Proto-Mayan

Proto-Mayan is the hypothetical common ancestor of the 30 living Mayan languages, as well as the Classic Maya language documented in the Maya inscriptions.

The Proto-Mayan language is reconstructed (Campbell and Kaufman 1985) as having the following sounds:

Five vowels: a, e, i, o and u. Each of these occurring as short and long: aa, ee, ii, oo and uu,

The following set of sound changes from proto-Mayan to the modern languages are used as the basis of the classification of the Mayan languages. Each sound change may be shared by a number of languages; a grey background indicates no change.

The palatalized plosives [tʲʼ] and [tʲ] are not carried down into any of the modern families. Instead they are reflected differently in different branches allowing a reconstruction of these phonemes as palatalized plosives. In the western branch (Chujean-Q'anjob'alan and Cholan) they are reflected as [t] and [tʼ]. In Mamean they are reflected as [ts] and [tsʼ] and in Yukatek and K'ichean as [tʃʰ] and [tʃʼ].

The Proto-Mayan liquid [r] is reflected as [j] in the western languages (Chujean- Q'anjob'alan and Cholan), Huastecan and Yukatek but as [tʃʰ] in Mamean and [r] in K'ichean and Poqom.

Proto-Mayan velar nasal *[ŋ] is reflected as [x] in the eastern branches (K'ichean Mamean), as [n] in Q'anjob'alan, Cholan and Yukatekan, and only conserved as [ŋ] in Chuj and Poptí. In Huastecan *[ŋ] is reflected as [h].

...
Wikipedia