IUCN threat status:

Endangered (EN)

Comprehensive Description

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Barbourula kalimantanensis is the only known lungless frog (Bickford et al. 2008). This species is a medium-sized frog (males to 66 mm SVL, females to 77.7 mm SVL), characterized by a distinct broad, extremely flattened, depressed head, rounded snout, and a stocky, depressed body (Iskandar 1978; Iskandar 1995). The nostrils of this frog are located at the end of the snout and are flush with the skin. There is no canthus rostralis and no lores. Eyes are located anterolaterally on the head, with a free nasolacrimal papilla positioned just below the lower eyelid. The tympanic annulus is lacking. Both the maxilla and premaxilla of B. kalimantanensis are toothed, with two partitioned rows behind the choanae. Vomerine teeth of this frog species resemble a pair of tubercles and are situated on the roof of the mouth just posterior to the choanae. The tongue is circular (Iskandar 1978; Iskandar 1995). No glottis (protected opening to the airway) is present, unlike any other known frog species, and the esophageal opening leads directly to the stomach (Bickford et al. 2008). Males lack vocal sacs (Iskandar 1978; Iskandar 1995).

The arms and legs are stout, with fully webbed hands and feet. The hands and feet are unusual in that they resemble paddles, with the second and third fingers being roughly equal and the third and fourth toes also. Fingertips of B. kalimantanensis are distinctively enlarged into discs, but lack a circummarginal groove. Three low metacarpal tubercles are present on the hand, but the hand lacks any subarticular tubercles. Toe discs are enlarged as a series, with the first toe disc being the largest. A thick ridge of skin is present along the median edge of the first toe. The foot of B. kalimantanensis has an inner metatarsal tubercle but lacks an outer metatarsal tubercle. There is a fold of skin along the rear of the thigh as well as one along the tibia. Female B. kalimantanensis are distinguishable by the appearance of triangular muscle projections on either side of their cloaca, known as anal claspers. Dorsally, the skin texture of B. kalimantanensis is rugose (wrinkly and creased), with small projecting tubercles or spinules located on the posterior portion of the dorsum and on the hindlimbs. Ventrally, the skin is smooth (Iskandar 1978; Iskandar 1995).

Specimens preserved in alcohol are uniformly black in dorsal coloration; the ventral coloration is dark with indistinct lighter marbling (brown mottling in the single preserved male specimen and yellow mottling in the single preserved female specimen) (Iskandar 1978; Iskandar 1995). The color in life is brown with black mottling.

This frog is the only known lungless frog (Bickford et al. 2008). Otherlungless amphibians include some salamanders (350 species in the familyPlethodontidae; 2 species in the family Hynobiidae, Onychodactylusfischeri and Onychodactylus japonicus) and one species of caecilian,Atretochoana eiselti.


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