Chthonerpeton indistinctum

C. indistinctum is found in Paraguay, Uruguay, Brazil and Argentina at altitudes ranging up to 1,000 m (3,300 ft). It is partially terrestrial and partly aquatic, possibly having annual migrations. When on land, it mostly stays close to the river bank, but occasionally ventures some way from water. Occasionally, it gets washed out to sea on mats of vegetation and has been found alive in the brackish water of estuaries. It is a common species, sometimes occurring in very large numbers, and the IUCN Red List of Threatened Species lists it as being of "Least Concern".^[1]

This species is viviparous, giving birth to live young.^[1]

It is considered to have several characteristics which indicate it is more primitive than other, more highly derived species. As caecilians evolved, their chromosomes are thought to have reduced in number. A number of species were karyotyped, and C. indistinctum was found to have a diploid number of 20 as against one of 28 for the more derived Typhlonectes compressicauda, an unexpected result. Further study is expected to clarify the taxonomic relationships between different species of caecilians.^[4]