• generally considered part of the Northern group of Totonacan
• spoken in four villages in the Necaxa River valley in the Sierra Norte of Puebla—Patla, Chicontla, Cacahuatlán, and San Pedro Tlaolantongo
• around 3,400 speakers, most in their 40s or older
• still spoken by school-aged children in Patla and Cacahuatlán
• probably the L1 of no more than half a dozen infants

Typological features:

• flexible word order, unmarked VOS (?)
• agglutinative and highly polysynthetic
• four aspects, three tenses, four moods
• agreement with subject and 2 objects
• two causatives, four applicatives
• no prepositions, bodypart terms used as locatives
• use of bodypart prefixes with verbs and adjectives
• ejective fricatives, no ejective stops
• vowels distinguish length and laryngealization

More information:

Upper Necaxa Totonac Project
Language shift in the Necaxa Valley
Upper Necaxa in Wikipedia