iNautiloids Fossil range: Late Cambrian - Recent
Fossil nautiloid Trilacinoceras from the Ordovician of China
Scientific classification
Kingdom: Animalia Phylum: Mollusca Class: Cephalopoda Subclass: Nautiloidea Agassiz, 1847
Orders
Palcephalopoda The Furongian (which represented approximately the old notions of Late Cambrian, Merioneth, Croixian, or Potsdamian) is the third and final geological epoch of the Cambrian Period. ... Photograph of the fossil nautiloid Trilacinoceras taken by Dlloyd. ... The Ordovician period is the second of the six (seven in North America) periods of the Paleozoic era. ... For other uses, see Scientific classification (disambiguation). ... Phyla Subregnum Parazoa Porifera Subregnum Eumetazoa Placozoa Orthonectida Rhombozoa Radiata (unranked) Ctenophora Cnidaria Bilateria (unranked) Acoelomorpha Myxozoa Superphylum Deuterostomia Chordata Hemichordata Echinodermata Chaetognatha Xenoturbellida Superphylum Ecdysozoa Kinorhyncha Loricifera Priapulida Nematoda Nematomorpha Onychophora Tardigrada Arthropoda Superphylum Platyzoa Platyhelminthes Gastrotricha Rotifera Acanthocephala Gnathostomulida Micrognathozoa Cycliophora Superphylum Lophotrochozoa Sipuncula Nemertea Phoronida Ectoprocta Bryozoa... Classes Caudofoveata Aplacophora Polyplacophora Monoplacophora Bivalvia Scaphopoda Gastropoda Cephalopoda † Rostroconchia † Helcionelloida The molluscs (British spelling) or mollusks (American spelling) are the large and diverse phylum Mollusca, which includes a variety of familiar animals well-known for their decorative shells or as seafood. ... 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) Sepiida Sepiolida Spirulida Teuthida Octopoda Vampyromorphida The cephalopods (Greek plural (kephalópoda); head-foot) are the mollusk class Cephalopoda... Louis Agassiz Jean Louis Rodolphe Agassiz (May 28, 1807-December 14, 1873) was a Swiss-born American zoologist, glaciologist, and geologist, the husband of educator Elizabeth Cabot Cary Agassiz, and one of the first world-class American scientists. ... 1847 was a common year starting on Friday (see link for calendar). ... Scientific classification or biological classification refers to how biologists group and categorize extinct and living species of organisms. ... †Plectronocerida †Ellesmerocerida †Actinocerida †Pseudorthocerida †Endocerida †Tarphycerida †Oncocerida †Discosorida Nautilida Neocephalopoda (in part) families †Proterocameroceratidae †Piloceratidae †Endoceratidae The endocerids were a diverse group of cephalopods that lived during the Middle Ordovician to Late Silurian periods. ... Species Allonautilus perforatus Allonautilus scrobiculatus Nautilus belauensis Nautilus macromphalus Nautilus pompilius pompilius Nautilus pompilius suluensis Nautilus stenomphalus The nautilus is a marine creature of the class Cephalopoda. ... subgroups Order Orthocerida  (in part)† Order Ascocerida† Order Bactritida† Subclass Ammonoidea† Subclass Coleoidea Belemnoidea† Neocoleoidea Synonyms (= Angusteradulata Lehmann 1967) Neocephalopods are a group of cephalopod mollusks that include the coleoids and all extinct species that are more closely related to extant coleoids than to the nautilus. ... †Orthocerida †Ascocerida †Bactritida

