Mawayana used to be spoken by a people of the same name in parts of Guyana and Brazil ... they ... merged with the larger Waiwai group in the early 20th century ... and have probably fully become Waiwai by the 1960s. But
while the Mawayana language is now all but forgotten in Guyana and Brazil, there are still native speakers left elsewhere, in Suriname. These were part of a group of Mawayana who were recruited in the late 1950s by an American missionary to help him convert the Trio people in southern Suriname ... Of this group, there are now only two elderly women left whose children and grandchildren do not speak Mawayana.

Guyana: few remembers, ? population. Suriname: <5 speakers, 60-80 population.
There are only a few rememberers of Mawayana among the Mawayana that live with the Waiwai of Guyana. There are only 3 Mawayana speakers and 2 other Mawayana with a good passive knowledge of their language in the Trio village Kwamalasamutu. The Mawayana are mixed with Waiwai and predominantly live among the Waiwai in Guyana; only a few are in Suriname. The Mawayana now speak Trio as their primary language.

Ethnologue has two codes for apparently a single language, Madipian [mpw] in Brazil (with alternate name Mawayana) and Mawayana [mzx] for Guyana -- both said to be 50 people living with the Waiwai.

Mawayana [mzx]: 50 in Guyana (1986 C. Howard); population total all countries: 60;
Mapidian [mpw] (Mahuayana, Maiopitian, Maopityan, Mawayana): 10 in Brazil (Moore 2006).

70 years old

Guyana: few remembers, ? population; Suriname: <5 speakers, 60-80

Ethnologue gives Mawayana [mzx] and Mapidian [mpw] as separate languages.