Clarkforkian Explained

The Clarkforkian North American Stage, on the geologic timescale, is the North American faunal stage according to the North American Land Mammal Ages chronology (NALMA), typically set from 56,800,000 to 55,400,000 years BP lasting .^[1]

Considered to be within the Paleocene, more specifically the Late Paleocene, the Clarkforkian shares its upper boundary with the Thanetian.

The Clarkforkian is preceded by the Tiffanian and followed by the Wasatchian NALMA stages.

Substages

It is considered to contain the following substages:

• Cf3: (shares the upper boundary) and lower boundary source of the base of Clarkforkian (approximate) and upper boundary source of the base of the Ypresian (approximate).
• Cf2: Is the lower boundary source of the base of the Clarkforkian (approximate)
• Cf1: Upper boundary source of the base of the Ypresian (approximate)

Fauna

Notable mammals

^{[2] [3]}

Multituberculata - non-therian mammals

• Ectypodus, neoplagiaulacid multituberculate

Metatheria - marsupials

• Peradectes, peradectid marsupial

Carnivora - carnivores, including living carnivorous mammals

• Didymictis, viverravid carnivoran

Condylarthra - archaic ungulates

• Apheliscus, hyopsodontid condylarth
• Ectocion, phenacodontid condylarth
• Phenacodus, phenacodontid condylarth
• Thryptacodon, raccoon-like arctocyonid condylarth

Creodonta - extinct group of carnivorous mammals

• Oxyaena, semi-arboreal creodont

Dinocerata - large, tusked herbivores

• Probathyopsis, early North American uintathere

Eulipotyphla - insectivorous mammals

• Plagioctenodon, nyctitheriid insectivore
• Wyonycteris, nyctitheriid insectivore

Mesonychia - carnivorous hoofed mammals

• Dissacus, dog-sized mesonychid

Pantodonta - large herbivorous mammals

• Coryphodon, semi-aquatic, hippo-like pantodont
• Titanoides, large pantodont

Primatomopha - primates and relatives

• Carpolestes, carpolestid plesiadapiform
• Chiromyoides, small plesiadapid
• Phenacolemur, paromomyid plesiadapiform
• Plesiadapis, plesiadapid plesiadapiform

Rodentia - rodents

• Alagomys, alagomyid rodent
• Paramys, ischyromyid rodent

Tillodontia - medium sized, digging herbivores

• Esthonyx, esthonychid tillodont

Notes and References

1. http://paleodb.org/cgi-bin/bridge.pl?action=displayInterval&interval_no=232 Paleobiology Database, Clarkforkian
2. Rose . Kenneth D. . 1981 . The Clarkforkian Land-Mammal Age and Mammalian Faunal Composition Across the Paleocene-Eocene Boundary . Papers on Paleontology . 2027.42/48626 . free.
3. Wilf. Peter. Beard. K. Christopher. Davies-Vollum. K. Sian. Norejko. Jay W.. December 1998. Portrait of a Late Paleocene (Early Clarkforkian) Terrestrial Ecosystem: Big Multi Quarry and Associated Strata, Washakie Basin, Southwestern Wyoming. PALAIOS. 13. 6. 514. 10.2307/3515344. 0883-1351. 3515344. 1998Palai..13..514W.