Chthonerpeton indistinctum

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Chthonerpeton indistinctum, the Argentine caecilian, is a limbless amphibian in the Typhlonectidae family. It lives in northeastern Argentina, Paraguay, Uruguay, and southeastern Brazil, up to about 1,000 meters in elevation.

This snakelike animal grows to about 53 cm long and has 70–80 transverse folds along its body, giving it a segmented look. The head bears a pair of sensory tentacles between the nostrils, and the skin in this area is white. The back is black and the underside is dark grey with tiny white flecks, with a creamy white, disc-like area around the cloaca.

Chthonerpeton indistinctum is partly terrestrial and partly aquatic, usually staying near riverbanks but sometimes moving away from water. It can be washed out to sea on mats of vegetation and has been found in brackish estuaries. It is a common species and is listed as Least Concern by the IUCN.

Reproduction is viviparous, meaning it gives birth to live young.

Some scientists consider it to have primitive features for caecilians. Its chromosomes number 20 (diploid), which is lower than the 28 seen in a related species, Typhlonectes compressicauda, a difference that helps researchers study evolutionary relationships among caecilians.