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Carboniferous

2007 Schools Wikipedia Selection. Related subjects: Geology and geophysics

   The Carboniferous is a major division of the geologic timescale that
   extends from the end of the Devonian period, about 359.2 Ma (million
   years ago), to the beginning of the Permian period, about 299.0 Ma (
   ICS 2004). As with most older geologic periods, the rock beds that
   define the period's start and end are well identified, but the exact
   dates are uncertain by 5–10 million years. The Carboniferous is named
   for the extensive coal beds of that age found in Western Europe. The
   first third of the Carboniferous is called the Mississippian epoch, and
   the remainder is called the Pennsylvanian. Conifer trees were
   introduced in this important and well-known time period.
                         Paleozoic era
   Cambrian Ordovician Silurian Devonian Carboniferous Permian
                          Carboniferous period
            Mississippian                    Pennsylvanian
   Lower/Early Middle  Upper/Late  Lower/Early  Middle    Upper/Late
   Tournaisian Viséan Serpukhovian Bashkirian  Moscovian Kasimovian |
                                                         Gzhelian

Subdivisions

   The Carboniferous is usually broken into Pennsylvanian (later) and
   Mississippian (earlier) Epochs. The Faunal stages from youngest to
   oldest, together with some of their subdivisions, are:

Late Pennsylvanian Gzhelian (most recent)

     * Noginskian/Virgilian

Late Pennsylvanian Kasimovian

     * Klazminskian
     * Dorogomilovksian/Virgilian
     * Chamovnicheskian/Cantabrian/Missourian
     * Krevyakinskian/Cantabrian/Missourian

Middle Pennsylvanian Moscovian

     * Myachkovskian/Bolsovian/Desmoinesian
     * Podolskian/Desmoinesian
     * Kashirskian/Atokan
     * Vereiskian/Bolsovian/Atokan

Early Pennsylvanian Bashkirian/Morrowan

     * Melekesskian/Duckmantian
     * Cheremshanskian/Langsettian
     * Yeadonian
     * Marsdenian
     * Kinderscoutian

Late Mississippian Serpukhovian

     * Alportian
     * Chokierian/Chesterian/Elvirian
     * Arnsbergian/Elvirian
     * Pendleian

Middle Mississippian Visean

     * Brigantian/St Genevieve/Gasperian/Chesterian
     * Asbian/Meramecian
     * Holkerian/Salem
     * Arundian/Warsaw/Meramecian
     * Chadian/Keokuk/Osagean/Osage

Early Mississippian Tournaisian (oldest)

     * Ivorian/Osagean/Osage
     * Hastarian/Kinderhookian/Chautauquan/Chouteau

Paleogeography

   A global drop in sea level at the end of the Devonian reversed early in
   the Carboniferous; this created the widespread epicontinental seas and
   carbonate depostion of the Mississippian. There was also a drop in
   south polar temperatures; southern Gondwanaland was glaciated
   throughout the period, though it is uncertain if the ice sheets were a
   holdover from the Devonian or not. These conditions apparently had
   little effect in the deep tropics, where lush coal swamps flourished
   within 30 degrees of the northernmost glaciers.

   A mid-Carboniferous drop in sea-level precipitated a major marine
   extinction, one that hit crinoids and ammonites especially hard. This
   sea-level drop and the associated unconformity in North America
   separates the Mississippian from the Pennsylvanian periods.

   The Carboniferous was a time of active mountain-building, as the
   supercontinent Pangea came together. The southern continents remained
   tied together in the supercontinent Gondwana, which collided with North
   America-Europe ( Laurussia) along the present line of eastern North
   America. This continental collision resulted in the Hercynian orogeny
   in Europe, and the Alleghenian orogeny in North America; it also
   extended the newly-uplifted Appalachians southwestward as the Ouachita
   Mountains. In the same time frame, much of present eastern Eurasian
   plate welded itself to Europe along the line of the Ural mountains.
   Most of the Mesozoic supercontinent of Pangea was now assembled,
   although North China (which would collide in the Latest Carboniferous),
   and South China continents were still separated from Laurasia. The Late
   Carboniferous Pangaea was shaped like an "O".

