Beak Terminology

Photographs here are in 3D, using anaglyph techniques which combines two photographs one in red and the other in cyan (blue + green) color. To get the 3D effect, you must use glasses with red and cyan lenses (filters) over your regular glasses. The form of the beak is far easier to interpret in 3D and we strongly recommend to the viewer that the glasses be obtained (this is especially helpful when viewing enlarged images - i.e. click on the image). These beak photographs were made using Red and Cyan Anachrome Aviator Glasses (see: http://www.anachrome.com/glassbuy.htm or http://www.amazon.com) which cost under $10.00 (USD).

Anterior edge of lateral wall - The leading edge of the lateral wall often extends into the rostral region with a free edge in the upper beak.
Crest - The ridge formed by the joining of the two lateral walls.
Crest length - Length of the crest from the tip of the rostrum to the posterior end of the crest.
Hood - Part of the outer region of the beak that is broadly continuous with the wing and the heavier rostrum.
Hood length - Length of the hood and rostrum from the tip of the rostrum to the posterior end of the hood.
Jaw angle - Angle formed at the intersection of the jaw edge and the shoulder blade.
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Figure. Drawings and photographs of the lower beak of the squid, Chiroteuthis picteti. Upper set - Side view. Lower set - Oblique view. Drawings/photographs by R. Young.
Jaw edge - The cutting edge of the beak.
Lateral wall - The side walls, along with the crest, form the more inner region of the beak, in contrast to the more outer region consisting of the hood, wings and outer walls of the rostrum.
Lateral wall fold - An oblique fold in the lateral wall that may become a solid, or partially solid, ridge. found only in some lower beaks.
Lower rostral length (LRL) - The standard size measurement of the lower beak taken from the apex of the jaw angle to the tip of the rostrum.
Upper rostral length (URL) - The standard size measurement of the upper beak taken from the apex of the jaw angle to the tip of the rostrum.
Mandible - Synonymous with the upper or lower beak. Useful term when "beaks" refers to the combination and upper and lower mandibles refer to each member of the pair.
Rostrum - The heavy, biting region of the beak that includes the jaw edge and is broadly continuous with the hood.
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Figure. Drawings and photographs of the upper beak of the squid, Chiroteuthis picteti. Upper set - Side view. Lower set - Oblique view. Drawings/photographs by R. Young.
Shoulder - Complex junction between the hood, wing and lateral wall.
Shoulder blade - Region of the outer surface of the shoulder that lies adjacent to the posterior, embedded extension of the jaw edge. The shoulder blade often is often more heavily pigmented than the rest of the shoulder. In some beaks the projecting free end of the shoulder blade has a strongly convex shape and is referred to as a tooth.
Wing - Part of the free edge of the beak that broadly joins the hood. The wing is nearly absent in the upper beak.
Wing fold - A fold of the wing in the region of the jaw angle in the lower beak. The fold often obscures the jaw angle in lateral view.