OBJECT DOSSIER · SMITHSONIAN OPEN ACCESS

Mosasaur with plesiosaur remains — Tylosaurus proriger and Plesiosauria indet.

SAGE Museum Deep Time scientific dossier

Date / Period

Late Cretaceous · Approximately 81 to 85 million years old in the Smithsonian interpretation of this feeding association.

Object Type

composite

Medium

representative_scientific_visual

About This Object

Geologic period: Late Cretaceous

Age: Approximately 81 to 85 million years old in the Smithsonian interpretation of this feeding association.

Feeding: Direct evidence shows this individual consumed a plesiosaur.

Locomotion: Fully marine swimming.

Body plan: Large marine squamate predator with paddle-like limbs, powerful jaws and an elongated body.

Evidence: Stomach contents are direct fossil evidence of feeding, not merely inference from tooth shape.

Why it matters: This is one of the strongest food-web objects in the room. The mosasaur contains a plesiosaur, and the plesiosaur's digestive contents preserve smaller prey, directly linking multiple trophic levels.

Plain Language Identity: A large mosasaur preserving the remains of a plesiosaur inside its stomach—plus evidence of what that plesiosaur had eaten.

What You Are Looking At: A composite Tylosaurus display incorporating fossil evidence of plesiosaur stomach contents.

Defense Or Attack: Large jaws and teeth were used in predation.

Ecosystem: Western Interior Seaway of North America.

Formation: Niobrara Formation for Smithsonian Tylosaurus material.

Find Location: Kansas, United States for documented Smithsonian material.

Preservation: Composite display built around fossil skeletal and stomach-content evidence.

Open Questions: Do not generalize one animal's meal into the universal diet of every Tylosaurus.

Source Urls: https://naturalhistory.si.edu/visit/virtual-tour/current-exhibits/deep-time-virtual-tour-fossil-list; https://www.si.edu/stories/thanksgiving-try-fossil-turducken; https://www.si.edu/object/tylosaurus-proriger-cope-1869:nmnhpaleobiology_3429339

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

Scientific name: Tylosaurus proriger and Plesiosauria indet.

Evidence / representation: Representative evidence-type visual; not the exact specimen.

Why It Is In This SAGE Exhibit

Representative evidence-type visual; not the exact specimen.

Cretaceous Worlds: Dinosaurs at Their Most Diverse.

Provenance

Smithsonian Deep Time source scene: Dinosaur Diversity Peaks / Cretaceous Seas 2

Exhibition History

Included in the SAGE Museum Dinosaurs & Deep Time staging exhibit.

Subjects & Themes

Tylosaurus proriger and Plesiosauria indet. Late Cretaceous composite Dinosaur Diversity Peaks / Cretaceous Seas 2 Cretaceous Worlds

ORIGINAL COLLECTION SOURCE

This object page stays inside SAGE Museum. The Smithsonian link below is provided only as the original scholarly collection record. It opens separately.