Deterioration of symbiont-bearing morozovellid (planktic foraminifera) habitat recorded within the Early Eocene Climatic Optimum: evidence from the Tethys and sub-tropical Atlantic Ocean - Valeria Luciani; D'Onofrio Roberta; Backman Jan; GIUSBERTI, LUCA; FORNACIARI, ELIANA; RIO, DOMENICO (Rendiconti online della Società Geologica Italiana, 2014)