J. Nannoplankton Res. 32 (2), 2012, pp3-51 © 2012 International Nannoplankton Association
ISSN 1210-8049 Printed by Harcourt Colour Print, Swansea

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Calcareous nannofossils from the Paleogene equatorial
Pacific (IODP Expedition 320 Sites U1331-1334)
Paul R. Bown

Department of Earth Sciences, University College London, Gower Street, London, WC1E 6BT, UK; p.bown@ucl.ac.uk

Tom Dunkley Jones

School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
Manuscript Received 11th November, 2011; Manuscript Accepted 12th April, 2012.

Abstract Integrated Ocean Drilling Program Expedition 320 cored six sites and 16 holes (Sites U1331-U1336)

as part of the Pacific equatorial age transect, recovering a virtually complete composite section ranging from upper
Pleistocene to lower Eocene. In general, the successions comprise abyssal biogenic sediments with nannofossil- andradiolarian-ooze end members. Stratigraphic highlights include recovery of richly nannofossiliferous Oligocene successions and complete Eocene/Oligocene and Oligocene/Miocene boundaries at four sites: U1331 through U1334 andU1332 through U1336, respectively. Here, we present a taxonomic overview of the Paleogene nannofossil assemblages
from Sites U1331-1334, illustrating 163 taxa and including the description of 11 new species (Reticulofenestra moorei,
Reticulofenestra westerholdii, Coccolithus scheri, Cruciplacolithus? klausii, Calcidiscus? edgariae, Calcidiscus? kamikurii, Helicosphaera robinsoniae, Pedinocyclus gibbsiae, Discoaster williamsii, Sphenolithus kempii, Sphenolithus
richteri, Sphenolithus peartiae) and two new combinations (Calcidiscus? detectus, Coccolithus biparteoperculatus).

Keywords Paleogene, Eocene, Oligocene, Pacific, taxonomy, calcareous nannofossils
1. Introduction
Integrated Ocean Drilling Program Expedition (IODP
Exp.) 320 (March-May 2009) cored six sites and 16 holes(Sites U1331-U1336; Figure 1) as part of the Pacificequatorial age transect (PEAT), recovering a virtuallycomplete composite section ranging from upper Pleistocene to lower Eocene, representing 51 Ma of Earth history. The main objective of the PEAT is to study key intervals of Cenozoic climate history via a transect of sites
all drilled at the palaeo-Equator. The drilling strategy was
optimised to enhance the recovery of the calcareous sediments required for many palaeoceanographic proxy methodologies. This was achieved by targeting sediments thatwere deposited above the carbonate compensation depth(CCD) on what was young, shallow crust near to the East
Pacific Rise ridge axis. These sediment packages were
subsequently transported away from the ridge axis by
the north-westward drift of the Pacific plate (Pälike et al.
2010), such that sites targeting the oldest intervals (early/
middle Eocene), were furthest from the modern ridge axis
and situated on the oldest/deepest oceanic crust and thosetargeting more recent intervals (Miocene) were closer tothe modern ridge axes on young/shallow crust.
The youngest 12 million year portion of the Exp. 320
record (middle Miocene to Recent) was only well represented at Site U1335 and elsewhere only present as a relatively thin (5-12m) veneer of non-calcareous brown clay
(Figure 2). The targeted lower Eocene to lower Miocene
stratigraphy, however, was well recovered and comprises a continuous succession of biogenic sediments, withnannofossil- and radiolarian-ooze end members, acrossthis interval. Chert and porcellanite levels were present
in the lower parts of Sites U1331, U1332 and U1336,
whilst turbidites (with reworked microfossils) were present in limited horizons at Sites U1331 and U1335. All
the sites contribute near-continuous successions to theoverall composite section, with stratigraphic highlights

Figure 1. Location map of the sites drilled during IODP Expeditions
320 and 321. Previous DSDP and ODP sites are shown in white. F.Z. =fracture zone. The positions of Honolulu and Papeete are indicated fororientation (after Pälike et al., 2010).

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Bown, Dunkley Jones

Figure 2. Summary of the stratigraphy recovered at
PEAT Sites U1331–U1336 (after Pälike et al., 2010).

including the recovery of complete Eocene/Oligocene
and Oligocene/Miocene boundaries at four sites: U1331
through U1334 and U1332 through U1336, respectively.
The complementary IODP Expedition 321 (May-July2009) cored a further two sites (Sites U1337-1338), as
an integral part of the PEAT, focussing on the MiocenePleistocene interval. This completed the recovery of acontinuous section of early Eocene to Pleistocene sediments from beneath the Pacific palaeo-equator (Pälike etal. 2010). These sections provide excellent records of thebiotic response to periods of rapid environmental change
in the principal phytoplanktonic and zooplankton groups
and the benthic foraminifera.
Initial biostratigraphic results are published in Pälike
et al. (2010) and high resolution integrated stratigraphic,
isotopic and palaeoecological studies are in progress. In
this paper, we present a taxonomic overview of the Paleogene nannofossil assemblages from Sites U1331-1334,
illustrating 163 taxa and including the description of 11
new species and three new combinations.

2. Material and methods
Nannofossils were viewed in simple smear-slides (Bown
and Young, 1998), using transmitted-light microscopy(Zeiss Axiophot) in cross-polarised (XPL) and phasecontrast (PC) light at x1000-1600.
3. Biostratigraphy
Semi-quantitative biostratigraphic data was generated
during Exp. 320 drilling and the stratigraphic range chartsfor sites U1331-1334, presented here as Charts 1 through4, incorporate these data with some post-expedition revisions. In the Paleogene part of the section the nannofossil biozonation of Martini (1971) was used and all
standard nannofossil biozones were recognised (Zones
NP12-NP25). At these equatorial sites, however, the temperate-high latitude favouring taxa Isthmolithus recurvus
and Chiasmolithus oamaruensis were rare and sporadically distributed, and so the upper Eocene zones NP18-20
could not be reliably distinguished (Pälike et al., 2010).
Further discussion of biostratigraphically significant taxa
is included in Pälike et al. (2010) and the Systemic Palaeontology section that follows herein.

