• “Globorotalia” acrostoma Wezel, 1966:1298-1301, pl. 101, figs. 1-8 [lower Miocene Globigerinoides trilobus Zone, Zona a scaglie tettoniche, Tempio River, Mirabella, Sicily, Italy].
• Globorotalia (Turborotalia) acrostoma Wezel.—Poore, 1979:470, pl. 9, figs. 6-9 [lower Miocene Zone N7, DSDP Site 408; middle Miocene Zone N8-N11, DSDP Site 407, North Atlantic Ocean].—Iaccarino and Salvatorini, 1979:263, pl. 3, figs. 7, 8 [lower Miocene Zone N8, DSDP Site 398, eastern North Atlantic Ocean].—Salvatorini and Cita, 1979, pl. 9, figs. 19-21 [lower Miocene Zones N7 and N8, DSDP Site 397, eastern North Atlantic Ocean].—Keller, 1981, pl. 2, figure designations unspecified [lower Miocene Zone N4, DSDP Site 292, northwest Pacific Ocean].—Iaccarino, 1985:304, 306, figs. 6.13a-c [reillustration of holotype drawing of Wezel, 1966].
• Globorotalia (Turborotalia) acrostoma Wezel.—Molina, 1979:244-246, pl. 29, figs. 1A-D [lower Miocene P. glomerosa curva Zone, Lavigado ES-5, Spain].
• Globorotalia (Jenkinsella) acrostoma Wezel.—Kennett and Srinivasan, 1983:176, pl. 43, figs. 7-9 [lower Miocene Zone N8, DSDP Site 408, North Atlantic Ocean].
• Paragloborotalia acrostoma (Wezel).—Spezzaferri, 1994:56, pl. 21, figs. 5a-d [lower Miocene, Zone N7/N8, DSDP Hole 548A, Goban Spur, eastern North Atlantic Ocean], pl. 22, figs. 3a-c [lower Miocene Zone N7/N8, DSDP Hole 548A, Goban Spur, eastern North Atlantic Ocean].

Wezel (1966) tentatively attributed acrostoma to the genus “Globorotalia” in quotation marks because of its cancellate rather than smooth wall of typical Globorotalia or Turborotalia; he further suggested that a new subgenus should be erected to accommodate “G.” acrostoma as well as other species like “G.” mayeri and “G.” continuosa.

Jenkins (1977) suggested that acrostoma is a junior synonym of semivera, while Poore (1979) suggested that acrostoma could be considered as a subspecies of mayeri. Despite the close morphologically similar characteristics with both semivera and mayeri, we recognize acrostoma as a unique taxon in large part because of its distinctive aperture and relatively limited biogeographic range in and around the Mediterranean and tropical Atlantic Ocean (e.g., Iaccarino, 1985). [Leckie et al. 2018]

Typical 5 chambered forms are pentagonal in outline, but not very lobulate. Paragloborotalia acrostoma is similar to semivera in having 5 chambers in the final whorl and a compact test with a narrow umbilicus, but it differs from semivera by its distinctly higher arched, semi-circular aperture bordered by an imperforate rim or thin lip. It is distinguished from siakensis by its higher arched aperture and tendency for curved spiral-side sutures. Specimens of acrostoma with 4½ chambers in the final whorl (e.g., Spezzaferri, 1994) closely resemble pseudocontinuosa, but are differentiated from the latter by having a higher arched aperture. Paragloborotalia acrostoma differs from continuosa in the same ways that it does with pseudocontinuosa, but acrostoma is also distinguished by its more umbilical-extraumbilical aperture, compared with a more extraumbilical aperture in continuosa.

Paragloborotalia acrostoma is distinguished from mayeri by its slightly greater spiral-side convexity, narrower umbilicus, fewer chambers (typically 5 compared with 6), and more umbilical-extraumbilical aperture. Paragloborotalia acrostoma is transitional in morphologic character between semivera and mayeri, however, the similar first occurrences of acrostoma and mayeri during the latest Oligocene suggest that acrostoma either falls within the range of variability for early forms of mayeri, or that the two taxa are more distantly related homeomorphs. Because of the more compact nature of acrostoma, including its narrow umbilicus, and its distinctive semi-circular apertural characteristics and one fewer chamber than typical mayeri, we have retained acrostoma as a valid taxon. [Leckie et al. 2018]

Gr. (J.) acrostoma closely resembles Gr. (J.) mayeri but is easily distinguished by its four to four and one-half chambers in the final whorl and larger and higher-arched aperture. [Kennett & Srinivasan 1983]

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