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Large Eocene Mammal Fossils Unearthed During Oceanside Construction

Plaster‑jacketed limb bones and ribs will be prepared in a lab to decide whether the 40–45 million‑year‑old remains are a brontothere or an amynodont and then be curated for study.

Overview

  • Crews working on a city infrastructure project in Oceanside uncovered multiple fossilized limb bones, ribs and fragments about 12 feet below the surface during routine excavation.
  • Consulting paleontologist Joseph El Adli secured the site and his team spent roughly a week to 10 days manually exposing the bones, encasing them in plaster field jackets and moving them to an off‑site lab in Carlsbad.
  • Paleontologists date the material to the Uintan stage of the Eocene, about 40 to 45 million years old, and recovered pieces include specimens reported as more than two feet long.
  • Initial on‑site assessment narrows likely candidates to a brontothere (a so‑called “thunder beast”) or an amynodont (a “swamp rhino”) but a definitive ID will require cleaning and study of skull or tooth material.
  • The City of Oceanside is withholding the exact location for safety and site protection, the fossils are expected to enter a museum collection, and officials say further finds are possible as work continues.