Description

Brachycephalus mirissimus males have a snout vent length of 9.9 − 11.7 mm and in females it ranges from 10.0 − 12.9 mm. The head that is wider than it is long, and the head length is 40% of the snout-vent length. In the lateral view, the snout is short and rounded. The protruding nostrils are directed anterolaterally. The canthus rostralis are indistinct. The lips form a “S-shape”. The loreal region is slightly concave. The eyes protrude in both the lateral and dorsal view. The eye diameter makes up 30% of the head length. The vocal sac does not extend externally. The typmanum is not distinct. The posterior portion of the tongue is not attached to the mouth floor and it is wider than it is long. The dorsal skin is rough from the head to the center of the body. The skin is granular on dorsolateral surfaces of body, flanks, and dorsal surface of thighs. There are also large warts that are glandular on the body, belly and thighs. The skin on the chin, arms, and legs is smooth. The upper arm and the forearm are relatively slender.

The tips of the first and second finger are rounded. The fourth finger is greatly reduced. The relative finger length is as follows: IV < I < II < III. There are no subarticular tubercles or inner and outer metacarpal tubercles. The legs are short and the thighs are thick. The hind thigh length is 39% of snout-vent length. The first and the fifth toe are not present externally. The second toe is short and distinct while the third toe is long. The relative toe lengths are as follows; II < III < IV. On the feet, the subarticular tubercles and inner metatarsal tubercles are absent like in the forearms, but the outer metatarsal tubercle is distinct, large, and oval shape (Pie et al. 2018).

Brachycephalus mirissimus can be distinguished from other Brachycephalus species by having a small robust toad-like body. It also has a smooth dorsum, and in life is orange with white dots and stripe in the middle of the head and along its vertebral column. The iris is completely black. The advertisement call has different groups of notes, isolated notes with 1-3 pulses and short isolated notes (Pie et al. 2018).

More specifically, the white dorsal coloration and patterning of Brachycephalus mirissimus is similar to some specimens of B. albolineatus, however, when this pattern is present it is green and not orange like in Brachycephalus mirissimus. Similarly, B. boticario, B. quiririensis, B. auroguttatus, and B. verrucosus all have white stripes on the dorsum but have yellow surrounding pigmentation. Also, the dorsum is light blue in B. mariaeterezae, brown in B. guarani and reddish-brown in B. ferruginus (Pie et al. 2018).

Brachycephalus ferruginus and B. guarani have a similarly colored orange dorsum but Brachycephalus mirissimus is distinguishable by the ventral surface being solid orange instead of orange with small green spots like in B. ferruginus (Pie et al. 2018).

The pulses per note in the advertisement call distinguishes Brachycephalus mirissimus (1 - 3 pulses in its isolated notes) from B. crispus(7 – 12 pulses per note), B. ephippium (5 – 15 pulses per note), B. darkside (5 – 8 pulses per note), B. pitanga (6.9 – 13.3 pulses per note) and B. sulfuratus (6.90 – 13.30 pulses per note). The isolated notes are short in Brachycephalus mirissimus and this causes further differentiation from B. crispus (mean of 0.28 ± 0.02 s), B. darkside (0.083 – 0.163 s), B. ephippium (0.093 – 0.125 s), B. pitanga (0.15 – 0.25 s) and B. sulfuratus (0.131 – 0.233 s). Brachycephalus tridactylus differs from Brachycephalus mirissimus because it has isolated notes while Brachycephalus mirissimus has grouped notes (Pie et al. 2018).

Brachycephalus mirissimus can only be distinguished from some specimens of B. albolineatus, B. hermogenesi and B. actaeus by genetics but this may be due to lack of details in description of their calls (Pie et al. 2018).

In life, the body of Brachycephalus mirissimus is orange, with white patches on the head and a white line down the middle of the dorsum. There are also white splotches on the distal dorsum that is surrounded by a border of yellow. The dorsal region of the leg joints are lighter orange and the irises are completely black (Pie et al. 2018).

