Fossil Butte National Monument, Lincoln County, Wyoming, USAi

Regional Level Types
Fossil Butte National Monument	Basin
Lincoln County	County
Wyoming	State
USA	Country

About 50 million years ago during the Eocene Epoch three large shallow, saline lakes formed in the Wyoming Basin as the Western Interior Seaway subsided. Prehistoric, Fossil Lake, was the smallest of these and as the result of a tropical climate abounded in life. The sediments in the Fossil Butte Member of the Green River Formation represent the existence of this lake and are filled with abundant fossils of great diversity. The quality of the preservation is outstanding and specimens can be seen in museums and collections around the world.

The sedimentation in the lake is now classified as both laminated and unlaminated calcimicrite sometimes referred to as lime-mudstone. The laminated “split fish layer” is varved, showing an annual cycle with alternating dark (summer organic bands) and light (winter inorganic bands). The cycles were counted indicating that during this period the lake was active for about 4,000 years.

The large plates of dead fish indicate mass mortality possibility caused by any of the following: change in water temperature, change in water pH, evaporation of pools along the shore, Blue-green algal bloom and the fluctuation of salt content.

Fossils

There are 12 fossil localities from the PaleoBioDB database within this region.

BETA TEST - These data are provided on an experimental basis and are taken from external databases. Mindat.org has no control currently over the accuracy of these data.

