The cranial ridges, also referred to as exocranial ridges or cranial plates are bony plates on the surface of the forehead on many humanoid species. Some species, such as Humans, Vulcans, and the ancient humanoids do not possess visible cranial ridges. Klingon-Human hybrids generally inherit cranial ridges from their Klingon parent, although they are less pronounced. (VOY: "Nothing Human") During the 23rd century of the alternate reality, helmets issued to the Klingon Defense Force gave all warriors the appearance of cranial ridges. (Star Trek Into Darkness)