Dipoides fossil map
Where fossils of Dipoides have been found, shown on the Earth as it looked about 5 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 5 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 | 23.04–0.0117 million years ago (Aquitanian to Late Pleistocene) |
| Periods | Neogene, Quaternary |
| Family | Castoridae |
| Named by | Jaeger 1835 |
| Fossil records | 144 occurrences at 57 locations (PBDB) |
| Found in | United States, Spain, Bulgaria, China |
| Rock formations | txn:41534, Alkali Canyon, Alfambra, Ash Hollow, Rexroad, Chalk Hills |
About Dipoides
Dipoides (possibly meaning "double form") is an extinct genus of beaver-grouped rodents.
Dipoides were approximately three to four times larger than modern Canadian beavers - ranging from 90 - 120KG. Where modern beavers have square chisel shaped teeth, Dipoides teeth were rounded. However an excavation of a site that was once a marsh, in Ellesmere Island, showed signs that they dined on bark and young trees, like modern beavers. The excavation seemed to show that, like modern beavers, Dipoides dammed streams. Other research suggests that the building of dams by Dipoides started as a side effect to the consumption of wood and bark, and was a specialization that evolved for cold weather survival due to the earth's cooling during the late Neogene period.
Natalia Rybczynski, of the Canadian Museum of Nature, analyzed the teeth, and wood chips, of modern beavers, and Dipoides. She concluded that they all used just one of their teeth at a time, when cutting down trees. She concluded that modern beavers' square teeth required half as many bites as Dipoides' less evolved round teeth.
Rybczynski argues that eating bark and building dams are unlikely to have evolved twice, so modern beavers and Dipoides shared a wood-eating common ancestor, 24 million years ago.
Text in “About” is quoted from the Wikipedia article Dipoides (revision 1332219642), 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: Q24883978.
