Excerpt from change request document:
Upper Necaxa Totonac and Tecpatlán Totonac do not seem to be naively mutually intelligible, although many speakers of one have enough experience with the other that in practice they can communicate. However, Upper Necaxa as spoken in Patla, Chicontla, San Pedro Tlalontongo, and Cacahuatlán is distinguished by (and recognized as a dialect in the region according to) a number of sound changes including the neutralization of a contrast between the voiceless lateral affricate and the voiceless lateral fricative.Tecpatlán Totonac has also undergone a shift of /w/ to /b/ (a sound not found at all in Upper Necaxa). There are a great many lexical distinctions that set Tecpatlán apart from the others.
Tecpatlán Totonac does, however, share one important sound change with the Upper Necaxa variety, the lenition of *q to a glottal stop and the concomittant collapse of historical fricative-q clusters to ejective fricatives. The shift is not quote complete in Tecpatlán, however, which retains /q/ in at least some lexical items. Tecpatlán and Upper Necaxa also share a shift in the grammatical paradigms so that many n-final verbs are treated as consonant-final stems for the purposes of perfective aspectual inflection (departing from the more common Totonacan pattern). These changes set Tecpatlán apart from Zihuateutla Totonac.