107-509: The Clydonautilidae are Middle and Upper Triassic nautiloid cephalopods, which are derivatives of the clydonautiloidean family Liroceratidae , that have generally smooth, involute, globular to compressed shells, characterized by a suture with prominent lobes and saddles. The family is known to contain five genera, These are: Of these only Styrionautilus is known from the Middle Triassic. The other four are so far restricted to
214-513: 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). 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
321-474: A grade group that is thought to have given rise to orthoceratoids, ammonoids and coleoids, and are defined by the exclusion of those descendent groups. Both ammonoids and coleoids have traditionally been assumed to have descended from bactritids , which in turn arose from straight-shelled orthoceratoids . The ammonoids appeared early in the Devonian period (some 400 million years ago) and became abundant in
428-417: A few species of the order Proetida . The subsequent end-Devonian extinction , which occurred at around 359 Ma, further impacted the ecosystems and completed the extinction of all calcite sponge reefs and placoderms. Devonian palaeogeography was dominated by the supercontinent Gondwana to the south, the small continent of Siberia to the north, and the medium-sized continent of Laurussia to
535-426: A growth spurt, the rear of the mantle secretes a new septum, adding another chamber to the series of shell chambers. At the same time, shell material is added around the shell opening ( aperture ), enlarging the body chamber and providing more room for the growing animal. Sutures (or suture lines) appear where each septum contacts the wall of the outer shell. In life, they are visible as a series of narrow wavy lines on
642-400: A head with two simple lens-free eyes and arms (or tentacles). They have a smooth shell over a large body chamber, which is divided into subchambers filled with an inert gas (similar to the composition of atmospheric air, but with more nitrogen and less oxygen ) making the animal neutrally buoyant in the water. As many as 90 tentacles are arranged in two circles around the mouth. The animal
749-405: A large external shell, divided into a narrowing chambered region (the phragmocone ) and a broad, open body chamber occupied by the animal in life. The outer wall of the shell, also known as the conch, defines its overall shape and texture. The chambers ( camerae ) of the phragmocone are separated from each other by thin curved walls ( septa ), which formed during growth spurts of the animal. During
856-763: A low-latitude archipelago to the north of Gondwana. They were separated from the southern continent by an oceanic basin: the Paleo-Tethys . Although the western Paleo-Tethys Ocean had existed since the Cambrian, the eastern part only began to rift apart as late as the Silurian. This process accelerated in the Devonian. The eastern branch of the Paleo-Tethys was fully opened when South China and Annamia (a terrane equivalent to most of Indochina ), together as
963-529: A massive extinction event . ( See Late Devonian extinction ). Primitive arthropods co-evolved with this diversified terrestrial vegetation structure. The evolving co-dependence of insects and seed plants that characterized a recognizably modern world had its genesis in the Late Devonian Epoch. The development of soils and plant root systems probably led to changes in the speed and pattern of erosion and sediment deposition. The rapid evolution of
1070-488: A narrower definition of Nautiloidea ( Nautiloidea sensu stricto ), as a singular subclass including only those cephalopods which are closer to living nautiluses than they are to either ammonoids or coleoids. Nautiloids are among the group of animals known as cephalopods , an advanced class of mollusks which also includes ammonoids , belemnites and modern coleoids such as octopus and squid. Other mollusks include gastropods , scaphopods and bivalves . Traditionally,
1177-430: 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 and can help distinguish them from ammonoids. The siphuncle is on the shell periphery in most ammonoids whereas it runs through the center of the chambers in some nautiloids, including living nautiluses. The subclass Nautiloidea, in its broader definition,
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#17327933977671284-420: A range of evidence, such as plant distribution, points to a Late Devonian warming. The climate would have affected the dominant organisms in reefs ; microbes would have been the main reef-forming organisms in warm periods, with corals and stromatoporoid sponges taking the dominant role in cooler times. The warming at the end of the Devonian may even have contributed to the extinction of the stromatoporoids. At
1391-535: 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
1498-417: A smooth shell. The shells are formed of aragonite, although the cameral deposits may consist of primary calcite. The coloration of the shell of the modern nautilus is quite prominent, and, although somewhat rarely, the shell coloration has been known to be preserved in fossil nautiloids. They often show color patterns only on the dorsal side, suggesting that the living animals swam horizontally. Much of what
1605-551: A subclass of its own, Bactritoidea . Recently some workers in the field have come to recognize Dissidocerida as a distinct order, along with Pseudorthocerida, both previously included in Orthocerida as subtaxa. Cladistic approaches are rare in nautiloid systematics. Many nautiloid orders (not to mention the group as a whole) are not monophyletic clades , but rather paraphyletic grades . This means that they include some descendant taxa while excluding others. For example,
