Atatláhuca–San Miguel Mixtec is a diverse Mixtec language of Oaxaca.
Dialects Egland & BartholomewEgland & Bartholomew (1983) La Inteligibilidad Interdialectal en México found six dialects (with > ≈80% internal intelligibility) which had about 70% mutual intelligibility with each other:
San Esteban Atatláhuca [mib] + Santa Lucía Monteverde [mdv] Molinos Itundujía [mce] Yosondúa [mpm] + San Miguel el Grande + Chalcatongo [mig] Yolotepec [xtt] Teita [xtj]
Ethnologue notes that two additional varieties Egland & Bartholomew had not looked at, Sinicahua [xti] and Tijaltepec [xtl], are about as similar.
References
Alexander, Ruth Mary. 1980. Gramática mixteca de Atatláhuca. Gramática yuhu sasau jee cahan ñayuu San Esteban Atatláhuca. Instituto Lingüístico de Verano. México. Series: Gramáticas de Lenguas Indígenas de México; 2. Macaulay, Monica. 1996. A grammar of Chalcatongo Mixtec, University of California Publications in Linguistics. .