Calcareous nannofossils from the Paleogene equatorial Pacific4. Preservation and the CCD
The dominant Paleogene lithologies recovered during
Exp. 320 were biogenic oozes but the nature of the preserved sedimentary record varies dramatically throughthe succession. The dominant controls on this variation
appears to be the extent of water-column and seafloor dissolution, principally of calcareous microfossils, related tothe changing carbonate saturation state of Pacific deepwaters, together with changes in the nature and export
rates of original biotic production. The strength of the
carbonate dissolution signal is a direct result of the palaeodepth histories of these abyssal sites, with sedimentation commencing above the CCD on newly formed oceanic crust at shallow palaeodepths (~2.75km) near to theridge crest and, through time, subsiding below the CCD
to their current depths of 4.3 km or more. Superimposed
upon this subsidence-driven signal are relatively highfrequency, short-term fluctuations (~10-100s kyr), andlong-term trends (1-10s myr) in the depth of the CCD at
the basin-scale, which are driven by changes in regional
to global-scale biogeochemical cycling (Pälike et al., in
prep.).
The effects of carbonate dissolution are most apparent
in the oldest successions of Sites U1331 through U1333,
as evidenced by low carbonate values, poor nannofossil
preservation and the dominance of radiolarian ooze lithologies (Fig. 2; Pälike et al., 2010). These observations are
consistent with previous reconstructions of a very shallow Eocene CCD around 3-4 km depth. The most striking and sustained switch in the CCD is recorded close to
the Eocene/Oligocene boundary, at Sites U1331 throughU1334, and seen as a shift from radiolarian-dominatedEocene sediments to Oligocene nannofossil oozes. The
depth transect afforded by these sites indicates a deepening of the CCD by ~1 km in less than 500 kyrs. The
recovery of carbonate-rich Oligocene successions at allsites is evidence for a considerably deeper CCD (~4.5
km depth) throughout this time interval. For the younger,
post-Eocene sites, the point at which the site drifted outof the palaeo-equatorial upwelling zone coincides with atransition to carbonate-poor or carbonate-free sediments.
Shipboard qualitative estimates of foraminifera andnannofossil preservation and abundance reveal a strong
coupling between the preserved fossil record and thesite’s location relative to the CCD at any given time. They
also highlight the very different sensitivities to dissolution across the fossil groups (Pälike et al., 2010). Planktic
foraminifera display the most dissolution-sensitive recordof the documented microfossil groups, and are typicallyabsent in sediments with carbonate contents less than 6070 wt%CaCO3. At the oldest site (Site U1331) they arealmost entirely absent, appearing only where carbonate
maxima occur in the Oligocene, middle Eocene and basal
lower Eocene. At Site U1332 they are restricted to thecarbonate-rich Oligocene nannofossil oozes. Only at Sites
U1334 and U1335, where carbonate values remain at 8090% or more for considerable thicknesses, are planktic
foraminifera consistently recovered at high abundances
and with good preservation.

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Calcareous nannofossils and benthic foraminifera areless susceptible than planktic foraminifera to complete
destruction by dissolution and their abundances closely
track the presence/absence of carbonate in these sediments. This is not surprising given that coccoliths are, forthe most part, the major carbonate contributors to thesesediments. In general, however, the majority of nannofossil assemblages observed during Exp. 320 show some degree of modification by dissolution, with more robust taxa
dominating most assemblages. Certain nannofossil taxa
are especially sensitive to carbonate dissolution intensity.
Holococcoliths, for example, are entirely absent except
for one or two samples from Sites U1334-U1336, where
the relatively robust Zygrhablithus bijugatus is recorded.
Helicosphaera and Pontosphaera are typically absent at
the older, deeper sites (Sites U1331-1333) and only consistently present in the younger sediments (OligoceneMiocene) with high carbonate values, showing trends thatare similar to the planktonic foraminifera. Similarly, Oligocene calcidiscids are only recorded consistently in theshallowest, best preserved sediments of Site U1334. The
Eocene assemblages in general are strongly modified bypreservation, typified by the absence of small coccoliths,
concentration of dissolution-resistant discoasters and theloss of central structures in, for example, Chiasmolithus.
5. Stratigraphic range charts
Stratigraphic range charts are provided for Sites U1331
through U1334 (Charts 1-4). In most cases only data fromHole A at each site are included, though three or four holes
were drilled at each site to provide complete composite
sections. Revised composite depth scales for all sites areprovided by Westerhold et al. (2011). The sampling resolution was dependent on the requirements of shipboard
biostratigraphy. The amount of time spent on each sample
is variable through the datasets, with most effort spent oncore catcher (CC) samples, and section samples generally
the focus for marker species logging. Most CC samples
have been more thoroughly studied post-expedition, andpost-expedition observations are indicated in bold on thecharts. Sites U1333 and U1334, in particular, are currently
being studied at higher resolution and will be the subjectof additional biostratigraphic publications.
6. Systematic palaeontology
We provide images of the principal taxa from the IODP Exp.
320 Paleogene sites (U1331-1334) in 14 plates. The images
are reproduced at constant magnification and a 2µm scalebar is provided beside at least one of the images on eachplate. The sample information is provided using standard
IODP notation (Hole-Core-Section, depth in cm in section). For a number of key groups (e.g., reticulofenestrids,
sphenoliths) we have included multiple images to illustrate
the high degree of morphological variability present. All
taxa figured are listed but taxonomic remarks are only provided where comment (stratigraphic or taxonomic) is necessary. Descriptive terminology follows the guidelines ofYoung et al. (1997). The higher taxonomy essentially follows the scheme for extant coccolithophores of Young et6Bown, Dunkley Jones

Chart 1. Stratigraphic range chart for calcareous nannofossils from Hole U1331A. Biostratigraphic marker species and other notable occurrences areshaded, with darker shading at base and top horizons. Species abundance: A >10/field of view (FOV), C 1-10/FOV, F 1/2-10 FOV, R 1/11-100FOV,
1-5 total counts of very rare occurrences, ? questionable occurrence. Italics are used to indicate reworked occurrences. Nannofossil abundance:Calcareous nannofossils from the Paleogene equatorial Pacific

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A>10%, C 1-10%, F 0.1-1%, R<0.1%, B barren. Nannofossil preservation: G - good, M - moderate, P - poor. Nannofossil event notations are B =base, T = top, Tc = top common, Bc = base common. Nannofossil zones are after Martini (1971) and the timescale construction in general follows
Pälike et al. (2010). Barren samples are shaded in black.

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Bown, Dunkley Jonesal. (2003) and, for the extinct taxa, thescheme of Young and Bown (1997)(see Dunkley Jones et al., 2009 forfurther discussion). Informal groups
have been used to indicate morphological affinity within high diversity
genera, such as, Reticulofenestra,
Sphenolithus and Discoaster. All new
taxonomic names are Latin and themeaning and/or derivation is given ineach case. Range information is given
for stratigraphic distributions in theExp. 320 sites. Morphometric data are
given for all new taxa based on measurement from the type specimens
and additional data is provided forthe reticulofenestrids, sphenoliths andcalcidiscids (Tables 1-3). Only thosetaxonomic references not listed in
Perch-Nielsen (1985), Bown (1998)
or Jordan et al. (2004) are included in
the reference list. The following abbreviations are used: LM – light microscope, XPL cross-polarised light,
PC – phase-contrast illumination, L– length, H – height, W – width, D –diameter. Type material and images
are stored in the Department of Earth
Sciences, University College London.
6.1. PLACOLITH COCCOLITHS

Chart 1. Continued
NB. Reworking, related to the occurrence of turbidites, was common at this site

Order ISOCHRYSIDALES
Pascher, 1910
Family NOELAERHABDACEAE
Jerkovic, 1970 emend. Young &Bown, 1997
Pl. 1, figs 1-48; Pl. 2, 1-19
Remarks: The majority of the Exp.
320 nannofossil assemblages are
dominated by reticulofenestrids (Reticulofenestra, Cyclicargolithus) thatshow a high degree of variability insize, outline, central area width andnet type (Table 1). The establishedtaxonomy for the Paleogene representatives of this group does notclearly accommodate or represent
this variability, but this is equallytrue of younger representatives ofthe family (see, for example, discussion in Gallagher, 1989 and Young,1990). Our classification herein applies widely-used species names
and several new taxa, and places
these within a framework of informal groups. We have not attempted
a revision of the reticulofenestrids asa whole but instead highlight someCalcareous nannofossils from the Paleogene equatorial Pacific9Figure 3. Stratigraphic distribution of Paleogene and early Neogene reticulofenestrids. The timescale is from Pälike et al. (2010). Dotted verticallines are questionable stratigraphic ranges, horizontal bars indicate well constrained range base or top.

of the outstanding taxonomic issues. An overview of thestratigraphic distribution of Paleogene reticulofenestrids
is given in Figure 3 and morphometric data is provided inTable 1. The informal groups are as follows:
1. Reticulofenestra umbilicus Group (common, middle
Eocene-lower Oligocene) - typically elliptical outline
and relatively open central area with thin, impercep-

tible net (non-birefringent or lost). There is a high degree of variability within this group, which was informally divided using simple coccolith length categories(see also Young, 1990). Forms with broadly ellipticalto subcircular outlines and/or narrower central areas
were in some cases difficult to distinguish from species of Cyclicargolithus.

