The Green River Formation is a geological formation located in the Intermountain West of the United States, in the states of Colorado, Utah, and Wyoming. It comprises sediments deposited during the Early Eocene in a series of large freshwater lakes: Lake Gosiute, Lake Uinta, and Fossil Lake (the last containing Fossil Butte National Monument). It preserves a high diversity of freshwater fish, birds, reptiles, and mammals, with some sections of the formation (including Fossil Lake and the Parachute Creek member of Lake Uinta) qualifying as Konservat-Lagerstätten due to their extremely well-preserved fossils.

Cartilaginous fish FamilyGenusSpeciesMemberAbundanceNotesImage†Asterotrygonidae†Asterotrygon†A. maloneyi Fossil LakeAn Asterotrygonidae stingray of uncertain higher affinities.†Heliobatidae†Heliobatis†H. radians Fossil LakeA Heliobatid stingray of uncertain higher affinities.

Bony fish Primarily based on Grande (2001), with changes where necessary:

Acipenseriformes FamilyGenusSpeciesMemberAbundanceNotesImagePolyodontidae†Crossopholis†C. magnicaudatus Fossil LakeA paddlefish.

Lepisosteiformes FamilyGenusSpeciesMemberAbundanceNotesImageLepisosteidaeAtractosteus†A. atrox Fossil LakeAn alligator gar relative.A. atrox is the largest Green River gar.†A. simplex Fossil Lake Lake Gosiute?An alligator gar relative.†Cuneatus†C. cuneatus Fossil Lake? Lake Gosiute Lake UintaA Cuneatini tribe gar.†C. wileyi Lake UintaA Cuneatini tribe gar.Lepisosteus†L. bemisi Fossil LakeA Lepisosteini tribe gar.†Masillosteus†M. janeae Fossil LakeA Cuneatini tribe gar.

Amiiformes FamilyGenusSpeciesMemberAbundanceNotesImageAmiidaeAmia†A. pattersoni Fossil Lake Lake GosiuteAn amiid bowfin.†Cyclurus†C. gurleyi Fossil LakeOnly 8 specimens knownAn amiid related to modern bowfins.

Hiodontiformes FamilyGenusSpeciesMemberAbundanceNotesImageHiodontidaeHiodon†H. falcatus Fossil LakeA hiodontid.First described as Eohiodon falcatus (1979).

Osteoglossiformes FamilyGenusSpeciesMemberAbundanceNotesImageOsteoglossidae†Phareodus†P. encaustus Fossil Lake Lake GosiuteA phareodontine bonytongue.†P. testis Fossil Lake

Ellimmichthyiformes FamilyGenusSpeciesMemberAbundanceNotesImage†Armigatidae†Diplomystus†D. dentatus Fossil Lake Lake Gosiute Lake UintaAn armigatid ellimmichthyiform.

Clupeiformes FamilyGenusSpeciesMemberAbundanceNotesImageClupeidae†Gosiutichthys†G. parvus Lake GosiuteA clupeine clupeid herring relative.†Knightia†K. alta Fossil Lake Lake Gosiute Lake UintaA pellonuline clupeid herring relative.†K. eocaena Fossil Lake Lake Gosiute Lake UintaThe most common articulated vertebrate fossil worldwide.A pellonuline clupeid herring relative.

Gonorynchiformes FamilyGenusSpeciesMemberAbundanceNotesImageGonorynchidae†Notogoneus†N. osculus Fossil LakeA beaked sandfish.Last gonorynchid known from North America. Bottom feeding trace fossils are attributed to N. osculus.

Cypriniformes FamilyGenusSpeciesMemberAbundanceNotesImageCatostomidae†Amyzon†A. gosiutensis Lake GosiuteAn ictiobine sucker.

Siluriformes FamilyGenusSpeciesMemberAbundanceNotesImage†Hypsidoridae†Hypsidoris†H. farsonensis Lake GosiuteAround 50 specimensA hypsidorid catfish.†Astephidae†Astephus†A. antiquus Fossil Lake Lake Gosiute Lake UintaOver 200 specimens; only one specimen known from Fossil Lake.An astephid catfish.

Salmoniformes FamilyGenusSpeciesMemberAbundanceNotesImageEsocidaeEsox†E. kronneri Fossil Lake1 specimenA pike, presumably related to the modern pickerels of North America. Likely native to surrounding streams or rivers and not the lakes.

Percopsiformes FamilyGenusSpeciesMemberAbundanceNotesImagePercopsidae†Amphiplaga†A. brachyptera Fossil LakeA trout-perch relative. Includes the jr synonym Erismatopterus endlichi (1877)†Erismatopterus†E. levatus Lake Gosiute Lake UintaA trout-perch relative.First described as Cyprinodon levatus (1870)includes the jr synonym Erismatopterus rickseckeri (1871)

Carangiformes FamilyGenusSpeciesMemberAbundanceNotesImageLatidae†Mioplosus†M. labracoides Fossil Lake Lake Gosiute Lake UintaA lates perches relative.

