Paleontologist Joseph El Adli found ribs, a femur and other limb bones 12 feet underground during routine monitoring of a City of Oceanside infrastructure project; the fossils are estimated to be 40–45 million years old, but may be from either a brontothere or an amynodont.
The fossils came from the Santiago Formation, a rock layer in northwestern San Diego County. Brontotheres were leaf-eaters roughly elephant-sized and often had a Y-shaped nasal horn; amynodonts were hornless, hippo-shaped herbivores with tusks in place of canine teeth.
The bones were exposed from several tons of mudstone over a week, then placed in a plaster jacket for transport to a climate-controlled lab. They will be cleaned, hardened and studied before going to a museum. Workers are searching for more bones, including a skull. Several blocks remain closed, and the city is withholding the find’s location to protect the site.
