Cephalopods Fossil range: Late Cambrian - Recent
A variety of cephalopod forms from Ernst Haeckel's 1904 Kunstformen der Natur. The Cambrian is a geologic period and system that began about Ma (million years ago at the end of the Proterozoic eon and ended about Ma with Ernst Heinrich Philipp August Haeckel ( February 16, 1834 — August 9, 1919)also written von Haeckel, was an eminent German Kunstformen der Natur ( German: Art Forms of Nature) is a book of lithographic and Autotype prints by German biologist
Scientific classification
Kingdom: Animalia Phylum: Mollusca Class: Cephalopoda Cuvier, 1797
Orders
Subclass Nautiloidea †Plectronocerida †Ellesmerocerida †Actinocerida †Pseudorthocerida †Endocerida †Tarphycerida †Oncocerida †Discosorida Nautilida †Orthocerida †Ascocerida †Bactritida Subclass †Ammonoidea †Goniatitida †Ceratitida †Ammonitida Subclass Coleoidea †Belemnoidea †Aulacocerida †Belemnitida †Hematitida †Phragmoteuthida Neocoleoidea (most living cephalopods) ?†Boletzkyida Sepiida Sepiolida Spirulida Teuthida Octopoda Vampyromorphida

The cephalopods (Greek plural Κεφαλόποδα (kephalópoda); "head-foot") are the mollusc class Cephalopoda characterized by bilateral body symmetry, a prominent head, and a modification of the mollusk foot, a muscular hydrostat, into the form of arms or tentacles. Molluscs are animals belonging to the phylum Mollusca. There are around 250000 extant Species within the phylum with an estimated 70000 Baron Georges Léopold Chrétien Frédéric Dagobert Cuvier ( August 23 1769 &ndash May 13, 1832) was a French naturalist Year 1797 ( MDCCXCVII) was a Common year starting on Sunday (link will display the full calendar of the Gregorian calendar (or a Common This article is about the taxonomic rank for the sequence of species in a taxonomic list see Taxonomic order In scientific classification used Nautiloids are a group of marine Mollusks in the subclass Nautiloidea, which all possess an external shell the best-known example being the modern Nautiluses The primitive and ancestral Plectronoceratidae are included in the suborder Plectronoceratina (Flower R The Ellesmerocerida comprise early Nautiloid cephalopods from the late Upper Cambrian (Trempealeauan and Ordovician that are typically rather small with close The endocerids were a diverse group of Cephalopods that lived from the Early Ordovician possibly to the Late Silurian. The Oncocerida comprise a diverse group of generally small nautiloid cephalopods known from the Middle Ordovician to the Mississippian (early Carboniferous) united by Discosorida is a unique order of Cephalopods that lived from the beginning of the Middle Ordovician, through the Silurian, and into the Devonian Nautilida is an order of mostly prehistoric Cephalopods that includes the modern Nautiluses and their immediate ancestors and relatives Orthocerida are an order of extinct Nautiloid Cephalopods that lived from the Early Ordovician (about 500 million years ago to the Late Permian Ascocerida is an order of extinct Nautiloid Cephalopods The shell slightly exogastrical is morphologically very reduced The Bactritida form a small order of more or less straight-shelled (orthoconic Cephalopods that first appeared during the Emsian Stage of the Devonian Ammonites are an extinct group of marine animals of the subclass Ammonoidea in the class Cephalopoda phylum Goniatites are an extinct group of ammonoid, which are shelled Cephalopods related to Squids Belemnites Octopuses Ceratitida is an order belonging to the extinct Cephalopod subclass Ammonoidea. Ammonites are an extinct group of marine animals of the subclass Ammonoidea in the class Cephalopoda phylum Subclass Coleoidea is the grouping of Cephalopods containing all the primarily soft-bodied creatures Belemnites (or belemnoids are an extinct group of marine Cephalopod, very similar in many ways to the modern Squid and closely related to the modern Cuttlefish Aulacocerida is an extinct order of Belemnoids Boletzkyida is an order of Cephalopods Cuttlefish are marine animals of the order Sepiida belonging to the Cephalopoda class (which also includes Squid, Octopuses Bobtail squid (order Sepiolida) are a group of Cephalopods closely related to Cuttlefish. Spirulida is an order of Cephalopods comprising one extant species and several extinct taxa. Squid are marine Cephalopods of the order Teuthida, which comprises around 300 species The Vampyromorphida is an order of Cephalopods comprising one extant species ( Vampyroteuthis infernalis) and several extinct Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly Molluscs are animals belonging to the phylum Mollusca. There are around 250000 extant Species within the phylum with an estimated 70000 A class is the Taxonomic rank in the Biological classification of organisms in Biology below phylum and above order. "Bilateral symmetry" redirects here For bilateral symmetry in mathematics see Reflection symmetry. A muscular hydrostat is a biological structure found in Animals It is used to manipulate items (including food or to move its host about and consists mainly of Muscles In Anatomy, an arm is one of the Upper limbs of an animal The term arm can also be used for analogous structures such as one of the paired upper limbs Tentacles can refer to the elongated flexible organs that are present in some animals especially Invertebrates and sometimes to the hairs of the leaves of some insectivorous Teuthology, a branch of malacology, is the study of cephalopods. Malacology is the branch of Invertebrate Zoology which deals with the study of Mollusks the second-largest Phylum of animals in terms of described

