Hydrodamalis fossil map
Where fossils of Hydrodamalis 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 | 11.63 million years ago to the present (Tortonian to Holocene) |
| Periods | Neogene, Quaternary |
| Family | Dugongidae |
| Named by | Retzius 1794 |
| Fossil records | 112 occurrences at 52 locations (PBDB) |
| Found in | Japan, United States, Russia, Mexico |
| Rock formations | txn:43286, San Mateo, Capistrano, San Diego, Sarumaru, Shimonopporo |
About Hydrodamalis
Hydrodamalis is a genus of extinct herbivorous sirenian marine mammals. It included the Steller's sea cow (Hydrodamalis gigas), the Cuesta sea cow (Hydrodamalis cuestae), and the Takikawa sea cow (Hydrodamalis spissa). The fossil genus Dusisiren is regarded as the sister taxon of Hydrodamalis: together, the two genera form the dugong subfamily Hydrodamalinae. They were the largest member of the order Sirenia, whose only extant members are the dugong (Dugong dugon) and the manatees (Trichechus spp.). They reached up to 9 metres (30 ft) in length, making the Steller's sea cow among the largest mammals other than whales to have existed in the Holocene epoch. Steller's sea cow was first described by Georg Wilhelm Steller, Cuesta by Daryl Domning, and Takikawa by Hitoshi Furusawa. The Steller's sea cow was the only member of the genus to survive into modern times, and, although had formerly been abundant throughout the North Pacific, by the mid 1700s, its range had been limited to a single, isolated population surrounding the uninhabited Commander Islands. It was hunted for its meat, skin, and fat by fur traders, and was also hunted by aboriginals of the North Pacific coast, leading to its and the genus' extinction 27 years after discovery. The Cuesta sea cow along with the Takikawa sea cow were probably extinct at the end of the Pliocene due to the onset of the Ice Ages and the subsequent recession of seagrasses—their main food source.
Text in “About” is quoted from the Wikipedia article Hydrodamalis (revision 1363905578), 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: Q1056723.
