Its name comes from the Greek words ( ' , â lessâ ) and ( ' , â newâ ) and means `` less recent '' , because it has 18 % fewer modern sea invertebrates than the Pliocene . Its name comes from the Greek words ( ' , â lessâ ) and ( ' , â newâ ) and means `` less recent '' because it has 18 % fewer modern sea invertebrates than the Pliocene .