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Chart 2. Stratigraphic range chart for calcareous nannofossils from Hole U1332A. See Chart 1 for further information.

Calcareous nannofossils from the Paleogene equatorial PacificChart 2. Continued

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Chart 2. Continued

Bown, Dunkley JonesCalcareous nannofossils from the Paleogene equatorial Pacific13

2. Reticulofenestra lockeri Group (common, upper Eocene-upper Oligocene)- elliptical outline and relatively open
central area with robust, visible net (birefringent).
3. Reticulofenestra reticulata Group(common, middle-upper Eocene) typically circular outline and relatively
narrow circular central area with robust, visible net (birefringent). This
group includes the only strictly circular
Paleogene reticulofenestrids but somesmaller forms had imperceptible (orlost) nets and there is some evidence oftransitional subcircularity.
4. Reticulofenestra bisecta Group (common, upper Eocene-lower Oligocene)– elliptical outline and central area
closed by very robust, conspicuous distal ‘plug’ (birefringent). As defined thisgroup is essentially restricted to the Paleogene.
5. Cyclicargolithus floridanus (common
in the Eocene and dominant, lower Oligocene-lower Miocene) – subcircular
to broadly elliptical outline and narrow
central area with thin, imperceptible net(non-birefringent or lost).
Group 3 broadly, but not completely, correlates with the general usage of the genus
Cribrocentrum Perch-Nielsen, 1971 andGroup 4 with the genus Dictyococcites
Black, 1967. These generic names are notapplied here, because we currently lack agood understanding of the phylogenetic
relationships between these reticulofenestrids.
6.1.1. Reticulofenestra
umbilicus Group
Reticulofenestra dictyoda(Deflandre in Deflandre & Fert, 1954)
Stradner in Stradner & Edwards, 1968
Pl. 1, figs 2-6, 9-10.
Remarks: Small to very large (3-14 µm),
elliptical reticulofenestrids with open
central area. There is a great deal of morphological variability within this group,
including degree of ellipticity/circularity, size of central area and width of tube
cycle. A broad species concept is applied
here.

Table 1. Morphometric data (L, W, L/W axial ratio) and descriptive shape terms for theillustrated reticulofenestrids. The descriptive terms and definitions are slightly modified
after Young et al. (1997): circular 1.00-1.03, subcircular 1.04-1.09, broadly elliptical 1.101.25, narrowly elliptical 1.26-1.45.

Reticulofenestra circus? de Kaenel &Villa, 1996
Pl. 1, figs 19-20
Remarks: Not consistently logged herein and close to theapplied species concept of Reticulofenestra hillae (see be-low), but should be subcircular. The specimens illustrated
here have axial ratios of 1.12, which is strictly broadly
elliptical (see Young et al., 1997 for outline definitions).

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Chart 3. Stratigraphic range chart for calcareous nannofossils from Hole U1333A. See Chart 1 for further information.

Calcareous nannofossils from the Paleogene equatorial PacificChart 3. Continued

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Chart 3. Continued

Bown, Dunkley JonesCalcareous nannofossils from the Paleogene equatorial PacificChart 3. Continued

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Bown, Dunkley Jones

Reticulofenestra hillae Bukry & Percival, 1971
Pl. 1, figs 21-24
Remarks: Used here for large (~>9µm), broadly elliptical
reticulofenestrids with narrow central area that can be distinctly quadrate or lens-shaped. This includes coccoliths
that are smaller than those of the original type material(14-20µm). This is similar to the species concept of Reticulofenestra circus de Kaenel & Villa, 1996 (described as
subcircular, 8-10µm) and Reticulofenestra circus var. lata
Maiorano, 2006 (12-14µm), but the specimens from Exp.
320 are broadly elliptical and most like the holotype of R.
hillae. Occurrence: Particularly conspicuous in the Eocene/Oligocene boundary interval and lower Oligocene(Zones NP19/20-NP22) but also present in the Eocene(Zones NP17-NP19/20); IODP Site U1334. R. circus isdocumented from Zones NP22–NP23 (de Kaenel & Villa,
1996; Maiorano, 2006).
Reticulofenestra minuta Roth, 1970
Pl. 1, figs 1, 8. Remarks: Small (<3 µm), elliptical with
open central area.
Reticulofenestra moorei sp. nov.
Pl. 1, figs 13-17
Derivation of name: Named after Ted Moore (University of Michigan, USA), Exp. 320 shipboard scientist, micropalaeontologist and palaeoceanographer. Diagnosis:
Normally elliptical reticulofenestrid with relatively wide
central area and an net that is faintly visible or imperceptible. Differentiation: Distinguished from other R. umbilicus group and R. lockeri group coccoliths by narrower
shape (axial ratio ~1.26-1.40; Table 1). Dimensions: Holotype L = 6.8 µm (Paratype L = 6.2 µm). Holotype: Pl.1,
fig.15. Paratype: Pl.1, figs 13. Type locality: IODP Hole
U1333A, Pacific Ocean. Type level: Oligocene, Sample
U1333A-11X-CC (Zone NP22). Occurrence: Zone
NP17-Zone NP23; IODP Sites U1333 (NP21-NP23),
1334. Particularly common in the Eocene/Oligocene
boundary interval and lower Oligocene (NP19/20-NP22).
Reticulofenestra pseudoumbilicus (Gartner, 1967)
Gartner, 1969
Pl. 1, figs 11-12
Remarks: The differentiation between Paleogene R. umbilicus Group coccoliths and Neogene Reticulofenestra
pseudoumbilicus is highly problematic, and beyond thescope of this paper. Suffice to say, the two groups overlap
morphologically and the species concepts are essentiallystratigraphy dependent.
Reticulofenestra umbilicus (Levin, 1965)
Martini & Ritzkowski, 1968
Pl. 1, fig. 7
Reticulofenestra wadeae Bown, 2005
Pl. 1, fig. 18
6.1.2. Reticulofenestra lockeri Group
Reticulofenestra daviesii (Haq 1968) Haq, 1971
Pl. 1, figs 29-30.
Remarks: Usually applied to forms that possess a visible
central net with an outer cycle of pores, but appears tointegrade with R. lockeri type coccoliths with nets without
visible pores. The appearance of these taxa may be affected by different preservation states.
Reticulofenestra c f. R. daviesii (Haq 1968) Haq, 1971
Pl. 1, fig. 36.
Like R. daviesii but the central area is very narrow.
Reticulofenestra filewiczii (Wise & Wiegand in Wise,
1983) Dunkley Jones et al., 2009
Pl. 1, figs 31-35.
Remarks: Broadly elliptical with a narrow central areaand birefringent net.
Reticulofenestra lockeri Müller, 1970
Pl. 1, figs 25-27
Reticulofenestra cf. R. lockeri Müller, 1970
Pl. 1, fig. 28.
Remarks: Like R. lockeri but with relatively wider central area.
6.1.3. Reticulofenestra reticulata Group
Reticulofenestra erbae Fornaciari et al., 2010
Pl. 1, fig. 47.
Remarks: Like R. reticulata but with a closed central
area. Occurrence: Zone NP19/20; Site U1334; NP17NP19, Fornaciari et al. (2010).
Reticulofenestra reticulata (Gartner & Smith, 1967)
Roth & Thierstein, 1972
Pl. 1, figs 44-46
Remarks: Medium to large (~8-12µm), circular reticulofenestrid with narrow central area crossed by a distinctive, robust, visible net. Subcircular to ellitical forms havealso been observed (Pl. 1., fig. 48; Pl. 2, figs 1-3) andmay intergrade with the R. filewiczii morphotype. Occurrence: Zone NP17-Zone NP19/20; IODP Sites U1331,
1333-1334.
Reticulofenestra cf. R. reticulata(Gartner & Smith, 1967) Roth & Thierstein, 1972
Pl. 1, figs 48; Pl. 2, figs 1-3.
Remarks: Like R. reticulata but subcircular to broadly
elliptical. These morphotypes are similar to R. filewiczii.
Occurrence: Zone NP19/20; Site U1334.
Reticulofenestra westerholdii sp. nov.
Pl. 1, figs 37-39.
Derivation of name: Named after Thomas Westerhold(University of Bremen, Germany), Exp. 320 shipboard
scientist, stratigrapher and palaeoceanographer. Diagnosis: Medium sized (5-8µm), circular reticulofenestrid with
open central area (similar in width to, or slightly narrower
than, the rim width) but no perceptible net. Subcircular
to broadly elliptical forms are rarely observed and distinguised as R. cf. R. westerholdii (Pl. 1. figs 40-43). Differentiation: Distinguished from R. reticulata by the smallersize, narrower tube, proportionally wider central area andabsence of visible net. Distinguished from C. floridanusby the circular outline, wider central area and low tube
cycle. Dimensions: Holotype L = 6.9 µm (Paratype L =Calcareous nannofossils from the Paleogene equatorial PacificChart 4. Stratigraphic range chart for calcareous nannofossils from Hole U1334A. See Chart 1 for further information.

