Trinacromerum fossil map
Where fossils of Trinacromerum have been found, shown on the Earth as it looked about 85 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 85 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 | 106.3–66 million years ago (Albian to Maastrichtian) |
| Periods | Cretaceous |
| Family | Polycotylidae |
| Named by | Cragin 1888 |
| Fossil records | 18 occurrences at 18 locations (PBDB) |
| Found in | United States, Canada |
| Rock formations | Carlile Shale, Greenhorn Limestone, txn:100152, Pierre Shale, Tropic Shale, Lake Waco |
About Trinacromerum
Trinacromerum is an extinct genus of sauropterygian reptile, a member of the polycotylid plesiosaurs. It contains two species, T. bentonianum and T. kirki. Specimens have been discovered in the Late Cretaceous fossil deposits of what is now modern Kansas and Manitoba. Some fossils are also found in the Southern United States such as in the Mooreville Chalk of Alabama.
Text in “About” is quoted from the Wikipedia article Trinacromerum (revision 1362305980), 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: Q2715504.