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. They flourished during the early Paleozoic era, where they consitituted the main predatory animals, and developed an extraordinary diversity of shell shapes and forms. Some 2,500 species of fossil nautiloids are known, but only a handful of species survive to the present day. Families Orthoceratidae Pseudorthoceratidae and many others Orthocerida are an order of extinct nautiloid cephalopods that lived from the Early Ordovician to the Late Triassic (about 500 to 200 million years ago), but were most common and diverse from the Ordovician to the Devonian. ... Ascocerida is an order of extinct nautiloid cephalopods. ... Bactritida are a small and poorly studied order of more or less straight-shelled (orthocone) nautiloids which first appeared during the Emsian Stage of the Devonian Period (390 my ago) and persisted until the Carnian Stage of the Triassic Period (235 my ago). ... Classes Caudofoveata Aplacophora Polyplacophora Monoplacophora Bivalvia Scaphopoda Gastropoda Cephalopoda † Rostroconchia The mollusks or molluscs are the large and diverse phylum Mollusca, which includes a variety of familiar creatures well-known for their decorative shells or as seafood. ... Genera Allonautilus Nautilus Nautilus (from Greek nautilos, sailor) is the common name of any marine creatures of the cephalopod family Nautilidae, the sole family of the suborder Nautilina. ... The Paleozoic Era is a major division of the geologic timescale, one of four geologic eras. ... An ammonite fossil Eocene fossil fish of the genus Knightia Petrified wood fossil formed through permineralization. ...

Taxonomic relationships

The nautiloids are among the group of animals called the cephalopods (class Cephalopoda), which also includes ammonoids, belemnites and modern coleoids such as octopus and squid. The cephalopods are an advanced class of a larger group of animals called the mollusks (phylum Mollusca), which includes gastropods and bivalves. 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) Sepiida Sepiolida Spirulida Teuthida Octopoda Vampyromorphida The cephalopods (Greek plural (kephalópoda); head-foot) are the mollusk class Cephalopoda... Extinct Orders Aulacocerida Phragmoteuthida Belemnitida Diplobelida Belemnoteuthina 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. ... Orders Aulacocerida (extinct) Hematitida  (extinct) Phragmoteuthida  (extinct) Belemnitida  (extinct) Sepiida Sepiolida Spirulida Teuthida Octopoda Vampyromorphida Subclass Coleoidea is the grouping of cephalopods containing all the primarily soft-bodied creatures. ... Subclasses Eogastropoda (True Limpets and relatives) Orthogastropoda The gastropods, gasteropods, or univalves, are the largest and most successful class of mollusks, with 60,000-75,000 known living species comprising the snails and slugs as well as a vast number of marine and freshwater species. ... Orders Subclass Anomalosdesmata Pholadomyoida Subclass Heterodonta - clams, zebra mussels †Cycloconchidae Hippuritoida †Lyrodesmatidae Myoida †Redoniidae Veneroida Subclass Paleoheterodonta Trigonioida; see Superfamily Trigoniacea Unionoida - freshwater mussels Subclass Protobranchia Nuculoida †Praecardioida Solemyoida Subclass Pteriomorphia - oysters, mussels Arcoida Mytiloida Ostreoida Pterioida Bivalves are mollusks belonging to the class Bivalvia. ...

Traditionally, the most common classification of the cephalopods has been a three-fold division (by Bather, 1888), into the nautiloids, ammonoids, and coleoids. This article is about nautiloids in that broad sense, sometimes called Nautiloidea sensu lato. This article is about the marine animal. ... Orders Sepiida Sepiolida Spirulida Teuthida Octopoda Vampyromorphida Subclass Coleoidea is the grouping of cephalopods containing all the primarily soft-bodied creatures. ...

Cladistically speaking, nautiloids are a paraphyletic assemblage united only by shared primitive (plesiomorphic) features that are not found in other cephalopods. In other words, they are a grade group that gave rise to both ammonoids and coleoids, and are defined by the exclusion of both those descendent groups. Both ammonoids and coleoids are thought to be descended from the bactritids, which in turn arose from straight-shelled orthocerid nautiloids. This cladogram shows the relationship among various insect groups. ... Paraphyletic - Wikipedia /**/ @import /skins-1. ... This cladogram shows the relationship among various insect groups. ... A grade may refer to many different concepts, including: in various contexts: Each item in a (generally ordered and finite) collection of symbols or designators used as a particular grade system to distinguish and rank corresponding groups, where distinct members or instances of each group are regarded as sufficiently similar... Bactritida are a small and poorly studied order of more or less straight-shelled (orthocone) nautiloids which first appeared during the Emsian Stage of the Devonian Period (390 my ago) and persisted until the Carnian Stage of the Triassic Period (235 my ago). ... An orthocone is a usually long straight shell of a nautiloid cephalopod. ... Families Orthoceratidae Pseudorthoceratidae and many others Orthocerida are an order of extinct nautiloid cephalopods that lived from the Early Ordovician to the Late Triassic (about 500 to 200 million years ago), but were most common and diverse from the Ordovician to the Devonian. ...

