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Although even the pronouns do not appear to be cognate, Foley classifies the Abau–Iwam languages with the Wogamus languages rather than with the Yellow and Wanibe River languages on the basis of a unique noun-class system in the numeral systems (see Wogamus languages#Noun classes). Additionally, Foley considers Sepik Iwam and Wogamusin noun class prefixes to be likely cognate with each other. Abau is more divergent, but its inclusion by Foley (2018) is based on the similarity of Abau verbal morphology to that of the Iwam languages.
Foley observes that much of the lexicon and pronouns of these languages do not derive from proto-Sepik.
Numerals
Upper Sepik morphological numerals are (Foley 2018):
^ Foley, William A. (2018). "The Languages of the Sepik-Ramu Basin and Environs". In Palmer, Bill (ed.). The Languages and Linguistics of the New Guinea Area: A Comprehensive Guide. The World of Linguistics. Vol. 4. Berlin: De Gruyter Mouton. pp. 197–432. ISBN978-3-11-028642-7.
Ross, Malcolm (2005). "Pronouns as a preliminary diagnostic for grouping Papuan languages". In Andrew Pawley; Robert Attenborough; Robin Hide; Jack Golson (eds.). Papuan pasts: cultural, linguistic and biological histories of Papuan-speaking peoples. Canberra: Pacific Linguistics. pp. 15–66. ISBN0858835622. OCLC67292782.
The Sepik languages as classified by Foley (2018)