Osco-Umbrian languages

The Osco-Umbrian, Sabellic or Sabellian languages are a group of Italic languages, the Indo-European languages that were spoken in Central and Southern Italy by the Osco-Umbrians before being replaced by Latin, as the power of Ancient Rome expanded. They developed from the middle of the 1st millennium BC to the early centuries of the 1st millennium AD. The languages are known almost exclusively from inscriptions, principally of Oscan and Umbrian, but there are also some Osco-Umbrian loanwords in Latin.
Relationship with the Italic languages.
Following an original theory by Antoine Meillet, the Osco-Umbrian languages were traditionally considered a branch of the Italic languages, a language family that grouped Latin and Faliscan together with several other related languages. 
However, this unitary scheme was criticized by, among others, Alois Walde, Vittore Pisani and Giacomo Devoto, who proposed a classification of the Italic languages into two distinct Indo-European branches. This view gained acceptance in the second half of the 20th century, although the exact processes of formation and penetration into Italy remains the object of research. However, proponents such as Rix would later reject the idea, and the unitary theory (proposing the descent of all Italic languages from a unique common ancestor) remains dominant.
Historical, social and cultural aspects.
Oscan was one of the many languages spoken in the heart of the Italian peninsula, such as Umbrian and other languages belonging to the Sabine languages, such as Volscian, Sabine, South Picene, Marsian, Paeligni, Hernican, Marrucinian, Pre-Samnite and Sidicini.
Aequian and Vestinian may also have been part of the group.
They have traditionally been ascribed to either an Oscan group or an Umbrian group. However, they are all poorly attested, and such a division is not supported by evidence. It appears that they may have formed a continuum, with Umbrian in the north, Oscan in the south and the 'Sabellic' languages in between (see next section) having features of both.
However, there were also colonies that spoke Oscan, scattered throughout Southern Italy and Sicily. Oscan was the language of the Samnite tribes, powerful enemies of the Romans, who took years to subdue them (the Samnite wars took place from 370 BC to 290 BC).
These languages are known from a few hundred inscriptions dating from between 400 BC and the 1st century. In Pompeii there are numerous Oscan inscriptions, such as dedications in public buildings and signs.
Umbrian began a process of decline when the Umbrians were subdued by the Romans and the process of Romanisation led to its demise. Of all the Osco-Umbrian languages, it is the one that is the best known, mainly because of the Iguvine Tablets.
Distribution.
These languages were spoken in Samnium and in Campania, partly in Apulia, Lucania and Bruttium, as well as by the Mamertines in the Sicilian colony of Messana (Messina).
Past usage.
"Sabellic" was originally the collective ethnonym of the Italic people who inhabited central and southern Italy at the time of Roman expansion. The name was later used by Theodor Mommsen in his "Unteritalische Dialekte" to describe the pre-Roman dialects of Central Italy that were neither Oscan nor Umbrian.
The term is currently used for the Osco-Umbrian languages as a whole. The word "Sabellic" was once applied to all such minor languages, Osco-Umbrian or not. North Picene was included, even if it has always been known to have been unrelated.
Classification.
The Osco-Umbrian languages or dialects of which testimony is preserved are:
Little-documented variants collectively known as "Sabellic dialects" are ascribed without much evidence to the two main groups. Some authors doubt such traditional classification, placing, for example, Aequian and Vestinian in opposite branches, instead of grouping them together.
Linguistic description.
The Osco-Umbrian languages are fusional inflected languages with about 5 different morphological cases in the singular, similar to those of Latin.
Differences from Latin.
Although the Osco-Umbrian languages are far more poorly attested than Latin, a corpus of a few thousand words' worth of inscriptions has allowed linguists to deduce some cladistic innovations and retentions. For example, while Proto-Indo-European aspirates appear as "b", "d" and "h/g" between vowels in Latin ("medius" < "*medʰyos"), the aspirates all appear in Sabellic as "f" (Oscan "mefiai"). In addition, while Latin retained the Proto-Indo-European labiovelar series ("Q-Italic"), the Osco-Umbrian languages merged them with the labials ("P-Italic"): Latin "quattuor", Oscan "petora".