By Richard Horgan Los Angeles (Knewz) — Anna Reginelli, organizer of the Mississippi Fossil and Artifact Symposium and Exhibition in Greenwood, could scarcely believe her eyes. On Oct. 29, at the Museum of the Mississippi Delta, where the event was being held, a young man from Oxford walked in without warning and presented fossil remains of a giant American Lion. Wiley Prewitt, 26, had discovered the artifacts just days earlier on an exposed sand bank in the Mississippi River. “I have had very important artifacts and fossils come into my outreach programs and events, but nothing as significant…