Diplacodon fossil map
Where fossils of Diplacodon 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 | 45.9–37 million years ago (Lutetian to Priabonian) |
| Periods | Paleogene |
| Family | Brontotheriidae |
| Named by | Marsh 1875 |
| Fossil records | 20 occurrences at 6 locations (PBDB) |
| Found in | United States, Myanmar |
| Rock formations | Uinta, Pondaung, Baca |
About Diplacodon
Diplacodon (lit. 'double-pointed tooth') is an extinct genus of horned brontothere that lived in North America during the Middle Eocene, in the late Uintan land mammal age. Two Diplacodon species are recognized, the type species D. elatus from the Uinta Formation and the larger D. gigan from the Wiggins Formation.
Diplacodon was comparable in size to a modern rhinoceros. Similar to some other brontotheres, fossils assigned to D. elatus vary in the size and morphology of the teeth and horns. These variations have been argued to differentiate the fossils at the species level or even genus level. Recent revisions instead favor the variation as the result of sexual dimorphism and other individual variation, also documented in other brontotheres. D. gigan is known from a single skull, complicating studies on intraspecific variation.
Diplacodon and other contemporary North American brontotheres, such as Protitanotherium, were part of an early evolutionary radiation of horned brontotheres (the subtribe Brontotheriina) in North America during the Middle Eocene and were descended from Central Asian ancestors. Diplacodon and its close relatives ultimately gave rise to the larger brontotheres of the Brontotheriita infratribe, such as Megacerops.
Text in “About” is quoted from the Wikipedia article Diplacodon (revision 1364410422), 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: Q5279799.
