Lampridiformes
Lampridiformes have a unique type of protrusible upper jaw. The maxillaries, instead of being ligamentously attached to the ethmoid and palatines, slide in and out with the highly protractile premaxillaries. The premaxillaries exclude the maxillaries from the gape. The fins have no true spines. Up to 17 rays in the pelvic fins. If present, the swimbladder is physoclistous.