Arcadia Formation, Australia

The Arcadia Formation is a geological formation located within central-eastern Queensland, Australia, which has been aged between the InduanOlenekian epoch of the Early-Triassic period. It is most well known for its abundance of Early-Triassic aged fossils, most notably its high diversity of amphibians.[1][2]

Arcadia Formation
Stratigraphic range: Induan-Olenekian
~251–247 Ma
TypeGeological formation
Unit ofRewan Group
UnderliesBrumby Sandstone Member
Overliesunconformity with Glenidal Formation
conformity Sagittarius Sandstone
ThicknessUp to 500 m (1,600 ft)
Lithology
PrimaryRed mudstone, siltstone, fine-grained sandstone
Location
Coordinates24°48′S 148°00′E / 24.8°S 148.0°E / -24.8; 148.0
Approximate paleocoordinates58°00′S 136°00′E / 58.0°S 136.0°E / -58.0; 136.0
Region Queensland
Country Australia
ExtentBowen Basin
Type section
Year defined1988
Arcadia Formation, Australia is located in Australia
Arcadia Formation, Australia
Arcadia Formation, Australia (Australia)
Arcadia Formation, Australia is located in Queensland
Arcadia Formation, Australia
Arcadia Formation, Australia (Queensland)

Description

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The Arcadia Formation is a sequence of sandstones and mudstones deposited as a result of freshwater rivers and lakes during the InduanOlenekian epoch.[3] The Arcadia Formation represents one of the oldest known Mesozoic formations within the entirety of Australia, as well as containing relatively well-preserved specimens for its age and country. At the time at which the Arcadia Formation was building up, the then region of today's Australia was still recovering from the recent Permian–Triassic extinction event which had resulted in the global biodiversity remaining at a low level throughout much of the lower Triassic.[4] The world currently was generally a hot and arid environment reaching an average temperature of more than 80o S. This is suggested by the red color of sediments found within the Bowen Basin.

The fauna and flora from the formation are not abruptly unique in comparison to the known fauna or flora from the rest of the world at this time, however the Arcadia Formation has an unusually high diversity of amphibians, with 90% of the fauna from the Arcadia Formation being made up of amphibians. So far, the formation's fauna is known to consist of brachiopods, fish, amphibians, reptiles and synapsids. There is also a high diversity of ichnotaxa based on coprolites.[5]

Vertebrate paleofauna

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Fish

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Fish
Genus Species Material Notes Images
Aphelodus A. anapes A single tooth[6] A sagenodontid
Namatozodia N. pitikanta An incomplete skull A gnathorhizid
Ptychoceratodus P. phillipsi A sagenodontid
 
Saurichthys S.giga Partial skull

Amphibians

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Amphibians
Genus / Taxon Species Material Notes Images
Acerastea A. wadeae Partial skeleton A rhytidosteid
Arcadia A. myriadens Partial skeleton A rhytidosteid
 
Capulomala C. arcadiaensis Postglenoid areas of the mandible A plagiosaurid
Keratobrachyops K. australis Partial skull A trematosaurian
Lapillopsis L. nana Two nearly complete skulls A stereospondyl
 
Nanolania N. anatopretia A partial skull A rhytidosteid
 
Plagiobatrachus P. australis A set of vertebrae A plagiosaurid
Rewana R. quadricuneata Incomplete skull and partial postcranial skeleton A stereospondyl
Tirraturhinus T. smisseni Partial section of the skull A trematosaurian
Warrenisuchus W. aliciae An incomplete skeleton A capitosaurid
Watsonisuchus W. gunganj & W. rewanensis Both known from incomplete skulls A capitosaurid
Xenobrachyops X. allos A partial skull A brachyopid
Trematosauridae Indeterminate Partial rostrum A brachyopid

Reptiles

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Reptiles
Genus / Taxon Species Material Notes Images
Eomurruna E. yurrgensis More than 40 referred specimens, including partial skeletons Australia's so far only reported procolophonoid
Kadimakara K. australiensis Partial skull, including the rear part of the skull and a fragment of the jaw An early archosauromorph similar to Prolacerta
 
Kalisuchus K. rewanensis Holotype consists of partial left maxilla A basal archosauriform
 
Kudnu K. mackinlayi Partial skull including anterior of cranium and both dentaries A lepidosauromorph

Synapsids

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Synapsids
Genus / Taxon Species Material Notes Images
Dicynodontia Indeterminate A quadrate, part of a tusk & a partial femur Some of the only dicynodont remains known from Australia

References

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  1. ^ "(Rewan Formation) (Triassic of Australia)". FossilWorks.
  2. ^ "Stratigraphic Unit Details Arcadia Formation". Australian Stratigraphic Units Database.
  3. ^ "Arcadia Formation". Australia: The Land Where Time Began.
  4. ^ Sahney, S.; Benton, M.J. (2008). "Recovery from the most profound mass extinction of all time". Proceedings of the Royal Society B: Biological Sciences. 275 (1636): 759–65. doi:10.1098/rspb.2007.1370. PMC 2596898. PMID 18198148.
  5. ^ Caroline, Northwood (2005). "Early Triassic coprolites from Australia and their palaeobiological significance". The Journal of the Palaeontological Association. doi:10.1080/02724634.2011.595858. S2CID 140599970.
  6. ^ "Aphelodus anapes". Retrieved 17 December 2021.