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Temporal range: Paleocene - Eocene
Ectocion Ralstonensis.jpg
Ectocion osbornianus
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Infraclass: Eutheria
Superorder: Laurasiatheria
Order: ?Perissodactyla
Family: Phenacodontidae
Genus: Ectocion
Cope, 1882

E. cedrus (Thewissen, 1990)
E. collinus (Russell, 1929)
E. ignotum (Novacek et al., 1991)
E. major (Patteron & West, 1973)
E. mediotuber (Thewissen, 1990)
E. osbornianus (Cope, 1882)
E. parvus (Granger, 1915)
E. superstes (Granger, 1915)

Ectocion (sometimes Ectocyon) is an extinct genus of placental mammals of the family Phenacodontidae. The genus was earlier classified as Gidleyina (Simpson 1935) and Prosthecion (Patterson and West 1973)[1]

Paleocene specimens of these hoofed, ground-dwelling herbivores have been found in Canada (Alberta, Saskatchewan) and the United States (Colorado, Montana, North Dakota, and Wyoming). Eocene specimens have been found in Mexico and the United States (Colorado, Mississippi, Wyoming).[1]

One of the dramatic effects of the Paleocene–Eocene Thermal Maximum (PETM) was some animals evolving smaller bodies. Fossilized Ectocion jaw bones show that this genus was smaller during (E. parvus, 55.5 mya) the PETM than its relatives before (E. osbornianus, 55.6 mya) and after (E. osbornianus, 55.3 mya) the brief climatic peak period.[2]


  1. ^ a b Ectocion in the Paleobiology Database. Retrieved May 2013.
  2. ^ Gingerich, Phil (2009). "Big Little Big". Smithsonian National Museum of Natural History. Retrieved January 2010.  Check date values in: |access-date= (help)