Roadian

Roadian
	272.95 ± 0.11 – 268.8 ± 0.5 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Chronology
	Key events in the Permian -300 — – -295 — – -290 — – -285 — – -280 — – -275 — – -270 — – -265 — – -260 — – -255 — – -250 — P; a; l; e; o; z; o; i; c M; Z C P; e; r; m; i; a; n T P L; P C; i; s; u; r; a; l; i; a; n G; u; a; d; a; l; u; p. L; o; p; i; n. E; T Gzhelian Asselian Sakmarian Artinskian Kungurian Roadian Wordian Capitanian Wuchiapingian Changhsingian Induan ← Permian-Triassic mass extinction event ← end-Capitanian extinction event ← Olson's Extinction An approximate timescale of key Permian events.; Axis scale: millions of years ago.;
Etymology
Name formality	Formal
Usage Information
Celestial body	Earth
Regional Usage	Global (ICS)
Time scale(s) used	ICS Time Scale
Definition
Chronological unit	Age
Stratigraphic unit	Stage
Time span formality	Formal
Lower boundary definition	FAD of the Conodont Jinogondolella nanginkensis
Lower boundary GSSP	Stratotype Canyon, Guadalupe Mountains, Texas, USA; 31.8767°N 104.8768°W
GSSP ratified	2001[1]
Upper boundary definition	FAD of the Conodont Jinogondolella aserrata
Upper boundary GSSP	Guadalupe Pass, Guadalupe Mountains, Texas, USA; 31.8658°N 104.8328°W
GSSP ratified	2001[1]

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]

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
Eigilia	Guadalupian	Kazakhstan	A non-neopterygian	Platysomus
Platysomus	Carboniferous to Lopingian	Russia	A non-neopterygian

†Temnospondyli

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

†Seymouriamorphs

Seymouriamorpha of the Roadian
Taxa	Presence	Location	Description	Images
Seymouria		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
Gecatogomphius	Guadalupian	Russia	A captorhinid reptile

Synapsids (non-therapsid)

Synapsida of the Roadian
Taxa	Presence	Location	Description	Images
Alierasaurus	Guadalupian	Italy, Sardinia	A caseasaurian	Alierasaurus

Therapsids

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

References

"GSSP for Roadian Stage". International Commission on Stratigraphy. International Commission on Stratigraphy. Retrieved 13 December 2020.
Gradstein, F.M.; Ogg, J.G. & Smith, A.G.; 2004: A Geologic Time Scale 2004, Cambridge University Press
Glenister, B.F. & Furnish, W.M.; 1961: The Permian ammonoids of Australia, Journal of Paleontology 35(4), pp 673–736.
Nassichuk, W.W.; 1964: Pennsylvanian and Permian rocks in the Parry Islands Group, Canadian Arctic Archipelago, Report of activities, field
Furnish & Glenister (1968)
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.
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.

External links

GeoWhen Database - Roadian
Upper Paleozoic stratigraphic chart at the website of the subcommission for stratigraphic information of the ICS

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[ICS_GSSP-1] "GSSP for Roadian Stage". International Commission on Stratigraphy. International Commission on Stratigraphy. Retrieved 13 December 2020.

[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.

[SahneyBenton2008RecoveryFromProfoundExtinction-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.