ABSTRACT

Studies of the morphology and ultrastructure of Globorotalia (Turborotalia) pachyderma (Ehrenberg) support the concept that this species arose from G. (T.) continuosa (Blow) in the uppermost part of Neogene Zone 12; both species occur together up to the Upper Miocene zones N16 or N17, which is the upper limit of G. (T.) continuosa. Early chambers of G. (T.) pachyderma have the high, arched, laterally directed aperture of G. (T.) continuosa. This is a lineage quite distinct from that leading from G. (T.) globorotaloidea (Colom) to the Neogloboquadrina dutertrei (d'Orbigny) subcretacea-eggeri group in the Upper Miocene (N17-N18). The pachyderma group invariably has a well developed thickened imperforate lip, and the umbilicus is small or closed; the dutertrei group has an open umbilicus, and the apertural edge has only a smooth band (temperate forms such as the subspecies subcretacea) or toothlike flanges (tropical forms such as the typical dutertrei). In G. (T.) pachyderma there is an inverse correlation of chambers per whorl with size; in the N. dutertrei group there is a direct correlation between number of chambers per whorl and size.

Preferential coiling ratios occur almost at the base of the range for G. (T.) pachyderma, derived from its ancestor G. (T.) continuosa. Sinistral populations adjusted to cold polar waters whereas dextral populations adapted to temperate waters, providing one of the better planktonic indices of paleoceanography for the late Neogene.

Upper Miocene and Pliocene forms have mostly 4 to sometimes 4 1/2 chambers in the final whorl; the aperture varies from being almost a closed slit to more of an open arched condition. In the glacial Pleistocene, additional populations developed with sometimes 5 chambers in the final whorl; other variants show the progressive restriction of the sperture, especially with the development of a highly thickened wall in polar waters.

Referring to wall thickening, the early stage is that with little thickening ("incompta" of Cifelli), a second stage is that in which some thickening is added ("pseudopachyderma" of Cita, Silva, and Rossi), and, finally, a third stage is the typical thick-walled form. Wall thickening progressively reduces the depressions between the chambers until it is very difficult to recognize the individual chambers in extreme cases. This transition occurs as the populations settle progressively deeper in the water column.

G. (T.) pachyderma is a turborotaloid, a member of the important and continuous stock of Cenozoic planktonic foraminiferans that gave rise to many lineages of sharp-edged globorotaloids. The new subgenera Fobsella, Margaritella, and Menardella are erected for types in 3 of these separate lineages.

FIGURE 1. Location of Mohole, Guadalupe size.

EDITOR'S NOTE: Unfortunately the printer received this paper too late for the text to be included. The illustrations are included.

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FIGURE 2. Planktonic data for Mohole showing frequency distribution of most common planktonic species, curve for coiling ratios of Globorotalia (Turborotalia) pachyderma (Ehrenberg), and bar graph for important, but relative rare planktonic species. Approximate correlations of section with tropical Neogene Zones of Banner and Blow (1965) and Blow (1969) are given along right-hand side of Figure. Adapted from Bandy and Ingle (1970).

FIGURE 3. Late Cenozoic paleoceanographic cycles correlated with Neogene planktonic foraminiferal zones (Banner and Blow, 1965). Globorotalia truncatulinoides datum plane separates Neogene Zones 21 and 22, Sphaeroidinella dehiscens datum plane is approximate boundary of Neogene zones 18 and 19. Polar-water (temperature less than 9 degrees C) indices are sinistrally coiled populations of Globorotalia (Turborotalia) pachyderma; temperate-water (temperature of about 9 degrees to 18 degrees C) indices are dextrally coiled populations of this species. Tropical water (temperatures greater than about 18 degrees C) indices are represented by Globorotalia menardii fauna including Sphaeroidinella group. Adapted from Bandy (1968, 1969).

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EXPLANATION OF PLATE 1

(Neogene Zone 14)

Figures

1-3 Globorotalia (Turborotalia) pachyderma (Ehrenberg), dextral forms, Upper Miocene, Neogene Zone 14. USC Sample 11, Mohole, Guadalupe Site. See Figure 2 in text.

1. Hypotype No. 1411, diameter 0.30 mm. A. edge view, B. ventral view.
2. Hypotype No. 1412, diameter 0.30 mm. A. edge view, B. ventral view, C. enlarged view of apertural region in A. D. enlarged view of apertural region as seen in B.
3. Hypotype No. 1413, diameter 0.28 mm. A. edge view, B. enlarged view of apertural region as seen in A. Additional views shown on Plate 2, fig. 4.

Note: Original Scanning Electron Microscope photographs taken at 200X for general views and at 800X for enlarged views.

EXPLANATION OF PLATE 2

(Neogene Zones 14 and 15)

Figures

1-4 Globorotalia (Turborotalia) pachyderma (Ehrenberg), dextral forms, Upper Miocene, Mohole, Guadalupe Site, figures 1-3 from USC Sample 14 (Neogene Zone 15), figure 4 from USC Sample 11 (Neogene Zone 14). See Figure 2 in text.

