Phenotypic variation in Gyroidinoides altiformis (Stewart & Stewart) and Gyroidinoides subangulatus (Plummer) (Foraminifera)

Abstract. The morphological variation of two benthic foraminiferal species, Gyroidinoides altiformis (Stewart & Stewart) and Gyroidinoides subangulatus (Plummer), are described from Late Neogene - Quaternary, and Palaeogene sequences from northern Italy and Greece. A number of morphotypes, two for each species, are thought to be ecophenotypes. The inferred ecological (bathymetric) conditioning derives from: 1) comparable shape variations occur in species of very different ages; 2) both species exhibit the same morphological changes as a result of a comparable environmental trend.