The class contains two extant subclasses. Extant is a term commonly used to refer to Taxa (such as Species, genera or families) that are still in existence (living A class is the Taxonomic rank in the Biological classification of organisms in Biology below phylum and above order. In the Coleoidea, the mollusk shell has been internalized or is absent; this subclass includes the octopuses, squid, and cuttlefish. Subclass Coleoidea is the grouping of Cephalopods containing all the primarily soft-bodied creatures The Squid are marine Cephalopods of the order Teuthida, which comprises around 300 species Cuttlefish are marine animals of the order Sepiida belonging to the Cephalopoda class (which also includes Squid, Octopuses In the Nautiloidea the shell remains; this subclass includes the nautilus. Nautiloids are a group of marine Mollusks in the subclass Nautiloidea, which all possess an external shell the best-known example being the modern Nautiluses Nautilus (from Greek ναυτίλος, 'sailor' is the common name of any marine creatures of the Cephalopod family Nautilidae, the sole There are around 786 distinct living species of Cephalopods. In Biology, a species is one of the basic units of Biological classification and a Taxonomic rank. Two important extinct taxa are Ammonoidea, the ammonites, and Belemnoidea, the belemnites. A taxon (plural taxa) or taxonomic unit, is a name designating an organism or a group of Organisms In Biological nomenclature according to Ammonites are an extinct group of marine animals of the subclass Ammonoidea in the class Cephalopoda phylum Belemnites (or belemnoids are an extinct group of marine Cephalopod, very similar in many ways to the modern Squid and closely related to the modern Cuttlefish

Cephalopods are found in all the oceans of Earth, at all depths. An ocean (from Greek, ''Okeanos'' (Oceanus) is a major body of saline water, and a principal component of the Hydrosphere. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 None of them can tolerate freshwater, but a few species tolerate more or less brackish water. Freshwater is a word that refers to bodies of water such as Ponds lakes rivers and streams containing low concentrations of dissolved Salts and other Total dissolved

Contents 1 Number of species 2 Nervous system and behaviour 3 Circulatory system 4 Locomotion 5 Reproduction and life cycle 6 Evolution 7 Classification 7.1 Shevyrev classification 7.2 Cladistic classification 8 See also 9 Notes 10 References 11 External links

Number of species

There are still discoveries of new species of cephalopods:

• 1998 - 703 recent species ^[1]
• 2001 - 786 recent species ^[2]
• 2004 - approximate guess, from 1000 to 1200 species ^[3]

There are many more fossil species. Year 1998 ( MCMXCVIII) was a Common year starting on Thursday (link will display full 1998 Gregorian calendar) Year 2001 ( MMI) was a Common year starting on Monday according to the Gregorian calendar. "MMIV" redirects here For the Modest Mouse album see " Baron von Bullshit Rides Again " It is estimated there are around 11,000 extinct taxa. A taxon (plural taxa) or taxonomic unit, is a name designating an organism or a group of Organisms In Biological nomenclature according to ^[4]