1712-664: A terrestrial ecosystem that contained copious animals opened the way for the first vertebrates to seek terrestrial living. By the end of the Devonian, arthropods were solidly established on the land. The Late Devonian extinction is not a single event, but rather is a series of pulsed extinctions at the Givetian-Frasnian boundary, the Frasnian-Famennian boundary, and the Devonian-Carboniferous boundary. Together, these are considered one of
1819-541: A unified continent, detached from the northeastern sector of Gondwana. Nevertheless, they remained close enough to Gondwana that their Devonian fossils were more closely related to Australian species than to north Asian species. Other Asian terranes remained attached to Gondwana, including Sibumasu (western Indochina), Tibet, and the rest of the Cimmerian blocks. While the South China-Annamia continent
1926-602: A volcanically active region during the Devonian, as it continued to assimilate smaller island arcs. The island arcs of the region, such as the Balkhash-West Junggar Arc, exhibited biological endemism as a consequence of their location. Siberia was located just north of the equator as the largest landmass in the Northern Hemisphere. At the beginning of the Devonian, Siberia was inverted (upside down) relative to its modern orientation. Later in
2033-622: A warm temperate climate . In the Late Devonian, by contrast, arid conditions were less prevalent across the world and temperate climates were more common. The Devonian Period is formally broken into Early, Middle and Late subdivisions. The rocks corresponding to those epochs are referred to as belonging to the Lower, Middle and Upper parts of the Devonian System. The Early Devonian lasted from 419.2 to 393.3 Ma. It began with
2140-488: 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. Most of these early forms died out, but a single family, the Ellesmeroceratidae , survived to the early Ordovician , where it ultimately gave rise to all subsequent cephalopods. In
2247-762: Is a geologic period and system of the Paleozoic era during the Phanerozoic eon , spanning 60.3 million years from the end of the preceding Silurian period at 419.2 million years ago ( Ma ), to the beginning of the succeeding Carboniferous period at 358.9 Ma. It is the fourth period of both the Paleozoic and the Phanerozoic. It is named after Devon , South West England , where rocks from this period were first studied. The first significant evolutionary radiation of life on land occurred during
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#17327933977672354-402: Is distinguished from other cephalopods by two main characteristics: the septa are smoothly concave in the forward direction, producing external sutures which are generally simple and smooth. The siphuncle is supported by septal necks which point to the rear (i.e. retrosiphonate) throughout the ontogeny of the animal. Modern nautiluses have deeply coiled shells which are involute, meaning that
2461-578: Is good evidence that Rheic oceanic crust experienced intense subduction and metamorphism under Mexico and Central America. The closure of the eastern part of the Rheic Ocean is associated with the assemblage of central and southern Europe. In the early Paleozoic, much of Europe was still attached to Gondwana, including the terranes of Iberia , Armorica (France), Palaeo-Adria (the western Mediterranean area), Bohemia , Franconia , and Saxothuringia . These continental blocks, collectively known as
2568-574: Is known about the extinct nautiloids is based on what we know about modern nautiluses , such as the chambered nautilus , which is found in the southwest Pacific Ocean from Samoa to the Philippines , and in the Indian Ocean off the coast of Australia . It is not usually found in waters less than 100 meters (328 feet) deep and may be found as far down as 500 to 700 meters (1,640 to 2,300 feet). Nautili are free swimming animals that possess
2675-460: Is most similar to coiled early nautiloids such as the Tarphycerida and Oncocerida. However, these orders diverged from coleoid ancestors in the early Ordovician at the latest, while genetic divergence estimates suggest that Nautilida diverged in the Silurian or Devonian. A more recent phylogenetic study by Lindgren et al. (2004), which supports the monophyly of cephalopods, does not bear on
2782-430: Is observed in many of those plants. Some of the early land plants such as Drepanophycus likely spread by vegetative growth and spores. The earliest land plants such as Cooksonia consisted of leafless, dichotomous axes with terminal sporangia and were generally very short-statured, and grew hardly more than a few centimetres tall. Fossils of Armoricaphyton chateaupannense , about 400 million years old, represent
2889-426: Is predatory, and has jaws which are horny and beak-like, allowing it to feed on crustaceans . 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 animal's death, allowing the empty shell to be carried some distance from where
2996-589: Is the Treatise on Invertebrate Paleontology Part K by Teichert et al. 1964, though new information has rendered this volume outdated and in need of revision. Treatise Part K was based on previous classification schemes by Flower & Kummel (1950) and the Russian Osnovy Paleontologii Vol. 5 (1962) textbook. Other comprehensive taxonomic schemes have been devised by Wade (1988), Teichert (1988), and Shevyrev (2006). Wade (1988) divided
