Diversity observed among larger foraminiferal specimens collected from locations along the Great Barrier Reef (GBR), Australia, is addressed in reference to the type species Marginopora vertebralis. The description of Marginopora vertebralis is amended to reflect morphological and molecular variability found within a population from sub-tidal waters off Lizard Island and a population collected from the Heron-Wistari Channel in the southern GBR. Specimens from Lizard Island exhibit two distinct megalospheric (A form) morphologies: a uniform biconcave test variant and a plicated variant characterized by a wrinkled or folded test often with irregularly shaped medial apertures. In contrast, the microspheric (B form) tests are discoidal with uniform thickness from the embryonic apparatus through the reproductive chambers. Deep-dwelling Marginopora specimens collected from the Heron-Wistari Channel in the southern GBR are distinguishable from the Lizard Island specimens by their relatively larger and flatter biconcave tests characterized by a large number of medial apertures aligned in depressions along the periphery. The amended description of M. vertebralis serves to provide a basis for comparisons to future Marginopora collections.