The mucous salivary glands are similar in structure to the buccal and labial glands. It usually occurs in the mandibular labial sulcus. The glandular system contains four glands&colon; the mandibular, maxillary, labial, and postpharyngeal glands. Their teeth could be smooth or fluted, or may differ on labial and lingual surfaces. Nauruan makes phonemic contrasts between velarized and palatalized labial consonants. The "pb" gene is responsible for the formation of the labial and maxillary palps. In sequence, these categories are&colon; velar, palatal, retroflex, dental, labial, sonorant and fricative. Then, both articulations can be similar such as labialized labial or palatalized velar . It has retained the Old Norse dental, velar and labial voiced fricatives. Scholars link labial elongation with genital tattooing. Fingers placed in the labial vestibule against the alveolar bone can detect fremitus. Original short usually merges with except in the vicinity of a labial or velar consonant. There were aspirated stops at three places of articulation&colon; labial, coronal, and velar . They are available only for labial consonants and coronal consonants . "Thrinaxodon" are all tricuspid with no labial or cingular cusps.