Edgarosaurus fossil map
Where fossils of Edgarosaurus have been found, shown on the Earth as it looked about 100 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 100 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 | Plesiosaurs & kin |
|---|---|
| Lived | 106.3–93.9 million years ago (Albian to Cenomanian) |
| Periods | Cretaceous |
| Family | Polycotylidae |
| Named by | Druckenmiller 2002 |
| Fossil records | 1 occurrences at 1 locations (PBDB) |
| Found in | United States |
| Rock formations | Thermopolis Shale |
About Edgarosaurus
Edgarosaurus is a genus of polycotylid plesiosaur from the Thermopolis Shale, containing one species, E. muddi. The type specimen was found in Early Cretaceous (late Albian) rocks in the state of Montana in the United States. At the time, this location was covered by part of the Western Interior Seaway. Edgarosaurus was one of the first polycotylids that evolved to become native to the Western Interior Seaway.
The holotype (which is currently the only known specimen) consists of the skull, neck, parts of the spine and the left front flipper.
Text in “About” is quoted from the Wikipedia article Edgarosaurus (revision 1283155986), 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: Q16746085.
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