Nervous system and behaviour

See also: Cephalopod intelligence

Cephalopods are widely regarded as the most intelligent of the invertebrates and have well developed senses and large brains; larger than the brains of gastropods or bivalves. The cephalopod class of Mollusks, particularly the Coleoidea subclass ( Cuttlefish, Squid and Octopuses, are considered the most An invertebrate is an Animal lacking a Vertebral column. The group includes 98% of all animal Species — all animals except those in the Chordate The brain is the center of the Nervous system in animals All Vertebrates and the majority of Invertebrates have a brain The class Gastropoda or the gastropods, also previously known as gasteropods, or univalves, and more commonly known as Snails Bivalves are Molluscs belonging to the class Bivalvia. They have two-part shells and typically both valves are symmetrical along the hinge line Except nautiluses, cephalopods have special skin cells called chromatophores that change color and are used for communication and camouflage. Nautilus (from Greek ναυτίλος, 'sailor' is the common name of any marine creatures of the Cephalopod family Nautilidae, the sole Chromatophores are pigment -containing and light-reflecting cells found in Amphibians Fish, Reptiles Crustaceans and Camouflage is a method of cryptic or concealing coloration that allows an otherwise visible Organism The nervous system of cephalopods is the most complex of the invertebrates. The nervous system is a Network of specialized cells that communicate information about an animal's surroundings and itself The giant nerve fibers of the cephalopod mantle have been a favorite experimental material of neurophysiologists for many years; their large diameter (due to lack of myelination) makes them easier to study. A nerve is an enclosed cable-like bundle of peripheral Axons (the long slender projections of Neurons. The mantle is an important part of the anatomy of Molluscs It is the dorsal body wall which covers the visceral mass Neurophysiology (from Greek grc νεῦρον neuron, "nerve" grc φύσις physis, "nature origin" and grc -λογία Myelin is an electrically-insulating Dielectric Phospholipid layer that surrounds only the Axons of many Neurons It is an outgrowth

Cephalopod vision is acute, and training experiments have shown that the Common Octopus can distinguish the brightness, size, shape, and horizontal or vertical orientation of objects. The Common Octopus ( Octopus vulgaris) is the most studied of all Octopus species Cephalopods' eyes are also sensitive to the plane of polarization of light. Polarization ( ''Brit'' polarisation) is a property of Waves that describes the orientation of their oscillations Surprisingly in light of their ability to change color, most are probably color blind. Color blindness, a Color vision deficiency is the inability to perceive differences between some of the Colors that others can distinguish ^[5] When camouflaging themselves, they use their chromatophores to change brightness and pattern according to the background they see, but their ability to match the specific color of a background probably comes from cells such as iridophores and leucophores that reflect light from the environment. Chromatophores are pigment -containing and light-reflecting cells found in Amphibians Fish, Reptiles Crustaceans and Chromatophores are pigment -containing and light-reflecting cells found in Amphibians Fish, Reptiles Crustaceans and ^[6] Evidence of color vision has been found in only one species, the Sparkling Enope Squid. Color vision is the capacity of an organism or machine to distinguish objects based on the Wavelengths (or frequencies) of the Light they reflect or emit The Sparkling Enope Squid ( Watasenia scintillans) also known as the Firefly Squid, is a member of the class Cephalopoda, subclass Coleoidea ^[5]

Circulatory system

Cephalopods are the only molluscs with a closed circulatory system. They have two gill hearts (also known as branchial hearts) that move blood through the capillaries of the gills. The heart is a muscular organ in all Vertebrates responsible for pumping Blood through the Blood vessels by repeated rhythmic A gill is an anatomical structure found in many aquatic organisms A single systemic heart then pumps the oxygenated blood through the rest of the body. ^[7]

Like most molluscs, cephalopods use hemocyanin, a copper-containing protein, rather than hemoglobin to transport oxygen. Hemocyanins (also spelled haemocyanins) are respiratory Proteins in the form of Metalloproteins containing two Copper atoms that reversibly Hemoglobin ( also spelled haemoglobin and abbreviated Hb or Hgb) is the Iron -containing Oxygen -transport Metalloprotein As a result, their blood is colorless when deoxygenated and turns blue when exposed to air. ^[8]

Locomotion

Cephalopods move primarily by jet propulsion, a very energy-consuming way to travel compared to the tail propulsion used by fish. See also Jet (nozzle A jet is a coherent stream of fluid that is projected into a surrounding medium usually from some kind of a nozzle or aperture The relative efficiency of jet propulsion degrades with larger animals. This is probably why many species prefer to use their fins or arms for locomotion if possible. Oxygenated water is taken into the mantle cavity to the gills and through muscular contraction of this cavity, the spent water is expelled through the hyponome, created by a fold in the mantle. The mantle is an important part of the anatomy of Molluscs It is the dorsal body wall which covers the visceral mass A gill is an anatomical structure found in many aquatic organisms The hyponome or siphon is the organ used by Cephalopods for locomotion Motion of the cephalopods is usually backward as water is forced out anteriorly through the hyponome, but direction can be controlled somewhat by pointing it in different directions. (Campbell, Reece, & Mitchell, p. 612)

