Ectocion fossil map
Where fossils of Ectocion have been found, shown on the Earth as it looked about 56 million years ago and on today’s map.
Dots are fossil collections recorded in the Paleobiology Database. The “then” view moves today’s fossil sites back to their positions 56 million years ago (the time slice nearest the median age of the fossils) using the Merdith et al. (2021) plate model; positions are approximate. Open on the timeline map →
| Group | Early mammals |
|---|---|
| Lived | 66–45.9 million years ago (Danian to Lutetian) |
| Periods | Paleogene |
| Family | Phenacodontidae |
| Named by | Cope 1882 |
| Fossil records | 806 occurrences at 158 locations (PBDB) |
| Found in | United States, Canada, Mexico |
| Rock formations | Willwood, txn:42284, Fort Union, DeBeque, Wasatch, Paskapoo |
About Ectocion
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) It reached 6 to 12 kg and was similar in size and morphology to Copecion. Both these herbivorous ungulates likely occupied similar ecological niches.
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.
Text in “About” is quoted from the Wikipedia article Ectocion (revision 1253095459), licensed under CC BY-SA 4.0; introduction excerpted verbatim, formatting removed. Ages, family, authority and fossil records: Paleobiology Database, accessed 23 October 2026. Ages are those of the rock layers the fossils were found in. Wikidata: Q5333993.