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Chart 4. Continued

Bown, Dunkley JonesCyclicargolithus cf. C. abisectus (~11 µm)

Clausicoccus cf. C. subdistichus small CA

Calcareous nannofossils from the Paleogene equatorial PacificChart 4. Continued

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Reticulofenestra cf. R. daviesii (narrow CA)

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Chart 4. Continued

Bown, Dunkley Jones

Reticulofenestra cf. R. westerholdii (subcirc.)

Reticulofenestra cf. R. reticulata (subcirc.)

Reticulofenestra pseudoumbilicus (>7µm)

Reticulofenestra pseudoumbilicus (5-7µm)

Calcareous nannofossils from the Paleogene equatorial PacificChart 4. Continued

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Bown, Dunkley Jones

5.9 µm). Holotype: Pl.1, fig.39. Paratype: Pl.1, figs 38.
Type locality: IODP Hole U1334A, Pacific Ocean. Typelevel: Upper Eocene, Sample U1334A-28H-CC (ZoneNP19/20). Occurrence: Can be common to abundant.
Zone NP16-Zone NP19/20; IODP Sites U1331-1334.
Reticulofenestra cf. R. westerholdii sp. nov.
Pl. 1, figs 40-43.
Remarks: Like R. westerholdii but subcircular to broadly
elliptical. Occurrence: Zone NP19/20; Site U1334.
6.1.4. Cyclicargolithus floridanus Group
Cyclicargolithus abisectus(Roth & Hay, in Hay et al., 1967) Bukry, 1971
Pl. 2, fig. 18.
Remarks: Large Cyclicargolithus (>11.0µm) with relatively consistent stratigraphic range in the equatorial Pacific (NP24-NP25), but similar morphotypes do occur
earlier (Pl. 2, figs 4-5) and morphometric studies suggests
the 11µm cut-off is rather arbitrary (Firth, 1992; Olafsson,1992).
Cyclicargolithus cf. C. abisectus(Roth & Hay, in Hay et al., 1967) Bukry, 1971
Pl. 2, fig. 4-5.
Remarks: Large subcircular to broadly elliptical reticulofenestrids with conspicuous tube cycle and narrow central area. Similar to upper Eocene Reticulofenestra cf. R.
reticulata and upper Oligocene Cyclicargolithus abisectus. They appear to have slightly lower tube cycles thanthe latter and so are differentiated here, although the difference is subtle. Occurrence: Zone NP21-lower NP22;
Sites U1333, 1334.
Cyclicargolithus floridanus(Roth & Hay, in Hay et al., 1967) Bukry, 1971
Pl. 2, figs 6-12
Cyclicargolithus? luminis (Sullivan, 1965) Bukry, 1971
Pl. 2, fig. 19
6.1.5. Reticulofenestra bisecta Group
Reticulofenestra bisecta (Hay et al., 1966) Roth, 1970
Pl. 2, figs 13-15.
Remarks: The holotype length of R. bisecta is 8µm and
we use the species name here for specimens <10µm in
length. It should be noted that this species concept, based
upon size ranges, is applied differently by some authors(see Young, 1998, p. 248).
Reticulofenestra stavensis(Levin & Joerger, 1967) Varol, 1989
Pl. 2, figs 16-17.
Remarks: The holotype size of R. stavensis is 14µm and
we use the species here for the size range 10-20µm.
Family PRINSIACEAE Hay & Mohler, 1967 emend.
Young & Bown, 1997
Genus Towieus Hay & Mohler, 1967
Pl. 2, figs 20-25.

Remarks: Toweius was one of the dominant placolithgroups of the late Paleocene to early Eocene but went into
decline broadly coincident with the appearance and rise todominance of the reticulofenestrid group (early Eocene,zones NP12-13) (e.g., Agnini et al. 2006). The extinctionlevels of the youngest Toweius species are not particularly well constrained, however, Bralower and Mutterlose(1995) report the top of Toweius spp. in Zone NP12 andGirgisia gammation in Zone NP14 at ODP Site 865, andPerch-Nielsen (1985) reports T. callosus and G. gammation into Zone NP15. The species G. gammation has beenplaced both in Toweius and a separate genus Girgisia andranges from Zone NP11-NP15. Relatively common Toweius coccoliths are present in the basal sediments at Site
U1331 (Zone NP12/NP13 transition), including T. pertusus, T. callosus and G. gammation-like forms, and Site
U1333 (Zone NP15), including T. pertusus and G. gammation-like forms, but are absent in the highly dissolved
basal sediments of Site U1332 (Zone NP14), which contain only discoasters.
Toweius callosus Perch-Nielsen, 1971
Pl. 2, fig. 22
Girgisia gammation? (Bramlette & Sullivan, 1961)
Varol, 1989
Pl. 2, figs 23-25
Remarks: The specimens seen at Site U1331 were identified as G. gammation but they do not show the distinctive
curving extinction lines that characterise the species. Thisis probably due to etching of the coccoliths, which may
also lead to enlargement of the central area and loss of the
tube cycle.
Toweius pertusus (Sullivan, 1965) Romein, 1979
Pl. 2, fig. 21

Order COCCOSPHAERALES Haeckel, 1894 emend.
Young & Bown, 1997
Family CALCIDISCACEAE Young & Bown, 1997
Pl. 2, figs 26-49; Pl. 3; Pl. 4, 1-11
Remarks: The Exp. 320 calcidiscid and calcidiscid-likecoccoliths are divided here into three informal groups:
1. Paleogene calcidiscid Group – a morphologically diverse group of elliptical to circular placoliths with
only some taxa having proven calcidiscid morphology,
while most await more detailed morphological analysis (Bown et al., 2007).
2. Calcidiscus leptoporus Group - predominantly Neogene to Modern group with early forms recorded in the
Oligocene in the Exp. 320 material.
3. Other calcidiscids – includes the predominantly Neogene to Modern forms not included in the C. leptoporus Group.
6.1.6. Paleogene calcisdiscid Group
Calcidiscus? detectus(de Kaenel & Villa, 1996) comb. nov.
Basionym: Ericsonia detecta (de Kaenel & Villa, 1996),
p. 125, pl. 4, figs 1-3. ODP Sci. Res., 149: 79-145.
Pl. 2, figs 26-35.

