All

extant Extant or Least-concern species, least concern is the opposite of the word extinct. It may refer to: * Extant hereditary titles * Extant literature, surviving literature, such as ''Beowulf'', the oldest extant manuscript written in English * Exta ...

cephalopod A cephalopod is any member of the molluscan Taxonomic rank, class Cephalopoda (Greek language, Greek plural , ; "head-feet") such as a squid, octopus, cuttlefish, or nautilus. These exclusively marine animals are characterized by bilateral symm ...

s have a two-part beak, or

rostrum Rostrum may refer to: * Any kind of a platform for a speaker: **dais **pulpit ** podium * Rostrum (anatomy), a beak, or anatomical structure resembling a beak, as in the mouthparts of many sucking insects * Rostrum (ship), a form of bow on naval ...

, situated in the buccal mass and surrounded by the muscular head appendages. The

dorsal Dorsal (from Latin ''dorsum'' ‘back’) may refer to: * Dorsal (anatomy), an anatomical term of location referring to the back or upper side of an organism or parts of an organism * Dorsal, positioned on top of an aircraft's fuselage The fus ...

(upper)

mandible In jawed vertebrates, the mandible (from the Latin ''mandibula'', 'for chewing'), lower jaw, or jawbone is a bone that makes up the lowerand typically more mobilecomponent of the mouth (the upper jaw being known as the maxilla). The jawbone i ...

fits into the

ventral Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position prov ...

(lower) mandible and together they function in a scissor-like fashion.Young, R.E., M. Vecchione & K.M. Mangold (1999)
Cephalopoda Glossary

Tree of Life Web Project The Tree of Life Web Project (ToL) is an Internet project providing information about the diversity and phylogeny of life on Earth. This collaborative peer reviewed project began in 1995, and is written by biologists from around the world. The s ...

. The beak may also be referred to as the mandibles or jaws.Tanabe, K., Y. Hikida & Y. Iba (2006). Two coleoid jaws from the Upper Cretaceous of Hokkaido, Japan. ''Journal of Paleontology'' 80(1): 138–145. These beaks are different from bird beaks because they crush bone while most bird beaks do not. Fossilized remains of beaks are known from a number of cephalopod-groups, both extant and extinct, including

squid A squid (: squid) is a mollusc with an elongated soft body, large eyes, eight cephalopod limb, arms, and two tentacles in the orders Myopsida, Oegopsida, and Bathyteuthida (though many other molluscs within the broader Neocoleoidea are also ...

s, octopodes,

belemnite Belemnitida (or belemnites) is an extinct order (biology), order of squid-like cephalopods that existed from the Late Triassic to Late Cretaceous (And possibly the Eocene). Unlike squid, belemnites had an internal skeleton that made up the cone ...

s, and vampyromorphs. Aptychi - paired plate-like structures found in

ammonite Ammonoids are extinct, (typically) coiled-shelled cephalopods comprising the subclass Ammonoidea. They are more closely related to living octopuses, squid, and cuttlefish (which comprise the clade Coleoidea) than they are to nautiluses (family N ...

s - may also have been jaw elements.

Composition

Composed primarily of

chitin Chitin (carbon, C8hydrogen, H13oxygen, O5nitrogen, N)n ( ) is a long-chain polymer of N-Acetylglucosamine, ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is the second most abundant polysaccharide in nature (behind only cell ...

and cross-linked

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

s, beaks are more or less indigestible and are often the only identifiable cephalopod remains found in the stomachs of predatory species such as

sperm whale The sperm whale or cachalot (''Physeter macrocephalus'') is the largest of the toothed whales and the largest toothed predator. It is the only living member of the Genus (biology), genus ''Physeter'' and one of three extant species in the s ...

s.Clarke, M.R. (1986). ''A Handbook for the Identification of Cephalopod Beaks''. Oxford University Press, Oxford. Cephalopod beaks gradually become less stiff as one moves from the tip to the base, a gradient that results from differing chemical composition. In hydrated beaks of the

Humboldt squid The Humboldt squid (''Dosidicus gigas''), also known as jumbo squid or jumbo flying squid, is a large, predatory squid living in the eastern Pacific Ocean. It is the Monotypic taxon, only known species of the genus ''Dosidicus'' of the subfamily ...

(''Dosidicus gigas'') this stiffness gradient spans two

orders of magnitude In a ratio scale based on powers of ten, the order of magnitude is a measure of the nearness of two figures. Two numbers are "within an order of magnitude" of each other if their ratio is between 1/10 and 10. In other words, the two numbers are wi ...

Measurements

The abbreviations LRL and URL are commonly used in teuthology to refer to ''lower rostral length'' and ''upper rostral length'', respectively. These are the standard measures of beak-size in Decapodiformes; ''hood length'' is preferred for

Octopodiformes Octopodiformes is a superorder of the subclass Coleoidea, comprising the octopuses and the vampire squid. All living members of Octopodiformes have eight arms, either lacking the two tentacles of squid (as is the case in octopuses) or modifying ...

. They can be used to estimate the mantle length and total body weight of the original animal as well as the total ingested

biomass Biomass is a term used in several contexts: in the context of ecology it means living organisms, and in the context of bioenergy it means matter from recently living (but now dead) organisms. In the latter context, there are variations in how ...

of the species.Gröger, J., U. Piatkowski & H. Heinemann (2000). ''Polar Biology'' 23(1): 70–74.

