Complex sentence: Joseph R. Caldwell first dug here in 1953 and was later followed by Carl Miller in 1958, but the most complete dig took place under the leadership of Arthur R. Kelly and Robert S. Nietzel from August, 1958 to January 1st, 1959.
Split into simpler sentences: Joseph R. Caldwell first excavated there in 1953 and he was later followed by Carl Miller in 1958. The most complete excavation took place under the leadership of Arthur R. Kelly and Robert S. Nietzel from August, 1958 to January 1,1959.