Roadian

In the geologic timescale, the Roadian is an age or stage of the Permian. It is the earliest or lower of three subdivisions of the Guadalupian epoch or series. The Roadian lasted between 272.95 and 268.8 million years ago (Ma). It was preceded by the Kungurian and followed by the Wordian.[2]

System/
Period		 Series/
Epoch		 Stage/
Age		 Age (Ma)
Triassic Lower/
Early		 Induan younger
Permian Lopingian Changhsingian 251.902 254.14
Wuchiapingian 254.14 259.1
Guadalupian Capitanian 259.1 265.1
Wordian 265.1 268.8
Roadian 268.8 272.95
Cisuralian Kungurian 272.95 283.5
Artinskian 283.5 290.1
Sakmarian 290.1 295.0
Asselian 295.0 298.9
Carboniferous Pennsylvanian Gzhelian older
Subdivision of the Permian system
according to the ICS, as of 2017.[1]
Hercosestria cribrosa, A reef-forming Roadian brachiopod from the Glass Mountains of Texas.

Stratigraphy

In 1961, the regional timescale used for the southeastern US had the Wordian and Capitanian as subdivisions of the Guadalupian.[3] Efforts to correlate the Permian stratigraphy of the southeastern US with that of Russia led to the conclusion that between the Wordian stage and the Russian Artinskian stage, another stage needed to be introduced.[4] This stage, the Roadian stage, was established in 1968 and took its name from the Road Canyon Formation in Brewster County, Texas, formerly considered the lower (oldest) part of the Word Formation.[5] The stage was added to the internationally used IUGS timescale in 2001.[6]

The base of the Roadian is defined as the place in the stratigraphic record where fossils of conodont species Jinogondolella nankingensis first appears. The global reference profile for the base (the GSSP) is located in Stratotype Canyon in the Guadalupe Mountains, Texas (31°52′36″N 104°52′36″W). The top of the Roadian (the base of the Wordian stage) is at the first appearance of fossils of conodont species Jinogondolella aserrata.

Biodiversity

Olson’s Extinction, a worldwide loss of terrestrial vertebrate life occurred during the Early Guadalupian (Roadian, Wordian).[7]

Roadian life

Actinopterygians
Actinopterygii of the Roadian
Taxa Presence Location Description Images
Guadalupian Kazakhstan A non-neopterygian
Platysomus
Carboniferous to Lopingian Russia A non-neopterygian

†Temnospondyli
Temnospondyls of the Roadian
Taxa Presence Location Description Images
Komi Republic, Russian Federation A basal stereospondylomorph, possibly an archegosauroid.
Intasuchus
San Angelo Formation, Texas A genus of dvinosaurian temnospondyl within the family Tupilakosauridae.

†Seymouriamorphs
Seymouriamorpha of the Roadian
Taxa Presence Location Description Images
Tambach, Germany, Europe and Seymour, Baylor County, Texas among others in North America A reptiliomorph
Seymouria

Eureptiles
Eureptilia of the Roadian
Taxa Presence Location Description Images
Guadalupian Russia A captorhinid reptile

Synapsids (non-therapsid)
Synapsida of the Roadian
Taxa Presence Location Description Images
Guadalupian Italy, Sardinia A caseasaurian
Alierasaurus

Therapsids
Therapsida of the Roadian
Taxa Presence Location Description Images
Guadalupian China A anomodont therapsid
Biseridens
Guadalupian China One of the oldest therapsids
Guadalupian China A dinocephalian therapsid

References
  1. "Chart/Time Scale". www.stratigraphy.org. International Commission on Stratigraphy.
  2. Gradstein, F.M.; Ogg, J.G. & Smith, A.G.; 2004: A Geologic Time Scale 2004, Cambridge University Press
  3. Glenister, B.F. & Furnish, W.M.; 1961: The Permian ammonoids of Australia, Journal of Paleontology 35(4), pp 673–736.
  4. Nassichuk, W.W.; 1964: Pennsylvanian and Permian rocks in the Parry Islands Group, Canadian Arctic Archipelago, Report of activities, field
  5. Furnish & Glenister (1968)
  6. Glenister, B.F.; Wardlaw, B.R.; Lambert, L.L.; Spinosa, C.; Bowring, S.A.; Erwin, D.H.; Menning, M. & Wilde, G.L.; 1999: Proposal of Guadalupian and Component Roadian, Wordian and Capitanian Stages as International Standards for the Middle Permian Series, Permophiles 34: pp 3–11.
  7. Sahney, S. & Benton, M.J. (2008). "Recovery from the most profound mass extinction of all time" (PDF). Proceedings of the Royal Society B: Biological Sciences. 275 (1636): 759–65. doi:10.1098/rspb.2007.1370. PMC 2596898. PMID 18198148.

Literature
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