3103-641: The Antler orogeny , which extended into the Carboniferous. Mountain building could also be found in the far northeastern extent of the continent, as minor tropical island arcs and detached Baltic terranes re-join the continent. Deformed remnants of these mountains can still be found on Ellesmere Island and Svalbard . Many of the Devonian collisions in Laurussia produce both mountain chains and foreland basins , which are frequently fossiliferous. Gondwana
3210-646: The Carboniferous and Permian . 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 this exception, only
3317-565: The Frasnian , 382.7 to 372.2 Ma, during which the first forests took shape on land. The first tetrapods appeared in the fossil record in the ensuing Famennian subdivision, the beginning and end of which are marked with extinction events. This lasted until the end of the Devonian, 358.9 Ma. The Devonian was a relatively warm period, although significant glaciers may have existed during the Early and Middle Devonian. The temperature gradient from
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3424-483: The Late Carboniferous . The first ammonites , a subclass of cephalopod molluscs , appeared. Trilobites , brachiopods and the great coral reefs were still common during the Devonian. The Late Devonian extinction , which started about 375 Ma, severely affected marine life, killing off most of the reef systems, most of the jawless fish, half of all placoderms, and nearly all trilobites save for
3531-640: The Lochkovian Stage 419.2 to 410.8 Ma, which was followed by the Pragian from 410.8 to 407.6 Ma and then by the Emsian , which lasted until the Middle Devonian began, 393.3 Ma. During this time, the first ammonoids appeared, descending from bactritoid nautiloids . Ammonoids during this time period were simple and differed little from their nautiloid counterparts. These ammonoids belong to
3638-541: The Mesozoic era , before their extinction at the end of the Cretaceous. 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 to the exclusion of other modern cephalopods. In this restricted definition, membership is somewhat variable between authors, but it usually includes Tarphycerida, Oncocerida, and Nautilida. All nautiloids have
3745-739: 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
3852-475: The cladoxylopsids and progymnosperm Archaeopteris . These tracheophytes were able to grow to large size on dry land because they had evolved the ability to biosynthesize lignin , which gave them physical rigidity and improved the effectiveness of their vascular system while giving them resistance to pathogens and herbivores. In Eifelian age, cladoxylopsid trees formed the first forests in Earth history. By
3959-511: The primary ventral saddle and a deep, asymmetric lateral lobe. Callaionautilus , Cosmonautilus , and Proclydonautulus fall in between. Nautiloidea Nautiloids are a group of marine cephalopods ( Mollusca ) which originated in the Late Cambrian and are represented today by the living Nautilus and Allonautilus . Fossil nautiloids are diverse and species rich, with over 2,500 recorded species. They flourished during
4066-452: The " Big Five " mass extinctions in Earth's history. The Devonian extinction crisis primarily affected the marine community, and selectively affected shallow warm-water organisms rather than cool-water organisms. The most important group to be affected by this extinction event were the reef-builders of the great Devonian reef systems. Amongst the severely affected marine groups were the brachiopods, trilobites, ammonites, and acritarchs , and
4173-710: The Armorican Terrane Assemblage, split away from Gondwana in the Silurian and drifted towards Laurussia through the Devonian. Their collision with Laurussia leads to the beginning of the Variscan Orogeny , a major mountain-building event which would escalate further in the Late Paleozoic. Franconia and Saxothuringia collided with Laurussia near the end of the Early Devonian, pinching out the easternmost Rheic Ocean. The rest of
4280-536: The Armorican terranes followed, and by the end of the Devonian they were fully connected with Laurussia. This sequence of rifting and collision events led to the successive creation and destruction of several small seaways, including the Rheno-Hercynian, Saxo-Thuringian, and Galicia-Moldanubian oceans. Their sediments were eventually compressed and completely buried as Gondwana fully collided with Laurussia in
4387-511: The Carboniferous. Sea levels in the Devonian were generally high. Marine faunas continued to be dominated by conodonts, bryozoans , diverse and abundant brachiopods , the enigmatic hederellids , microconchids , and corals . Lily-like crinoids (animals, their resemblance to flowers notwithstanding) were abundant, and trilobites were still fairly common. Bivalves became commonplace in deep water and outer shelf environments. The first ammonites also appeared during or slightly before
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4494-533: The Devonian Period. The newly evolved forests drew carbon out of the atmosphere, which were then buried into sediments. This may be reflected by a Mid-Devonian cooling of around 5 °C (9 °F). The Late Devonian warmed to levels equivalent to the Early Devonian; while there is no corresponding increase in CO 2 concentrations, continental weathering increases (as predicted by warmer temperatures); further,
4601-408: The Devonian seas. The first abundant genus of cartilaginous fish, Cladoselache , appeared in the oceans during the Devonian Period. The great diversity of fish around at the time has led to the Devonian being given the name "The Age of Fishes" in popular culture. The Devonian saw significant expansion in the diversity of nektonic marine life driven by the abundance of planktonic microorganisms in
