OBJECT DOSSIER · SMITHSONIAN OPEN ACCESS

Ammonoid cephalopod — Agoniatites expansus

SAGE Museum Deep Time scientific dossier

Date / Period

Middle Devonian · Middle Devonian; documented material occurs in the Onondaga interval.

Object Type

shell fossil

Medium

representative_scientific_visual

About This Object

Geologic period: Middle Devonian

Age: Middle Devonian; documented material occurs in the Onondaga interval.

Feeding: Cephalopod feeding ecology is inferred from anatomy and related forms; soft feeding structures are not preserved by the shell.

Locomotion: Aquatic locomotion reconstructed from cephalopod biology.

Body plan: Planispirally coiled external shell divided internally into chambers.

Evidence: Shell shape, chambering and sutures are direct evidence. Soft anatomy is reconstructed.

Why it matters: Agoniatites represents the early radiation of ammonoids, a cephalopod lineage that later became enormously diverse.

Plain Language Identity: An early coiled ammonoid cephalopod from the Devonian.

What You Are Looking At: A coiled chambered shell belonging to an extinct cephalopod.

Ecosystem: Devonian marine ecosystem.

Preservation: Mineralized or mold-preserved shell fossil.

Open Questions: Do not give the animal a specific color or detailed soft body appearance as observed fact.

Source Urls: https://naturalhistory.si.edu/visit/virtual-tour/current-exhibits/deep-time-virtual-tour-fossil-list; https://pubs.usgs.gov/bul/0508/report.pdf

Enrichment Method: SAGE curated research pass; title and scientific name matched; evidence separated from inference

Scientific name: Agoniatites expansus

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.

Oceans Before Dinosaurs: The Rise of Complex Animal Life.

Provenance

Smithsonian Deep Time source scene: Early Life in the Ocean

Exhibition History

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

Subjects & Themes

Agoniatites expansus Middle Devonian shell fossil Early Life in the Ocean Oceans Before Dinosaurs

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.