Occurrences	116
Youngest Fossil Listed	50.3 Ma (Eocene)
Oldest Fossil Listed	55.8 Ma (Eocene)
Stratigraphic Units	Unit No. Occurrences Age Green River - Fossil Butte 1 37.2 - 33.9 Ma (Paleogene) Wasatch 115 55.8 - 50.3 Ma (Eocene)
Fossils from Region	Click here to show the list.
Accepted Name Hierarchy Age Palaeoryctidae family Animalia : Chordata : Mammalia : Palaeoryctidae 55.8 - 50.3 Ma Eocene Phenacolemur genus Animalia : Chordata : Mammalia : Primates : Paromomyidae : Phenacolemur 55.8 - 50.3 Ma Eocene Coryphodon genus Animalia : Chordata : Mammalia : Coryphodontidae : Coryphodon 55.8 - 50.3 Ma Eocene Ectoganus genus Animalia : Chordata : Mammalia : Stylinodontidae : Ectoganus 55.8 - 50.3 Ma Eocene Hyaenodontidae family Animalia : Chordata : Mammalia : Hyaenodontidae 55.8 - 50.3 Ma Eocene Miacidae family Animalia : Chordata : Mammalia : Carnivora : Miacidae 55.8 - 50.3 Ma Eocene Viverravus genus Animalia : Chordata : Mammalia : Carnivora : Viverravidae : Viverravus 55.8 - 50.3 Ma Eocene Equidae family Animalia : Chordata : Mammalia : Perissodactyla : Equidae 55.8 - 50.3 Ma Eocene Palaeanodon genus Animalia : Chordata : Mammalia : Metacheiromyidae : Palaeanodon 55.8 - 50.3 Ma Eocene Copelemur australotutus species Animalia : Chordata : Mammalia : Primates : Notharctidae : Copelemur : Copelemur australotutus 55.8 - 50.3 Ma Eocene Microsyops knightensis species Animalia : Chordata : Mammalia : Primates : Microsyopidae : Microsyops : Microsyops knightensis 55.8 - 50.3 Ma Eocene Microsyops latidens species Animalia : Chordata : Mammalia : Primates : Microsyopidae : Microsyops : Microsyops latidens 55.8 - 50.3 Ma Eocene Ectocion superstes species Animalia : Chordata : Mammalia : Phenacodontidae : Ectocion : Ectocion superstes 55.8 - 50.3 Ma Eocene Esthonyx bisulcatus species Animalia : Chordata : Mammalia : Tillotheriidae : Esthonyx : Esthonyx bisulcatus 55.8 - 50.3 Ma Eocene Haplomylus scottianus species Animalia : Chordata : Mammalia : Hyopsodontidae : Haplomylus : Haplomylus scottianus 55.8 - 50.3 Ma Eocene Hexacodus uintensis species Animalia : Chordata : Mammalia : Artiodactyla : Dichobunidae : Hexacodus : Hexacodus uintensis 55.8 - 50.3 Ma Eocene Hyopsodus minor species Animalia : Chordata : Mammalia : Hyopsodontidae : Hyopsodus : Hyopsodus minor 55.8 - 50.3 Ma Eocene Hyopsodus powellianus species Animalia : Chordata : Mammalia : Hyopsodontidae : Hyopsodus : Hyopsodus powellianus 55.8 - 50.3 Ma Eocene Xenicohippus craspedotum species Animalia : Chordata : Mammalia : Perissodactyla : Equidae : Xenicohippus : Xenicohippus craspedotum 55.8 - 50.3 Ma Eocene Protorohippus venticolum species Animalia : Chordata : Mammalia : Perissodactyla : Equidae : Protorohippus : Protorohippus venticolum 55.8 - 50.3 Ma Eocene Lambdotherium popoagicum species Animalia : Chordata : Mammalia : Perissodactyla : Brontotheriidae : Lambdotherium : Lambdotherium popoagicum 55.8 - 50.3 Ma Eocene Didymictis protenus species Animalia : Chordata : Mammalia : Viverravidae : Didymictis : Didymictis protenus 55.8 - 50.3 Ma Eocene Heptodon calciculus species Animalia : Chordata : Mammalia : Perissodactyla : Heptodon : Heptodon calciculus 55.8 - 50.3 Ma Eocene Meniscotherium chamense species Animalia : Chordata : Mammalia : Phenacodontidae : Meniscotherium : Meniscotherium chamense 55.8 - 50.3 Ma Eocene Diacodexis secans species Animalia : Chordata : Mammalia : Artiodactyla : Diacodexeidae : Diacodexis : Diacodexis secans 55.8 - 50.3 Ma Eocene Paramys excavatus species Animalia : Chordata : Mammalia : Rodentia : Ischyromyidae : Paramys : Paramys excavatus 55.8 - 50.3 Ma Eocene Knightomys huerfanensis species Animalia : Chordata : Mammalia : Rodentia : Sciuravidae : Knightomys : Knightomys huerfanensis 55.8 - 50.3 Ma Eocene Cantius frugivorus species Animalia : Chordata : Mammalia : Primates : Notharctidae : Cantius : Cantius frugivorus 55.8 - 50.3 Ma Eocene Herpetotherium innominatum species Animalia : Chordata : Mammalia : Marsupialia : Herpetotheriidae : Herpetotherium : Herpetotherium innominatum 55.8 - 50.3 Ma Eocene Phenacodus trilobatus species Animalia : Chordata : Mammalia : Phenacodontidae : Phenacodus : Phenacodus trilobatus 55.8 - 50.3 Ma Eocene Apheliscus insidiosus species Animalia : Chordata : Mammalia : Macroscelidea : Apheliscidae : Apheliscus : Apheliscus insidiosus 55.8 - 50.3 Ma Eocene Prototomus secundarius species Animalia : Chordata : Mammalia : Hyaenodontidae : Prototomus : Prototomus secundarius 55.8 - 50.3 Ma Eocene Knightomys depressus species Animalia : Chordata : Mammalia : Rodentia : Sciuravidae : Knightomys : Knightomys depressus 55.8 - 50.3 Ma Eocene Copelemur tutus species Animalia : Chordata : Mammalia : Primates : Notharctidae : Copelemur : Copelemur tutus 55.8 - 50.3 Ma Eocene Bunophorus grangeri species Animalia : Chordata : Mammalia : Artiodactyla : Diacodexeidae : Bunophorus : Bunophorus grangeri 55.8 - 50.3 Ma Eocene Paramyinae subfamily Animalia : Chordata : Mammalia : Rodentia : Ischyromyidae : Paramyinae 55.8 - 50.3 Ma Eocene Limnofregata azygosternon species Animalia : Chordata : Aves : Suliformes : Fregatidae : Limnofregata : Limnofregata azygosternon 55.8 - 50.3 Ma Eocene Palaeosinopa lacus species Animalia : Chordata : Mammalia : Pantolestidae : Palaeosinopa : Palaeosinopa lacus 55.8 - 50.3 Ma Eocene Notoparamys blochi species Animalia : Chordata : Mammalia : Rodentia : Ischyromyidae : Notoparamys : Notoparamys blochi 55.8 - 50.3 Ma Eocene
Fossil Localities	Click to show 12 fossil localities

Other Databases

Wikipedia:	https://en.wikipedia.org/wiki/Fossil_Butte_National_Monument
Wikidata ID:	Q1439427
GeoNames ID:	5825450

Localities in this Region

Other Regions, Features and Areas that Intersect

References