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Encyclopedia > Graptolite

Graptolites (Graptolithina) are fossil colonial animals known chiefly from the Upper Cambrian through the Mississippian (Lower Carboniferous). A possible early graptolite, Chaunograptus, is known from the Middle Cambrian. Phyla Subregnum Parazoa Porifera (sponges) Subregnum Agnotozoa Placozoa (trichoplax) Orthonectida (orthonectids) Rhombozoa (dicyemids) Subregnum Eumetazoa Radiata (unranked) (radial symmetry) Ctenophora (comb jellies) Cnidaria (coral, jellyfish, anemones) Bilateria (unranked) (bilateral symmetry) Acoelomorpha (basal) Myxozoa (slime animals) Superphylum Deuterostomia (blastopore becomes anus) Chordata (vertebrates, etc. ... The Cambrian is a major division of the geologic timescale that begins about 542 Ma (million years ago) at the end of the Proterozoic eon and ended about 488. ... This article is about the geologic period; for the North American culture, see Mississippian culture. ... The Carboniferous is a major division of the geologic timescale that extends from the end of the Devonian period, about 359. ...


The name graptolite comes from the Greek graptos, meaning "written", and lithos, meaning "rock", as many graptolite fossils resemble hieroglyphics written on the rock. Linnaeus originally regarded them as 'pictures resembling fossils rather than true fossils', though later workers supposed them to be related to the hydrozoans. A hieroglyph is one part of an ideographic writing system that is often found carved in stone. ... Orders Actinulida Capitata Chondrophora Filifera Hydroida Siphonophora Trachylina Organisms that are in Class Hydrozoa come from the Phylum Cnidaria. ...

Contents


Taxonomy

The name originates from the genus Graptolithus, which was used by Linneus in 1735 for inorganic mineralizations and crustations which resembled actual fossils. In 1768, in the 12th volume of Systema Naturae, he included G. sagittarius and G. scalaris, respectively a possible plant fossil and a possible graptolite. His 1751 Skånska Resa, he included a figure of a "fossil or graptolite of a strange kind" currently thought to be a type of Climacograptus (a genus of biserial graptolites). Later workers used the name to refer to a specific group of organisms. Graptolithus was officially abandoned in 1954 by the ICZN, partly because of its original purpose as a grouping for inorganic mimicries of fossils. (Bulman, 1970: V 6)


Since the 1970s, as a result of advances in electron microscopy, graptolites have generally been thought to be most closely allied to the pterobranchs, a rare group of modern marine animals belonging to the phylum Hemichordata (hemichordates). Comparisons are drawn with the modern hemichordates Cephalodiscus and Rhabdopleura. Cephalodiscus numbers about 18 species, and was first discovered in 1882. Pterobranchia is a zoological group established by Ray Lankester in 1877. ... Classes Enterepneusta Pterobranchia Planctosphaeroidea Hemichordata is a phylum of worm-shaped marine deuterostome animals, generally considered the sister group of our own, the chordates. ... Classes Enterepneusta Pterobranchia Planctosphaeroidea Hemichordata is a phylum of deuterostome animals, generally considered the sister group of our own, the chordates. ... 1882 (MDCCCLXXXII) was a common year starting on Sunday (see link for calendar) of the Gregorian calendar or a common year starting on Tuesday of the 12-day slower Julian calendar. ...


Graptolites as zone fossils

Graptolites are common fossils and have a worldwide distribution. They are important index fossils for dating Palaeozoic rocks as they evolved rapidly with time and formed many different species. British geologists can divide the rocks of the Ordovician and Silurian periods into graptolite biozones; these are generally less than one million years in duration. It has been suggested that Fossil record be merged into this article or section. ... Index fossils (or zone fossils) are fossils used to define and identify geologic periods (or faunal stages). ... The Palaeozoic is a major division of the geologic timescale, one of four geologic eras. ... The Ordovician period is the second of the six (seven in North America) periods of the Paleozoic era. ... The Silurian is a major division of the geologic timescale that extends from the end of the Ordovician period, about 443. ...


Morphology

Fossil graptolite Tetragraptus fruticosus from the Ordovician of Australia
Fossil graptolite Tetragraptus fruticosus from the Ordovician of Australia

Each graptolite colony is known as a rhabdosome and has a variable number of branches (called stipes) originating from an initial individual (called a sicula). Each subsequent individual (zooid) was housed within a tubular or cup-like structure (called a theca). The number of branches and the arrangement of the thecae are important features in the identification of graptolite fossils. Photograph of the fossil graptolite Tetragraptus taken by Dlloyd. ... Photograph of the fossil graptolite Tetragraptus taken by Dlloyd. ...


Most of the dendritic or many-branched types are classified as dendroid graptolites (order Dendroidea). They appear earlier in the fossil record (in the Cambrian period), and were generally benthic animals (attached to the sea-floor by a root-like base). Graptolites with relatively few branches were derived from the dendroid graptolites at the beginning of the Ordovician period. This latter type (order Graptoloidea) were pelagic, drifting freely on the surface of ancient seas or attached to floating seaweed by means of a slender thread. They were a successful and prolific group, being the most important animal members of the plankton until they died out in the early part of the Devonian period. The dendroid graptolites survived until the Carboniferous period. The Ordovician period is the second of the six (seven in North America) periods of the Paleozoic era. ... Seaweed-covered rocks in the UK Biologists, specifically marine biologists, consider seaweed to be any of a large number of marine benthic algae that are multicellular, macrothallic, and thus differentiated from most algae that tend to be microscopic in size [1]. Many phycologists prefer the term marine macroalgae over seaweeds... 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. ...


