How was South Picene related to the Osco-Umbrian languages?

South Picene is classified as an ancient Italic language and is most closely related to the Osco-Umbrian languages.1

The linguistic relationship between South Picene and the Osco-Umbrian group is evidenced by shared morphological features that distinguish them from other Italic languages like Latin and Faliscan. Specifically, South Picene and Osco-Umbrian share the following characteristics:12

• Genitive singular of o-stems: Both groups utilize the -eis suffix, whereas Latin, Faliscan, and Venetic use -ī.2
• Nominative plural of o-stems: Both groups mark this class with -ōs, contrasting with the -oi marker found in early Latin.2
• Ablative singular case: Both demonstrate the extension of the ablative singular case from o-stems to other declension classes, such as the South Picene arítih (where -h represents an earlier -d) and the Oscan toutad.2

While these languages share these specific innovations, they also exhibit distinct morphological developments in other areas, such as the formation of perfect stems for secondary verbs, which vary significantly across the broader Italic family.2