1. Hypotype No. 1414, diameter 0.22 mm. A. ventral view, B. enlarged view of apertural region.
2. Hypotype No. 1415, diameter 0.23 mm. Ventral view.
3. Hypotype No. 1416, diameter 0.23 mm. A. ventral view, B. enlarged view of apertural region.
4. Hypotype No. 1413 (see P1. 1). A. ventral view, B. enlarged view of apertural region.

Note: Original SEM photographs were taken at 200X for general views and at 800X for enlarged views.

EXPLANATION OF PLATE 3

(Neogene Zone 18)

Figures

1-3 Globorotalia (Turborotalia) pachyderma (Ehrenberg), sinistral forms, Upper Miocene, Neogene Zone 18. Mohole section, Guadalupe Site, USC Sample 21, See Figure 2 in text.

1. Hypotype No. 1417, diameter 0.30 mm. A. ventral view, B. edge view, C. enlarged view of apertural region.
2. Hypotype No. 1418, diameter 0.34 mm. A. oblique ventral view, B. edge view, C. enlarged view of apertural area in B.
3. Hypotype No. 1419, diameter 0.30 mm. A. ventral view, slightly tilted to show apertural area, B. edge view.

Note: Original SEM photographs were taken at 200X for general views and at 800X for enlarged views.

EXPLANATION OF PLATE 4

(Late Pleistocene)

Figures

1-5 Globorotalia (Turborotalia) pachyderma (Ehrenberg), sinistral forms, Upper Pleistocene, continental borderland, California.

1. Hypotype No. 1420, diameter 0.28 mm. A. ventral view, B. enlarged view of apertural lip. AHF Station 4674, West Cortes Basin, 32° 16.5 N. Lat., 119° 19.5 W. Long., 1,595 m, 432-438 cm, ca. 29,000 years B. P.
2. Hypotype No. 1421, diameter 0.30 mm. Ventral view. Same location as Figure 1.
3. Hypotype No. 1422, diameter 0.27 mm. A. ventral view, B. edge view. AHF Station 4673, No Name Basin, 31° 54.0 N. Lat., 118° 11 W. Long., 1,780 m, 173-186 cm. Age between 12,000 and 30,000 years B. P.
4. Hypotype No. 1423, diameter 0.27 mm. A. ventral view, B. edge view. Same locality as Figure 3.
5. Hypotype No. 1424, diameter 0.26 mm. A. dorsal view, B. enlarged area of apertural region.

Note: Original SEM photographs were taken at about 200X for general views and at 1,000X for enlarged views.

EXPLANATION OF PLATE 5

(Temperate Areas)

1-8 Globorotalia (Turborotalia) pachyderma (Ehrenberg), Holocene dextral forms from temperate areas (1-5 off California, 6-8 Bay of Biscay).

1. Hypotype No. 1425, diameter 0.33 mm. Edge view. AHF Station 2165, 31° 31 N. Lat., 118° 26 W. Long., 2,452 m.
2. Hypotype No. 1426, diameter 0.28 mm. Edge view. AHF Station 4673, No Name Basin, 31° 54.0 N. Lat., 118° 11 W. Long., 1,780 m, 33-46 cm, slightly less than 11,000 years B. P.
3. Hypotype No. 1427, diameter 0.30 mm. A. dorsal view, B. ventral view. Same location as Figure 2.
4. Hypotype No. 1428, diameter 0.31 mm. A. ventral view, B. enlarged view of apertural lip. Same location as Figure 1.
5. Hypotype No. 1429, diameter 0.29 mm. Ventral view, slightly oblique. Same location as Figure 1.
6. Hypotype No. 1430, diameter 0.25 mm. Ventral view. Core P-16, Bay of Biscay, 43° 37 N., 1° 50 W., 830 m, 10-15 cm.
7. Hypotype No. 1431, diameter 0.30 mm. Dorsal view. Same location as Figure 6.
8. Hypotype No. 1432, diameter 0.27 mm. Ventral view. Same location as Figure 6.

Note: Original SEM photographs were taken at about 200X for general views and at 1,000X for enlarged views.

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EXPLANATION OF PLATE 6

(Arctic)

Figures

1-11 Globorotalia (Turborotalia) pachyderma (Ehrenberg) Modern sinistral forms of the Arctic Ocean.