The ammonoids (a group which includes the ammonites and the goniatites) are extinct cousins of the nautiloids that evolved early in the Devonian period, some 400 million years ago. Also in the Devonian or Early Carboniferous, the bactritids separately gave rise to the first coleoids, in the form of early belemnoids. Hence, all cephalopods living today are descended from Paleozoic nautiloids. This article is about the marine animal. ... Orders and Suborders Order Ammonitida Ammonitina Acanthoceratina Ancyloceratina Phylloceratina Lytoceratina Order Goniatitida Goniatitina Anarcestina Clymeniina Order Ceratitida Ceratitina Prolecanitina Ammonites are an extinct group of marine animals (subclass Ammonoidea) in the phylum Mollusca and class Cephalopoda. ... Families all extinct Goniatites are an extinct group of ammonite, which are related to the nautiloids. ... Disambiguation: Devonian is sometimes used to refer to the Southwestern Brythonic language, and the people of the county of Devon are sometimes referred to as Devonians The Devonian is a geologic period of the Paleozoic era. ... The Carboniferous is a major division of the geologic timescale that extends from the end of the Devonian period, about 359. ... Extinct Orders Aulacocerida Phragmoteuthida Belemnitida Diplobelida Belemnoteuthina 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. ... The Paleozoic Era is a major division of the geologic timescale, one of four geologic eras. ...

Some workers apply the name Nautiloidea to a more exclusive group, called Nautiloidea sensu stricto. This taxon consists only of those orders that are clearly related to the modern nautilus. The membership assigned varies somewhat from author to author, but usually includes Tarphycerida, Oncocerida, and Nautilida.

Characteristics

There are three key features which are common to the shells of the nautiloids. These are the internal chambers, the siphuncle and the sutures of the shell, features that are also found in the shells of all ammonoids. The siphuncle is a strand of tissue passing longitudinally through the shell of a cephalopod mollusk. ...

The thin walls between the internal chambers (camerae) of the shell are called the septa. As the nautiloid grew, it would detach its body from the walls of the shell, move forward, and secrete a new septum behind it. Each septum added created a new camera in the shell. The body of the animal itself occupied the last chamber of the shell - the living chamber. Camerae (sing. ... Septa (sing. ... The body chamber, also called the living chamber, is the outermost or last chamber in the shell of a nautiloid or ammonoid cephalopod. ...

The septa were perforated by the siphuncle, which ran through each of the internal chambers of the shell. Surrounding the fleshy tube of the siphuncle were structures made of calcium carbonate: septal necks and connecting rings. Some of the earlier nautiloids deposited calcium carbonate in the empty chambers (called cameral deposits) or within the siphuncle (endosiphuncular deposits), a process which may have been connected with controlling buoyancy. The nature of the siphuncle and its position within the shell are important in classifying nautiloids. Calcium carbonate is a chemical compound, with chemical formula CaCO3. ... // In physics, buoyancy is the upward force on an object arising from the displacement of the fluid (i. ...

Sutures (or suture lines) are visible as a series of narrow wavy lines on the surface of the shell, and they appear where each septa contacts the wall of the outer shell. The sutures of the nautiloids are simple in shape, being either straight or slightly curved. This is different from the "zigzag" sutures of the goniatites and the highly complex sutures of the ammonites.

Modern nautiloids

Much of what is known about the extinct nautiloids is based on what we know about the modern nautiluses, such as the Chambered Nautilus which is found in the south west Pacific Ocean, from Samoa to the Philippines, and the in the Indian Ocean off of the coast of Australia. It is not usually found in waters less than 100 meters deep and may be found as far down as 500 to 700 meters (2,300 feet). Binomial name Nautilus pompilius Linnaeus, 1758 Subspecies Nautilus pompilius pompilius Linnaeus, 1758 Nautilus pompilius suluensis Habe & Okutani, 1988 Synonyms Nautilus repertus Iredale, 1944 The Chambered Nautilus (Nautilus pompilius) is the best known species of nautilus. ...

