The systematic paleontology section includes brief taxonomic notes on a number of key taxa and the description of two new species, Sphenolithus arthurii and Fasciculithus fenestrellatus. The taxonomy follows the classification and organization of Young and Bown (1997) and Young (1998). Only bibliographic references not included in Perch-Nielsen (1985a, 1985b) and Bown (1998) are included in the reference list. A full taxonomic list of species cited in this paper follows in "Appendix B". Descriptive terminology follows the guidelines of Young et al. (1997), and the following abbreviations are used in taxonomic descriptions: LM = light microscope, XPL = cross polarized light, PC = phase-contrast illumination. The taxa are illustrated in Plates P1–P12.
Description: Large murolith coccolith with a broad rim, unicyclic in XPL, and a narrow, vacant central area. The central area width is variable, usually around the same width as the rim, but may be narrower or closed. Similar in morphology to the Jurassic species Crepidolithus crassus and distinguished from other Paleogene Neocrepidolithus species by its larger size, open central area, and simple unicyclic rim image.
Dimensions: length = 9.0–13.5 µm; width = 6.5–10.0 µm.
Occurrence: lower Eocene (Zone CP9) at Site 1208; Zone CP8–Subzone CP9b, Tanzania (Bown, 2005).
Remarks: Large discoasters with 6–8 rays, free for around half their length, and curving, although the degree of curvature is variable. Arrangement of rays usually shows asymmetry. The central area is broad and appears to be flat and unadorned.
Differentiation: Does not possess a central area stem like D. araneus and differentiated from D. lodoensis by asymmetry, variable degree of ray curvature, and shorter free ray length.
Occurrence: upper Paleocene–lower Eocene (Zone CP8–Subzone CP9b) at Site 1208.
Description: Large, robust sphenolith with tall proximal cycle (lower quadrants in XPL; see Young et al., 1997) and tall, tapering, monocrystalline apical spine. The base is taller than it is wide and appears as four quadrants separated by a clear extinction cross at 0°; the lower quadrants are as much as twice as tall as the upper quadrants. At 45° the base is crossed by diagonal extinction lines, and lateral cycles are visible, showing varying birefringence. The spine is tall (usually equivalent to the height of the base, but may be shorter) and inserted into the upper quadrants in a V-shape. The spine appears to be monocrystalline and is dark at 0° and brightest at 45°. Comparable in general morphology to the Miocene Sphenolithus belemnos; however, S. villae is larger and more robustly constructed, with blockier spine and base.
Dimensions: height = 9.0–12.0 µm; width = 3.0–5.0 µm.
Occurrence: lower Eocene (Zone CP9) at Site 1208; Subzones CP8b–CP9b, Tanzania (Bown, 2005)
Derivation of name: Named for Mike Arthur, paleoceanographer and ODP 198 shipboard scientist.
Diagnosis: Large, robust sphenolith with squat, square base and short, sharply tapering spine. The base is coarsely constructed, square-shaped, and crossed by an extinction cross at 0°; the lower and upper quadrants are near equidimensional. At 45° the base is crossed by diagonal extinction lines. The spine is short (equal to or shorter than the base) and tapers sharply to a point. The spine is compound and may be divided by a median extinction line at 0°, where it is darkest but still visible. The spine is brightest at 45°.
Differentiation: Comparable in general morphology to Sphenolithus radians; however, S. arthurii is larger and more coarsely constructed, with blockier spine and base.
Dimensions: height = 7.0–11.0 µm; width = 5.0–8.0 µm.
Holotype: Pl. P9, fig. 3 (fig. 4 is the same specimen).
Paratype: Pl. P9, fig. 5 (fig. 6 is the same specimen); Pl. P9, fig. 2 (fig. 1 is the same specimen).
Type locality: Leg 198, Site 1208, Shatsky Rise, northwest Pacific Ocean.
Type level: lower Eocene, Sample 198-1208A-36X-CC, 1.5 cm (Subzone CP9b).
Occurrence: lower Eocene (Subzone CP9b) at Site 1208.
Derivation of name: From fenestra, ella, and atus, meaning "with little windows," and referring to the distinct ornamentation of this fasciculith.
Diagnosis: Large, tall fasciculith that tapers toward its base and is ornamented with large, rectangular fenestrae delineated by distinct longitudinal and transverse ridges. The fasciculith is taller than it is wide. The LM image is not the typical two blocks seen in smaller fasciculiths, the median extinction line being indistinct.
Dimensions: height = 12.3 µm; width = 9.8 µm.
Holotype: Pl. P12, fig. 21 (figs. 21–24 are the same specimen).
Paratype: Pl. P12, fig. 19 (fig. 20 is the same specimen).
Type locality: Leg 198, Site 1208, Shatsky Rise, northwest Pacific Ocean.
Type level: upper Paleocene, Sample 198-1208A-36X-CC, 12 cm (Zone CP8).
Occurrence: upper Paleocene (Zone CP8) at Site 1208.
Description: Large fasciculith that tapers slightly toward its base and is ornamented with thick, rounded, protruding ridges. This fasciculith is broader than it is tall and possesses a relatively wide central opening. The LM image is not the typical two blocks seen in smaller fasciculiths.
Dimensions: height = 11.0 µm; width = 14.4 µm.
Occurrence: upper Paleocene (Zone CP8) at Site 1208.
Remarks: Broadly cubic-rhombic morphology with variable-length ray extensions from the corners. Cubic shape prevents the nannolith lying on one corner, as seen in Rhomboaster bramlettei.
Remarks: LM image shows two offset, superimposed, triradiate structures; rarely observed in side view (Pl. P11, figs. 22, 23).