Calcareous nannofossils from the Paleogene equatorial Pacific25

Table 2. Morphometric data (L, W, L/W axial ratio, central area CA width) and descriptive shape terms for the illustrated calcidiscids. For descriptive
terms and definitions see Table 1.

Remarks: Medium to large (~5-9µm), elliptical placolithcoccoliths with narrow bicyclic rim (in XPL) and wide,
apparently vacant, central area. The rim width is aroundhalf that of the central area (rim width/central area width:
0.5-0.7; Table 2). Differentiation: Similar to Calcidiscus
protoannulus but strongly elliptical, and to Calcidiscus?
edgariae sp. nov., but with narrower shields. Remarks:
Only consistently present in the site with best Oligocene
preservation (Site U1334), suggesting it is susceptible todissolution. Occurrence: Zones NP22-25 (single occurrence in Zone NP21, one questionable Zone NP17 occurrence); Sites U1333, U1334. Present in very few samples
at U1333 (Zones NP22-23) and absent at U1332.
Calcidiscus? edgariae sp. nov
Pl. 2, figs 36-49
Derivation of name: Named after Kirsty Edgar (University of Cardiff, UK), Exp. 320 shipboard scientist, micropalaeontologist and palaeoceanographer. Diagnosis:
Medium to large (~5-10µm), broadly elliptical placolithcoccoliths with broad bicyclic rim (in XPL) and vacantcentral area. The rim width is similar to, or slightly greater than, that of the central area (rim width/central area
width: 1.0-1.4; Table 2). Differentiation: Distinguishedfrom Calcidiscus? detectus by the broader rim and relatively narrower central area. Remarks: Only consistently
present in the site with best Oligocene preservation (Site
U1334), suggesting it is susceptible to dissolution. Dimensions: Holotype L = 8.9 µm (Paratypes L = 5.5, 7.8µm). Holotype: Pl.2, fig.46. Paratype: Pl.2, figs 36, 42.
Type locality: IODP Hole U1334A, Pacific Ocean. Typelevel: Oligocene, Sample U1334A-19H-CC (Zone NP23).
Occurrence: Zone NP23-Zone NP25 (single occurrencein Zone NP21); IODP Sites U1333, 1334. Present in very
few samples at U1333 (Zone NP23) and absent at U1332.
Calcidiscus? kamikurii sp. nov.
Pl. 3, figs 1-6

Derivation of name: Named after Shin-ichi Kamikuri(Hokkaido University, Japan), IODP Expedition 320
shipboard scientist and micropalaeontologist. Diagnosis:
Medium to large (~7-10µm), broadly elliptical placolithcoccoliths with broad bicyclic rim (in XPL) and vacant,narrow central area. The rim width is greater than the central area width (rim width/central area width: 1.6-1.9; Table 2). Differentiation: Similar to Calcidiscus? edgariae
but more broadly elliptical with relatively broader rim andnarrower central area. Pedinocyclus larvalis and P. okayi(Pl. 3, figs 7-16) have elements joined along sutures withstrong obliquity. Dimensions: L = 9.2 µm (Paratype L =9.0 µm). Holotype: Pl.3, fig.1. Paratype: Pl.3, fig.3. Type
locality: IODP Hole U1334A, Pacific Ocean. Type level:
Oligocene, Sample U1334A-20H-CC (Zone NP23). Occurrence: Zone NP23-Zone NP24; IODP Site U1334.
Calcidiscus? bicircus Bown, 2005
Pl. 4, fig. 7
Calcidiscus? henrikseniae Bown, 2005
Pl. 4, fig. 8
Calcidiscus? pacificanus (Bukry, 1971) Varol, 1989
Pl. 4, fig. 9
Calcidiscus protoannulus(Gartner, 1971) Loeblich & Tappan, 1978
Pl. 3, figs 19-20
Coronocyclus nitescens(Kamptner 1963) Bramlette & Wilcoxon 1967
Pl. 3, figs 23-24
Umbilicosphaera bramlettei(Hay & Towe, 1962) Bown et al., 2007
Pl. 3, figs 17-18
6.1.7. Calcidiscus leptoporus Group
Calcidiscus pataecus Gartner, 1967
Pl. 3, figs 25-40
Remarks: Used herein for small to medium (~3-8µm), el-26

Bown, Dunkley Jones

liptical Calcidiscus coccoliths with a closed central area.
Specimens were informally divided into less than or greater than 5µm in length. Larger specimens (>5µm) appear
in Zone NP25. Only consistently present in the site withthe best Oligocene preservation (Site U1334; sporadicallypresent at Site U1333), suggesting it is susceptible to dissolution. Occurrence: Zone NP23-Zone NN6 (questionable, rare and sporadic occurrences from NP19/20 at Site
U1334, but consistently present from NP23); IODP Sites
U1332 (one sample), U1333, U1334. Larger specimens(>5µm) appear in Zone NP25.
Calcidiscus leptoporus (Murray and Blackman, 1898)
Loeblich and Tappan, 1978
Pl. 3, figs 45-48
Remarks: Present from Zone NN2 in Site U1334.
Calcidiscus cf. C. leptoporus (Murray and Blackman,
1898) Loeblich and Tappan, 1978
Pl. 3, figs 43-44
Remarks: Small, circular Calcidiscus with closed central
area.
Calcidiscus premacintyrei Theodoridis, 1984
Pl. 3, figs 49-50
6.1.8. Other calcidiscids
Umbilicosphaera jafari Müller, 1974
Pl. 4, figs 1-4
Remarks: Common from the upper Oligocene (Zone
NP24) but present only in the best-preserved samples
from Site U1334, suggesting high sensitivity to dissolution. Umbilicosphaera rotula is present from Zone NN2.
Umbilicosphaera jordanii Bown, 2005
Pl. 3, figs 21-22
Umbilicosphaera rotula (Kamptner, 1956) Varol, 1982
Pl. 4, figs 5-6
Hayaster perplexus(Bramlette & Riedel, 1954) Bukry, 1973
Pl. 4, figs 10-11
Family COCCOLITHACEAE Poche, 1913 emend.
Young & Bown, 1997
Remarks: The coccolithacean and coccolithacean-likecoccoliths are divided here into three informal groups:
1. Coccolithus pelagicus Group – C. pelagicus and similar coccoliths with narrow central areas that may be
spanned by a transverse bar.
2. Chiasmolithus-Cruciplacolithus Group – forms withcentral area cross bars.
3. Clausicoccus Group – forms with perforate central
area plates.
6.1.9. Coccolithus pelagicus Group
Coccolithus biparteoperculatus Varol, 1991 comb. nov.
Basionym: Birkelundia biparteoperculatus
Varol, 1991, p. 220, pl. 7, figs 11-12. N. Jb. Geol.
Paläont. Abh. 182: 211-237.
Pl. 4, figs 12-18

