The Northwest Caucasian languages, also called West Caucasian, Abkhazo-Adyghean, Abkhazo-Circassian, Circassic, or sometimes Pontic languages (from the historical region of Pontus, in contrast to Caspian languages for the Northeast Caucasian languages), are a family of languages spoken in the northwestern Caucasus region, chiefly in three Russian republics (Adygea, Kabardino-Balkaria, Karachay–Cherkessia), the disputed territory of Abkhazia, Georgia, and Turkey, with smaller communities scattered throughout the Middle East. The group's relationship to any other language family is uncertain and unproven. One language, Ubykh, became extinct in 1992, while all of the other languages are in some form of endangerment, with UNESCO classifying all as either "vulnerable," "endangered," or "severely endangered." The Northwest Caucasian languages possess highly complex sets of consonant distinctions paired with a lack of vowel distinctions, often providing archetypical cases of vertical vowel systems, also known as "linear" vowel systems. Main features Phonetics Linguistic reconstructions suggest that both the richness of the consonantal systems and the poverty of the vocalic systems may be the result of a historical process, whereby vowel features such as labialisation and palatalisation were reassigned to adjacent consonants. For example, ancestral may have become and may have become , losing the old vowels and but gaining the new consonants and . The linguist John Colarusso has further postulated that some instances of this may also be due to the levelling of an old grammatical class prefix system (so may have become ), on the basis of pairs like Ubykh vs. Kabardian and Abkhaz heart. This same process is claimed by some to lie behind the development of labiovelars in Proto-Indo-European, which once neighboured Proto-NWC. Lack of distinctive vowels and wealth of distinctive consonants The entire family is characterised by a paucity of phonemic vowels (two or three, depending upon the analysis) coupled with rich consonantal systems that include many forms of secondary articulation. Ubykh (Ubyx), for example, had two vowels and probably the largest inventory of consonants outside Southern Africa. Grammar Northwest Caucasian languages have rather simple noun systems, with only a handful of cases at the most, coupled with highly agglutinative verbal systems that can contain almost the entire syntactic structure of the sentence. All finite verbs are marked for agreement with three arguments: absolutive, ergative, and indirect object, and there are also a wide range of applicative constructions. There is a split between "dynamic" and "stative" verbs, with dynamic verbs having an especially complex