Note

Mastigoteuthis magna: Description of the beaks in 2D

Michael Vecchione and Richard E. Young

LOWER BEAK

We examined four beaks of M. magna from individuals (135, 141, 150, 160 mm ML). The following characters are taken from Clarke (1986). Arithmetic means, based on the four squid are used for characters requiring measurements.

  1. Pigmentation - Light side of normal.
  2. Pigmentation pattern - No beaks were examined from squid less than 135 mm ML. At this size, the beak is fully pigmented except for the aboral side of the wing opposite the shoulder.
  3. (Wing length)/(visible rostral edge) (profile) - 1.85
  4. Height/baseline (profile) - 0.86
  5. (Length from rostral tip to wing tip projected on baseline)/baseline (profile) - 0.27
  6. (Hood length)/(crest length) (profile) - 0.51
  7. (Crest length)/baseline (profile) - 0.64
  8. (Rostral base)/(visible rostral edge) (profile) - 1.05
  9. (Hood length)/(visible rostral edge) (profile) - 0.85
  10. Rostral width ratio [LRL/(length between jaw angles)] - 1.47
  11. Wing angle (= visible jaw angle in profile) - Obtuse.
  12. Shape of jaw edge - Almost straight but with small, gradual hook.
  13. Rostrum (profile) - Broad taper to tip.
  14. Hood distance from crest - Close to crest.
  15. Crest - Nearly straight.
  16. Lateral wall notch - Virtually absent.
  17. Hood-wing - Broad.
  18. Hood notch - Broad to narrow.
  19. Lateral walls to free corner - Broadly separated with increasing but low divergence from one another.
  20. Hood midline - Moderately curved.
  21. Hood surface without prominent longitudinal ridges or grooves.
  22. Wing fold - Low, rounded, obscures jaw angle in profile.
  23. Shoulder - Shoulder blades well developed in one beak (141 mm ML) but are only stubby remnants in another (135 mm ML). In the former, the shoulder blade is large and trapezoidal with oral ends projecting very slightly.
  24. Shoulder groove - Absent to moderate.
  25. Jaw angle - Slightly obtuse, without associated step or transparent strip.
  26. Jaw edge extension - Extends well beyond shoulder padding and terminates in a sharp or blunt angle point well short of lateral wall edge.
  27. Terminal shoulder filling pigmentation - Sharply defined; final stage a thin, unpigmented line adjacent to lateral wall and extending to aboral edge of padding at posterior padding apex.
  28. Jaw edge in cross-section - Sharp.
  29. Crest in cross-section - Somewhat broad.
  30. Lateral wall - Low, broad lateral-wall fold extends to posterior edge of lateral wall; broad medial groove matches lateral fold; fold slightly thickened. Fold barely noticeable at first glance.
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. magna, 160 mm ML, 4.2 mm LRL, immature male, Northwest Atlantic, 40°N, 67°W. Photographs by R. Young.

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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. magna, 135 mm ML, 4.4 mm LRL, sex unknown, Northwest Atlantic. 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. magna, 160 mm ML, immature male, Northwest Atlantic, 40°N, 67°W. Photographs by R. Young.

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

Figure. Posterior oblique (left) and posterior (right) views of the same lower beak of M. magna, 160 mm ML, immature male, Northwest Atlantic, 40°N, 67°W. Arrows point to the lateral wall fold. Photographs by R. Young.

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

Figure. Side view of the lower beak of M. magna, 160 mm ML, immature male, that has been cut in half and laid flat with a drawn cross-sections of the lateral wall overlayed where the cut occurred. The rostrum broke when cutting the beak in half. 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. magna, 160 mm ML, immature male, Northwest Atlantic, 40°N, 67°W. 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 views of the lower beak of M. magna, 160 mm ML, immature male, Northwest Atlantic, 40°N, 67°W. Left - Top view. Right - Posterior-oblique view showing the width of the lateral wall ridge (arrow). Photographs by R. Young.

Comments

M. magna is easly separated from its closest relative among broad-beaked mastigoteuthids (ie, M. microlucens) by the presence of a low lateral-wall fold (absent is M. microlucens) that may be slightly thickened but lacks a solid ridge (distinct ridge pressent in M. microlucens). The fold extends to the posterior margin whose shape is modified by it. In contrast no modification occurs at this point in M. microlucens.   

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 the upper beak of M. magna. Left - 160 mm ML, immature male, Northwest Atlantic, 40°N, 67°W. Right - 135 mm ML, sex unknown, Northwest Atlantic. 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 the upper beak of M. magna sp. A, 160 mm ML, immature male, Northwest Atlantic, 40°N, 67°W. Left - Top view. Middle - Bottom view. Right - Front view. Photographs by R. Young.

Comments

To be added. 

About This Page


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


University of Hawaii, Honolulu, HI, USA

Page: Tree of Life Mastigoteuthis magna: Description of the beaks in 2D Authored by Michael Vecchione and Richard E. Young. 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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