Remarks: Similar to Coccolithus pelagicus but the tube
cycle may be indistinct and the narrow central area is filled
by a two-part oval bar with a transverse suture. Also similar to Coccolithus cachaoi Bown, 2005 but distinguishedby the two-part bar. The similarity between these coccolithacean coccoliths has led us to propose this recombination. Occurrence: Zone NP15-Zone NP22; IODP Sites
U1331-1334. NP12-NP23 (Varol, 1991).
Coccolithus eopelagicus(Bramlette & Riedel, 1954) Bramlette & Sullivan, 1961
Pl. 4, fig. 27
Coccolithus mutatus (Perch-Nielsen, 1971) Bown, 2005
Pl. 4, fig. 26
Coccolithus pelagicus (Wallich, 1877) Schiller, 1930
Pl. 4, fig. 25

Coccolithus scheri sp. nov.
Pl. 4, figs 19-24
Derivation of name: Named after Howie Scher (University of South Carolina, USA), Exp. 320 shipboard scientist and palaeoceanographer. Diagnosis: Small to medium-sized elliptical Coccolithus with narrow central area
filled by a birefringent broad, oval transverse bar, whichis bright at around 45° to the polarizing direction. Differentiation: Distinguished from other Coccolithus species
by the diagnostic birefringent transverse bar. Remarks:
Most consistently present in the site with best Oligocene
preservation (Site U1334), suggesting it is susceptible
to dissolution. Dimensions: Holotype L = 5.3µm (Paratype L = 6.0µm). Holotype: Pl.4, fig.23. Paratype: Pl.4,
fig.21. Type locality: IODP Hole U1334A, Pacific Ocean.
Type level: Oligocene, Sample U1334A-19H-CC (Zone
NP23). Occurrence: Zone NP22-Zone NP24; IODP Sites
U1332 (one NP23 sample), U1333 (only NP23), U1334.
Ericsonia robusta (Bramlette & Sullivan, 1961)
Edwards & Perch-Nielsen, 1975
Pl. 4, figs 30-32
Remarks: The large variant of this species has a documented last occurrence in the late Paleocene (Raffi et al.,2005) but the smaller form, illustrated here, is occasionally reported above this level. The species is recorded sporadically in the Exp. 320 Eocene sediments, from zones
NP12 (Site U1331), NP15 (Site U1333) and NP17-19/20(Site U1334). This suggests that the species was present
throughout the Eocene but was rare and perhaps ecologically restricted.
6.1.10. Chiasmolithus-CruciplacolithusGroup
Bramletteius serraculoides Gartner, 1969
Pl. 4, figs 33-35
Campylosphaera dela(Bramlette & Sullivan, 1961) Hay & Mohler, 1967
Pl. 5, fig. 12
Chiasmolithus altus Bukry and Percival, 1971
Pl. 4, figs 39-40
Chiasmolithus gigas(Bramlette & Sullivan, 1961) Radomski, 1968
Pl. 4, fig. 28

Calcareous nannofossils from the Paleogene equatorial Pacific

Chiasmolithus grandis(Bramlette & Riedel, 1954) Radomski, 1968
Pl. 4, fig. 29
Chiasmolithus nitidus Perch-Nielsen, 1971
Pl. 4, fig. 36
Chiasmolithus oamaruensis(Deflandre, 1954) Hay et al., 1966
Pl. 4, fig. 41
Chiasmolithus titus Gartner, 1970
Pl. 4, figs 37-38
Cruciplacolithus cruciformis(Hay & Towe, 1962) Roth, 1970
Pl. 5, fig. 11
Cruciplacolithus? klausii sp. nov.
Pl. 5, figs 1-10
Derivation of name: Named after Adam Klaus (IODP,
Texas A & M, USA), IODP Expedition 320 shipboard
staff scientist and palaeoceanographer. Diagnosis: Medium sized (~6-8µm), elliptical placolith coccoliths witha low birefringence rim and narrow central area almost
filled by broad low birefringence axial cross bars. The
brigher tube cycle may be indistinct. Differentiation:
Distinguished from other Cruciplacolithus species by
the indistinct tube cycle and low birefringence appearance in XPL. Remarks: Only consistently present in
the site with best Oligocene preservation (Site U1334),
suggesting it is susceptible to dissolution. Dimensions:
Holotype L = 7.0µm (Paratype 6.1µm). Holotype: Pl.5,
fig.1. Paratype: Pl.5, fig.3. Type locality: IODP Hole
U1334A, Pacific Ocean. Type level: Upper Oligocene,
Sample U1334A-15H-CC (Zone NP25). Occurrence:
Zone NP21-Zone NP25 (singular occurrence in NP19/20
at U1334); IODP Sites U1332 (one NP23 sample), U1333(NP22-23), U1334.
Cruciplacolithus cf. C. primus Perch-Nielsen, 1977
Pl. 5, figs 13-14
6.1.11. Clausicoccus Group
Clausicoccus fenestratus(Deflandre & Fert, 1954) Prins 1979
Pl. 5, fig. 17
Clausicoccus subdistichus(Roth & Hay in Hay et al., 1967) Prins, 1979
Pl. 5, figs 15-16
Clausicoccus cf. C. subdistichus(Roth & Hay in Hay et al., 1967) Prins, 1979
Pl. 5, figs 19-20
Remarks: Like C. subdistichus but with very narrow central area.
Clausicoccus vanheckiae(Perch-Nielsen, 1986) de Kaenel & Villa, 1996
Pl. 5, fig. 18
Clausicoccus? sp. rim
Pl. 5, figs 21-23
Remarks: Small bicyclic rims with open central areas but
otherwise similar to C. subdistichus. Conspicuous in theupper Oligocene/lower Miocene part of Site U1334.

27

Hughesius gizoensis Varol, 1989
Pl. 5, figs 25-30
Hughesius tasmaniae (Edwards and Perch-Nielsen,1975) de Kaenel and Villa, 1996
Pl. 5, figs 24, 31-35
Hughesius? sp.
Pl. 5, figs 37-42
Remarks: Small bicyclic coccoliths with very narrow
central area but otherwise similar to Hughesius gizoensis.
Tetralithoides symeonidesii? Theodoridis, 1984
Pl. 5, figs 36, 43-48
Remarks: Oligocene forms are small inconspicuous coccoliths with four-part plate filling the central area. Reminiscent of the Modern narrow-rimmed placolith group(Young et al., 2003, p. 70) and the Neogene Tetralithoides
symeonidesii (Pl. 5, fig. 36).
6.1.12. Placolith coccoliths Incertae
Sedis
Pedinocyclus larvalis Bukry & Bramlette, 1971
Pl. 3, figs 7-9
Pedinocyclus gibbsiae sp. nov.
Pl. 3, figs 10-16
Derivation of name: Named after Samantha Gibbs (University of Southampton, UK) nannopalaeontologist andpalaeoceanographer. Diagnosis: Medium to large (~610µm), circular coccoliths with broad rim, narrow, brightinner tube cycle (in XPL) and open central-area. The rim
width is just less than half that of the central area (rimwidth/central area width: ~0.4.) and the rim elements arestrongly inclined. Differentiation: Distinguished from
Pedinocyclus larvalis by the relatively narrower rim andwider central area, and from the early Eocene Geminilithella okayi Varol, 1989 by the broader inner tube cycle.
Remarks: Most consistently present in the site with best
Oligocene preservation (Site U1334), suggesting it is susceptible to dissolution. Dimensions: L = 8.3 µm (Paratype
L = 8.8 µm). Holotype: Pl.3, fig.10. Paratype: Pl.3, fig.13.
Type locality: IODP Hole U1334A, Pacific Ocean. Typelevel: Oligocene, Sample U1334A-19H-CC (Zone NP23).
Occurrence: Zone NP23-Zone NP25 with rare and sporadic occurrences NP21-22; IODP Sites U1332-1334.
Hayella challengeri (Müller, 1974) Theodoridis, 1984
Pl. 6, figs 1-3
Hayella situliformis Gartner, 1969
Pl. 6, figs 4-5
Ilselithina fusa Roth, 1970
Pl. 6, figs 6-9
Ellipsolithus macellus(Bramlette & Sullivan, 1961) Sullivan, 1964
Pl. 6, figs 10, 11?
6.2. Mesozoic muroliths
Neocrepidolithus sp. Pl. 6, fig. 12

