Article: The development of Globigerinoides ruber (d'Orbigny 1839) from the Miocene to Recent

Previous workers considered that Globigerinoides ruber d'Orbigny 1839 ranged, with no appreciable morphological change, from early Miocene (Globigerinita dissimilis zone) to Recent. The present study, based on material from various parts of the world, suggests that the early to Middle Miocene forms can be distinguished from the Uppermost Miocene to Recent forms on the basis of ontogeny and phylogeny. The early to Middle Miocene forms are referred to Globigerinoides subquadratus Bronnimann 1954, which is redefined, the younger forms (Uppermost Miocene to Recent) to G. ruber. The ancestral form of G. subquadratus was G. quadrilobatus altiaperturus (Bolli 1957), and G. subquadratus s.s. (G. ruber of previous workers, e.g. Bolli 1957) first appears in the stainforthi and not in the G. dissimilis zone. Evidence from Jamaica suggests that a form broadly similar to G. obliquus Bolli 1957 is the ancestral form of G. ruber (here denned). An examination of the wall structure of the group reveals considerable variation, but there appears to be no fundamental differences between the earlier and later occurrences.