Original Description Test - Low trochospiral with strongly enveloping final chamber, globular to spherical; peripheral outline rounded, slightly lobate to circular. Wall: rather coarsely perforate. Chambers: very much inflated, globular or spherical, increasing rapidly in size; three to four in a whorl in early portion of test, somewhat embracing so that the initial portion of the test has a rounded appearance; final chamber much inflated, embracing the earlier portion of the test from 40 to over 75 percent. Sutures: slightly depressed to flush with surface. Apertures: umbilical on the initial whorl of chambers; numerous, long to short narrow slits or very small circular openings situated along the sutural contact between the ultimate chamber and the previous chambers, may also be present along sutural contacts of earlier-formed chambers. Extra details from original publication Remarks.-Praeorbulina n. gen. is similar in morphology to the genus Porticulasphaera. In fact, Praeorbulina is here considered a homeomorph of this middle Eocene genus. Praeorbulina differs (from Porticulasphaera) in the fewer chambers of the initial whorl, the more rapid increase in chamber size, and the somewhat embracing nature of the early chambers. The initial portion of Porticulasphaera is formed by a very low trochospire of numerous globular chambers that increase moderately in size; chambers in the final stage of test development become somewhat streptospirally arranged, increase more rapidly in size, and are more inflated. Perhaps the most noticeable difference between Praeorbulina and Porticulasphaera is in the nature of the apertural development. In the early whorl of chambers the primary aperture in Porticulasphaera is a very large, open arch that is umbilical-extraumbilical in position; whereas, in Praeorbulina the initial primary aperture is smaller and restricted to an umbilical position. In the adult stage the apertures of Praeorbulina consist of numerous narrow slits or very small circular openings; in contrast, the apertures in Porticulasphaera consist of a row of arches that are considerably larger than the circular openings openings that may be present in Praeorbulina. Other differences include the delicate hairlike spines on the early chambers of Porticulasphaera, which are apparently absent in Praeorbulina, and the more coarsely perforate wall of Praeorbulina.
Praeorbulina differs from Orbulina in the lack of areal apertures and from Globigerinoides in the lack in the adult stage of a distinct umbilicus and umbilical aperture.
External and internal morphologic studies were made on the following specimens housed in the U.S. National Museum, Washington, D. C.: Globigerina mexicana Cushman, holotype (CC 4334), type species of Porticulasphaera; Porticulasphaera mexicana (Cushman), whole and dissected hypotypes (USNM P 3901, 3902, 3906) deposited by Bolli, Loeblich, & Tappan (1957); Globigerinoides glomerosa glomerosa Blow, holotype (CC 64585), whole and dissected paratypes (CC 64586); Globigerinoides glomerosa curva Blow, holotype (CC 64587), whole and dissected paratypes (CC 64588); and Globigerinoides glomerosa circularis Blow, holotype (CC 64589), whole and dissected paratypes (CC 64590).
Olsson, R. K. (1964a). Praeorbulina Olsson, a new foraminiferal genus. Journal of Paleontology. 4: 770-771. gs
Praeorbulina compiled by the pforams@mikrotax project teamviewed: 7-6-2023
Reference should be
OLSSON, R. K., 1964. Praeorbulina Olsson, a new foraminiferal genus.
Journal of Paleontology, 4: 770–771.