28

Bown, Dunkley Jones

6.3. Cenozoic muroliths
Order ZYGODISCALES Young & Bown, 1997
Family HELICOSPHAERACEAE Black, 1971
Genus Helicosphaera Kamptner, 1954
Remarks: Helicosphaera are only present in those Exp.
320 sediments with highest carbonate content, providing
strong evidence for the high preservation sensitivity inthis group (see also Pontosphaera). Occurrences are typically rare and sporadic. We have applied the following
informal groups:
1. Helicosphaera carteri Group – diffuse birefringent
blanket and flange ending with distinct wing (Oligocene-Modern).
2. Helicosphaera compacta-recta Group – well-definedand distinctly birefringent blanket (upper Middle Eocene-upper Oligocene: Zone NP17-NN1).
3. Helicosphaera seminulum Group – diffuse birefringent blanket, relatively wide central area and disjuntbars (Lower Eocene - Oligocene: Zone NP12-NP25?).
6.3.1. Helicosphaera carteri Group
Helicosphaera granulata(Bukry and Percival, 1971) Jafar and Martini, 1975
Pl. 6, figs 13-18
Helicosphaera intermedia Martini, 1965
Pl. 6, figs 19-24
6.3.2. Helicosphaera compacta-recta
Group
Helicosphaera clarissima Bown, 2005
Pl. 6, fig. 25
Helicosphaera compacta Bramlette & Wilcoxon, 1967
Pl. 6, figs 26-28
Helicosphaera recta Haq, 1966 (Jafar & Martini, 1975)
Pl. 6, figs 35-39
Helicosphaera reticulata Bramlette & Wilcoxon, 1967
Pl. 6, figs 40-42
Helicosphaera robinsoniae sp. nov.
Pl. 6, figs 29-34
Derivation of name: Named after Rebecca Robinson(University of Rhode Island, USA), Exp. 320 shipboard
scientist and palaeoceanographer. Diagnosis: Large Helicosphaera with birefringent blanket, indistinct but disjunct, birefringent oblique bar, and anterior spur. Differentiation: Similar to H. compacta and H. clarissima but withanterior spur and indistinct disjunct birefringent obliquebar. H. recta has a conjunct, transverse bar. Dimensions: L= 11.8µm (Paratype L = 11.6µm). Holotype: Pl.6, fig.31.
Paratype: Pl.6, fig.34. Type locality: IODP Hole U1334A,
Pacific Ocean. Type level: Lower Oligocene, Sample
U1334A-26X-3, 100 cm (Zone NP21). Occurrence: Upper Zone NP21-lower Zone NP22; IODP Sites U1334.
6.3.3. Helicosphaera seminulum Group
Helicosphaera bramlettei(Müller, 1970) Jafar & Martini, 1975
Pl. 6, figs 43-44

Helicosphaera lophota(Bramlette & Sullivan, 1961) Locker, 1973
Pl. 6, fig. 45
Helicosphaera cf. H. wilcoxoni Gartner, 1971
Pl. 6, figs 46-48
Remarks. Helicosphaera with open central area spannedby a disjunct transverse bar with dark median suture. The
wing morphology is unclear. Occurrence. Rare NP21-22,
Site U1334.
Family PONTOSPHAERACEAE Lemmermann, 1908
Genus Pontosphaera Lohmann, 1902
Pl. 7, figs 1-2
Remarks: Pontosphaera are very rare and only present
in the highest carbonate content sediments of Expedition
320 indicating high preservation sensitivity in this group(see also Helicosphaera).
Family ZYGODISCAEAE Hay & Mohler, 1967
Isthmolithus recurvus
Deflandre in Deflandre and Fert, 1954
Pl. 7, figs 3-4
Neococcolithes protenus(Bramlette and Sullivan, 1961) Black, 1967
Pl. 14, figs 1-3
Order SYRACOSPHAERALES Hay, 1977 emend.
Young et al., 2003
Family SYRACOSPHAERACEAE
Lemmermann, 1908 Syracosphaera sp.
Pl. 7, figs 5-6
Family RHABDOSPHAERACEAE Haeckel, 1894
Genus Blackites Hay & Towe, 1962
Pl. 7, figs 7-15
Remarks: Can be common from Zone NP15 to NP23 but
present only in the better-preserved samples, althoughtypically as disarticulated spines. Occurrence: Zone
NP15-Zone NP23; IODP Site U1331-1334.
Blackites spines
Pl. 7, figs 8-15
Remarks: The disarticulated spines were identified to
species level as follows:
1. Blackites spinosus – gently tapering spines with wideaxial canal;
2. Blackites tenuis – narrow spines with narrow axial canal that initially broaden slightly before gentle tapering;
3. Pseudotriquetrorhabdulus inversus – tapers at bothends, ragged appearance and narrow axial canal.
Blackites amplus Roth & Hay, 1967
Pl. 7, fig. 7Blackites spinosus(Deflandre & Fert, 1954) Hay & Towe, 1962
Pl. 7, figs 8-9, 13Blackites tenuis Bramlette and Sullivan, 1961
Pl. 7, figs 14-15

Calcareous nannofossils from the Paleogene equatorial PacificPseudotriquetrorhabdulus inversus (Bukry & Bramlette,1969) Wise in Wise & Constans, 1976
Pl. 7, figs 10-12
Remarks: Considered a Triquetrorhabdulus-like nannolith by Wise in Wise and Constans (1976) but occurs withother Blackites spines here and may represent a distinct
species or a preservational (overgrown) morphotype.
6.4. HOLOCOCCOLITHS
Family CALYPTROSPHAERACEAE
Boudreaux & Hay, 1967
Zygrhablithus bijugatus bijugatus(Deflandre in Deflandre & Fert, 1954) Deflandre, 1959
Pl. 13, fig. 46
Remarks: Of the holococcoliths, only one or two specimens of Z. bijugatus were found throughout the entire
Exp. 320 sample set, illustrating the pervasive effect ofdissolution in these deep abyssal-plain sediments. Dissolution susceptible holococcoliths are removed during thelong export path from the photic zone or during sedimentation and diagenesis at the sea floor.
6.5. HAPTOPHYTE NANNOLITHS
Family BRAARUDOSPHAERACEAE
Deflandre, 1947
Remarks: No pentaliths (Braarudosphaera, Micrantholithus, Pemma) were observed in the Exp. 320 material,confirming the predominantly neritic distribution of thesetaxa (e.g., Young et al., 2003).
Family TRIQUETRORHABDULACEAE Lipps, 1969
Genus Triquetrorhabdulus Martini, 1965
Pl. 7, figs 16-22
Remarks: These elongate nannoliths are common toabundant in the uppermost Oligocene and lower Miocene,
especially in sediments where selective dissolution has
concentrated them, together with discoasters. Three species were identified:
1. T. carinatus - relatively long with median ridge.
2. T. longus - long to very long and narrow.
3. T. milowii - short and broad (rice grain shaped); someof these may represent overgrown T. challengeri
Perch-Nielsen, 1977 specimens, but multiple ridges
were not observed.
Triquetrorhabdulus carinatus Martini, 1965
Pl. 7, figs 17-19
Triquetrorhabdulus longus Blaj et al., 2010
Pl. 7, fig. 16
Triquetrorhabdulus milowii Bukry, 1971
Pl. 7, figs 20-22
Orthorhabdus serratus Bramlette and Wilcoxon, 1967
Pl. 7, fig. 23

