Twin development in the foraminiferal genus Alveolina

Abstract

The abnormal Alveolina individuals found by various researchers in different outcrops in Turkey are studied. The abnormal Alveolina individuals are classified as normal twins, Siamese twins, and teratogenetic specimens. No specimens with restored test or specimens having any other type of abnormal growth were growth were observed. In normal twins, two embryos usually merge along the horizontiontal plane parallel to the growth direction of the test. However, some normal twins display an unusual type of merging along the vertical plane, which is incongruous to the growth direction.