   There were two major oceans in the Carboniferous - Panthalassa and
   Paleo-Tethys, which was inside the "O" in the Carboniferous Pangaea.
   Other minor oceans were shrinking and eventually closed - Rheic Ocean
   (closed by the assembly of South and North America), the small, shallow
   Ural Ocean (which was closed by the collision of Baltica and Siberia
   continents, creating the Ural Mountains) and Proto-Tethys Ocean (closed
   by North China collision with Siberia/ Kazakhstania.

Rocks and coal

   Carboniferous rocks in Europe and eastern North America largely consist
   of a repeated sequence of limestone, sandstone, shale and coal beds,
   known as " cyclothems" in the U.S. and "coal measures" in Britain. In
   North America, the early Carboniferous is largely marine limestone,
   which accounts for the division of the Carboniferous into two periods
   in North American schemes. The Carboniferous coal beds provided much of
   the fuel for power generation during the Industrial Revolution and are
   still of great economic importance.

   The large coal deposits of the Carboniferous primarily owe their
   existence to two factors. The first of these is the appearance of
   bark-bearing trees (and in particular the evolution of the bark fibre
   lignin). The second is the lower sea levels that occurred during the
   Carboniferous as compared to the Devonian period. This allowed for the
   development of extensive lowland swamps and forests in North America
   and Europe. Some hypothesize that large quantities of wood were buried
   during this period because animals and decomposing bacteria had not yet
   evolved that could effectively digest the new lignin. The extensive
   burial of biologically-produced carbon led to a buildup of surplus
   oxygen in the atmosphere; estimates place the peak oxygen content as
   high as 35%, compared to 21% today. This oxygen level probably
   increased wildfire activity, as well as resulted in insect and
   amphibian gigantism--creatures whose size is constrained by respiratory
   systems that are limited in their ability to diffuse oxygen.

   In eastern North America, marine beds are more common in the older part
   of the period than the later part and are almost entirely absent by the
   late Carboniferous. More diverse geology existed elsewhere, of course.
   Marine life is especially rich in crinoids and other echinoderms.
   Brachiopods were abundant. Trilobites became quite uncommon. On land,
   large and diverse plant populations existed. Land vertebrates included
   large amphibians.

Life

Marine Invertebrates

   In the oceans the most important groups are the foraminifera, corals,
   bryozoa, brachiopods, ammonoids, echinoderms (especially crinoids), and
   Chondrichthyes (sharks and their relatives).

   For the first time foraminifera take a prominent part in the marine
   faunas. The large spindle-shaped genus Fusulina and its relatives were
   abundant in what is now Russia, China, Japan, North America; other
   important genera include Valvulina, Endothyra, Archaediscus, and
   Saccammina (the latter common in Britain and Belgium). Some
   Carboniferous genera are still extant.

   The microscopic shells of Radiolaria are found in cherts of this age in
   the Culm of Devonshire and Cornwall, and in Russia, Germany and
   elsewhere.

   Sponges are known from spicules and anchor ropes, and include various
   forms such as the Calcispongea Cotyliscus and Girtycoelia, and the
   unusual colonial glass sponge Titusvillia.

   Both reef-building and solitary corals diversify and flourish; these
   include both rugose (e.g. Canina, Corwenia, Neozaphrentis),
   heterocorals, and tabulate (e.g. Chaetetes, Chladochonus, Michelinia)
   forms.

   Conularids were well represented by Conularia

   Bryozoa are abundant in some regions; the Fenestellids including
   Fenestella, Polypora, and the remarkable Archimedes, so named because
   it is in the shape of an Archimedean screw.

   Brachiopods are also abundant; they include Productids, some of which
   (e.g. Gigantoproductus) reached very large (for brachiopods) size and
   had very thick shells, while others like Chonetes were more
   conservative in form. Athyridids, Spiriferids, Rhynchonellids, are
   Terebratulids are also very common. Inarticulate forms include Discina
   and Crania. Some species and genera had a very wide distribution with
   only minor variations.