Nautiluses are free swimming animals that possess a head with two well developed eyes, arms (or tentacles). They each have a smooth shell, with a large body chamber, which is divided into chambers that are filled with an inert gas (similar to air but with more nitrogen and less oxygen) making the animal buoyant in the water. As many as 90 tentacles are arranged in two circles around their mouth. The animal has jaws which are horny and beak-like, and it is a predator, feeding mainly on crustaceans. General Name, Symbol, Number nitrogen, N, 7 Chemical series nonmetals Group, Period, Block 15, 2, p Appearance colorless Atomic mass 14. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Atomic mass 15. ... 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 plants. ... Classes & Subclasses Branchiopoda Phyllopoda Sarsostraca Remipedia Cephalocarida Maxillopoda Thecostraca Tantulocarida Branchiura Pentastomida Mystacocarida Copepoda Ostracoda Myodocopa Podocopa Malacostraca Phyllocarida Hoplocarida Eumalacostraca The crustaceans (Crustacea) are a large group of arthropods, comprising approximately 52,000 described species [1], and are usually treated as a subphylum [2].They include various familiar animals...

Empty nautilus shells may drift a considerable distance and have been reported from Japan, India and Africa. Undoubtedy the same applies to the shells of fossil nautiloids, the gas inside the shell keeping it buoyant for some time after the animals death so that the empty shell was carried some distance from where the animal lived before it finally sank to the sea-floor. A world map showing the continent of Africa. ... An ammonite fossil Eocene fossil fish of the genus Knightia Petrified wood fossil formed through permineralization. ...

Nautiluses propel themselves by jet propulsion, expelling water from an elongated funnel called the hyponome, which can be pointed in different directions to control their movement. They do not have an ink sac like that found in belemnites and some of the other cephalopods, and there is no evidence to suggest that the extinct forms possessed an ink sac either. Unlike the extinct ammonoids, the modern nautiluses lack any sort of plate for closing their shell. With one exception, no such plate has been found in any of the extinct nautiloids either. The hyponome is the organ used by cephalopods for locomotion. ...

The coloration of the shell of the modern nautiluses is quite prominent, and, although it is somewhat rare, the shell coloration has been known to be preserved in fossil nautiloids. They often show color patterns on the dorsal side only, which suggests the living animals swam horizontally. In anatomy, the dorsum is the upper or back side of an animal, as opposed to the ventrum. ...

Fossil record

Nautiloids are often found as fossils in early Palaeozoic rocks (less so in more recent strata). The shells of fossil nautiloids may be either straight (i.e., orthoconic as in Orthoceras and Rayonnoceras), curved (as in Cyrtoceras) coiled (as in Cenoceras), or a hellical coil (as in Lorieroceras). Some shells are ornamented with spines and ribs, but most have a smooth shell. An ammonite fossil Eocene fossil fish of the genus Knightia Petrified wood fossil formed through permineralization. ... The Palaeozoic is a major division of the geologic timescale, one of four geologic eras. ... An orthocone is a usually long straight shell of a nautiloid cephalopod. ... Binomial name Orthoceras regulare (Schlotheim, 1820) Orthoceras (straight horn) is a genus of extinct cephalopod. ... Species all extinct Rayonnoceras is a genus of extinct cephalopod of the order Actinoceratida and that lived around 325 million years ago, during Ordovician to Carboniferous times. ...

The rocks of the Ordovician period in the Baltic coast and parts of the United States contain a variety of nautiloid fossils, and specimens such as Discitoceras and Rayonnoceras may be found in the limestones of the Carboniferous period in Ireland. The marine rocks of the Jurassic period in Britain often yield specimens of Cenoceras, and nautiloids such as Eutrephoceras are also found in the Pierre Shale formation of the Cretaceous period in the midwestern part of the United States. The Ordovician period is the second of the six (seven in North America) periods of the Paleozoic era. ... The Baltic Sea is located in Northern Europe, from 53°N to 66°N latitude and from 20°E to 26°E longitude. ... Limey shale overlaid by limestone. ... The Carboniferous is a major division of the geologic timescale that extends from the end of the Devonian period, about 359. ... // The image above is believed to be a replaceable fair use image. ... The Cretaceous Period is one of the major divisions of the geologic timescale, reaching from the end of the Jurassic Period (i. ...

