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Onykia aequatorialis (Thiele 1920)

K.S.R. Bolstad
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Containing group: Onykia

Introduction

This specimen was found floating dead at the surface and described by Thiele (1920) as a new species, distinct from the two other then-known species of "Moroteuthis" (M. ingens and M. robusta) based on its size, the rostrum of the gladius, and several other bodily proportions. 

Diagnosis

An Onykia ...

Characteristics

  1. Tentacles 
    1. Unknown - lost in both known specimens (spent females).

  2. Arms
    1. 48-60% ML, with Arms IV distinctly longest.

  3. Head
    1. Lower beak rounded, length and depth approximately equal.
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    Figure.  Lower beak of Onykia aequatorialis Holotype.  Left - left profile view.  Right - left oblique view.  Photographs by K. Bolstad.

  4. Mantle
    1. Epidermis with soft, irregular warts.
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      Figure. Dorsolateral mantle skin of O. aequatorialis Holotype.  Photograph by K. Bolstad.

  5. Fins
    1. Rhomboidal shape, not drawn out into a tail.
    2. Length ~55% of ML.
    3. Width ~70% of ML.

  6. Gladius
    1. Maximum width of vanes ca. 13% of gladius length (to tip of conus).
    2. Extant portion of rostrum ~12% of the ML, oval in cross-section.
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      Click on an image to view larger version & data in a new window
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      Figure. Ventral view, gladius of Onykia aequatorialis. Line drawing by K. Bolstad. 

Comments

Due to previously uncertain deposition of the Holotype, this species has been considered a nomen dubium (Tsuchiya & Okutani 1991).  However, examination of the type has revealed that it is distinct from other known Onykia species.  The beak is readily distinguishable from both O. robsoni and O. ingens.  The shorter rostrum of the gladius and the rhombic (not drawn-out) fins also separate O. aequatorialis from O. robsoni, while oval cross-section of the rostrum of the gladius and the distinctly longest Arms IV separate it from O. ingens.

Both known specimens of this species are spent females.

Other Names for Onykia aequatorialis (Thiele 1920)

References

Thiele, J. 1920. Die Cephalopoden der Deutschen Südpolar Expedition. Deutsche Südpolar Expedition, Zoologie, 16: 433–465, Pl. 53, 54.

Tsuchiya, K.; Okutani, T. 1991. Growth Stages of Moroteuthis robusta (Verrill, 1881) with the Re-evaluation of the Genus. Bulletin of Marine Science 49(1/2): 137–147.

Title Illustrations
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Scientific Name Moroteuthis aequatorialis
Location Equatorial Atlantic, 0°16′ N, 18°07′ W
Specimen Condition Preserved
Sex Female
Life Cycle Stage Spent
View Dorsal
Size 380 mm ML (preserved; 400 mm fresh according to description)
Collection ZMB Holotype Moll.-110000
Type Holotype
Copyright © 2007
About This Page


EOS Research Institute, Auckland University of Technology, New Zealand

Correspondence regarding this page should be directed to K.S.R. Bolstad at

Page: Tree of Life Onykia aequatorialis (Thiele 1920). Authored by K.S.R. Bolstad. The TEXT of this page is licensed under the Creative Commons Attribution 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.

Citing this page:

Bolstad, K.S.R. 2007. Onykia aequatorialis (Thiele 1920). Version 09 July 2007 (under construction). http://tolweb.org/Onykia_aequatorialis/108190/2007.07.09 in The Tree of Life Web Project, http://tolweb.org/

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