Some octopus species are also able to walk along the sea bed. Squids and cuttlefish can move short distances in any direction by rippling of a flap of muscle around the mantle. Muscle (from Latin musculus, diminutive of mus "mouse" is contractile tissue of the body and is derived from the

Reproduction and life cycle

With a few exceptions, Coleoidea live short lives with rapid growth. Most of the energy extracted from their food is used for growing. The penis in most male Coleoidea is a long and muscular end of the gonoduct used to transfer spermatophores to a modified arm called a hectocotylus. A hectocotylus is one of the arms of the male of most kinds of Cephalopods that is modified in various ways to effect the fertilization of the female's eggs That in turn is used to transfer the spermatophores to the female. In species where the hectocotylus is missing, the penis is long and able to extend beyond the mantle cavity and transfers the spermatophores directly to the female. They tend towards a semelparous reproduction strategy; they lay many small eggs in one batch and die afterwards. Reproduction is the Biological process by which new individual Organisms are produced The Nautiloidea, on the other hand, stick to iteroparity; they produce a few large eggs in each batch and live for a long time. Reproduction is the Biological process by which new individual Organisms are produced

Evolution

The class developed during the Late Cambrian, and were during the Paleozoic and Mesozoic dominant and diverse marine life forms. The Cambrian is a geologic period and system that began about Ma (million years ago at the end of the Proterozoic eon and ended about Ma with The Paleozoic or Palaeozoic Era (from the Greek palaio (παλαιο "old" and zoe (ζωη "life" meaning "ancient life" The Mesozoic Era is one of three geologic eras of the Phanerozoic eon. Small shelly fossils such as Tommotia were previously interpreted as early cephalopods, but today these tiny fossils are recognized as sclerites of larger animals. Tommotia is a Small shelly fossil from the Early Cambrian Period A sclerite ( Greek skleros meaning " hard " is a hardened body part ^[9] Hence, the earliest cephalopod known is Plectronoceras from the Late Cambrian Period. Early cephalopods were at the top of the food chain.

The ancient (cohort Belemnoidea) and modern (cohort Neocoleoidea) coleoids, as well as the ammonoids, all diverged from the external shelled nautiloid during the middle Paleozoic Era, between 450 and 300 million years ago. Ammonites are an extinct group of marine animals of the subclass Ammonoidea in the class Cephalopoda phylum Nautiloids are a group of marine Mollusks in the subclass Nautiloidea, which all possess an external shell the best-known example being the modern Nautiluses Unlike most modern cephalopods, most ancient varieties had protective shells. These shells at first were conical but later developed into curved nautiloid shapes seen in modern nautilus species. Nautilus (from Greek ναυτίλος, 'sailor' is the common name of any marine creatures of the Cephalopod family Nautilidae, the sole However, some of the straight-shelled nautiloids evolved into belemnites, out of which some evolved into squid and cuttlefish, and others died off. Nautiloids are a group of marine Mollusks in the subclass Nautiloidea, which all possess an external shell the best-known example being the modern Nautiluses Belemnites (or belemnoids are an extinct group of marine Cephalopod, very similar in many ways to the modern Squid and closely related to the modern Cuttlefish Squid are marine Cephalopods of the order Teuthida, which comprises around 300 species Cuttlefish are marine animals of the order Sepiida belonging to the Cephalopoda class (which also includes Squid, Octopuses Internal shells still exist in many non-shelled living cephalopod groups but most truly shelled cephalopods, such as the ammonites, became extinct at the end of the Cretaceous. The Cretaceous (kriːˈteɪʃəs, usually abbreviated 'K' for its German translation "Kreide" is a geologic period and system, reaching from the end of

Classification

The classification as listed here (and on other cephalopod articles) follows largely from Current Classification of Recent Cephalopoda (May 2001), plus fossil groups from several sources. The Common Cuttlefish or European Common Cuttlefish ( Sepia officinalis) is one of the largest and best known Cuttlefish species The Atlantic Bobtail ( Sepiola atlantica) is a species of Bobtail squid native to the northeastern Atlantic Ocean (65ºN to 35ºN from Iceland The European Squid ( Loligo vulgaris) is a large Squid belonging to the family Loliginidae. The Common Octopus ( Octopus vulgaris) is the most studied of all Octopus species The three subclasses are traditional, corresponding to the three orders of cephalopods recognized by Bather (1888b). Parentheses indicate extinct groups.

