Sidwell (2018: 23) lists the following Khasian lexical innovations (i.e., defining lexical forms) that are found exclusively in the Khasian branch, but not in other Austroasiatic branches).
Proto-Khasian and Proto-Pnar-Khasi-Lyngngam have been reconstructed by Paul Sidwell (2018). Proto-Khasian is estimated to have originated about 2,000-2,500 years ago, with War splitting from other Khasian linguistic varieties about 1,500 years ago (Sidwell 2018: 20).
Proto-Khasian morphology includes a causative *pN- prefix and verbalizing *-r- infix (Sidwell 2018: 66-67).
The following reconstructed paradigmatic and closed class morphemes in Proto-Khasian are from Sidwell (2018: 51-67).
Personal pronouns
Masculine
Feminine
Plural
1st person
*ŋa (topic/oblique); *ʔɔ (default)
*ŋa (topic/oblique); *ʔɔ (default)
*ʔi
2nd person
*me
*pʰa
*pʰi
3rd person (animate)
*ʔu
*ka
*ki
3rd person (inanimate ~ diminutive)
*ʔi
*ʔi
*ʔi
Demonstratives
*ni 'proximal'
*tu 'mesiodistal'
*taj 'distal (visible)'
*te 'mesioproximal'
*tɛ 'distal (non-visible)'
Negators
*ʔǝm 'not'
*ham 'do not'
*ta 'not'
Prepositions/case markers
*ha 'locative/oblique'
*ʤɔŋ 'to possess'
*da 'instrumental'
*ba (?) 'and/with'
*tV 'oblique'
Tense/aspect morphemes
*la:j 'to go'
*dɛp 'finish'
*diʔ 'to go'
*daː 'have'
*ʤuʔ 'same'
Morphological affixes
*pN- 'prefix'
*-r- 'verbalizer'
Numerals
Gloss
Proto-Khasian
Proto-Pnar- Khasi-Lyngngam
one
*wiː~*miː
one
*ʧiː
two
*ʔaːr
three
*laːj
four
*saːw
five
*san
six
*tʰruː
seven
*ʰnɲəw
eight
*pʰraː
nine
*kʰndaːj
ten
*pʰəw
Sound changes
Sidwell (2018) lists the following sound changes from Pre-Khasian (i.e., the ancestral stage of Khasian that preceded Proto-Khasian) to Proto-Khasian.
Sidwell, Paul. 2018. The Khasian Languages: Classification, Reconstruction, and Comparative Lexicon. Languages of the World 58. Munich: Lincom Europa. ISBN9783862889143