Specimens of the Ordovician nautiloid Endoceras have been recorded measuring up to 3.5 meters (13 feet) in length. These large nautiloids must have been formidable predators of other marine animals at the time they lived. The Ordovician period is the second of the six (seven in North America) periods of the Paleozoic era. ... The Endoceroids were a diverse group of cephalopods that lived during the Middle Ordovician to Late Silurian periods. ...

In some localities, such as Scandinavia and Morocco, the fossils of orthoconic nautiloids accumulated in such large numbers that they form Orthoceras limestones. Although the term Orthoceras now only refers to a Baltic coast Ordovician genus, in prior times it was employed as a general name given to all straight-shelled nautiloids that lived from the Ordovician to the Triassic periods (but were most common in the early Paleozoic era. For other uses, see Scandinavia (disambiguation). ... An ammonite fossil Eocene fossil fish of the genus Knightia Petrified wood fossil formed through permineralization. ... An orthocone is a usually long straight shell of a nautiloid cephalopod. ... Binomial name Orthoceras regulare (Schlotheim, 1820) Orthoceras (straight horn) is a genus of extinct cephalopod. ... The Baltic Sea is located in Northern Europe, from 53°N to 66°N latitude and from 20°E to 26°E longitude. ... The Ordovician period is the second of the six (seven in North America) periods of the Paleozoic era. ... An orthocone is a usually long straight shell of a nautiloid cephalopods. ... The Triassic is a geologic period that extends from about 251 to 200 Ma (million years ago). ... The Paleozoic Era is a major division of the geologic timescale, one of four geologic eras. ...

Evolutionary history

Nautiloids are first known from the late Cambrian Fengshan Formation of northeastern China, where they seem to have been quite diverse (at the time this was a warm shallow sea rich in marine life). However, although four orders have been proposed from the 131 species named, there is no certainty that all of these are valid, and indeed it is likely that these taxa are seriously oversplit. In biology, a species is one of the basic units of biodiversity. ...

Most of these early forms died out, but a single family, the Ellesmeroceratidae, survived to the early Ordivician, where it ultimately gave rise to all subsequent cephalopods. In the Early and Middle Ordovician the nautiloids underwent an evolutionary radiation, perhaps due to the new ecological niches made available by the extinction of anomalocarids at the end of the Cambrian. Some eight new orders appeared at this time, covering a great diversity of shell types and structure, and ecological lifestyles. Subphyla and Classes Anomalocaridae - Anomalocarids, extinct     Genus Anomalocaris     Genus Laggania     Genus Parapeytoia Opabinidae - Extinct     Genus Opabinia Unclassified anomalocarid-like specimens     Genus Kerygmachela     Genus Pambdelurion Anomalocarids (meaning odd shrimp) are a group of very early marine animals known from fossils found in Cambrian deposits in China, North America, and Australia. ...

Nautiloids remained at the height of their range of adaptations and variety of forms throughout the Ordovician, Silurian, and Devonian periods, with various straight, curved and coiled shell forms coexisting at the same time. Several of the early orders became extinct over that interval, but others rose to prominence. The Silurian is a major division of the geologic timescale that extends from the end of the Ordovician period, about 443. ... Disambiguation: Devonian is sometimes used to refer to the Southwestern Brythonic language, and the people of the county of Devon are sometimes referred to as Devonians The Devonian is a geologic period of the Paleozoic era. ...

Nautiloids began to decline in the Devonian, perhaps due to competition with their descendants and relatives the Ammonoids and Coleoids, with only the Nautilida holding their own (and indeed increasing in diversity). Their shells became increasingly tightly coiled, while both numbers and variety of non-Nautilid species continued to decrease throughout the Carboniferous and Permian. Orders Sepiida Sepiolida Spirulida Teuthida Octopoda Vampyromorphida Subclass Coleoidea is the grouping of cephalopods containing all the primarily soft-bodied creatures. ... Species Allonautilus perforatus Allonautilus scrobiculatus Nautilus belauensis Nautilus macromphalus Nautilus pompilius pompilius Nautilus pompilius suluensis Nautilus stenomphalus The nautilus is a marine creature of the class Cephalopoda. ... The Carboniferous is a major division of the geologic timescale that extends from the end of the Devonian period, about 359. ... The Permian is a geologic period that extends from about 299. ...