Class Cephalopoda

• Subclass Nautiloidea: all cephalopods except ammonoids and coleoids
  • (Order Plectronocerida): the ancestral cephalopods from the Cambrian Period
  • (Order Ellesmerocerida): include the ancestors of all later cephalopods
  • (Order Endocerida)
  • (Order Actinocerida)
  • (Order Discosorida)
  • (Order Pseudorthocerida)
  • (Order Tarphycerida)
  • (Order Oncocerida)
  • Order Nautilida: nautilus and its fossil relatives
  • (Order Orthocerida)
  • (Order Ascocerida)
  • (Order Bactritida): include the ancestors of ammonoids and coleoids
• (Subclass Ammonoidea): extinct ammonites and kin
  • (Order Goniatitida)
  • (Order Ceratitida)
  • (Order Ammonitida): the true ammonites
• Subclass Coleoidea
  • (Cohort Belemnoidea): extinct belemnites and kin
    • (Genus Jeletzkya)
    • (Order Aulacocerida)
    • (Order Phragmoteuthida)
    • (Order Hematitida)
    • (Order Belemnitida)
  • Cohort Neocoleoidea
    • Superorder Decapodiformes (also known as Decabrachia or Decembranchiata)
      • (?Order Boletzkyida)
      • Order Spirulida: Ram's Horn Squid
      • Order Sepiida: cuttlefish
      • Order Sepiolida: pygmy, bobtail and bottletail squid
      • Order Teuthida: squid
    • Superorder Octopodiformes (also known as Vampyropoda)
      • Order Vampyromorphida: Vampire Squid
      • Order Octopoda: octopus

Other classifications differ, primarily in how the various decapod orders are related, and whether they should be orders or families. Nautiloids are a group of marine Mollusks in the subclass Nautiloidea, which all possess an external shell the best-known example being the modern Nautiluses The primitive and ancestral Plectronoceratidae are included in the suborder Plectronoceratina (Flower R The Cambrian is a geologic period and system that began about Ma (million years ago at the end of the Proterozoic eon and ended about Ma with The Ellesmerocerida comprise early Nautiloid cephalopods from the late Upper Cambrian (Trempealeauan and Ordovician that are typically rather small with close The endocerids were a diverse group of Cephalopods that lived from the Early Ordovician possibly to the Late Silurian. Discosorida is a unique order of Cephalopods that lived from the beginning of the Middle Ordovician, through the Silurian, and into the Devonian The Oncocerida comprise a diverse group of generally small nautiloid cephalopods known from the Middle Ordovician to the Mississippian (early Carboniferous) united by Nautilida is an order of mostly prehistoric Cephalopods that includes the modern Nautiluses and their immediate ancestors and relatives Orthocerida are an order of extinct Nautiloid Cephalopods that lived from the Early Ordovician (about 500 million years ago to the Late Permian Ascocerida is an order of extinct Nautiloid Cephalopods The shell slightly exogastrical is morphologically very reduced The Bactritida form a small order of more or less straight-shelled (orthoconic Cephalopods that first appeared during the Emsian Stage of the Devonian Ammonites are an extinct group of marine animals of the subclass Ammonoidea in the class Cephalopoda phylum Goniatites are an extinct group of ammonoid, which are shelled Cephalopods related to Squids Belemnites Octopuses Ceratitida is an order belonging to the extinct Cephalopod subclass Ammonoidea. Ammonites are an extinct group of marine animals of the subclass Ammonoidea in the class Cephalopoda phylum Subclass Coleoidea is the grouping of Cephalopods containing all the primarily soft-bodied creatures Belemnites (or belemnoids are an extinct group of marine Cephalopod, very similar in many ways to the modern Squid and closely related to the modern Cuttlefish Aulacocerida is an extinct order of Belemnoids Decapodiformes is a Superorder of Cephalopoda, which includes all species with ten limbs the name derives from the Greek word meaning ten feet Boletzkyida is an order of Cephalopods Spirulida is an order of Cephalopods comprising one extant species and several extinct taxa. Cuttlefish are marine animals of the order Sepiida belonging to the Cephalopoda class (which also includes Squid, Octopuses Bobtail squid (order Sepiolida) are a group of Cephalopods closely related to Cuttlefish. Squid are marine Cephalopods of the order Teuthida, which comprises around 300 species Octopodiformes is a superorder of the subclass Coleoidea. It comprises the Octopuses and the Vampire squid. Vampyromorphida is an order of Cephalopods comprising one extant species ( Vampyroteuthis infernalis) and several extinct The Decapodiformes is a Superorder of Cephalopoda, which includes all species with ten limbs the name derives from the Greek word meaning ten feet