4708-645: The Devonian to often be dubbed the Age of Fishes . The armored placoderms began dominating almost every known aquatic environment. In the oceans, cartilaginous fishes such as primitive sharks became more numerous than in the Silurian and Late Ordovician . Tetrapodomorphs , which include the ancestors of all four- limbed vertebrates (i.e. tetrapods ), began diverging from freshwater lobe-finned fish as their more robust and muscled pectoral and pelvic fins gradually evolved into forelimbs and hindlimbs , though they were not fully established for life on land until
4815-434: The Devonian, as free- sporing land plants ( pteridophytes ) began to spread across dry land , forming extensive coal forests which covered the continents. By the middle of the Devonian, several groups of vascular plants had evolved leaves and true roots , and by the end of the period the first seed -bearing plants ( pteridospermatophytes ) appeared. This rapid evolution and colonization process, which had begun during
4922-506: The Early Devonian and the existence of fossils such as Protichnites suggest that amphibious arthropods may have appeared as early as the Cambrian ). By far the largest land organism at the beginning of this period was the enigmatic Prototaxites , which was possibly the fruiting body of an enormous fungus, rolled liverwort mat, or another organism of uncertain affinities that stood more than 8 metres (26 ft) tall, and towered over
5029-471: The Early and Middle Devonian, the west coast of Laurussia was a passive margin with broad coastal waters, deep silty embayments, river deltas and estuaries, found today in Idaho and Nevada . In the Late Devonian, an approaching volcanic island arc reached the steep slope of the continental shelf and began to uplift deep water deposits. This minor collision sparked the start of a mountain-building episode called
5136-431: The Early and Middle Ordovician the nautiloids underwent an evolutionary radiation. Some eight new orders appeared at this time, covering a great diversity of shell types and structure, and ecological lifestyles. 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
5243-637: The Late Devonian the tectonic situation had relaxed and much of South America was covered by shallow seas. These south polar seas hosted a distinctive brachiopod fauna, the Malvinokaffric Realm, which extended eastward to marginal areas now equivalent to South Africa and Antarctica. Malvinokaffric faunas even managed to approach the South Pole via a tongue of Panthalassa which extended into the Paraná Basin . The northern rim of Gondwana
5350-682: The Late Devonian. The Altai-Sayan region was shaken by volcanism in the Early and Middle Devonian, while Late Devonian magmatism was magnified further to produce the Vilyuy Traps , flood basalts which may have contributed to the Late Devonian Mass Extinction. The last major round of volcanism, the Yakutsk Large Igneous Province, continued into the Carboniferous to produce extensive kimberlite deposits. Similar volcanic activity also affected
5457-521: The Palcephalopod/Neocephalopod question, since the only cephalopods included were Nautilus and coleoids. For an in-process revision of Treatise Part K, King & Evans (2019) reclassified nautiloids sensu lato into five subclasses. Major groups were primarily defined by variation in their muscle attachment types. Other traits referenced during this reclassification include protoconch morphology, connecting ring structure, and
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#17327933977675564-505: The Pierre Shale formation of the Cretaceous period in the north-central United States. Specimens of the Ordovician nautiloid Endoceras have been recorded measuring up to 5.7 meters (19 feet) in shell length, and there is a description of a specimen estimated to have reached 9.1 meters (30 feet), although that specimen is reported as destroyed. These large nautiloids would have been formidable predators of other marine animals at
5671-585: The Silurian and Devonian, it decreased across the span of the Devonian, particularly during the Pragian, and that the overall diversity of nektonic taxa did not increase significantly during the Devonian compared to during other geologic periods, and was in fact higher during the intervals spanning from the Wenlock to the Lochkovian and from the Carboniferous to the Permian. The study's authors instead attribute
5778-502: The Silurian, is known as the Silurian-Devonian Terrestrial Revolution . The earliest land animals , predominantly arthropods such as myriapods , arachnids and hexapods , also became well-established early in this period, after beginning their colonization of land at least from the Ordovician period. Fishes , especially jawed fish , reached substantial diversity during this time, leading
5885-551: The Upper Triassic. The five genera in the Clydonautilidae form a sequence of increasing sutural complexity, beginning with Styrionautilus and ending with Clydonautilus . Styrionautilis , which has the simplest suture of the five, has a broad ventral saddle with a flat bottom and a gently curved lateral lobe. Clydonauatilus at the opposite extreme has a secondary ventral saddle within the ventral lobe modifying
5992-456: The ancestors of subsequent stocks; Orthoceratoidea, which unites different primarily orthoconic orders (including the ancestors for Bacritida and Ammonoidea); and Nautilitoidea, which includes the first coiled cephalopods, Tarphycerida, as well as Nautilida, which includes the recent Nautilus . Another order, Bactritida , which is derived from Orthocerida , is sometimes included with Nautiloidea, sometimes with Ammonoidea , and sometimes placed in
