Photographs here are in 3D, using anaglyph techniques which combine 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 or dorsal, bottom or ventral, front or anterior and back or posterior based on the conventional view of the extracted beaks. The page on Beak Structure and Evolution is also helpful in understanding beak terminology.
- Anterior-free-edge of the Hood - The free edge produced by the apparent overgrowth of the Lateral Wall Fold by the pigmented Hood surface in older beaks (LB).
- Bridge - The strip of beak material that connects the Hood to the Lateral Wall on each side of the beak (UB & LB).
- Crest - The rounded, dorsal fold of the Wall (UB & LB).
- Crest Ridges - A pair of rounded ridges on the anterior Crest beneath the Hood.
- Free Corner - The posteroventral 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 (UB).
- Free Crest - Portion of the Crest posterior to the Hood.
- Free Edge of the Palatoshoulder Ridge (= anterior Free Edge of the Lateral Wall) - The edge of the Palatoshoulder Ridge that is not attached to other parts of the Shoulder and that may extend onto the Palate (UB).
- Free Shoulder - The posterior part of the Shoulder that is free from the Lateral Wall sometimes referred to as the upper beak Wing due to its continuity with the Hood (UB).
- Fused Shoulder - The Shoulder anterior the the junction of the Free and Sessile Shoulders.
- Hood - The outer region of the beak; the Rostrum is its anterior portion (UB) or its posterodorsal portion (LB). The ventral portion of the Hood is the Wing (LB). The region between the Rostrum and the Wing (LB) or posterior to the Jaw Angle (UB) is the Posterior Hood.
- Hyaline material - The hyaline material is translucent to transparent unsclerotized (i.e., unpigmented) material of the beak (UB & LB).
- Hyaline Matrix - A subset of hyaline material, often very thick, that is found in the Shoulder and sometimes onto the Lateral Palate.
- Inner Component of the Shoulder Blade - In complex Shoulder Blades where one part of the Blade is continuous with the Free Shoulder (Outer Component) and the other continuous with the Sessile Shoulder (Inner Component) (UB).
- Inner Part of the Shoulder. In the primitive decapodiform UB the Shoulder consists of three parts (Inner, Middle, Outer). The Outer Part contains the Free Shoulder and Shoulder Blade; the Middle Part contains most of the Hyaline Matrix and the Inner Part primarily contains the Palatoshoulder Ridge. In more advanced beaks, the structure is more complicated but the general terminology is still of some use (UB).
- Jaw Angle - In most cases, the angle formed at the intersection of the Jaw Edge and the Shoulder Blade (UB & LB).
- Jaw-angle Pocket - Anterior depression in the Shoulder adjacent to the Jaw Angle (UB & LB).
- Jaw Edge - The cutting edge of the beak (UB & LB).
- Jaw-edge Extension - The embedded extension of the Jaw Edge that is the junction of the Lateral Wall (LB) or Posterior Hood (UB) and the Shoulder.
- Lateral Palate - The portion of the Palate lateral to the Median Palate on either side; it represents the Bridge between the anteromedian Wall and the Hood.
- Lateral Wall - The side walls, which along with the crest, form most of the inner beak or Wall (UB & LB). The outer beak consist mostly of the Posterior Hood + Rostrum + Wings when present (Wings are absent in upper beaks). The other parts of the beak are the Shoulder and Bridge.
- LW-B Continuum - Junction of the Bridge and the pigmented Lateral Wall in the region of the posterior surface of the Shoulder (UB).
- 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. (See General Measurements below.)
- Mandible - Synonymous with the upper or lower beak. Useful term when "beaks" refers to the combination of both members, and upper and lower mandible refers to each member.
- Median Palate - The oral-surface of the Crest approximately anterior to the Shoulder. The Median Palate is often recognizable by the anterior edges of the Lateral Wall if they rise off the surface of the Palate
- Middle Part of the Shoulder (UB) - See Inner Part of the Shoulder.
- Notch - An indentation of the posterior edge of the pigmented Lateral Wall just ventral to the Crest (LB) or the posterior edge of the pigmented Hood in the dorsal midline.
- Outer Component of the Shoulder Blade - See Inner Component.
- Outer Part of the Shoulder (UB) - See Inner Part of the Shoulder.
- Palatoshoulder Ridge - The anterior part of the Lateral Wall that forms the Medial (= inner) Part of the Shoulder (UB).