The massive extinctions at the end of the Permian were less damaging to nautiloids than to other taxa and a few groups survived into the early Mesozoic, including pseudorthocerids, bactritids, nautilids and possibly orthocerids. The last straight-shelled forms were long thought to have disappeared at the end of the Triassic, but a possible orthocerid has been found in Cretaceous rocks. Apart from that exception, only a single nautiloid suborder, the Nautilina, continued throughout the Mesozoic, where they co-existed quite happily with their more specialised ammonoid cousins. Most of these forms differed only slightly from the modern nautilus. They had a brief resurgence in the early Tertiary (perhaps filling the niches vacated by the ammonoids in the end Cretaceous extinction), and maintained a worldwide distribution up until the middle of the Cenozoic Era. With the global cooling of the Miocene and Pliocene, their geographic distribution shrank and these hardy and long-lived animals declined in diversity again. Today there are only five living species, all belonging to two genera, Nautilus (the pearly nautilus), and Allonautilus. A taxon (plural taxa), or taxonomic unit, is a grouping of organisms (named or unnamed). ... The Mesozoic Era is one of three geologic eras of the Phanerozoic eon. ... Bactritida are a small and poorly studied order of more or less straight-shelled (orthocone) nautiloids which first appeared during the Emsian Stage of the Devonian Period (390 my ago) and persisted until the Carnian Stage of the Triassic Period (235 my ago). ... Families Orthoceratidae Pseudorthoceratidae and many others Orthocerida are an order of extinct nautiloid cephalopods that lived from the Early Ordovician to the Late Triassic (about 500 to 200 million years ago), but were most common and diverse from the Ordovician to the Devonian. ... The Triassic is a geologic period that extends from about 251 to 200 Ma (million years ago). ... The Cretaceous Period is one of the major divisions of the geologic timescale, reaching from the end of the Jurassic Period (i. ... Genera Allonautilus Nautilus Nautilus (from Greek nautilos, sailor) is the common name of any marine creatures of the cephalopod family Nautilidae, the sole family of the suborder Nautilina. ... The Mesozoic Era is one of three geologic eras of the Phanerozoic eon. ... For other uses, see Tertiary (disambiguation). ... Badlands near Drumheller, Alberta where erosion has exposed the KT boundary. ... The Cenozoic Era (sen-oh-ZOH-ik; sometimes Caenozoic Era in the United Kingdom) meaning new life (Greek kainos = new + zoe = life) is the most recent of the three classic geological eras. ... Global cooling is a theory positing an overall cooling of the Earth and perhaps the commencement of glaciation. ... The Miocene epoch is a period of time that extends from about 23 to 5. ... The Pliocene epoch (spelled Pleiocene in some older texts) is the period in the geologic timescale that extends from 5. ... Genera Allonautilus Nautilus Nautilus (from Greek nautilos, sailor) is the common name of any marine creatures of the cephalopod family Nautilidae, the sole family of the suborder Nautilina. ... Species Allonautilus perforatus Allonautilus scrobiculatus (type) The genus Allonautilus contains two species of nautiluses, which differ significantly in terms of morphology from those placed in the sister taxon Nautilus. ...

Classification

The following 1988 classification by Curt Teichert, updates the 1964 version in the Treatise on Invertebrate Paleontology, and is based mostly on shell structure (Teichert 1988, p.19). 1988 (MCMLXXXVIII) was a leap year starting on Friday of the Gregorian calendar. ... 1964 (MCMLXIV) was a leap year starting on Wednesday (the link is to a full 1964 calendar). ... The Treatise on Invertebrate Paleontology, published by the Geological Society of America and the University of Kansas Press, is a definitive multi-authored work of some 50 volumes, written by more than 300 authors, and covering every phylum, class, order, family, and genus of fossil and extant (still living) invertebrate...

