Especially notable is the palatalization that produced the satem languages, along with the associated ruki sound law.
A number of innovations, both phonological and morphological, represent areal features common to the Italic and Celtic languages; among them the development of labiovelars to labial consonants in some Italic and Celtic branches, producing "p-Celtic" and "q-Celtic" languages (likewise "p-Italic" and "q-Italic", although these terms are less used).
The following table shows the Proto-Indo-European consonants and their reflexes in selected Indo-European daughter languages.
Notes for table 1: Proto-Indo-European also had numerous consonant clusters, such as *st, *ḱs.
Many consonant clusters however also show special developments in multiple languages.