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).
The beak orientation presents problems for beak terminology. Common terms such as dorsal, ventral, anterior, posterior are difficult to use since the actual beak orientation in life is dependent on the degree of opening of the mandibles. Also the orientation of the upper and lower beaks are the inverse of one another. Typically beaks are viewed in illustrations with the hood/rostrum at the top of the image regardless if it is the upper or lower beak. As a result, for terminology, we treat each mandible the same regardless of its orientation in life and we use the terms top, bottom, front and back based on the conventional view of the extracted beaks.
- Front edge of lateral wall - The front, often free-edge of the lateral wall of the shoulder (UB). This often extends onto the pallet.
- Bridge - The strip of beak on either side that joins the rostrum/hood to each lateral wall (UB & LB).
- Crest - The rounded bend in the lateral wall near the top of the beak resulting in a right and left lateral wall (UB & LB).
- Crest length - Length of the crest from the tip of the rostrum to the posterior end of the crest (UB & LB).
- Jaw-edge extension - the extension of the jaw edge that is embedded in the junction of the lateral wall (LB) or rostrum/hood (UB) and the shoulder.
- Free corner - The back corner of the lateral wall (LB) adjacent to the baseline. There is no clear counterpart in the upper beak due to greater rounding of the lateral wall.
- Hood - The outer region of the beak that is broadly continuous with the wing (LB) or the outer region above the shoulder (UB).
- Hood length - Length of the hood from the tip of the rostrum to the posterior end of the hood (UB & LB).
- Jaw angle - Angle formed at the intersection of the jaw edge and the shoulder blade (UB & LB).
- Jaw edge - The cutting edge of the beak (UB & LB).
- Lateral wall - The side walls, along with the crest, form most of the inner (medial) component of the beak (UB & LB). The outer component of the beak consist mostly of the hood/rostrum and wings when present (wings are absent in upper beaks). The other component of the beak is the shoulder.
- Lateral wall fold - An oblique fold in the lateral wall that may become a solid, or partially solid, ridge (some LBs).
- LB - Lower beak or lower mandible.
- 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 (see URL for upper beak).
- 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.
- Palete - The oral roof of the mouth (UB) formed by the oral-surfaces of the crest and bridges. A comparable feature of the lower beak (i.e., the oral floor of the mouth) is present but as its contours closely follow those of the hood/rostrum, it is less useful in beak taxonomy.
- Rostrum - The anterior portion of the hood consisting of the heavy, biting region of the beak that includes the jaw edge (UB & LB).
- Rostral tip - The front end of the rostrum where the rostrum and jaw edges converge (UB & LB).
- Shoulder - Complex region mostly below the jaw angle in which the wing forms the outer wall (LB) or the lateral wall forms the inner wall (UB).
- Shoulder blade - Region of the outer surface of the shoulder (upper beak) or inner surface of the shoulder (lower beak) that lies adjacent to the Jaw-edge Extension. The shoulder blade is more heavily pigmented than, and easily distinguished from, the rest of the shoulder in beaks of young squid but becomes less distinguishable in older beaks as the remainder of the shoulder becomes pigmented.
- Tooth - When the upper (LB) or front (UB) edge of the shoulder has a convex shape.
- 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.
- Wing - Part of the free edge of the beak that broadly joins the hood (LB) . The wing is absent from the upper beak.
- Wing fold - A fold of the wing in the region of the jaw angle (LB). The fold often obscures the jaw angle in lateral view.
Figure. Drawings with labels and photographs of the lower beak of the squid, Chiroteuthis picteti. Upper set - Side view. Lower set - Oblique view. Drawings/photographs by R. Young.
- Baseline Length (BL) - Distance from the level of the anterior end of the wing tip to the free corner of the lateral wall (lower beak).
- Beak Height (BH) - Distance from the posterior end of the hood to the crest (both beaks).
- Crest Length (CL) - Distance from the tip of the rostrum to the posterior end of the crest (both beaks).
- Hood Height (HH) - Distance from the posterior end of the hood to the crest (both beaks).
- Hood Length (HL) - Distance from the tip of the rostrum to the posterior end of the hood (both beaks).
- Jaw Length (JL) - Distance from the tip of the rostrum to the posterior junction between the shoulder packing and the embedded jaw edge (upper beak).
- Jaw-edge Length (JeL) - Distance from the tip of the rostrum to the point where the rostral edge intercepts the wing fold viewed in profile (or the jaw angle if there is no wng fold) (Lower beak).
- Lateral Wall Height (LWH) - Distance from the top of the crest, in line with the posterior end of the hood, to the bottom of the lateral wall,measured in profile (upper beak).
- Rostral Set-back Length - (RSL) - Distance the rostral tip lies behind the anterior end of the wing (lower beak).
- Wing Angle (WA) - Angle formed by the intersection of the Jaw-edge line and the wing-length line, viewed in profile (lower beak).
- Wing Length (WL) - Distance from the tip of the wing to the point where the jaw-edge line intercepts the jaw angle or wing fold, measured in profile (lower beak).
Figure. Side views of the beaks of the squid, Chiroteuthis picteti. Upper set - Lower beak. Lower set - Upper Beak. Photographs in 3D. Drawings/photographs by R. Young.
Definitions and measurements based on Clarke (1986).