   Annelids such as Spirorbis and Serpulites are common fossils in some
   horizons.

   Among the mollusca, the bivalves continue to increase in numbers and
   importance. Typical genera include Aviculopecten, Posidonomya, Nucula,
   Carbonicola, Edmondia, and Modiola

   Conocardium is a common rostroconch.

   Gastropods are also numerous, including the genera Murchisonia,
   Euomphalus, Naticopsis.

   Nautiloid cephalopods are represented by tightly coiled nautilids, with
   straight-shelled and curved-shelled forms becoming increasingly rare.
   Goniatite Ammonoids are common.

   Trilobites are rare, represented only by the proetid group. Ostracods
   such as Cythere, Kirkbya, and Beyrichia are abundant.

   Amongst the echinoderms, the crinoids were the most numerous. Dense
   submarine thickets of long-stemmed crinoids appear to have flourished
   in shallow seas, and their remains were consolidated into thick beds of
   rock. Prominent genera include Cyathocrinus, Woodocrinus, and
   Actinocrinus. Echinoids such as Archaeocidaris and Palaeechinus were
   also present. The Blastoids, which included the Pentreinitidae and
   Codasteridae and superficially resembled crinoids in the possession of
   long stalks attached to the sea-bed, attain their maximum development
   at this time.

Fish

   Many fish inhabited the Carboniferous seas; predominantly Elasmobranchs
   (sharks and their relatives). These included some, like Psammodus, with
   crushing pavement-like teeth adapted for grinding the shells of
   brachiopods, crustaceans, and other marine organisms. Other sharks had
   piercing teeth, such as the Symmoriida; some, the petalodonts, had
   peculiar cycloid cutting teeth. Most of the sharks were marine, but the
   Xenacanthida invaded fresh waters of the coal swamps. Among the bony
   fish, the Palaeonisciformes found in coastal waters also appear to have
   migrated to rivers. Sarcopterygian fish were also prominent, and one
   group, the Rhizodonts, reached very large size.

   Most species of Carboniferous marine fish have been described largely
   from teeth, fin spines and dermal ossicles, with smaller freshwater
   fish preserved whole.

   Freshwater fishes were abundant, and include the genera Ctenodus,
   Uronemus, Acanthodes, Cheirodus, and Gyracanthus.

Plants

   Early Carboniferous land plants were very similar to those of the
   preceding Latest Devonian, but new groups also appeared at this time.

   The main Early Carboniferous plants were the Equisetales (Horse-tails),
   Sphenophyllales (vine-like plants), Lycopodiales (Club mosses),
   Lepidodendrales (scale trees), Filicales (Ferns), Medullosales
   (previously included in the " seed ferns", an artificial assemblage of
   a number of early gymnosperm groups) and the Cordaitales. These
   continued to dominate throughout the period, but during late
   Carboniferous, several other groups, Cycadophyta (cycads), the
   Callistophytales (another group of "seed ferns"), and the Voltziales
   (related to and sometimes included under the conifers), appeared.

   The Carboniferous lycophytes of the order Lepidodendrales, which are
   cousins (but not ancestors) of the tiny club-moss of today, were huge
   trees with trunks 30 meters high and up to 1.5 meters in diameter.
   These included Lepidodendron (with its fruit cone called
   Lepidostrobus), Halonia, Lepidophloios and Sigillaria. The roots of
   several of these forms are known as Stigmaria.

   The fronds of some Carboniferous ferns are almost identical with those
   of living species. Probably many species were epiphytic. Fossil ferns
   and "seed ferns" include Pecopteris, Cyclopteris, Neuropteris,
   Alethopteris, and Sphenopteris; Megaphyton and Caulopteris were tree
   ferns.

   The Equisetales included the common giant form Calamites, with a trunk
   diameter of 30 to 60 cm and a height of up to 20 meters. Sphenophyllum
   was a slender climbing plant with whorls of leaves, which was probably
   related both to the calamites and the lycopods.