1. Hypotype No. 1433, diameter 0.27 mm. Ventral view. Station 47 A (plankton tow, 0-100 m), Fletcher Ice Island T-3, 84° 13 N. Lat., 114° 42 W. Long.
2. Hypotype No. 1434, diameter 0.25 mm. Ventral view. Station 2, Fletcher Ice Island T-3, 86° 54 N. Lat., 80° 00 W. Long., 2,760 m.
3. Hypotype No. 1435, diameter 0.22 mm. Ventral view. Station 1A (plankton tow, 0-100 m.), Fletcher Ice Island T-3, 84° 22 N. Lat., 112° 32 W. Long.
4. Hypotype No. 1436, diameter 0.29 mm. Ventral view. Station 5, Fletcher Ice Island T-3, 86° 06 N. Lat., 95° 20 W. Long., 2,386 m.
5. Hypotype No. 1437, diameter 0.29 mm. A. ventral view, B. enlarged view of apertural lip. Same location as Figure 4.
6. Hypotype No. 1438, diameter 0.23 mm. Ventral view. Same location as Figure 4.
7. Hypotype No. 1439, diameter 0.26 mm. Ventral view. Same location as Figure 2.
8. Hypotype No. 1440, diameter 0.23 mm. Dorsal view. Same location as Figure 3.
9. Hypotype No. 1441, diameter 0.27 mm. Dorsal view. Same location as Figure 1.
10. Hypotype No. 1442, diameter 0.22 mm. Edge view. Same location as Figure 3.
11. Hypotype No. 1443, diameter 0.28 mm. Edge view. Same location as Figure 4.

EXPLANATION OF PLATE 7

(Antarctic)

1-14 Globorotalia (Turborotalia) pachyderma (Ehrenberg) Modern sinistral (Figs. 1-7) and dextral forms (Figs. 8-14) from Antarctic region.

1. Hypotype No. 1444, diameter 0.25 mm. Ventral view. Eltanin Station 308, 0-3 cm, 59° 00 S. Lat., 71° 00 W. Long., 3,789 m.
2. type No. 1445, diameter 0.30 mm. Ventral view, slightly oblique to show height of aperture Eltanin Station 39-40, 5-10 cm, 52° 03 S. Lat., 133° 57 E. Long., 3,255 m.
3. type No. 1446, diameter 0.29 mm. Ventral view. Same location as Figure 1.
4. type No. 1447, diameter 0.28 mm. Ventral view. Same location as Figure 2.
5. type No. 1448, diameter 0.26 mm. A. ventral view, B. edge view. Eltanin Station 39-67, 5-10 cm, 43° 38 S. Lat., 151° 58.9 E. Long., 2,112 m.
6. type No. 1449, diameter 0.30 mm. Ventral view. Same location as Figure 1.
7. type No. 1450, diameter 0.28 mm. Dorsal view. Same location as Figure 1.
8. type No. 1451, diameter 0.30 mm. Ventral view, slightly tilted to show height of aperture. Drake Passage, surface plankton, 57° 45 S. Lat., 67° 33 W. Long.
9. type No. 1452, diameter 0.24 mm. Ventral view. Eltanin Station 39-82, 5-10 cm, 32° 39 S. Lat., 171° 50 E. Long., 2,395 m.
10. type No. 1453, diameter 0.28 mm. Edge view. Same location as Figure 9.
11. type No. 1454, diameter 0.25 mm. Ventral view. Same location as Figure 9.
12. type No. 1455, diameter 0.33 mm. Ventral view. Eltanin Station 39-76, 75-80 cm., 36° 30 S. Lat., 161° 14 E. Long., 3,785 m.
13. type No. 1456, diameter 0.27 mm. Ventral view. Same location as Figure 5.
14. type No. 1457, diameter 0.32 mm. Ventral view. Same location as Figure 9.

EXPLANATION OF PLATE 8

Temperate Forms of Neogloboquadrina

1-5 Neogloboquadrina dutertrei subcretacea (Lomnicki). AHF Station 4673, 33-46 cm, No Name Basin, 31° 54 n. Lat., 118° 11 W. Long., 1,780 m.

1. Hypotype No. 1458, diameter 0.54 mm. Dorsal view.
2. Hypotype No. 1459, diameter 0.58 mm. Edge view.
3. Hypotype No. 1460, diameter 0.58 mm. Ventral view.
4. Hypotype No. 1461, diameter 0.47 mm. Ventral view.
5. Hypotype No. 1462, diameter 0.35 mm. Ventral view.

Tropical Forms of Neogloboquadrina

6-8 Neogloboquadrina dutertrei dutertrei (d'Orbigny), ANTON BRUUN Station 366C, Mozambique Channel, 23° 09 S. Lat., 43° 07 E. Long., 2,710 m. (trawl sample).

6. Hypotype No. 1463 maximum diameter 0.54 mm. A. ventral view, B. enlarged view of apertural teeth.
7. Hypotype No. 1464, maximum diameter 0.42 mm. A. ventral view, B. enlarged view of apertural teeth.
8. Hypotype No. 1465, diameter 0.58 mm. ventral view, B. edge view.

Note: Original SEM photographs were taken at 100X for Figures 1-4, 6, and 8; 200X for Figures 5 and 7A; and at 1,000X for Figures 6B and 7B.

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PLATE 1. [Grey Scale] See caption on page 435.

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PLATE 2. [Grey Scale] See caption on page 435.

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PLATE 3. [Grey Scale] See caption on page 435.

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PLATE 4. [Grey Scale] See caption on page 435.

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PLATE 5. [Grey Scale] See caption on page 435.

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PLATE 6. [Grey Scale] See caption on page 436.

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PLATE 7. [Grey Scale] See caption on page 436.

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PLATE 8. [Grey Scale] See caption on page 436.

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