Arcadia Formation, Australia

Not to be confused with Arcadia Formation.

Arcadia Formation
Stratigraphic range: Induan-Olenekian ~
Type	Geological formation
Unit of	Rewan Group
Sub-units	Rewan Formation & Sagittarius Sandstone Members
Underlies	Brumby Sandstone Member, conformity Sagittarius Sandstone
Overlies	unconformity Glenidal Formation
Thickness	Up to 500 m (1,600 ft)
Lithology
Primary	Red mudstone, siltstone, fine grained sandstone
Location
Coordinates	24.8°S 148.0°E / -24.8; 148.0
Approximate paleocoordinates	58.0°S 136.0°E / -58.0; 136.0
Region	Queensland
Country	Australia
Extent	Bowen Basin
Type section
Year defined	1988
Arcadia Formation, Australia (Australia)

The Arcadia Formation is a geological formation located within central-eastern Queensland, Australia, which has been aged between the Induan–Olenekian 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.

Description

The Arcadia Formation is a sequence of sandstones and mudstones deposited as a result of freshwater rivers and lakes during the Induan–Olenekian epoch. The Arcadia Formation represents one of the oldest known Mesozoic formation within the entirety of Australia, as well as it is preserving relatively well-preserved specimens for its age and country. The time at which the Arcadia Formation takes place was still recovering from the recent Permian–Triassic extinction event and as a result the global biodiversity had remained low throughout much of the lower Triassic. The world currently was generally a hot and arid environment reaching an average temperature 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 from 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 of been made up of brachiopods, fish, amphibians, and reptiles. There is also a high diversity of ichnotaxa based on coprolites.

Vertabrate paleofauna

Fish

Fish
Genus	Species	Material	Notes	Images
Aphelodus	A. anapes	A single tooth	An Sagenodontid.
Namatozodia	N. pitikanta	An Incomplete skull	An Gnathorhizid.
Ptychoceratodus	P. phillipsi		An Sagenodontid.
Actinopterygii	Indeterminate	Scales
Osteichthyes	Indeterminate	Scales and coprolites
Saurichthys	Indeterminate	Partial Skull

Reptiles

Amphibians
Genus	Species	Material	Notes	Images
Acerastea	A. wadeae	Partial Skeleton.	A Rhytidosteid.
Arcadia	A. myriadens	Partial Skeleton.	A Rhytidosteid.
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 vertabrae.	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 incopmplete skulls.	A Capitosaurid.
Xenobrachyops	X. allos	A partial skull.	A Brachyopid.
Trematosauridae	Indeterminate	Partial rostrum.	A Brachyopid.

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