The Washington Formation is a coal, sandstone, and limestone geologic formation located in Ohio, Pennsylvania and West Virginia. It dates back to the Lower Permian period, with its base at or near the Permian/Carboniferous boundary. The Washington formation and the Dunkard Group as a whole was deposited at a time when the continents were in the process of forming the "Super Continent" Pangaea as well as a gradual drop in sea levels. The result during this period was coals being thinner and impure with high ash content. The limestones found with in the formation are exclusively freshwater deposits.
Paleofauna
The paleofauna of the Washington Formation is considered similar to that of the Texas Red Beds, sharing many fish and tetrapod taxa. Some of the taxa listed suggest an Artinskian age. Lucas et al 2013 discusses the fauna of the formation.
Synapsida +Synapsids of the Washington FormationGenusSpeciesNotesDimetrodonD.limbatusStated to be from a large specimen.EdaphosaurusE.boanergesA large edaphosaurid.OphiacodonO.retroversusAn ophiacodontid. Stated to be large.Sphenacodontia indet.IndeterminateAn indeterminate sphenacodont.
Reptiliomorpha +Reptiliomorphs of the Washington FormationGenusSpeciesNotesDiadectesD. sp.A large diadectid.ProtorothyrisP.archeriA protorothyrid.
Amphibia +Amphibians of the Washington FormationGenusSpeciesNotesEryopsE.megacephalusA large temnospondyl.AchelomaA.spA terrestrial temnospondyl.TrimerorhachisT.insignisA fully aquatic temnospondyl.DiploceraspisD.burkeiAn aquatic lepospondyl with large outward growths of the head.ZatrachysZ.spAn armored terrestrial temnospondyl.EdopsE.spAn aquatic temnospondyl.MegamolgophisM.agostiniA possible lysophorian.BrachydectesB.spA lysophorian.
Selachia
+Selachians of the Washington FormationGenusSpeciesNotesOrthacanthusO.texensisA large selachian.XenacanthusX.luederensisA small selachian.BarbclaborniaB.luederensisA giant selachian.
Osteichthyes +Osteicthyes of the Washington FormationGenusSpeciesNotesEctosteorhachisE.spA large lobe finned fish.Palaeoniscoidea indet.Indet.Indeterminate paleoniscoids.MonongahelaM.sp.A dipnoan.
References