Triisodon fossil map
Where fossils of Triisodon have been found, shown on the Earth as it looked about 66 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 66 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 | 63.4–60.9 million years ago (Danian to Selandian) |
| Periods | Paleogene |
| Family | Triisodontidae |
| Named by | Cope 1881 |
| Fossil records | 24 occurrences at 4 locations (PBDB) |
| Found in | United States |
| Rock formations | Nacimiento |
About Triisodon
Triisodon (ancient Greek: "Tri" (three),"isos" (equal), and modern Greek: "donti" (tooth/teeth), supposedly describing tritubercular lower cheek teeth) is a genus of an extinct family of hoofed mammals known as Triisodontidae. Triisodon existed during the Early Paleocene of New Mexico, North America, from about 63.5-62.0 Ma. The genus was named by Edward Drinker Cope in 1881 as a member of the Creodonta, a now invalid group that encompassed hyaenodonts, oxyaenids, mesonychians and certain arctocyonians. Cope described the type specimen of T. quivirensis as "about the size of a wolf." A smaller species, T. crassicuspis, has also been identified from the same region. Since material from this genus is incomplete, the exact size of adults and whether they showed sexual dimorphism or regional variations in size is unknown.
Triisodon would go extinct during a faunal turnover between the Tj4-5 and Tj6 biozones, caused by the U27r excursion, a warming period that saw an increase in aridity.
Text in “About” is quoted from the Wikipedia article Triisodon (revision 1379556599), 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: Q2602946.
