Extreme premaxillary protrusion in the king-of-the-salmon, Trachipterus altivelis.

The king-of-the-salmon, Trachipterus altivelis (Lampriformes), has an unusual set of oral jaws which allow it the ability to protrude the entire upper jaw, containing the premaxilla and the maxilla bones, to extreme distances. Here, we provide a short description of the cranial anatomy and mechanism of jaw protrusion in T. altivelis using hand-drawn illustrations (by KF), supplemented by CT-scans.