6099-426: The animal lived before finally sinking to the seafloor. Nautili 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. Unlike the belemnites and other cephalopods, modern nautili do not have an ink sac, and there is no evidence to suggest that the extinct forms possessed one either. Furthermore, unlike
6206-661: The beginning of the Mississippian subperiod of the Carboniferous. In 19th-century texts the Devonian has been called the "Old Red Age", after the red and brown terrestrial deposits known in the United Kingdom as the Old Red Sandstone in which early fossil discoveries were found. Another common term is "Age of the Fishes", referring to the evolution of several major groups of fish that took place during
6313-408: The cephalopods). Palcephalopoda is meant to correspond to groups which are closer to living nautilus, while Neocephalopoda is meant to correspond to groups closer to living coleoids. One issue which this scheme is the necessity of establishing a firm ancestry for nautilus, to contextualize which cephalopods are closer to which of the two living end members. On the basis of morphological traits, Nautilida
6420-684: The continent (such as Greenland and Ellesmere Island ) established tropical conditions, most of the continent was located within the natural dry zone along the Tropic of Capricorn , which (as nowadays) is a result of the convergence of two great air-masses, the Hadley cell and the Ferrel cell . In these near-deserts, the Old Red Sandstone sedimentary beds formed, made red by the oxidised iron ( hematite ) characteristic of drought conditions. The abundance of red sandstone on continental land also lends Laurussia
6527-548: The continents Laurentia (modern day North America) and Baltica (modern day northern and eastern Europe). The tectonic effects of this collision continued into the Devonian, producing a string of mountain ranges along the southeastern coast of the continent. In present-day eastern North America, the Acadian Orogeny continued to raise the Appalachian Mountains . Further east, the collision also extended
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#17327933977676634-405: The development of OMZs , preventing nautiloids from retreating into deeper water, are also cited as other potential causes of extinction. A consensus on nautiloid classification has traditionally been elusive and subject to change, as different workers emphasize different fundamental traits when reconstructing evolutionary events. The largest and most widely cited publication on nautiloid taxonomy
6741-562: The early Paleozoic era, when they constituted the main predatory animals. Early in their evolution, nautiloids developed an extraordinary diversity of shell shapes, including coiled morphologies and giant straight-shelled forms ( orthocones ). No orthoconic and only a handful of coiled species, the nautiluses , survive to the present day. In a broad sense, "nautiloid" refers to a major cephalopod subclass or collection of subclasses ( Nautiloidea sensu lato ). Nautiloids are typically considered one of three main groups of cephalopods, along with
6848-405: The early Devonian Period around 400 Ma. Bactritoids make their first appearance in the Early Devonian as well; their radiation, along with that of ammonoids, has been attributed by some authors to increased environmental stress resulting from decreasing oxygen levels in the deeper parts of the water column. Among vertebrates, jawless armored fish ( ostracoderms ) declined in diversity, while
6955-662: The east. Major tectonic events include the closure of the Rheic Ocean , the separation of South China from Gondwana, and the resulting expansion of the Paleo-Tethys Ocean . The Devonian experienced several major mountain-building events as Laurussia and Gondwana approached; these include the Acadian Orogeny in North America and the beginning of the Variscan Orogeny in Europe. These early collisions preceded
7062-569: The end of the Devonian, the first seed-forming plants had appeared. This rapid appearance of many plant groups and growth forms has been referred to as the Devonian Explosion or the Silurian-Devonian Terrestrial Revolution. The 'greening' of the continents acted as a carbon sink , and atmospheric concentrations of carbon dioxide may have dropped. This may have cooled the climate and led to
7169-412: The equator to the poles was not as large as it is today. The weather was also very arid, mostly along the equator where it was the driest. Reconstruction of tropical sea surface temperature from conodont apatite implies an average value of 30 °C (86 °F) in the Early Devonian. Early Devonian mean annual surface temperatures were approximately 16 °C. CO 2 levels dropped steeply throughout
7276-423: The extent of cameral and endosiphuncular deposits. While most previous studies referred to subclasses with the suffix '-oidea', these authors instead opted for the suffix '-ia', to prevent confusion between group levels. For example, Nautiloidea sensu stricto was renamed to Nautilia, to differentiate it from the informal broader definition of "nautiloid". In addition, they used the unsimplified names for orders, with
7383-408: The extinct ammonoids (ammonites) and living coleoids (such as squid , octopus , and kin). While ammonoids and coleoids are monophyletic clades with exclusive ancestor-descendant relationships, this is not the case for nautiloids. Instead, nautiloids are a paraphyletic grade of various early-diverging cephalopod lineages, including the ancestors of ammonoids and coleoids. Some authors prefer