- Palate - The oral roof of the mouth formed by the oral-surfaces of the Crest (= Median Palate) and left and right Bridges (= Lateral Palates) (UB). 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 Rrostrum, it is less useful in beak taxonomy.
- Posterior Apex of the Shoulder - The posteroventral corner of the Shoulder seen beneath the Hood (LB).
- Posterior Hood - The portion of the Hood without the Rostrum (UB) or without the Rostrum and Wing (LB).
- Posterior Lobe of the Lateral Wall (UB) -
- Rostrum - The anterior portion of the Hood consisting of the heavy, biting region of the beak that includes the Jaw Edge (UB & LB). This means the region of the Hood anterior to the Jaw Angle where the posterior limit is a line (viewed in profile) from the Jaw Angle (1) perpendicular to the top of the Hood (UB) (The length of this line in profile is used to measure the Height of the Rostrum (see Rostral Height under Measurements below.)) or (2) to the posterior limit of the top of the Hood (LB).
- Rostral tip - The anterior end of the Rostrum where the Jaw Edges converge (UB & LB).
- Sessile Shoulder - The Shoulder minus the Free Shoulder (UB).
- Shoulder - Complex region approximately bounded by the posterior Bridge dorsally and including some of the Lateral Wall medially (UB) or by the posterior Bridge posteriorly and including some of the Wing laterally (LB).
- Shoulder Blade - Pigmented region of the Outer Part of the Shoulder (UB) or Inner Part of the Shoulder (LB) 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 recognizable in older beaks as the remainder of the Shoulder becomes pigmented.
- Shoulder Pocket - Large, posterior concavity in the Middle Layer of the Shoulder (UB).
- Step - Sudden drop from the Jaw Edge to the surface of the Shoulder (UB) or from the Jaw-edge Extension to the Shoulder Blade (LB).
- Tooth - When the upper (LB) or front (UB) edge of the Shoulder Blade has a strong convex shape.
- UB - Upper beak or upper Mandible.
- Upper Rostral Length (URL) - The standard size measurement of the upper beak. (See General Measurements below).
- Wall - The hypothetical primary inner part of the beak as opposed to the primary outer part which is the Hood. In primitive decapodiform beaks the Wall consists of a Crest and two Lateral Walls (UB & LB).
- White Patch - White, reflective material with ill-defined boundaries located near the Jaw Angle in Sepiolida and some Loliginidae (UB).
- Wing - The part of the Hood that extends anteroventrally (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 a profile view.
- Yellow Line - A narrow, yellowish line at the dorsal junction of the Shoulder Blade and the Jaw-edge Extension (LB & UB).
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 (LB).
- Beak Height (BH) - Distance from the posterior end of the Hood to the Crest (UB & LB).
- Crest Length (CL) - Distance from the Rostral Tip to the posterior end of the Crest (UB & LB).
- Hood Height (HH) - Distance from the posterior end of the Hood to the Crest (UB & LB).
- Hood Length (HL) - Distance from the Rostral Tip to the posterior end of the Hood (UB & LB).
- Jaw-edge Length (JeL) - Distance from the Rostral Tip to the point where the Jaw Edge intercepts the Wing Fold viewed in profile (or the Jaw Angle if there is no Wing Fold) (LB).
- Lateral Wall Height (LWH) - Distance from the top of the Crest, in line with the Hood Height, to the bottom of the Lateral Wall,measured in profile (UB).
- Lower Rostral Length (LRL) - Distance from the apex of the Jaw Angle to the Rostral Tip (LB). (see URL for upper beak).
- Rostral Height (RH) - The length of a line (in profile) from the Jaw Angle perpendicular to the top the Hood that defines the posterior limit of the Rostrum (UB).
- Rostral Set-back Length - (RSL) - Distance the Rostral Tip lies behind the anterior point of the Wing (LB).
- Rostral Width - Distance between Jaw Angles (LB & UB)
- Upper Rostral Length (URL) - Distance from the apex of the Jaw Angle to the Rostral Tip (UB).
- Wing Angle (WA) - Angle formed by the intersection of the Jaw-Edge line and the Wing-Length line, viewed in profile (LB).
- 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 (LB).
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.
General measurement ratios
- Rostral Width Ratio - LRL/RW or URL/RW
Definitions and measurements based on Clarke (1986).