''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). Retrieved May 2013. 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). One of the dramatic effects of the

Paleocene–Eocene Thermal Maximum The Paleocene–Eocene thermal maximum (PETM), alternatively (ETM1), and formerly known as the "Initial Eocene" or "", was a time period with a more than 5–8 °C global average temperature rise across the event. This climate event o ...

(PETM) was some animals evolving smaller bodies. Fossilized ''Ectocion'' jaw bones show that this genus was smaller during (''E. parvus'', 55.5

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) the PETM than its relatives before (''E. osbornianus'', 55.6 mya) and after (''E. osbornianus'', 55.3 mya) the brief climatic peak period.

References

Paleogene mammals of North America Condylarths Prehistoric placental genera {{Paleo-mammal-stub