7490-430: The extinct ammonoids , the modern nautilus lacks an aptychus , a biomineralized plate which is proposed to act as an operculum which closes the shell to protect the body. However, aptychus-like plates are known from some extinct nautiloids, and they may be homologous to the fleshy hood of a modern nautilus. Nautiloids are often found as fossils in early Palaeozoic rocks (less so in more recent strata). The rocks of
7597-418: The fleshy tube of the siphuncle are structures made of aragonite (a polymorph of calcium carbonate – which during fossilisation is often recrystallized to calcite, a more stable form of calcium carbonate [CaCO 3 ]): 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 ),
7704-459: The formation of the single supercontinent Pangaea in the Late Paleozoic. The period is named after Devon , a county in southwestern England, where a controversial argument in the 1830s over the age and structure of the rocks found throughout the county was resolved by adding the Devonian Period to the geological timescale. The Great Devonian Controversy was a lengthy debate between Roderick Murchison , Adam Sedgwick and Henry De la Beche over
7811-492: The free water column as well as high ecological competition in benthic habitats, which were extremely saturated; this diversification has been labeled the Devonian Nekton Revolution by many researchers. However, other researchers have questioned whether this revolution existed at all; a 2018 study found that although the proportion of biodiversity constituted by nekton increased across the boundary between
7918-744: The increased overall diversity of nekton in the Devonian to a broader, gradual trend of nektonic diversification across the entire Palaeozoic. A now-dry barrier reef, located in present-day Kimberley Basin of northwest Australia , once extended 350 km (220 mi), fringing a Devonian continent. Reefs are generally built by various carbonate -secreting organisms that can erect wave-resistant structures near sea level. Although modern reefs are constructed mainly by corals and calcareous algae , Devonian reefs were either microbial reefs built up mostly by autotrophic cyanobacteria or coral-stromatoporoid reefs built up by coral-like stromatoporoids and tabulate and rugose corals . Microbial reefs dominated under
8025-425: The increasing competition, predation, and diversity of jawed fishes . The shallow, warm, oxygen-depleted waters of Devonian inland lakes, surrounded by primitive plants, provided the environment necessary for certain early fish to develop such essential characteristics as well developed lungs and the ability to crawl out of the water and onto the land for short periods of time. Finally, the Late Devonian started with
8132-403: The jawed fish (gnathostomes) simultaneously increased in both the sea and fresh water . Armored placoderms were numerous during the early ages of the Devonian Period and became extinct in the Late Devonian, perhaps because of competition for food against the other fish species. Early cartilaginous ( Chondrichthyes ) and bony fishes ( Osteichthyes ) also become diverse and played a large role within
8239-481: The land lay under shallow seas, where tropical reef organisms lived. The enormous "world ocean", Panthalassa , occupied much of the Northern Hemisphere as well as wide swathes east of Gondwana and west of Laurussia. Other minor oceans were the Paleo-Tethys Ocean and Rheic Ocean . By the early Devonian, the continent Laurussia (also known as Euramerica ) was fully formed through the collision of
8346-651: The larger and more recent whorls overlap and obscure older whorls. 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 rarely a helical coil (as in Lorieroceras ). Some species' shells—especially in the late Paleozoic and early Mesozoic—are ornamented with spines and ribs, but most have
8453-575: The low, carpet-like vegetation during the early part of the Devonian. Also, the first possible fossils of insects appeared around 416 Ma, in the Early Devonian. Evidence for the earliest tetrapods takes the form of trace fossils in shallow lagoon environments within a marine carbonate platform/shelf during the Middle Devonian, although these traces have been questioned and an interpretation as fish feeding traces ( Piscichnus ) has been advanced. Many Early Devonian plants did not have true roots or leaves like extant plants, although vascular tissue
8560-547: 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 six living species, all belonging to two genera, Nautilus (the pearly nautilus), and Allonautilus . The recent decrease in the once worldwide distribution of nautiloids is now believed to have been caused by
8667-447: The most common classification of the cephalopods has been a four-fold division (by Bather, 1888), into the orthoceratoids , nautiloids, ammonoids , and coleoids . This article is about nautiloids in that broad sense, sometimes called Nautiloidea sensu lato . Cladistically speaking, nautiloids are a paraphyletic assemblage united by shared primitive ( plesiomorphic ) features not found in derived cephalopods. In other words, they are
8774-562: The name "the Old Red Continent". For much of the Devonian, the majority of western Laurussia (North America) was covered by subtropical inland seas which hosted a diverse ecosystem of reefs and marine life. Devonian marine deposits are particularly prevalent in the midwestern and northeastern United States. Devonian reefs also extended along the southeast edge of Laurussia, a coastline now corresponding to southern England , Belgium , and other mid-latitude areas of Europe. In