In preservation, the almost completely orange body becomes a pale cream color. The white patches on the head, distal dorsum and the line down the middle of the dorsum either became pale cream, or became pale cream with white edges (Pie et al. 2018).

Individuals of Brachycephalus mirissimus can vary in coloration, some have a yellow hue to their overall orange color in both the dorsal and in ventral regions. The width of the white line on the dorsum also varies and the extent of the white spots on the distal dorsum also vary. The distal dorsum can be yellow in some individuals (Pie et al. 2018).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Brazil

View distribution map in BerkeleyMapper.

Brachycephalus mirissimus is known exclusively from its type locality, in a steep montane forest with canopies 18 - 28 m high of Morro Santo, Rio de Janeiro, Brazil. It can be found in areas that spans 470 – 540 m a.s.l. It is not found in forest with canopies less than 10 m. The habitat is a mix of flora and fauna from both high and low elevations and is isolated by invasive species and palm plantations. The full extent of their range is estimated to be approximately 56.8 ha (Pie et al. 2018).

Life History, Abundance, Activity, and Special Behaviors

Brachycephalus mirissimus has an advertisement call that is composed of relatively short notes. Intense vocal activity occurred in the morning but calling males could be found in the leaf litter during the day. The duration of the call is highly variable and ranges from 37.700 to 255.205 s. The call has a rate of 7.484 – 15.935 notes/minute and can have 6 – 52 notes/call.

Brachycephalus mirissimus is distinguishable by having note groups and not just isolated notes. Note groups can be 0.361 – 0.590 s in duration, which is relatively short. Inter-note group intervals are 5.321 – 10.930 s. The note dominant frequency is 6.000 – 7.230 KHz, with the highest frequency between 7.143 – 10.060 s and the lowest frequency between 2.667 – 5.841s . The distribution of calls is patchy (Pie et al. 2018).

Trends and Threats

This micro-endemic species has a listing recommendation of “Critically Endangered”. The type locality has been altered from natural vegetation to swaths a monoculture of palms. Brachycephalus mirissimus is also threatened by edge effects, erosion, deforestation and selective tree harvesting (Pie et al. 2018). This provisional status for this species is further corroborated by Bornschein et al (2019) in their review of the conservation assessment of the genus (criteria B1ab(i,iii)+2ab(ii,iii).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing
Disturbance or death from vehicular traffic
Habitat fragmentation

Comments

The species authority is Pie, M., Ribeiro, L., Confetti, A., Nadaline, M., and Bornschein, M., 2018. “A new species of Brachycephalus (Anura: Brachycephalidae) from southern Brazil” PeerJ 6:e5683

Brachycephalus mirissimusis a member of the B. pernix group which includes B. fuscolineatus and B. albolineatus. Bayesian inference of 16S rRNA shows that Brachycephalus mirissimus is a part of the southernmost clade of Brachycephalus. It is poorly resolved but is closely related to B. albolineatus and B. fuscolineatus, which (by air) are also the two species that are geograpically the closest (Pie et al. 2018).

The species epithet, “mirissimus” is a superlative of the Latin adjective “mirus”, which means “marvelous or wonderful” (Pie et al. 2018).

Brachycephalus mirissimus has one of smallest ranges of vascular plants and fish.

References

Bornschein, M. R., Pie, M. R., Teixeira, L. (2019). "Conservation status of Brachycephalus toadlets (Anura: Brachycephalidae) from the Brazilian Atlantic rainforest.” Diversity, 11(150), 1-29. doi: 10.3390/d11090150 [link]

Pie, M., Ribeiro, L., Confetti, A., Nadaline, M., and Bornschein, M. (2018). ''A new species of Brachycephalus (Anura: Brachycephalidae) from southern Brazil.'' PeerJ, 6, e5683.

Species Account Citation: AmphibiaWeb 2022 Brachycephalus mirissimus <https://amphibiaweb.org/species/8916> University of California, Berkeley, CA, USA. Accessed Apr 20, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 20 Apr 2024.

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