Preservation

Graptolite fossils are often found in shales and slates where sea-bed fossils are rare, this type of rock having formed from sediment deposited in relatively deep water that had poor bottom circulation, was deficient in oxygen, and had no scavengers. The dead planktonic graptolites, having sunk to the sea-floor, would eventually become entombed in the sediment and are thus well preserved. Shale Shale is a fine-grained sedimentary rock whose original constituents were clays or muds. ... Slate Slate is a fine-grained, homogeneous, metamorphic rock derived from an original sedimentary rock composed of clay or volcanic ash through low grade regional metamorphism. ... Sediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of water or other liquid. ... General Name, Symbol, Number oxygen, O, 8 Chemical series Nonmetals, chalcogens Group, Period, Block 16, 2, p Appearance transparent (gas) very pale blue (liquid) Atomic mass 15. ...


Graptolites are also found in limestones and cherts, but generally these rocks were deposited in conditions which were unfavorable for bottom-dwelling life, including scavengers, and undoubtedly most graptolite remains were generally eaten by other animals. Limey shale overlaid by limestone. ... Chert Chert is a fine-grained silica-rich cryptocrystalline sedimentary rock that may contain small fossils. ...


Graptolite fossils are often found flattened along the bedding plane of the rocks in which they occur, though may be found in three dimensions when they are infilled by iron pyrite. They vary in shape, but are most commonly dendritic or branching (such as Dictoyonema), saw-blade like, or "tuning fork" shaped (such as Didymograptus murchisoni). Their remains may be mistaken for fossil plants by the casual observer. The mineral pyrite, or iron pyrite, is iron disulfide, FeS2. ... The term Dendrite stems from the Greek word dendron (literally “tree”), and typically refers to the branched projections of a neuron that act to conduct the electrical stimulation received from other cells to and from the cell body, or soma of the neuron from which the dendrites project. ... Divisions Green algae Chlorophyta Charophyta Land plants (embryophytes) Non-vascular plants (bryophytes) Marchantiophyta - liverworts Anthocerotophyta - hornworts Bryophyta - mosses Vascular plants (tracheophytes) Lycopodiophyta - clubmosses Equisetophyta - horsetails Pteridophyta - true ferns Psilotophyta - whisk ferns Ophioglossophyta - adderstongues Seed plants (spermatophytes) †Pteridospermatophyta - seed ferns Pinophyta - conifers Cycadophyta - cycads Ginkgophyta - ginkgo Gnetophyta - gnetae Magnoliophyta - flowering plants...


Graptolites are normally preserved as a black carbonized film on the rock's surface or as light grey clay films in tectonically distorted rocks. They may be sometimes difficult to see, but by slanting the specimen to the light they reveal themselves as a shiny marking. Pyritized graptolite fossils are also found. General Name, Symbol, Number carbon, C, 6 Chemical series nonmetals Group, Period, Block 14, 2, p Appearance black (graphite) colorless (diamond) Atomic mass 12. ... ... The mineral pyrite, or iron pyrite, is iron disulfide, FeS2. ...


A well known locality for graptolite fossils in the United Kingdom is Abereiddy Bay, Dyfed, Wales where they occur in rocks from the Ordovician period. Dyfed was one of the ancient kingdoms (or principalities) of Wales prior to the Norman Conquest. ... Motto: (Welsh for Wales for ever) Anthem: Hen Wlad Fy Nhadau Capital Cardiff Largest city Cardiff Official language(s) English, Welsh Government Constitutional monarchy  - Queen Queen Elizabeth II  - Prime Minister Tony Blair MP  - First Minister Rhodri Morgan AM Unification    - by Gruffudd ap Llywelyn 1056  Area    - Total 20,779 km² (3rd...


References

Bulman, 1970. In Teichert, C. (ed.). Treatise on Invertebrate Paleontology. Part V. Graptolithina , with sections on Enteropneusta and Pterobranchia. (2nd Edition). Geological Society of America and University of Kansas Press, Boulder, Colorado and Lawrence, Kansas, xxxii + 163 pp.


External links

  • Graptolite Net - Graptolite.net
  • Classification of the Cephalodiscoidea (Graptolithoidea) - Graptolite.net - Cephalodiscus
  • BIG G - The British & Irish Graptolite Group - British and Irish Graptolite Group (BIG-G)
  • Graptolite Mudrocks - The palaeoecology and palaeoenvironment of graptolitic mudrocks

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SWEDEN [Sverige] - Online Information article about SWEDEN [Sverige] (7148 words)
graptolites; the other calcareous, with brachiopods, trilobites, andc.
The sub-divisions of the system may be grouped as follows: (I) Ceratopyge Limestone; (2) Lower Graptolite Shales and Orthoceras Limestone; (3) Middle Graptolite Shales, Chasmops and other Limestones, Trinucleus beds.
England and consists partly of graptolite shales, partly of limestones and sandstones.
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