The Arcadia Formation is a geological formation located within central-eastern Queensland, Australia, which has been dated to 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 formations in Australia, as well as containing relatively well-preserved specimens for its age. 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.
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.
Vertebrate paleofauna
Fish Fish Genus Species Material Notes Images Aphelodus A. anapes A single tooth A sagenodontid Namatozodia N. pitikanta An incomplete skull A gnathorhizid Ptychoceratodus P. phillipsi A sagenodontid Saurichthys S.giga Partial skull
Amphibians 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 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 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