Background The present issue of Language Typology and Universals is devoted to studies of comparative, historical and descriptive typology of the Ghana-Togo Mountain (GTM) languages of West Africa. They are a group of fifteen languages spoken by groups or polities that inhabit the Akuapem-Togo-Atakora hills. The languages and peoples of these groups have continued to puzzle and fascinate researchers from myriad disciplinary perspectives. The hilly location as well as the geographical distribution of the groups cuts across low-level genetic affiliations. Their histories and the complexity of the origins of the different people intertwined with migration and settlement of segments of individual groups provide an interesting network of "allochthone" and "autochthone" dichotomies. This pattern has a significant socio-historical linguistic aspect: The majority incomers tended to acquire and adopt the language of the minority autochthones and appropriate hegemony over them. This seems to be what happened in the history of the Likpe, Nyagbo and Avatime, among others (Nugent 2005; Brydon 2008; Kropp Dakubu 2009). The Akuapem-Togo-Atakora hills begin in southeastern Ghana ranging in a southwest-northeast line across the Ghana-Togo border and continuing eastward across the Togo-Benin border into the Niger Delta. These hills are significant for several reasonsgeological, geographical, historical and ethnographic. They also seem to have served as a refuge zone for people fleeing wars and slave raids in the eighteenth and nineteenth centuries (Nugent 2005). One of the languages, Basila (Anii), is the northernmost member of the group and is also an outlier spoken across the Togo-Benin border. The other languages spoken along and on both sides of the Ghana-Togo border are found clustered in three geographical groups in a north-to-south arrangement (see Map 1): Adele, Animere (North), Akebu, Ikposo, Lelemi, Igo (Ahlon), Tuwuli, Siwu (Lolobi-Akpafu), Sɛlɛɛ (Santrokofi), Sɛkpɛle (Likpe) (Central) and Ikpana (Logba), Siya(sɛ) (Avatime), Nyagbo (Tutrugbu) and Tafi (Tɪgbɔ) (Southern). Each cluster of languages is