Subclass Orthoceratoidea Kuhn, 1940

Order Plectronocerida Flower, 1964 (Cambrian)

Order Yanhecerida Chen & Qi, 1979 (Cambrian)

?Order Protactinocerida Chen & Qi, 1979 (Cambrian)

Order Ellesmerocerida Flower, 1950

Suborder Ellesmerocerina Flower, 1950 (Cambrian to Ordovician)

Suborder Cyrtocerina Flower, 1964 (Ordovician)

Order Orthocerida Kuhn, 1940 (Ordovician to Triassic)

Order Ascocerida Kuhn, 1949 (Ordovician to Silurian)

Subclass Actinoceratoidea Teichert, 1933

Order Actinocerida Teichert, 1933 (Ordovician to Carboniferous)

Subclass Endoceratoidea Teichert, 1933

Order Endocerida Teichert, 1933 (Ordovician to Silurian)

?Order Injetocerida Balashov, 1960 (Ordovician)

Subclass Nautiloidea Agassiz, 1847

Order Tarphycerida Flower, 1950

Suborder Tarphycerina Flower, 1950 (Ordovician to Silurian)

Suborder Barrandeocerina Flower (Ordovician to Devonian)

Order Oncocerida Flower, 1950 (Ordovician to Carboniferous)

Order Discosorida Flower, 1950 (Ordovician to Devonian)

Order Nautilida Agassiz, 1847

Suborder Rutocerina Shimanskiy, 1957 (Devonian to Triassic)

Suborder Lirocerina Shimanskiy, 1957 (Carboniferous to Triassic)

Suborder Nautilina Agassiz, 1847 (Triassic to Recent)

A further order, Bactritida, are sometimes considered nautiloids close to the Orthocerida, sometimes very primitive ammonoids, and sometimes placed in a subclass of their own, called Bactritoidea. Bactritida are a small and poorly studied order of more or less straight-shelled (orthocone) nautiloids which first appeared during the Emsian Stage of the Devonian Period (390 my ago) and persisted until the Carnian Stage of the Triassic Period (235 my ago). ... Families Orthoceratidae Pseudorthoceratidae and many others Orthocerida are an order of extinct nautiloid cephalopods that lived from the Early Ordovician to the Late Triassic (about 500 to 200 million years ago), but were most common and diverse from the Ordovician to the Devonian. ... This article is about the marine animal. ...

Since 1988, two other orders have gained recognition by some workers: the Pseudorthocerida and the Dissidocerida, both previously included in the Orthocerida. 1988 (MCMLXXXVIII) was a leap year starting on Friday of the Gregorian calendar. ... Families Orthoceratidae Pseudorthoceratidae and many others Orthocerida are an order of extinct nautiloid cephalopods that lived from the Early Ordovician to the Late Triassic (about 500 to 200 million years ago), but were most common and diverse from the Ordovician to the Devonian. ...

A more recent interpretation by Theo Engeser (Engeser 1997-1998) suggests that nautiloids, and indeed cephalopods in general, fall into two main groups, the Palcephalopoda (including all the nautiloids except Orthocerida and Ascocerida) and the Neocephalopoda (the rest of the cephalopods). subgroups Order Orthocerida  (in part)† Order Ascocerida† Order Bactritida† Subclass Ammonoidea† Subclass Coleoidea Belemnoidea† Neocoleoidea Synonyms (= Angusteradulata Lehmann 1967) Neocephalopods are a group of cephalopod mollusks that include the coleoids and all extinct species that are more closely related to extant coleoids than to the nautilus. ...

References

• Doguzhaeva, Larisa. (1994) An Early Cretaceous orthocerid cephalopod from north-western Caucasus. Palaeontology 37(4): 889-899.
• Engeser, T., (1997-1998) The Palcephalopoda/Neocephalopoda Hypothesis
• Teichert, C. (1988) "Main Features of Cehalopod Evolution", in The Mollusca vol.12, Paleontology and Neontology of Cephalopods, ed. by M.R. Clarke & E.R. Trueman, Academic Press, Harcourt Brace Jovanovich,

External links

• Nautiloids: The First Cephalopods (TONMO.com)
• The Fossil Nautiloidea Page
• Palaeos
• Articles on various cephalopod topics for non-specialists
• CephBase: Nautiloidea

See also

• Ammonoidea
• Belemnoidea
• Lituites