Hydrodamalis gigas

Overview

Steller’s sea cow, Hydrodamalis gigas, was a sirenian that survived into historical times. Museums describe its toothless mouth and seaweed-eating way of life. Human records and surviving bones convey different stories.^[1]

Key facts

The historical extinction date presented by the museum is 1768. In addition to fossils in old layers, human records reveal the animal’s final period.^[1]

Time and place

It is treated as a Quaternary animal and survived into historical times. The Quaternary extends from about 2.6 million years ago to the present. Museums give 1768 as the date of its historical extinction.^[1][4]

The time range describes source context, not the complete duration of this species.

Size, form and skeleton

Its body is examined through comparisons with shared sirenian and dugong-family anatomy. Foreflippers and a posterior tail connect to the trunk. Species accounts also emphasize the toothless mouth.^[1][2]

A museum account gives a maximum body length of about 10 m.^[1]

Habitat and reproduction

The museum explains that Steller’s sea cow ate seaweed. Its toothless condition and food-handling methods raise questions about its way of life. Body records can be considered alongside historical ecological descriptions.^[1]

Fossil discovery

Stejneger’s 1883 excavation account records decayed skeletons and the limitations encountered when searching for extremity and tail bones. Historical observations and bone-collecting records convey information from different times. Even after extinction, surviving material contributes to understanding the body.^[3]

References

1. Extinction and known ecology of Steller’s sea cow
2. FAO — Body structure of Sirenia and Dugongidae
3. Stejneger (1883) — Natural-history observations in the Commander Islands
4. International Commission on Stratigraphy (2024) — Geological time chart
5. Domning & Gingerich1994 — Discovery of Protosiren smithae
6. Sirenia — Sea cow skeletons and evolution

Research questions

What different information do historical observations and excavation records supply? One conveys ecology and the final period of survival; the other records which bones survived and were collected. This animal invites several kinds of records to be read together.^[1][3]

Observation

Move your gaze from the foreflippers to the trunk and tail. Considering the toothless mouth alongside seaweed feeding helps connect body organization with the way of life preserved in historical records.^[1][2]