Hydrotherosaurus fossil map
Where fossils of Hydrotherosaurus have been found, shown on the Earth as it looked about 66 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 66 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 | 72.2–66 million years ago (Maastrichtian) |
| Periods | Cretaceous |
| Family | Elasmosauridae |
| Named by | Welles 1943 |
| Fossil records | 1 occurrences at 1 locations (PBDB) |
| Found in | United States |
| Rock formations | Moreno |
About Hydrotherosaurus
Hydrotherosaurus (meaning "fisherman lizard") is an extinct genus of elasmosaurid plesiosaur from the Upper Cretaceous (Maastrichtian stage) Moreno Formation of Fresno County, California, USA. The only known species, H. alexandrae, was named for Annie Montague Alexander in 1943 by Samuel Paul Welles.
Text in “About” is quoted from the Wikipedia article Hydrotherosaurus (revision 1348846901), 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: Q10299036.
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