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177 / Cenozoic
Desmostylus
Desmostylus hesperus
Bundles of enamel-wrapped tooth columns and broad limbs helped it crop aquatic plants in tidal flats and shallow water.
Structured expansion · editorial review pending
- Time range
- About 28–7 million years ago
- Final stage
- Late Miocene
- Geographic range
- Shallow North Pacific coasts · Japan, Russia and western North America
01 / ANSWER FIRST
What was Desmostylus?
This archive records Desmostylus under the scientific name Desmostylus hesperus, with an age of About 28–7 million years ago and a range of Shallow North Pacific coasts · Japan, Russia and western North America. Bundles of enamel-wrapped tooth columns and broad limbs helped it crop aquatic plants in tidal flats and shallow water.
Desmostylus belonged to the only entirely extinct order of marine mammals. Its hippo-like body, splayed limbs and small forward tusks suited a coastal life feeding on seagrass, algae or estuary plants.
02 / QUICK FACTS
Desmostylus at a glance
- Scientific name
- Desmostylus hesperus
- Age
- About 28–7 million years ago
- Last recorded stage
- Late Miocene
- Known range
- Shallow North Pacific coasts · Japan, Russia and western North America
- Broad group
- mammal or synapsid
- Archive era
- Cenozoic
- Habitat signals
- Ocean
- Documented regions
- Asia · North America
03 / ANATOMY
How was Desmostylus built?
Overall body plan
Bundles of enamel-wrapped tooth columns and broad limbs helped it crop aquatic plants in tidal flats and shallow water.
Skull, teeth and feeding mechanics
The available record is interpreted through preserved proportions, attachment surfaces, wear and comparison with related organisms. For Desmostylus, those observations must be separated from features added only for visual reconstruction.
Limbs, posture and body mass
Desmostylus belonged to the only entirely extinct order of marine mammals. Its hippo-like body, splayed limbs and small forward tusks suited a coastal life feeding on seagrass, algae or estuary plants.
Growth and individual variation
A single specimen does not define the whole species. Size, maturity, preservation and possible sex differences are considered before anatomical traits are treated as typical of Desmostylus.
04 / DIET & BEHAVIOUR
How did Desmostylus live?
Desmostylus belonged to the only entirely extinct order of marine mammals. Its hippo-like body, splayed limbs and small forward tusks suited a coastal life feeding on seagrass, algae or estuary plants. This ecological reconstruction is strongest where anatomy, associated organisms and the depositional setting point in the same direction.
05 / DIET & BEHAVIOUR
What shaped its ecological limits?
Its populations depended on food webs, vegetation, water, climate and competition. Changes in any one factor did not necessarily cause immediate extinction, but interacting pressures could reduce range, recruitment and resilience.
06 / RANGE & HABITAT
Where and when did Desmostylus live?
This archive currently lists About 28–7 million years ago; Shallow North Pacific coasts · Japan, Russia and western North America. Fossil or historical occurrence data describe where evidence has been found, not every place the taxon once occupied. Species-level age and range limits still require source-specific review.
Documented geographic range
Shallow North Pacific coasts · Japan, Russia and western North America. This boundary can change when specimens are reidentified or new localities are published.
Time window
About 28–7 million years ago, with the final recorded stage listed as Late Miocene. Rock units and dating uncertainty mean the true biological range may extend beyond the known record.
Environmental setting
The archive uses the broad habitat labels Ocean. These labels help explore related records; a habitat reconstruction requires evidence from individual localities.
07 / FOSSIL EVIDENCE
What evidence supports reconstructions of Desmostylus?
Primary record
Skulls, columnar molars and skeletons document its anatomy. A 2013 study found a relatively spongy internal bone structure in Desmostylus, contrasting with increased bone mass in several relatives, and interpreted it as a more active swimmer.
Comparative anatomy
Preserved structures are compared with close and functionally similar organisms. The method can constrain posture and function, but analogy alone cannot prove colour, behaviour or soft tissue.
Age and locality
Stratigraphy and occurrence records place Desmostylus within About 28–7 million years ago and Shallow North Pacific coasts · Japan, Russia and western North America. Reworked fossils and uncertain provenance are treated cautiously.
Open entity records
Links below connect the archive to available taxonomic and occurrence records. A matching name does not verify every ecological claim, and related-taxon links provide comparison rather than an exact species match.
Evidence limits for this record
Bone microstructure differs within Desmostylia. Increased bone mass in some relatives must not be transferred to Desmostylus, which showed a spongier pattern in the 2013 study.
08 / DISAPPEARANCE & DEBATE
Why did Desmostylus disappear?
Late Miocene changes in sea temperature, coastal vegetation and sea level, plus competition among large marine herbivores, may have ended desmostylians.
The last fossil or observation marks the youngest evidence currently known, not necessarily the death of the final individual. Explanations are strongest when timing, environmental change and population biology agree; otherwise the profile preserves uncertainty instead of assigning a single dramatic cause.
09 / FREQUENTLY ASKED QUESTIONS
Desmostylus FAQ
What was Desmostylus?
This archive records Desmostylus under the scientific name Desmostylus hesperus, with an age of About 28–7 million years ago. Bundles of enamel-wrapped tooth columns and broad limbs helped it crop aquatic plants in tidal flats and shallow water.
When did Desmostylus live?
The current archive range is About 28–7 million years ago; its youngest recorded stage is Late Miocene.
Where was Desmostylus found?
The archive currently lists Shallow North Pacific coasts · Japan, Russia and western North America. Species-level locality assignments and the full geographic range still require source-specific review.
How do scientists know about Desmostylus?
Skulls, columnar molars and skeletons document its anatomy. A 2013 study found a relatively spongy internal bone structure in Desmostylus, contrasting with increased bone mass in several relatives, and interpreted it as a more active swimmer.
04 / SOURCES & FURTHER READING
Check the source record
Use the scientific name to compare taxonomy, occurrence records and the fossil record. Database coverage and classifications may differ.
05 / REVISION HISTORY
How has this record changed?
- Completed an AI-assisted bilingual audit of the archive record, corrected identified issues and clarified evidence limits; independent editorial review is pending.
- Expanded into a structured bilingual profile with anatomy, ecology, range, evidence, debate and FAQs; independent editorial review is pending.
- Verified authoritative entity sources and added three responsive reconstruction sizes.
- Initial bilingual species record published.
06 / CORRECTIONS & ADDITIONS