LOWER BEAK
We examined beaks of M. psychrophila from ten individuals (62-122 mm ML) captured from localities scattered throughout the Atlantic. We obseerved large variation in the form of the beaks. Some indication of this variation can be seen in additional photographs shown here. The following characters are taken from Clarke (1986). Means are used, when possible, for measurements.
- Pigmentation - Normal.
- Pigmentation pattern - See photographs.
- (Wing length)/(visible rostral edge) (profile) - 2.07
- Height/baseline (profile) - 0.95
- (Length from rostral tip to wing tip projected on baseline)/baseline (profile) - 0.28
- (Hood length)/(crest length) (profile) - 0.57
- (Crest length)/baseline (profile) - 0.60
- (Rostral base)/(visible rostral edge) (profile) - 1.10
- (Hood length)/(visible rostral edge) (profile) - 0.93
- Rostral width ratio [LRL/(length between jaw angles)] - 1.58
- Wing angle (= visible jaw angle in profile) - Obtuse.
- Shape of rostral edge - Nearly straight to gentle curve, may or may not have a slight hook.
- Rostrum (profile) - Broad taper.
- Hood distance from crest - Normal to close.
- Crest - Generally straight.
- Lateral wall notch - Slight (nearly absent).
- Hood-wing - Broad to narrow.
- Hood notch - Nearly absent.
- Lateral walls to free corner - Well separated with increasing but low divergence from one another.
- Hood midline - Slightly curved.
- Hood surface without prominent longitudinal ridges or grooves.
- Wing fold - Low, rounded, may become slightly more angled distal to jaw angle, usually just obscures jaw angle in profile.
- Shoulder blades - Shoulder blade oral edges project slightly; blades nearly unrecognizable in large beaks.
- Shoulder groove - Virtually absent.
- Jaw angle - Nearly right angle or more generally obtuse.
- Jaw edge extension without step and with prominent angle point extending well past shoulder padding; jaw edge extension without clear strip between it and shoulder blade.
- Jaw edge in cross-section - Sharp.
- Crest in cross-section - Narrow to moderate but mideline rather sharply angled.
- Lateral wall - Distinct lateral-wall fold capped by solid ridge that usually overhangs base anteriorly, ridge nearly reaches posterior margin of lateral wall; lateral wall fold, with anterior sharp, medial groove and steeply sloping sides, extends to posterior margin of lateral wall.
Figure. Left and right side views of the same lower beak of M. agassizii, 78 mm ML, 3.3 mm LRL, immature male, Gulf of Mexico. Photographs by R. Young.
Figure. Left and right side views of the same lower beak of M. agassizii, 122 mm ML, 4.0 mm LRL, nearly mature male, Gulf of Mexico. The tip of the beak is broken off. Photographs by R. Young.
Figure. Left and right side-oblique views of the same lower beak of M. agassizii, 78 mm ML, immature male, Gulf of Mexico. Photographs by R. Young.
Figure. Two posterior-oblique views of the same lower beak of M. agassizii, 78 mm ML, immature male, Gulf of Mexico, showing the width of the lateral wall ridge (arrows). Photographs by R. Young.
Figure. Side view of the lower beak of M. agassizii, 122 mm ML, nearly mature male, that has been cut in half and laid flat with drawn cross-sections of the lateral wall overlayed where the cuts occurred. Photograph by R. Young.
Figure. Front (left) and rear (right) views of the same lower beak of M. agassizii, 78 mm ML, immature male, Gulf of Mexico. Photographs by R. Young.
Figure. Top view of the lower beak of M. agassizii, 78 mm ML, immature male, Gulf of Mexico. Photographs by R. Young.
Comments
To be added.
UPPER BEAK
Figure. Side views of upper beaks of M. agassizii, Gulf of Mexico. Left - 78 mm ML, immature male. Right - 122 mm ML, nearly mature female. Photographs by R. Young.
Figure. Various views of upper beaks of M. agassizii, Gulf of Mexico. Left - Top view, 78 mm ML, immature male. Left middle - Bottom view, 78 mm ML, immature male. Right middle - Front view, 78 mm ML, immature male. Right - Front view, 122 mm ML, nearly mature female.78 mm ML, immature male. Photographs by R. Young.
Comments
To be added.
