Urubú Sign Language (also known as "Urubú-Kaapor Sign Language") is a sign language used by a small community of Indigenous Brazilians in the state of Maranhão. Linguist Jim Kakumasu observed in 1968 that the number of deaf people in the community was 7 out of a population of 500. This relatively high ratio of deafness (1 in 75) has led to both hearing and deaf members of the community using the language, and most hearing children grow up bilingual in the spoken and signed languages. Other Indian tribes in the region have also been reported to use sign languages.
Notable features of Urubú Sign Language are its Object Subject Verb word order, and its locating of the past in front of the signer and the future behind, like Japanese Sign Language and in contrast to sign languages of European origin, including American Sign Language, Auslan and New Zealand Sign Language. Kyle and Woll (1985) speculate that this is represents a world view of the past as something visible, and the future as unknowable.
Kakumasu noted several features which sign language linguists today recognise as common to other sign languages, such as the use of name signs. Conditional and imperative grammatical moods are marked by non-manual features such as a widening of the eyes and tensing of facial muscles. Questions are marked with a question sign either before or after the clause, described as "a motion of the index finger towards the referent (addressee) with a slight wrist twist."