References

* Aldridge, A.E. (2009). Can beak shape help to research the life history of squid? ''New Zealand Journal of Marine and Freshwater Research'' 43(5): 1061–1067. * Bolstad, K.S. (2006). Sexual dimorphism in the beaks of ''Moroteuthis ingens'' Smith, 1881 (Cephalopoda: Oegopsida: Onychoteuthidae). ''New Zealand Journal of Zoology'' 33(4): 317–327. * Chen, X., H. Lu, B. Liu, Y. Chen, S. Li & M. Jin (2012). Species identification of ''Ommastrephes bartramii'', ''Dosidicus gigas'', ''Sthenoteuthis oualaniensis'' and ''Illex argentinus'' (Ommastrephidae) using beak morphological variables. ''Scientia Marina'' 76(3): 473–481. * Cherel, Y. & K.A. Hobson (2005). Stable isotopes, beaks and predators: a new tool to study the trophic ecology of cephalopods, including giant and colossal squids. ''Proceedings of the Royal Society B: Biological Sciences'' 272(1572): 1601–1607. * Clarke, M.R. & N. MacLeod (1974). Cephalopod remains from a sperm whale caught off Vigo, Spain. ''Journal of the Marine Biological Association of the United Kingdom'' 54(4): 959–968. * Clarke, M.R. & L. Maddock (1988). Beaks of living coleoid Cephalopoda. In: M.R. Clarke & E.R. Trueman (eds.) ''The Mollusca. Volume 12. Paleontology and Neontology of Cephalopods''. Academic Press, San Diego. pp. 121–131. * Clarke, M.R. & R.E. Young (1998). Description and analysis of cephalopod beaks from stomachs of six species of odontocete cetaceans stranded on Hawaiian shores. ''Journal of the Marine Biological Association of the United Kingdom'' 78(2): 623–641. * Hernańdez-García, V., U. Piatkowski & M.R. Clarke (1998). Development of the darkening of ''Todarodes sagittatus'' beaks and its relation to growth and reproduction. ''South African Journal of Marine Science'' 20(1): 363–373. * Hernández-López, J.L. & J.J. Castro-Hernández (2001). ''Fishery Bulletin'' 99(4): 679–684. * Hobson, K.A. & Y. Cherel (2006). Isotopic reconstruction of marine food webs using cephalopod beaks: new insight from captively raised ''Sepia officinalis''. ''Canadian Journal of Zoology'' 84(5): 766–770. * Hsu, C.-C. (2002)
Geomorphometric study of ''Octopus'' and ''Cistopus'' (Cephalopoda: Octopodidae) based on landmarks of beaks
Master's thesis, National Sun Yat-sen University, Kaohsiung, Taiwan. * Ivanovic, M.L. & N.E. Brunetti (1997)
Description of ''Illex argentinus'' beaks and rostral length relationships with size and weight of squids
''Revista de Investigación y Desarrollo Pesquero'' 11: 135–144. * Lalas, C. (2009). Estimates of size for the large octopus ''Macroctopus maorum'' from measures of beaks in prey remains. ''New Zealand Journal of Marine and Freshwater Research'' 43(2): 635–642. * Lefkaditou E. & P. Bekas (2004)
Analysis of beak morphometry of the horned octopus ''Eledone cirrhosa'' (Cephalopoda: Octopoda) in the Thracian Sea (NE Mediterranean)
''Mediterranean Marine Science'' 5(1): 143–149. * Lu, C.C. & R. Ickeringill (2002). ''Museum Victoria Science Reports'' 6: 1–65. * Martínez, P., A. Sanjuan & Á. Guerra (2002). Identification of ''Illex coindetii'', ''I. illecebrosus'' and ''I. argentinus'' (Cephalopoda: Ommastrephidae) throughout the Atlantic Ocean; by body and beak characters. ''Marine Biology'' 141(1): 131–143. * Ogden, R.S., A.L. Allcock, P.C. Watts & J.P. Thorpe (1998). The role of beak shape in octopodid taxonomy. ''South African Journal of Marine Science'' 20(1): 29–36. * Roeleveld, M.A.C. (2000). Giant squid beaks: implications for systematics. ''Journal of the Marine Biological Association of the UK'' 80(1): 185–187. * Uchikawa, K., M. Sakai, T. Wakabayashi & T. Ichii (2009). The relationship between paralarval feeding and morphological changes in the proboscis and beaks of the neon flying squid ''Ommastrephes bartramii''. ''Fisheries Science'' 75(2): 317–323. * Xavier, J.C., M.R. Clarke, M.C. Magalhães, G. Stowasser, C. Blanco & Y. Cherel (2007). ''Arquipélago: Life and Marine Sciences'' 24: 41–48. * Xavier, J.C. & Y. Cherel (2009). British Antarctic Survey, Cambridge. 129 pp. * Xavier, J.C., R.A. Phillips & Y. Cherel (2011). Cephalopods in marine predator diet assessments: why identifying upper and lower beaks is important. ''ICES Journal of Marine Science'' 68(9): 1857–1864. {{Cephalopod anatomy Cephalopod zootomy

Composition

Measurements

References

Further reading