Shevyrev classification

Shevyrev (2005) suggested a division into eight subclasses, mostly comprising the more diverse and numerous fossil forms.

Class Cephalopoda Cuvier 1795

• Subclass Ellesmeroceratoidea Flower 1950
• Subclass Endoceratoidea Teichert, 1933
• Subclass Actinoceratoidea Teichert, 1933
• Subclass Nautiloidea Agassiz, 1847
• Subclass Orthoceratoidea Kuhn, 1940
• Subclass Bactritoidea Shimansky, 1951
• Subclass Ammonoidea Zittel, 1884
• Subclass Coleoidea Bather, 1888

The first mention of Coleoidea appears in (Bather, 1888a) among this article's references.

Cladistic classification

Another recent system divides all cephalopods into two clades. A clade is a taxonomic group comprising a single Common ancestor and all the descendants of that ancestor One includes nautilus and most fossil nautiloids. The other clade (Neocephalopoda or Angusteradulata) is closer to modern coleoids, and includes belemnoids, ammonoids, and many orthocerid families. Neocephalopods are a group of Cephalopod Mollusks that include the Coleoids and all extinct species that are more closely related to extant Orthocerida are an order of extinct Nautiloid Cephalopods that lived from the Early Ordovician (about 500 million years ago to the Late Permian There are also stem group cephalopods of the traditional Ellesmerocerida that belong to neither clade (Berthold & Engeser, 1987; Engeser 1997). The Ellesmerocerida comprise early Nautiloid cephalopods from the late Upper Cambrian (Trempealeauan and Ordovician that are typically rather small with close

See also

• Cephalopod intelligence
• Cephalopod size
• Kraken

Notes

References

• Bather, F. A. 1888a. Shell-growth in Cephalopoda (Siphonopoda). Annals and Magazine of Natural History, Series 6, Vol. 1: 298-310
• Bather, F. A. 1888b. Professor Blake and Shell-Growth in Cephalopoda. Annals and Magazine of Natural History. Series 6, Vol. 1: 421-426.
• Berthold, Thomas, & Engeser, Theo. 1987. Phylogenetic analysis and systematization of the Cephalopoda (Mollusca). Verhandlungen Naturwissenschaftlichen Vereins in Hamburg. (NF) 29: 187-220.
• Engeser (1997). Fossil Nautiloidea Page. Archived from the original on 2006-09-25. Year 2006 ( MMVI) was a Common year starting on Sunday of the Gregorian calendar. Events 303 - On a voyage preaching the Gospel, Saint Fermin of Pamplona is beheaded in Amiens, France
• Felley, J. , Vecchione, M. , Roper, C. F. E. , Sweeney, M. & Christensen, T. , 2001-2003: Current Classification of Recent Cephalopoda. internet: National Museum of Natural History: Department of Systematic Biology: Invertebrate Zoology: http://www.mnh.si.edu/cephs/
• Shevyrev, A. A. 2005. The Cephalopod Macrosystem: A Historical Review, the Present State of Knowledge, and Unsolved Problems: 1. Major Features and Overall Classification of Cephalopod Mollusks. Paleontological Journal. 39(6):606-614. Translated from Paleontologicheskii Zhurnal No. 6, 2005, 33-42.
• Campbell, Neil A. , Reece, Jane B. , and Mitchell, Lawrence G. : Biology, fifth edition. Addison Wesley Longman, Inc. Menlo Park, California. 1999 ISBN 0-8053-6566-4

External links

• CephBase - cephalopod database
• TONMO.COM - The Octopus News Magazine Online - cephalopod articles and discussion
• Tree of Life Web Project - Cephalopoda
• Mikko's Phylogeny Tree
• Fish vs. Cephalopods
• Will Fast Growing Squid Replace Slow Growing Fish?
• Biomineralisation in modern and fossil cephalopods
• Cephalopods

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