Description
Ischnocnema nanahallux is a relatively small, robust-bodied frog with a snout vent length range in males of 13.1 - 14.2 mm and in females of 14.3 - 16.9 mm. The tympanic membrane is not externally visible. The hands have glandular nuptial pads on the posterior and dorsal surfaces of the thumb. The finger discs are small and slightly pointed. The foot has a well-developed calcar tubercle. Toe I is reduced, and the well-developed dorsal surfaces of all the toe discs have a deep V-shaped, median slit. For a more complete description, see Brusquetti et al. 2013.

DIAGNOSIS:

Ischnocnema nanahallux can be differentiated from members of the I. guentheri, I. lactea, and I. verrucosa species complexes by their slightly pointed finger discs. For a more complete diagnosis, see Brusquetti et al. 2013.

COLORATION:

In life, the background color tends to be brown with an X or V-shaped black mark on the dorsum. There are two pairs of black dots anterior and posterior to the dorsal mark. Throughout their dorsal surface, they have a distribution of small reddish dots. There is a dark horizontal stripe on their head between the eyes area. Two transversal stripes can be found on their forelimbs and four can be found covering the thigh and foot. On the ventral surface they tend to have yellowish dots in the ventral area. Their glandular nuptial pads on posterior and dorsal surfaces of thumb are white (Brusquetti et al. 2013). For a more complete coloration, see Brusquetti et al. 2013.

VARIATION:

The species has sexual dimorphism with females tending to be larger and with fewer ventral dots than males. Individual variation comes in the form of some specimens tending to have white stripes on their body and some have V-shaped instead of X-shaped dorsal marks (Brusquetti et al. 2013)

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Brazil

View distribution map in BerkeleyMapper.

Ischnocnema nanahallux has only been found in Parque Estadual do Desengano (Desengano State Park) in the Municipality of Santa Maria Madalena, Rio de Janeiro, Brazil at an elevational range of approximately 1200 m altitude (Brusquetti et al. 2013)

Comments

PHYLOGENETIC RELATIONSHIPS:

Ischnocnema nanahallux was previously grouped in the I. parva species complex. However, when the species was described, the authors noted the need for revision of the I. parva species complex as the genetic distances between I. nanahallux and members of the I. parva group is greater than genetic distances within the group (Brusquetti et al. 2013).

Bayesian Inference, Maximum Likelihood, and Maximum Parsimony analyses of 12S and 16S mtDNA, and Tyrosinase and Rag1 nDNA found that I. nanahallux does not belong to any species group and is sister to the clades composed of the I. parva, I. venancioi, and I. guntheri species groups. The next most closely related species group is the I. verrucosa species group (Taucce et al. 2018).

ETYMOLOGY:

The species epithet is derived from the Latin words, “nanus”, meaning “dwarf,” and “hallux” meaning “big toe.” Together they describe the reduced toe in the species (Brusquetti et. al. 2013)

References

Brusquetti, F., Thomé, M.T.C., Canedo, C., Condez, T.H., Haddad, C.F.B. (2013) “A new species of Ischnocnema parva species series (Anura, Brachycephalidae) from northern State of Rio De Janeiro, Brazil.” Herpetologica 69(2), 175–85 [link]

Taucce, P.P.G., Canedo, C. Parreiras, J.S., Drummond, L.O., Nogueira-Costa, P., Haddad, C.F.B. (2018) “Molecular phylogeny of Ischnocnema (Anura: Brachycephalidae) with the redefinition of its series and the description of two new species.” Molecular Phylogenetics and Evolution 128, 123-146 [link]

Species Account Citation: AmphibiaWeb 2022 Ischnocnema nanahallux <https://amphibiaweb.org/species/8013> University of California, Berkeley, CA, USA. Accessed Nov 21, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 21 Nov 2024.

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