Linguolabial consonant

Linguolabials or apicolabials are consonants articulated by placing the tongue tip or blade against the upper lip, which is drawn downward to meet the tongue. They represent one extreme of a coronal articulatory continuum which extends from linguolabial to subapical palatal places of articulation. Cross-linguistically, linguolabial consonants are very rare, though they do not represent a particularly exotic combination of articulatory configurations, unlike click consonants or ejectives. They are found in a cluster of languages in Vanuatu, in the Kajoko dialect of Bijago in Guinea-Bissau, as well as in Umotína, a recently extinct Bororoan language of Brazil, and as extraphonotactic sounds worldwide.

The linguolabial consonants are transcribed in the International Phonetic Alphabet by adding the "seagull" diacritic, to the corresponding alveolar consonant, or with the apical diacritic,  on the corresponding bilabial consonant instead.

Sound shifts
In Vanuatu, some of the Santo–Malekula languages have shifted historically from labial to dental consonants via an intermediate linguolabial stage, which remains in other Santo and Malekula languages. In Nese, for example, labials have become linguolabial before nonrounded vowels; in Tolomako, this has gone further, so that *bebe 'butterfly' ( in Tangoa, above) has become in Tolomako, and *tama 'father' (Tangoa ) has become.