Acanthuriformes FamilyGenusSpeciesMemberAbundanceNotesImageMoronidae†Cockerellites†C. liops Fossil LakecommonA planktivorous/insectivorous temperate bass.First described as Priscacara liops (1877)First moved to Cockerellites liops in 1923.†Hypsiprisca†H. hypsacantha Fossil LakerareA temperate bass.First named Priscacara hypsacantha 1886)†H. sp.Fossil LakerareAn undescribed species of Hypsiprisca. A slenderer species with a more rounded tail fin outline.†Priscacara†P. serrata Fossil Lake Lake UintaA temperate bass.†P. sp. aFossil Lake1 specimenAn undescribed Priscacara Specimens have a rounder body and weak dorsal spines.†P. sp. b.Fossil Lake1 specimenAn undescribed Priscacara Possibly a new species or a variant specimen with 4 anal spines.

Incertae sedis FamilyGenusSpeciesMemberAbundanceNotesImage†Asineopidae†Asineops†A. squamifrons Fossil Lake Lake Gosiute Lake UintaAn acanthomorph of uncertain affinitiesPossibly a percopsiform, polymixiiform, or perciform.A. sp.Fossil LakeAn undescribed Asineops speciesRestricted to Fossil Lake.

Amphibians

Frogs FamilyGenusSpeciesMemberAbundanceNotesImagePelodytidae†Aerugoamnis†A. paulus Fossil Lake2 specimensA stem-relative of parsley frogs.

Salamanders FamilyGenusSpeciesMemberAbundanceNotesImageAmphiumidae†Paleoamphiuma†P. tetradactylum Fossil LakeA sirenid salamander.

Reptiles

Squamates FamilyGenusSpeciesMemberAbundanceNotesImageBoidae†Boavus†B. idelmani Fossil LakeA boa.Dactyloidae†Afairiguana†A. avius Fossil LakeA stem-anole.Shinisauridae†Bahndwivici†B. ammoskius Fossil LakeA relative of the Chinese crocodile lizard.Tropidophiidae?†DunnophisD. sp.Fossil LakeAn undescribed possible dwarf boa.Varanidae†Saniwa†S. ensidens Fossil LakeA stem-monitor lizard.Incertae sedisIndeterminateIndeterminateLake Uinta (Parachute Creek)1 specimenA possible gecko or iguanidPreserved with soft tissue and skin, but bones dissolved.Incertae sedisIndeterminateIndeterminateLake Uinta (Parachute Creek)1 specimenA relative of ShinisauridsPreserved with soft tissue and skin, but bones dissolved.

Crocodilians FamilyGenusSpeciesMemberAbundanceNotesImageAlligatoridae†Tsoabichi†T. greenriverensis Fossil LakeA caiman.Incertae sedis†Borealosuchus†B. wilsoni Fossil LakeA eusuchian crocodyliform of uncertain affinities.Moved from Leidyosuchus wilsoni (1959)Cf. †B. sp.Fossil LakeIndeterminate eusuchian bones close to Borealosuchus."Crocodylus"†"Crocodylus" acer Lake Uinta (Manti beds)1 specimenA Crocodyloidea of unplaced affinity.Not a Crocodylus species, but not given a new genus as of 2024. Cf. †"Crocodylus" affinis Lake GosiuteBones close in morphology to †"Crocodylus" affinisA Crocodyloidea of unplaced affinity.Not a Crocodylus species, but not given a new genus as of 2024.

Turtles FamilyGenusSpeciesMemberAbundanceNotesImageBaenidae†Chisternon†C. undatum Fossil LakeA baenid.Dermatemydidae†Baptemys†B. wyomingensis Fossil LakeA dermatemydid.†B. Cf. wyomingensis Lake UnitaA dermatemydid.Geoemydidae†Echmatemys†E. haydeni 1 specimenA geoemydid tortoise.†E. naomi Fossil Lake1 specimenA geoemydid tortoise.†E. wyomingensis Fossil LakeA geoemydid tortoise.Testudinidae†Hadrianus†Cf. †H. corsoni Fossil LakeA tortoise species.A single complete hatchlingTrionychidae†AxestemysA. sp.Fossil LakeA softshell turtle.†Oliveremys†O. uintaensis Fossil LakeA softshell turtle.†Plastomenus†P. thomasii Fossil LakeA softshell turtle.

Birds

Lithornithiformes FamilyGenusSpeciesMemberAbundanceNotesImage†Lithornithidae†Lithornis†L. grandeiFossil LakeA lithornithid. First described as Calciavis grandei.†Pseudocrypturus†P. cercanaxiusFossil LakeA lithornithid.

Anseriformes FamilyGenusSpeciesMemberAbundanceNotesImage†Presbyornithidae†Presbyornis†P. pervetusFossil LakeA presbyornithid anseriform.Incertae sedis†Paakniwatavis†P. grandeiFossil LakeAn anseriform of uncertain affinities.