   Cordaites, a tall plant (6 to over 30 meters) with strap-like leaves,
   was related to the cycads and conifers; the catkin-like inflorescence,
   which bore yew-like berries, is called Cardiocarpus. These plants were
   thought to live in swamps and mangroves. True coniferous trees (
   Waichia, of the order Voltziales) appear later in the Carboniferous,
   and preferred higher drier ground..

Freshwater and Lagoonal Invertebrates

   Freshwater Carboniferous invertebrates include various bivalve molluscs
   that lived in brackish or fresh water, such as Anthracomya, Naiadiles,
   and Carbonicola; diverse Crustacea such as Bairdia, Carbonia, Estheria,
   Acanthocaris, Dithyrocaris, and Anthrapalaemon.

   The Eurypterids were also diverse, and are represented by such genera
   as Eurypterus, Glyptoscorpius, Anthraconectes, Megarachne (originally
   misinterpreted as a giant spider) and the specialised very large
   Hibbertopterus. Many of these were amphibious.

   Frequently a temporary return of marine conditions resulted in marine
   or brackish water genera such as Lingula, Orbiculoidea, and Productus
   being found in the thin beds known as marine bands.

Terrestrial Invertebrates

   Fossil remains of air-breathing insects, myriapods and arachnids are
   known from the late Carboniferous, but so far not from the early
   Carboniferous. Their diversity when they do appear however show that
   these arthropods were both well developed and numerous. Among the
   insect groups are the Syntonopterodea (relatives of present-day
   mayflies), the abundant and often large sap-sucking
   Palaeodictyopteroidea, the huge predatory Protodonata (griffinflies),
   the diverse herbivorous " Protorthoptera", and numerous basal
   Dictyoptera (ancestors of cockroaches). Many insects have been obtained
   from the coalfields of Saarbruck and Commentry, and from the hollow
   trunks of fossil trees in Nova Scotia. Some British coalfields have
   yielded good specimens: Archaeoptitus, from the Derbyshire coalfield,
   had a spread of wing extending to more 35 cm; some specimens ( Brodia)
   still exhibit traces of brilliant wing colors. In the Nova Scotian tree
   trunks land snails ( Archaeozonites, Dendropupa) have been found.

Tetrapods

   Carboniferous amphibians were diverse and common by the middle of the
   period, more so than they are today; some were as long as 6 meters, and
   those fully terrestrial as adults had scaly skin. They included a
   number of basal tetrapod groups classified in early books under the
   Labyrinthodontia. These had long bodies, a head covered with bony
   plates and generally weak or undeveloped limbs. The largest were over 2
   meters long. They were accompanied by an assemblage of smaller
   amphibians included under the Lepospondyli, often only about 15 cm
   long. Some Carboniferous amphibians were aquatic and lived in rivers (
   Loxomma, Eogyrinus, Proterogyrinus); others may have been semi-aquatic
   ( Ophiderpeton, Amphibamus) or terrestrial ( Dendrerpeton, Hyloplesion,
   Tuditanus, Anthracosaurus).

   One of the greatest evolutionary innovations of the Carboniferous was
   the amniote egg, which allowed for the further exploitation of the land
   by certain tetrapods. These included the earliest Sauropsid reptiles (
   Hylonomus), and the earliest known Synapsida ( Archaeothyris). These
   small lizard-like animals quickly gave rise to many descendants. The
   amniote egg allowed these ancestors of all later birds, mammals, and
   reptiles to reproduce on land by preventing the desiccation, or
   drying-out, of the embryo inside. By the end of the Carboniferous
   period, the reptiles had already diversified into a number of groups,
   including protorothyridids, captorhinids, aeroscelids, and several
   families of pelycosaurs.

Fungal life

   Because plants and animals were growing in size, and abundance in this
   time (ie. Lepidodendron) land fungi diversified further. Marine fungi
   still occupied the oceans.

   This article incorporates text from the Encyclopædia Britannica
   Eleventh Edition, a publication now in the public domain.

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