Swiftopecten djoserusSwiftopecten djoserus ' is an extinct species of bivalve belonging to the subclass Pteriomorphia and family Pectinidae that lived during the Late Pliocene, approximately 2.75 Ma. Their two valves have step-like growth ribs.Origin of scientific nameThe species name comes from the Pyramid of Djoser in Saqqara, Egypt; the commarginal constrictions of Swiftopecten djoserus resemble the unique stepwise form of this pyramid.