Galliformes FamilyGenusSpeciesMemberAbundanceNotesImage†Gallinuloididae†Gallinuloides†G. wyomingensisFossil LakeA gallinuloid galliform.

Coliiformes FamilyGenusSpeciesMemberAbundanceNotesImage†Sandcoleidae†Anneavis†A. annaeFossil LakeA sandcoleid mousebird.Incertae sedis†Celericolius†C. acriala Fossil LakeA stem-mousebird.

Leptosomiformes FamilyGenusSpeciesMemberAbundanceNotesImageincertae sedis†Plesiocathartes†P. major Fossil LakeA stem-cuckoo roller.†P. wyomingensis Fossil LakeA stem-cuckoo roller

Coraciiformes FamilyGenusSpeciesMemberAbundanceNotesImagePrimobucconidae†Primobucco†P. mcgrewiFossil LakeA primobucconid coraciiform.Incertae sedis†Paracoracias†P. occidentalisA coraciiform.

Piciformes FamilyGenusSpeciesMemberAbundanceNotesImageIncertae sedis†Neanis†N. schuchertiFossil LakeA possible piciform of uncertain affinities.†Pristineanis†P. kistneriFossil Lake (Fossil Butte Member) Lake Gosiute (Tipton tongue Member)2 specimensA possible piciform of uncertain affinities.First described as Primobucco kistneri (1973) Moved from Neanis kistneri 1976)

Strisores FamilyGenusSpeciesMemberAbundanceNotesImageEocypselidae†Eocypselus†E. roweiFossil LakeAn eocypselid apodiform.Fluvioviridavidae†Fluvioviridavis†F. platyrhamphus Fossil Lake2 specimensA basal strisore, possibly a stem-frogmouth.Incertae sedis†Prefica†P. niveaFossil LakeA stem-oilbird.

Musophagiformes FamilyGenusSpeciesMemberAbundanceNotesImageMusophagidae?†Foro†F. panariumFossil Lake1 specimenA possible stem-turaco.

Mirandornithes FamilyGenusSpeciesMemberAbundanceNotesImageIncertae sedis†Juncitarsus†J. merkeliFossil LakeA stem-mirandornithine.

Suliformes FamilyGenusSpeciesMemberAbundanceNotesImageFregatidae†LimnofregataL. azygosternonFossil LakeAn early frigatebird.L. hasegawaiFossil LakeAn early frigatebird

Pelecaniformes FamilyGenusSpeciesMemberAbundanceNotesImageThreskiornithidae†Rhynchaeites†R. mcfaddeni1 specimenKnown from a largely complete specimen.†Vadaravis†V. brownaeFossil LakePotentially a stem-ibis, but may be an indeterminate aequornithine.

Charadriiformes FamilyGenusSpeciesMemberAbundanceNotesImageIndeterminateIndeterminateIndeterminateLake Uinta1 trace specimenA shorebirdPotentially the earliest record of recurvirostridsKnown from a 3 footprint trackway.

Gruiformes FamilyGenusSpeciesMemberAbundanceNotesImage†Messelornithidae†Messelornis†M. nearcticaFossil LakeA messelornithid.

Eufalconimorphae FamilyGenusSpeciesMemberAbundanceNotesImage†Halcyornithidae†Cyrilavis†C. colburnorumFossil LakeA halcyornithid.†C. olsoniFossil Lake†Messelasturidae†Tynskya†T. eocaenaFossil LakeA messelasturid.†Morsoravidae†Consoravis†C. turdirostrisFossil LakeA morsoravid.†Psittacopedidae†Eofringillirostrum†E. boudreauxiFossil LakeA psittacopedid.†Vastanavidae†Avolatavis†A. tenensFossil LakeA vastanavid.†Zygodactylidae†Eozygodactylus†E. americanusFossil LakeA zygodactylid.†Zygodactylus†Z. grandeiFossil LakeA zygodactylid.

Neoaves incertae sedis FamilyGenusSpeciesMemberAbundanceNotesImageIncertae sedis†Nahmavis†N. grandeiFossil Lake1 specimenEither a stem-gruiform or a stem-charadriiform. Two other genera, "Eoeurypyga" (a stem-sunbittern) and "Wyomingcypselus" (an early apodiform) are mentioned only in a 2002 dissertation, and are presently nomina nuda.

Avian ichnofossils FamilyGenusSpeciesMemberAbundanceNotesImage†Avipedidae†AvipedaCf. †A. phoenix Lake UnitaAvian trackways with three forward facing toes without inter-digit webbing.†Ignotornidae†Quadridigitus†Q. semimembranus Lake UnitaAvian trackways with three forward facing toes, a hallux, and inter-digit webbing.†Jindongornipodidae†Jindongornipes†J. falkbuckleyi Lake UnitaLarge avian trackways with four toes, and wide spread between digits II and IV.Incertae sedis†Presbyornithiformipes†P. feduccii Lake UintaDuck-like trackways with dabble marks attributed to Presbyornis.

Mammals