Southern Māori contains almost all of the same phonemes as other Māori dialects (), along with the same diphthongs but lacks ("ng"), a sound that merged with in prehistoric times: becomes ). The change did not occur in the northern part of the Ngāi Tahu area, and the possible presence of additional phonemes () has been debated. Nonstandard consonants are sometimes identified in the spellings of South Island place names, such as "g" (as distinct from "k", e.g., Katigi, Otago), "v" (e.g., Mavora), "l" instead of "r" (e.g., Little Akaloa, Kilmog, Waihola, Rakiula), and "w" or "u" instead of "wh" as reflecting dialect difference, but similar spellings and pronunciations also occur in the North Island (e.g. Tolaga Bay).