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Mastigoteuthis agassizii: Description of beaks

Richard E. Young and Michael Vecchione

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.

  1. Pigmentation - Normal.
  2. Pigmentation pattern - See photographs.
  3. (Wing length)/(visible rostral edge) (profile) - 2.07
  4. Height/baseline (profile) - 0.95
  5. (Length from rostral tip to wing tip projected on baseline)/baseline (profile) - 0.28
  6. (Hood length)/(crest length) (profile) -  0.57
  7. (Crest length)/baseline (profile) - 0.60
  8. (Rostral base)/(visible rostral edge) (profile) - 1.10
  9. (Hood length)/(visible rostral edge) (profile) - 0.93
  10. Rostral width ratio [LRL/(length between jaw angles)] - 1.58
  11. Wing angle (= visible jaw angle in profile) - Obtuse.
  12. Shape of rostral edge - Nearly straight to gentle curve, may or may not have a slight hook.
  13. Rostrum (profile) - Broad taper.
  14. Hood distance from crest - Normal to close.
  15. Crest - Generally straight.
  16. Lateral wall notch - Slight (nearly absent).
  17. Hood-wing - Broad to narrow.
  18. Hood notch - Nearly absent.
  19. Lateral walls to free corner - Well separated with increasing but low divergence from one another.
  20. Hood midline - Slightly curved.
  21. Hood surface without prominent longitudinal ridges or grooves.
  22. Wing fold - Low, rounded, may become slightly more angled distal to jaw angle,  usually just obscures jaw angle in profile.
  23. Shoulder blades - Shoulder blade oral edges project slightly; blades nearly unrecognizable in large beaks.
  24. Shoulder groove - Virtually absent.
  25. Jaw angle - Nearly right angle or more generally obtuse.
  26. 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.
  27. Jaw edge in cross-section - Sharp.
  28. Crest in cross-section - Narrow to moderate but mideline rather sharply angled.
  29. 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.
Click on an image to view larger version & data in a new window
Click on an image to view larger version & data in a new window

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.

Click on an image to view larger version & data in a new window
Click on an image to view larger version & data in a new window

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.

Click on an image to view larger version & data in a new window
Click on an image to view larger version & data in a new window

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.

Click on an image to view larger version & data in a new window
Click on an image to view larger version & data in a new window

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.

Click on an image to view larger version & data in a new window
Click on an image to view larger version & data in a new window

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.

Click on an image to view larger version & data in a new window
Click on an image to view larger version & data in a new window

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.

Click on an image to view larger version & data in a new window
Click on an image to view larger version & data in a new window

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

Click on an image to view larger version & data in a new window
Click on an image to view larger version & data in a new window

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.

Click on an image to view larger version & data in a new window
Click on an image to view larger version & data in a new window

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. 

More beaks of M. agassizii from the North can be seen here. 

About This Page


University of Hawaii, Honolulu, HI, USA


National Museum of Natural History, Washington, D. C. , USA

Correspondence regarding this page should be directed to Michael Vecchione at

Page: Tree of Life Mastigoteuthis agassizii: Description of beaks Authored by Richard E. Young and Michael Vecchione. The TEXT of this page is licensed under the Creative Commons Attribution-NonCommercial License - Version 3.0. Note that images and other media featured on this page are each governed by their own license, and they may or may not be available for reuse. Click on an image or a media link to access the media data window, which provides the relevant licensing information. For the general terms and conditions of ToL material reuse and redistribution, please see the Tree of Life Copyright Policies.

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