Catalog - Globigerinita hardingae

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Globigerinita hardingae

Citation: Globigerinita hardingae Blow 1979

Type specimens: Paratype PM PF 64641 Holotype PM PF 64640

Type age (chronostrat): Upper Eocene, lower Lutetian, Zone P11 (Globigerapsis kugleri/ Subbotinafrontosa boweri concurrent-range zone).

Type locality: Kilwa-Masoko water pipe trench, 200 yards west of Kilwa prison, southeastern Tanzania.

The small test is coiled in a low, tightly expressed, trochospire with about Il chambers comprising the spire and with four primary chambers in the last convolution. In dorsal aspect, the chambers are inflated but closelyset, appressed and embracing with slightly depressed, radially disposed intercameral sutures. The later chambers enlarge slowly within the progression of the trochospire but the final chamber is approximately equal in volume to the penultimate chamber. The equatorial profile is slightly lobulate and almost circular in outline. In ventral aspect, the primary chambers are closely appressed and embracing with indistinct intercameral sutures which are radially disposed. The umbilicus of the primary test is almost totally covered by an inflated, comparatively thin-walled, bulla which opens only at its umbilical (posterior) margin via a single, large, infralaminal aperture which bears a 'lip'. Oblique inspection of the primary aperture suggests that the primary umbilicus is deep and open. The primary aperture cannot be seen in the holotype. The walls of the primary chambers have extremely large-mural pores which open into extraordinarily large pore-pits with massive inter-pore ridges. Spine bases are formed at the confluent junction of adjacent inter-pore ridges.

Maximum diameter of holotype 0.235 mm as measured electronically.

This small taxon is extremely distinctive because of its extraordinary development of wall characters. Thus, morphotypes referable to the taxon consist ently show relatively very large mural-pores, large pore-pits and massively developed inter-pore ridges. It would seem that the morphotypes were normally spinose during life for large spine-bases are formed at the junction of the inter-pores ridges. The broken paratype shown on fig. 5, indicates that no portical structure is present for the primary aperture of the last chamber and this can be also verified from the paratype figured obliquely on fig. 3. This latter illustration also shows how strongly inflated the thin-walled, less coarsely perforate, bulla may be. The specimen illustrated on fig. I shows a comparatively small, but still inflated, bulla as well as the deep and open primary umbilicus. From the paratypes figured in ventral view, it seems that the primary aperture is not widely open but is essentially intraumbilical in position. The writer has not been able to relate the characters seen in his new taxon with those developed for any co-existing or prior existing morphotype. Thus, the peculiar characters of the test appear to be always associated with the presence of a bulla.
Although Globigerinita hardingae Blow, 1979, bears close morphological similarities to Globigerinita martini martini Blow and Banner, 1962 (see also Blow, 1979 op. cit., Part 3, pl. 24, fig. 5, and pl. 245, figs. 5, 6), the new taxon has an even more coarsely perforate primary wall. Furthermore, in G. hardingae, the primary chambers Increase more slowly in size as added within the progression of the trochospire and are less inflated but are more appressed and embracing than in the martini-morphotypes. Again, the bullae seen in the morphotypes referable to hardingae are consistently relatively smaller than as seen in martini martini. The holotype of martini martini has a maximum dimension of 0.19 mm (see Catalogue sheet) whilst the specimens figured on pl. 24, fig. 5 and pl. 245, figs. 5 and 6 [Blow, 1979, loc. cit.], have maximum dimensions of 0.25 mm, 0.165 mm and 0.204 mm, respectively. Similarly, the holotype and paratypes of hardingae show a size variation of between 0.235 mm (holotype) and 0.205 mm (paratype on fig. l). Consequently, it will be seen that the martini martini-morphotypes and the hardingae-morphotypes are of similar size-range and the features illustrated for the tests, such as wall texture, chamber size, width of umbilicus and dimensions of bullae, are strictly comparable from one photograph to another. Thus, very little allowance need be made for magnification effects in a comparison of the two taxa as figured herein.

References:

Blow, W. H. (1979). Blow, W. H. (1979). The Cainozoic Globigerinida: A study of the morphology, taxonomy, evolutionary relationships and stratigraphical distribution of some Globigerinida (mainly Globigerinacea). E. J. Brill, Leiden. 2: 1-1413. E. J. Brill, Leiden. 2: 1-1413. gs

Olsson, R. K., Hemleben, C., Huber, B. T. & Berggren, W. A. (2006a). Olsson, R. K., Hemleben, C., Huber, B. T. & Berggren, W. A. (2006). Taxonomy, biostratigraphy, and phylogeny of Eocene Globigerina, Globoturborotalita, Subbotina, and Turborotalita. In, Pearson, P. N. , Olsson, R. K. , Hemleben, C. , Huber, B. T. & Berggren, W. A. (eds) Atlas of Eocene Planktonic Foraminifera. Cushman Foundation for Foraminiferal Research, Special Publication. 41(Chap 6): 111-168. In, Pearson, P. N., Olsson, R. K., Hemleben, C., Huber, B. T. & Berggren, W. A. (eds) Atlas of Eocene Planktonic Foraminifera. Cushman Foundation for Foraminiferal Research, Special Publication . 41(Chap 6): 111-168. gs O

CATALOG OF ORIGINAL DESCRIPTIONS: Globigerinita hardingae Blow 1979

Globigerinita hardingae

References:

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