The most common labialized consonants are labialized velars. Hirt introduced the "o/e" vocalism, syllabic resonants, labiovelars and palatalized velars. Before rounded vowels, only labialized velars occur, e.g. ('ringworm'). The velars followed by the close back rounded vowel assimilate into the labialized velars . The velars are palatalized after (e.g. "alika" 'dog'). Pre-Indic palatalization of velars resulted in the variant form , which was initially phonologically conditioned. The palatalized velars , and might also be regarded as soft on this basis. Near or , the labialized velars had already lost their labialization in the Mycenaean period. The affricates "ts" and "dz" developed from velars before front vowels. The original allophonic distinction was disturbed when the labiovelars were merged with the plain velars. In most analyses velars followed by are treated as labio-velars. Both affected the Proto-Slavic velars . It is uncertain as to when the palatal allophones for velars /k/ and /x/ appeared. In satem languages, they remained distinct, and the labiovelars merged with the plain velars. These are with velars and with bilabials and .