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Anisian

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Title: Anisian  
Author: World Heritage Encyclopedia
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Subject: Triassic, Ichthyosaur, Aristoptychites, Ladinian, Middle Triassic
Collection: Anisian, Geochronology, Geologic Time Scale, Geological Ages, Middle Triassic, Triassic, Triassic Geochronology
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Anisian

System/
Period
Series/
Epoch
Stage/
Age
Age (Ma)
Jurassic Lower/
Early
Hettangian younger
Triassic Upper/
Late
Rhaetian 201.3–208.5
Norian 208.5–~228
Carnian ~228–~235
Mid/
Middle
Ladinian ~235–~242
Anisian ~242–247.2
Lower/
Early
Olenekian 247.2–251.2
Induan 251.2–252.2
Permian Lopingian Changhsingian older
Subdivision of the Triassic system
according to the IUGS, as of July 2012.

In the geologic timescale, the Anisian is the lower stage or earliest age of the Middle Triassic series or epoch and lasted from 247.2 million years ago until ~242 million years ago.[1] The Anisian age succeeds the Olenekian age (part of the Lower Triassic epoch) and precedes the Ladinian age.

Contents

  • Stratigraphic definitions 1
  • Palaeontology 2
  • Archosaurs 3
    • Archosauromorphs 3.1
    • Therapsids 3.2
    • †Nothosauroids 3.3
    • †Placodonts 3.4
    • †Thalattosaurians 3.5
    • †Ceratitida 3.6
      • Lower 3.6.1
      • Middle 3.6.2
      • Upper 3.6.3
    • †Phylloceratida 3.7
    • Nautilida 3.8
      • Lower 3.8.1
      • Middle 3.8.2
      • Upper 3.8.3
    • †Aulacocerida 3.9
      • Lower 3.9.1
    • Pterioida 3.10
  • References 4
    • Notes 4.1
    • Literature 4.2
  • External links 5

Stratigraphic definitions

The stage and its name were established by Austrian geologists Wilhelm Heinrich Waagen and Carl Diener in 1895. The name comes from Anisus, the Latin name of the river Enns. The original type locality is at Großreifling in the Austrian state of Styria.

The base of the Anisian stage (also the base of the Middle Triassic series) is sometimes laid at the first appearance of conodont species Chiosella timorensis in the stratigraphic record. Other stratigraphers prefer to use the base of magnetic chronozone MT1n. The global reference profile for the base (the GSSP or golden spike) is at a flank of the mountain Deşli Caira in the Romanian Dobruja.[2]

The top of the Anisian (the base of the Ladinian) is at the first appearance of ammonite species Eoprotrachyceras curionii and the ammonite family Trachyceratidae. The conodont species Neogondolella praehungarica appears at the same level.

Sometimes (especially in Central Europe) the Anisian stage is subdivided into four substages: Aegean, Bythinian, Pelsonian and Illyrian.

The Anisian contains six ammonite biozones:

Cherninia, giant temnospondyl from India

Palaeontology

Examples of vertebrates from this age are:

Archosaurs

Archosaurs of the Anisian
Taxa Presence Location Description Images
Donguz Formation, Russia

Archosauromorphs

Archosauromorphs of the Anisian
Taxa Presence Location Description Images
250-230 Ma, Olenekian to Carnian South America An early archosauriform and the largest predator of its time.

Therapsids

Therapsids of the Anisian
Taxa Presence Location Description Images

†Nothosauroids

Nothosauroids of the Anisian
Taxa Presence Location Description Images
Guizhou and Hubei, China

†Placodonts

Placodonts of the Anisian
Taxa Presence Location Description Images
Northern Italy

†Thalattosaurians

Thalattosauria of the Anisian
Taxa Presence Location Description Images
Italy A very thin, elongated creature (about 2 meters long) that probably swam like an eel, that was probably a fish eater and hunted in deep waters, based on its large eyes (which would allow it to see better in dark water) and the protective bony ring around them (also seen in ichthyosaurs), which prevented them from getting squashed in by the immense water pressure at great depths.

†Ceratitida

Ananorites Arthaberites Beyrichites Bosnites Buddhaites Bukowskiites Caucasites Danubites Gangadharites Japonites Laboceras Longobarditoides Mesocladiscites Noetlingites Parapinacoceras Parasageceras Phyllocladiscites Proavites Pseudodanubites Psilocladiscites Salterites Tropigymnites Xiphogymnites Pararcestes Sageceras

Lower

Alloptychites Anagymnites Grambergia Groenlandites Gymnites Lenotropites Pearylandites Silberlingites Isculites Stenopopanoceras

Middle

Acrochordiceras Alanites Anagymnotoceras Arctohungarites Balatonites Bulogites Cuccoceras Czekanowskites Epacrochordiceras Hollandites Huishuites Inaigymnites Ismidites Kiparisovia Malletophychites Nicomedites Phillipites Platycuccoceras Pronoetlingites Reiflingites Discoptychites Intornites Nevadisculites Paraceratites Parapopanoceras Proarcestes Longobardites Ptychites

Upper

Amphipopanoceras Aplococeras Arctogymnites Eudiscoceras Eutomoceras Gymnotoceras Halilucites Judicarites Kellnerites Metadinarites Nevadites Parakellnerites Proteusites Repossia Semiornites Serpianites Stoppaniceras Ticinites Tozerites Tropigastrites Joannites Epigymnites Ceratites Flexoptychites Frechites Norites Gevanites Hungarites

†Phylloceratida

Spinoleiophyllites Ussurites Monophyllites

Nautilida

Trachynautilus Thuringionautilus Styrionautilus

Lower

Indonautilus Sibyllonautilus

Middle

Paranautilus

Upper

Holconautilus Proclydonautilus

†Aulacocerida

Crassiatractites Breviatractites

Lower

Mojsisovicsteuthis

Pterioida

Ramonalinidae

References

Notes

  1. ^ According to Gradstein et al. (2004); Brack et al. (2005) give 248 to 241 Ma
  2. ^ The GSSP was established by Grǎdinaru et al. (2007)

Literature

  • Brack, P.; Rieber, H.; Nicora, A. & Mundil, R.; 2005: The Global boundary Stratotype Section and Point (GSSP) of the Ladinian Stage (Middle Triassic) at Bagolino (Southern Alps, Northern Italy) and its implications for the Triassic time scale, Episodes 28(4), pp. 233–244.
  • Grǎdinaru, E.; Orchard, M.J.; Nicora, A.; Gallet, Y.; Besse, J.; Krystyn, L.; Sobolev, E.S.; Atudorei, N.-V. & Ivanova, D.; 2007: The Global Boundary Stratotype Section and Point (GSSP) for the base of the Anisian Stage: Deşli Caira Hill, North Dobrogea, Romania, Albertiana 36, pp. 54–71.
  • Gradstein, F.M.; Ogg, J.G. & Smith, A.G.; 2004: A Geologic Time Scale 2004, Cambridge University Press.

External links

  • GeoWhen Database - Anisian
  • Lower Triassic timescale at the website of the subcommission for stratigraphic information of the ICS
  • Lower Triassic timescale at the website of Norges Network of offshore records of geology and stratigraphy.


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