8881-563: The naming of the period. Murchison and Sedgwick won the debate and named it the Devonian System. While the rock beds that define the start and end of the Devonian Period are well identified, the exact dates are uncertain. According to the International Commission on Stratigraphy , the Devonian extends from the end of the Silurian 419.2 Ma, to the beginning of the Carboniferous 358.9 Ma – in North America , at
8988-411: The nearby microcontinent of Amuria (now Manchuria , Mongolia and their vicinities). Though certainly close to Siberia in the Devonian, the precise location of Amuria is uncertain due to contradictory paleomagnetic data. The Rheic Ocean, which separated Laurussia from Gondwana, was wide at the start of the Devonian, having formed after the drift of Avalonia away from Gondwana. It steadily shrunk as
9095-401: The oldest known plants with woody tissue. By the Middle Devonian, shrub-like forests of primitive plants existed: lycophytes , horsetails , ferns , and progymnosperms evolved. Most of these plants had true roots and leaves, and many were quite tall. The earliest-known trees appeared in the Middle Devonian. These included a lineage of lycopods and another arborescent, woody vascular plant,
9202-703: The order Agoniatitida , which in later epochs evolved to new ammonoid orders, for example Goniatitida and Clymeniida . This class of cephalopod molluscs would dominate the marine fauna until the beginning of the Mesozoic Era. The Middle Devonian comprised two subdivisions: first the Eifelian , which then gave way to the Givetian 387.7 Ma. During this time the jawless agnathan fishes began to decline in diversity in freshwater and marine environments partly due to drastic environmental changes and partly due to
9309-793: The order level (although various isolated families also originated during this diversification event): Plectronocerida Yanhecerida Ellesmerocerida ( paraphyletic to Endoceratoidea, Multiceratoidea, and Orthoceratoidea) Endocerida Bisonocerida Cyrtocerinida Tarphycerida (possibly paraphyletic to Nautilida ) Oncocerida (paraphyletic to Ascocerida and Discosorida) Ascocerida Discosorida Riocerida (possibly paraphyletic to later orthoceratoids) Dissidocerida (paraphyletic to later orthoceratoids) Lituitida Actinocerida Pseudorthocerida Orthocerida (paraphyletic to Bactritida , Ammonoidea , and Coleoidea ) Devonian The Devonian ( / d ə ˈ v oʊ n i . ən , d ɛ -/ də- VOH -nee-ən, deh- )
9416-400: The outer surface of the shell. Like their underlying septa, 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. The septa are perforated by the siphuncle , a fleshy tube which runs through each of the internal chambers of the shell. Surrounding
9523-455: The paraphyletic order Orthocerida includes numerous orthocerids stretching through the Paleozoic, but it excludes colloids, despite colloids having a well-established ancestry among the orthocerids. Interpretations by Engeser (1996–1998) suggests that nautiloids, and indeed cephalopods in general, should be split into two main clades: Palcephalopoda (including all the nautiloids except Orthocerida and Ascocerida) and Neocephalopoda (the rest of
9630-403: The period continued, as the two major continents approached near the equator in the early stages of the assembly of Pangaea . The closure of the Rheic Ocean began in the Devonian and continued into the Carboniferous. As the ocean narrowed, endemic marine faunas of Gondwana and Laurussia combined into a single tropical fauna. The history of the western Rheic Ocean is a subject of debate, but there
9737-472: The period it moved northwards and began to twist clockwise, though it was not near its modern location. Siberia approached the eastern edge of Laurussia as the Devonian progressed, but it was still separated by a seaway, the Ural Ocean . Although Siberia's margins were generally tectonically stable and ecologically productive, rifting and deep mantle plumes impacted the continent with flood basalts during
9844-529: The period. Older literature on the Anglo-Welsh basin divides it into the Downtonian, Dittonian, Breconian, and Farlovian stages, the latter three of which are placed in the Devonian. The Devonian has also erroneously been characterised as a "greenhouse age", due to sampling bias : most of the early Devonian-age discoveries came from the strata of western Europe and eastern North America , which at
9951-613: The rise of the Caledonian Mountains of Great Britain and Scandinavia . As the Caledonian Orogeny wound down in the later part of the period, orogenic collapse facilitated a cluster of granite intrusions in Scotland. Most of Laurussia was located south of the equator, but in the Devonian it moved northwards and began to rotate counterclockwise towards its modern position. While the most northern parts of
10058-581: The same time. Several of the early orders became extinct over that interval, but others rose to prominence. 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
10165-593: The spread of pinnipeds . From the Oligocene onward, the appearance of pinnipeds in the geological record of a region coincides with the disappearance of nautiloids from that region. As a result, nautiloids are now limited to their current distribution in the tropical Indo-Pacific Ocean, where pinnipeds are absent. The genus Aturia seem to have temporarily survive regions where pinnipeds were present through adaptations to fast and agile swimming, but eventually went extinct as well. Predation by short-snouted whales and
