Cephalopod Beak Terminology and Measurements

Richard E. Young, Malcolm Clarke, Michael Vecchione, and Katharina M. Mangold (1922-2003)




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: or 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.

***Add: Posterior pigment of the HM; Bridge Continuum. Hood+

General Measurements

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 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


Definitions and measurements based on Clarke (1986).


Clarke, M. R. 1986. A Handbook for the Identification of Cephalopod Beaks. Clarendon Press, Oxford. 273 pp.

About This Page

University of Hawaii, Honolulu, HI, USA

Retired, formerly at the Marine Biological Association, UK

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

Katharina M. Mangold (1922-2003)
Laboratoire Arago, Banyuls-Sur-Mer, France

Page: Tree of Life Cephalopod Beak Terminology and Measurements Authored by Richard E. Young, Malcolm Clarke, Michael Vecchione, and Katharina M. Mangold (1922-2003). 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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