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Linked specimens: USNM-689041
Current identification/main database link: Globigerinatheka index (Finlay 1939)
The genus [Globigerinoides] seems to be completely absent throughout the Middle Tertiary and does not reappear until the Lower Ototaranor Kaiatan is reached. From this horizon down into Upper Bortonian (i.e. Lower Oligocene to Mid. Eocene) a distinct species, which may be called Globigerinoides index n.sp. (plate 14, figs. 85-88), occurs in great ablmdance and becomes the dominant Globigerinid. From conglobata it is separable at sight in its fewer and regularly inflated, instead of flatly rounded, chambers and its totally different apertural system, each chamber having instead of the several tiny openings of conglobata one very large and widely gaping final opening and two others somewhat smaller above the sutures of previous chambers. The two species are similar in their deeply cleft sutures and robust shell walls.
Size: Diameter, 0.4 mm.
Extra details from original publication
There is a slight resemblance to a Mexican Eocene from figured by Nuttall (1930, Journ. Pal., vol. 4, no. 3, p.290, pl. 24, figs. 12, 15), which he compared with Orbiformis Cole. The latter species has been recorded from the West Australian Eocene by Parr (1938, Journ. Roy. Soc. West. Aust., Vol. 24, p. 87, pl. 3, figs. 7a, c), who quotes Thalmann's consideration of it as synonymous with Globigerinoides mexicana (Cush.); all these forms are more tightly coiled and have more chambers than the New Zealand form.
This is an important key species of Upper Bortonian to Kaiatan time, its ubiquitous nature and constancy within that range and easy determination increasing its usefulness. It is the only Globigerinoides in the New Zealand early Tertiary and, though abundant in the Lower Ototaran Oamaru limestones and Kaiata beds, has vanished completely from the overlying Whaingaroan, where Globigerina angipora Stache is quite dominant and equally abundant. It is not to be confused with a small subspherical Globorotalia (aff. dehiscens Chapman, Parr and Collins), which ranges through Bortonian.
Finlay, H. J. (1939b). New Zealand foraminifera: Key species in stratigraphy - no. 2. Transactions of the Royal Society of New Zealand. 69(1): 89-128. gs Finlay, H. J. (1939c). New Zealand foraminifera: Key species in stratigraphy - no. 3. Transactions of the Royal Society of New Zealand. 69(3): 309-329. gs
Finlay, H. J. (1939b). New Zealand foraminifera: Key species in stratigraphy - no. 2. Transactions of the Royal Society of New Zealand. 69(1): 89-128. gs
Finlay, H. J. (1939c). New Zealand foraminifera: Key species in stratigraphy - no. 3. Transactions of the Royal Society of New Zealand. 69(3): 309-329. gs
Globigerinoides index compiled by the pforams@mikrotax project team viewed: 16-1-2021
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