10272-447: The subclass Nautiloidea ( sensu lato ) into 6 superorders, incorporating orders that are phylogenetically related. They are: Three of these superorders were established for orders of uncertain placement: Endocerida, Actinocerida, and Discosorida. The other three unite related orders which share a common ancestor and form a branch of the nautiloid taxonomic tree: Plectronoceratoidea, which consists mostly of small Cambrian forms that include
10379-444: The suffix '-atida' rather than the common simplified form, '-ida'. Traditional nautiloid classification schemes emphasize certain character traits over others, potentially involving personal bias as to which traits are worth emphasizing according to different authors. This issue may be resolved by sampling all morphological traits equally through bayesian phylogenetic inference . The first cephalopod-focused paper to use this technique
10486-628: The terminus of the Devonian, Earth rapidly cooled into an icehouse , marking the beginning of the Late Paleozoic icehouse . The Devonian world involved many continents and ocean basins of various sizes. The largest continent, Gondwana , was located entirely within the Southern Hemisphere . It corresponds to modern day South America , Africa , Australia , Antarctica , and India , as well as minor components of North America and Asia . The second-largest continent, Laurussia,
10593-535: The time straddled the Equator as part of the supercontinent of Euramerica where fossil signatures of widespread reefs indicate tropical climates that were warm and moderately humid. In fact the climate in the Devonian differed greatly during its epochs and between geographic regions. For example, during the Early Devonian, arid conditions were prevalent through much of the world including Siberia, Australia, North America, and China, but Africa and South America had
10700-402: The time they lived. In some localities, such as Scandinavia and Morocco , the fossils of orthoconic nautiloids accumulated in such large numbers that they form limestones composed of nonspecific assemblages known as cephalopod beds , cephalopod limestones , nautiloid limestones , or Orthoceras limestones in the geological literature. Although the term Orthoceras now only refers to
10807-521: The warmer conditions of the early and late Devonian, while coral-stromatoporoid reefs dominated during the cooler middle Devonian. By the Devonian Period, life was well underway in its colonization of the land. The moss forests and bacterial and algal mats of the Silurian were joined early in the period by primitive rooted plants that created the first stable soils and harbored arthropods like mites , scorpions , trigonotarbids and myriapods (although arthropods appeared on land much earlier than in
10914-555: The world saw the disappearance of an estimated 96% of vertebrates like conodonts and bony fishes , and all of the ostracoderms and placoderms. Land plants as well as freshwater species, such as our tetrapod ancestors, were relatively unaffected by the Late Devonian extinction event (there is a counterargument that the Devonian extinctions nearly wiped out the tetrapods ). The reasons for the Late Devonian extinctions are still unknown, and all explanations remain speculative. Canadian paleontologist Digby McLaren suggested in 1969 that
11021-680: Was by far the largest continent on the planet. It was completely south of the equator, although the northeastern sector (now Australia) did reach tropical latitudes. The southwestern sector (now South America) was located to the far south, with Brazil situated near the South Pole . The northwestern edge of Gondwana was an active margin for much of the Devonian, and saw the accretion of many smaller land masses and island arcs. These include Chilenia , Cuyania , and Chaitenia , which now form much of Chile and Patagonia . These collisions were associated with volcanic activity and plutons , but by
11128-442: Was mostly a passive margin, hosting extensive marine deposits in areas such as northwest Africa and Tibet . The eastern margin, though warmer than the west, was equally active. Numerous mountain building events and granite and kimberlite intrusions affected areas equivalent to modern day eastern Australia , Tasmania , and Antarctica. Several island microcontinents (which would later coalesce into modern day Asia) stretched over
11235-438: Was northwest of Gondwana, and corresponds to much of modern-day North America and Europe . Various smaller continents, microcontinents , and terranes were present east of Laurussia and north of Gondwana, corresponding to parts of Europe and Asia. The Devonian Period was a time of great tectonic activity, as the major continents of Laurussia and Gondwana drew closer together. Sea levels were high worldwide, and much of
11342-475: Was published by Pohle et al. (2022). They recovered several previously hypothesized groups, though many orders were determined to be paraphyletic. The study was focused on early cephalopod diversification in the Late Cambrian and Ordovician, and did not discuss in detail the origin of post-Ordovician groups. The following is a simplified version of their cladogram , showing early cephalopod relationships to
11449-577: Was the newest addition to the Asian microcontinents, it was not the first. North China and the Tarim Block (now northwesternmost China) were located westward and continued to drift northwards, powering over older oceanic crust in the process. Further west was a small ocean (the Turkestan Ocean), followed by the larger microcontinents of Kazakhstania , Siberia , and Amuria . Kazakhstania was
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