Aclistomycter fossil map
Where fossils of Aclistomycter have been found, shown on the Earth as it looked about 45 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 45 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 | 39.7–33.9 million years ago (Bartonian to Priabonian) |
| Periods | Paleogene |
| Family | Merycoidodontidae |
| Named by | Wilson 1971 |
| Fossil records | 14 occurrences at 2 locations (PBDB) |
| Found in | United States, Mexico |
| Rock formations | txn:42488, Chambers Tuff, Devil's Graveyard, Preitos |
About Aclistomycter
Aclistomycter is an extinct genus of oreodont from the late Eocene of Texas and Mexico. It is the oldest known member of Merycoidodontidae (the family containing most oreodonts), and its distinctive qualities allow it to occupy its own monotypic subfamily, Aclistomycterinae. Aclistomycter was a small herbivorous artiodactyl with a short face and small, tusk-like canine teeth. Though small by the standards of Oligocene-Miocene oreodonts, it was somewhat larger than other late Eocene oreodonts.
The type species Aclistomycter middletoni was first reported from the Porvenir local fauna in the Chambers Tuff Formation, near Adobe Springs in Presidio County, Texas. This site is late Duchesnean in age (about 38 Ma). It has also been reported from the Rancho Gaitan site in Chihuahua, Mexico. A second potential species, Aclistomycter? dunagani, occurs in the nearby Little Egypt local fauna, which is slightly younger (earliest Chadronian, about 37 Ma).
Text in “About” is quoted from the Wikipedia article Aclistomycter (revision 1369796675), 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: Q4674330.
