Ectocion

{{Short description|Extinct genus of mammals}}

{{Automatic taxobox

| fossil_range = Paleocene - Eocene

| image = Ectocion Ralstonensis.jpg

| image_caption= Ectocion osbornianus

| taxon = Ectocion

| authority = Cope, 1882

| subdivision_ranks = Species

| subdivision =

• E. cedrus Thewissen, 1990
• E. collinus Russell, 1929
• E. ignotum Novacek et al., 1991
• E. major Patteron & West, 1973
• E. mediotuber Thewissen, 1990
• E. nanabeensis Beard & Dawson, 2009{{cite journal |last1=Beard |first1=K. C. |last2=Dawson |first2=M. R. |title=Early Wasatchian Mammals of the Red Hot Local Fauna, Uppermost Tuscahoma Formation, Lauderdale County, Mississippi |journal=Annals of Carnegie Museum |date=2009 |volume=78 |issue=3 |pages=193–243 |doi=10.2992/007.078.0301 |s2cid=86281527 |url=https://www.researchgate.net/publication/237065529}}
• E. osbornianus Cope, 1882
• E. parvus Granger, 1915
• E. stockeyae Montellano-Ballesteros et al., 2021{{cite journal |last1=Montellano-Ballesteros |first1=M. |last2=Fox |first2=R. C. |last3=Scott |first3=C. S. |title=A new, "dwarfed" species of the phenacodontid "condylarth" Ectocion from the late Paleocene of Alberta, Canada, and its implications |journal=Canadian Journal of Earth Sciences |date=2021 |volume=58 |issue=11 |pages=1155–1169 |doi=10.1139/cjes-2019-0234|bibcode=2021CaJES..58.1155M |hdl=1807/107869 |hdl-access=free }}
• 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){{Paleodb|42261|Ectocion}}. Retrieved May 2013. It reached 6 to 12 kg and was similar in size and morphology to Copecion. Both these herbivorous ungulates likely occupied similar ecological niches.{{cite journal|author=Andrew Schwartz|date=November 2023|url=https://www.researchgate.net/publication/375634652|title=Investigating Niche Overlap in Two Sympatric Phenacodonts using Dental Microwear Texture Analysis|journal=83rd Annual Meeting Society of Vertebrate Paleontology at Cincinnati, Ohio}}

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 (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.{{cite web

| first = Phil | last = Gingerich

| title = Big Little Big | year = 2009

| publisher = Smithsonian National Museum of Natural History

| url = http://forces.si.edu/atmosphere/03_00_05.html | access-date =

}}