Sea turtle — Protostega gigas

Geologic period: Late Cretaceous

Age: Approximately 85 million years old in the Smithsonian interpretation.

Feeding: Marine feeding; exact preferred prey remains reconstructed.

Locomotion: Open-water swimming.

Body plan: Very large marine turtle with powerful flipper-like limbs and a reduced shell compared with many modern hard-shelled turtles.

Evidence: Skeleton and limb anatomy directly establish large body size and marine adaptation.

Why it matters: Protostega demonstrates that giant marine turtles evolved while dinosaurs still dominated terrestrial ecosystems.

Plain Language Identity: One of the largest sea turtles known from the Late Cretaceous.

What You Are Looking At: Fossil skeletal remains of the giant marine turtle Protostega gigas.

Ecosystem: Western Interior Seaway.

Preservation: Original fossil skeletal material.

Open Questions: Do not assume its ecology was identical to any one living sea-turtle species.

Source Urls: https://naturalhistory.si.edu/visit/virtual-tour/current-exhibits/deep-time-virtual-tour-fossil-list; https://ocean.si.edu/ocean-life/reptiles/one-large-turtle-protostega-gigas

Enrichment Method: SAGE curated research pass; title + scientific name + source scene matched; comparative chronology retained; evidence separated from inference

Scientific name: Protostega gigas

Evidence / representation: comparative_taxon_visual

comparative_taxon_visual

Cretaceous Worlds: Dinosaurs at Their Most Diverse.

Media license: CC BY-SA 2.0

https://creativecommons.org/licenses/by-sa/2.0