in vegetation that alternates with open moorlands and bodies of water. Bogs are created from poor drainage of these bodies. Chaltenobatrachus grandisonae is most often found from 500 to 830 meters above sea level, near the edge of ponds, hiding under rocks or vegetation (Basso et al. 2011).

Life History, Abundance, Activity, and Special Behaviors
Chaltenobatrachus grandisonae are mainly found under fallen logs near small bodies of water, however, they are occasionally found fully submerged in water. Although, as of 2016, there is no known data on C. grandisonae mating, it is believed that they mate in water (Basso et al. 2011).

Chaltenobatrachus grandisonae have been found living sympatrically with Eupsophus coppingeri and Nannophryne variegata at the Wellington Island locality (Basso et al. 2011).

Plants found in C. grandisonae habitat include site-specific bryophytes, pteridophytes, Nothofagus antarctica that create a dense mat on the forest floor, Nothofagus pumilio, and austral beeches that rise above the shrubs (Basso et al. 2011, Díaz-Páez et al. 2015).

Larva
Six Chaltenobatrachus grandisonae tadpole species examined were between stages 31 and 39. With an elliptical build, the examined tadpoles had a mean length of 49.25 ± 1.72 mm. The body, which is somewhat indented, is 2 times longer than tall and 1.2 times wider than tall. The posterior region of the head exhibits slight constriction. The snout is rounded and nostrils are small and circular with an elevated internal rim. The nostril is slightly closer to the snout than to the eyes, with the distance between the nostrils 0.4 to 0.6 times smaller than the distance between the eyes. The large eyes, oriented dorsolaterally, are positioned lateral with a visible, yet small umbraculum. The oral disc is located towards the lower end of the head. It displays a single row of emarginated papillae, with a very large rostral gap. Supra-angular, angular, and infra-angular intra-marginal lateral papillae are all present and sharp pointed. The intra-marginal papillae are absent. The labial teeth are well developed and keratinized with a 2(2)/3(1) tooth row-formula. The first posterior row gap is very narrow. The upper and lower jaw sheaths are well developed. They are wider than high, with fine serrate margins. The lower jaw sheath is strongly curved. The lateral and ventral skin is transparent, making the chondrocranium, gills, and heart all visible. The spiracle is located in posterolateral region, beneath the mid-line of the body. The spiracular tube is situated on the far-left side, free from the body wall. The ventral tube is short and located on the dextral side. The tail, which is marginally taller than the body, accounts for about 60 to 65% of the tadpole’s total length. The caudal musculature is robust, and does not quite reach the tip of tail. The dorsal and ventral fins are well developed, of comparable height, and exhibit lightly arched margins. The dorsal fin arises from either the last part of the body or at the tail-body junction. The ventral fin arises at the cloacal opening. The tip of the caudal fin is rounded (Basso et al. 2011).

Features that differentiate C. grandisonae tadpoles from Atelognathus tadpoles are that the former have transparent skin and papillae that protrude laterally from the oral disc in the dorsal view (Basso et al. 2011).

In life, the tadpoles are dark brown with golden spots. The body has a translucent contour, due to its ventral and lateral skin being transparent, making the chondrocranium, gills, and heart all visible. The ventral side of the head is unpigmented and the abdomen is spotted with a few groups of golden, superficial guanophores. The caudal musculature is dark brown with asymmetrical golden patches. The fins are translucent with scattered melanophores and guanophores. The iris is gold, with black spots. The nostrils have a pigmented rim. The spiracular tube is transparent. The keratinized buccal structures are highly pigmented (Basso et al. 2011).

Chaltenobatrachus grandisonae tadpoles can be found in many different localities, all of which are in water. They have been found in small to larger pools of 3 - 20 meters in diameter and 0.1 - 1.0 m deep with a pH around 6.5. They can also be found in bogs and wetlands. The tadpoles co-inhabit these bodies of water with macrophytes, liverworts, Gunnera magellanica, and spherical Nostoc colonies. At the Lago del Desierto locality, C. grandisonae tadpoles were found cohabitating shallow pools with Nannophryne variegata tadpoles (Basso et al. 2011).

Larval development is aquatic and the larvae are known to be active feeders. Metamorphosis takes place at the end of summer. In the beginning of summer tadpoles of different life stages were found living together. This suggests that these tadpoles developed from clutches laid in different years, and that these tadpoles have prolonged aquatic development over the winter (Basso et al. 2001).

Trends and Threats
As of 2016, Chaltenobatrachus grandisonae has an IUCN listing of “Data Deficient”. However, since the Wellington Island locality isn’t under any significant threats, it is unlikely that C. grandisonae is threatened (Veloso and Núñez 2010). Additionally, it is now known at three other localities, Lago Nansen, Lago del Desierto, in Argentina and Laguna Caiquenes in Chile (Díaz-Páez et al. 2015).

Comments
A DNA dataset of 3108 base pairs from 12S, 16S, cytb, and rhod sequencing developed a single most parsimonious tree that revealed that C. grandisonae is a distinct genus and is sister to the genus Atelognathus. The genera Chaltenobatrachus and Atelognathus share a common ancestor with the genera Hylorina and Batrachyla. The subfamily, Batrachylinae encompasses the genera Chaltenobatrachus, Atelognathus, Hylorina, and Batrachyla (Basso et al. 2011).

Chaltenobatrachus grandisonae is the founding species in its genus (Basso et al. 2011).

Chaltenobatrachus grandisonae is synonymous with Atelognathus grandisonae and Telmatobius grandisonae (Veloso and Núñez 2010).

The common name, Puerto Eden Frog, comes from the first location that it was found (Basso et al. 2011).

References

Basso, N.G., Úbeda, C.A., Bunge, M.M., Martinazzo, L.B. (2011). ''A new genus of neobatrachian frog from southern Patagonian forests, Argentina and Chile.'' Zootaxa, 3002, 31-44.

Díaz-Páez, H., Alveal, N., Cisternas-Medina, I., Ortiz, J.C. (2015). ''New distribution records of Chaltenobatrachus grandisonae (Anura: Batrachylidae) in Patagonia, Chile.'' Check List, 11(4), 1668.

Lynch, J.D. (1975). ''A new chilean frog of the extra-Andean assemblage of Telmatobius (Amphibia: Leptodactylidae).'' Southern California Academy of Sciences Bulletin, 74(3), 160-161.

Veloso, A., Núñez. H. (2010). Chaltenobatrachus grandisonae. The IUCN Red List of Threatened Species 2010: e.T2295A9402009. http://dx.doi.org/10.2305/IUCN.UK.2010-2.RLTS.T2295A9402009.en. Downloaded on 15 November 2016.

Species Account Citation: AmphibiaWeb 2025 Chaltenobatrachus grandisonae: Puerto Eden Frog <https://amphibiaweb.org/species/2564> University of California, Berkeley, CA, USA. Accessed Jun 6, 2025.

Citation: AmphibiaWeb. 2025. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 6 Jun 2025.

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