29

6.6. EXTINCT NANNOLITHS
Order DISCOASTERALES
Hay, 1977 emend. Bown, 2010
Family DISCOASTERACEAE Tan, 1927
6.6.1. Discoaster deflandrei GroupPl. 7, figs 24-39, Pl. 9, figs 40-41
Remarks: Discoasters with long free-rays that have distinct terminal bifurcations. Species are differentiatedbased on ray thickness, modal ray number and overall
size, e.g. D. deflandrei has 5-6 rays, D. septemradiatushas 7-8 rays, and D. nonaradiatus has 9 rays (but includes
10-12 rays).
Discoaster exilis Martini and Bramlette, 1963
Pl. 7, fig. 37
Discoaster deflandrei Bramlette and Riedel, 1954
Pl. 7, figs 24-27
Discoaster martinii Stradner, 1959
Pl. 7, figs 32-33, 38-39
Discoaster nonaradiatus Klumpp, 1953
Pl. 7, figs 35-36
Discoaster petaliformis Moshkovitz and Ehrlich, 1980
Pl. 9, figs 40-41
Discoaster septemradiatus(Klumpp, 1953) Martini, 1958
Pl. 7, figs 28-31, 34
6.6.2. Discoaster nodifer GroupPl. 8, figs 1-40
Remarks: Discoasters with short to long free-rays thathave paired lateral nodes just before the pointed or
notched ray tips. Species herein broadly differentiated onmodal ray number and ray length: D. tanii has 5 rays, D.
nodifer has 6-9 rays, D. druggii has 6 rays and is large(>15µm), D. binodosus has 8 rays with free ray lengththat approaches half the diameter of the central area or
greater, and D. mediosus has 10 rays or more with freerays less than half the length of the central area.
Discoaster druggii Bramlette & Wilcoxon, 1967
Pl. 8, fig 18
Discoaster mediosus Bramlette & Sullivan, 1961
Pl. 8, fig. 1-3
Remarks: Discoaster mediosus usually has ten rays ormore with free rays less than half the length of the central area; D. binodosus usually has 8 rays with longer
free length and prominent lateral nodes and pointed ray
tips (see discussion in Bown, 2005, p. 44). Occurrence:
Zones NP15-16; IODP Site U1331 (but this site was subject to reworking).
Discoaster nodifer(Bramlette & Riedel, 1954) Bukry, 1973
Pl. 8, fig. 4-8, 13
Remarks: Six- to nine-rayed stellate discoasters withprominent lateral nodes on their rays and ray-end notches
or bifurcations.
Discoaster strictus Stradner, 1961
Pl. 8, fig. 9

30

Bown, Dunkley Jones

S. disbelemnos
S. disbelemnos
S. disbelemnos
S. disbelemnos
S. belemnos

Table 3. Morphometric data (base height H, base width W, base W/H ratio, H’ height to spine bifurcation) for selected illustrated sphenoliths. BaseW/H ratio categories are based on Blaj et al. (2010): S. ciperoensis <1.7, S. distentus 1.7-2.5, S. predistentus >2.5.

Discoaster tanii Bramlette & Riedel, 1954
Pl. 8, fig. 10-12, 15-17, 19-28
Remarks: Five-rayed stellate discoasters with long freerays terminating in a flat or slightly notched ray-end.
Paired lateral nodes are variably developed. Large, threedimensional specimens (Pl. 8, figs 15-17) and forms withprominent central bosses (Pl. 8, figs 19-28) were distinguished as separate varieties, described below.
Discoaster tanii Bramlette & Riedel, 1954 variety 1
Pl. 8, fig. 15-17
Remarks: Large (typically >15µm), three-dimensional
D. tanii variety. Occurrence: Zone NP17- lower Zone
NP24; IODP Site U1334.
Discoaster tanii Bramlette & Riedel, 1954 variety 2
Pl. 8, fig. 19-28
Remarks: Medium to large (9-19µm) D. tanii variety
with wide central area and prominent boss on one face.
The rays are relatively shorter than D. tanii s.s. but thismay be due to poor preservation. Occurrence. Zones
NP18-20; IODP Sites U1331, U1333, U1334.
Discoaster williamsii sp. nov.
Pl. 8, figs 32-40
Derivation of name: Named after Trevor Williams(Lamont Doherty Earth Observatory of Columbia University, USA), IODP Exp. 320 logging staff scientist andpalaeoceanographer. Diagnosis: Six rayed discoaster withbroad central area that is distinctly elevated on both faces.
The rays are narrow and free for around half their length.
Paired lateral nodes just before the ray tips are present insome specimens (Pl. 8, figs 38-40). Differentiation: Distinguished from D. nodifer by the broad central area andlarge central area bosses. Dimensions: L = 14.0µm (Paratype L = 13.0µm). Holotype: Pl.8, fig.40. Paratype: Pl.8,
fig.34. Type locality: IODP Hole U1331A, Pacific Ocean.
Type level: Middle Eocene, Sample U1331A-13H-5, 70
cm (Zone NP15). Occurrence: Subzone NP15b-Zone
NP18/20; IODP Sites U1331-1333.

Calcareous nannofossils from the Paleogene equatorial Pacific31

Discoaster cf. D. williamsii sp. nov.
Pl. 8, figs 29-31
Remarks: Like Discoaster williamsii but with 5 rays.
Similar to some small D. tanii variety 2 specimens but thecentral area is elevated on both faces. Occurrence: Subzone NP15b-Zone NP18/20; IODP Sites U1331-1333.

conicus, S. dissimilis, S. calyculus, etc.). A representative
range of morphologies is represented in Plates 10-13 andmorphometric data for selected taxa are given in Table 3.
A number of informal groups are used, including the S.
radians, S. furcatolithoides, S. predistentus and S. moriformis groups.

6.6.3. Rossette discoaster Group

6.6.5. Sphenolithus radians Group

Discoaster barbadiensis Tan, 1927
Pl. 9, figs 13-14
Discoaster bifax Bukry, 1971
Pl. 9, figs 16-23
Discoaster kuepperi Stradner, 1959
Pl. 9, figs 3-5
Discoaster lenticularis Bramlette & Sullivan, 1961
Pl. 9, fig. 6
Discoaster salisburgensis Stradner, 1961
Pl. 9, figs 1-2
Discoaster saipanensis Bramlette and Riedel, 1954
Pl. 9, figs 25-36
Remarks: Morphologically variable in the Exp. 320 material, with 8-5 rays, short to long free rays, but sharing
distinctive, sharply tapering ray morphology with pointed
ray tips. Six- and five-rayed varieties (distinguished as D.
saipanensis var. 1 and var. 2) with long free rays and someray curvature (Pl. 9, figs 30-36) are conspicuous in the upper Eocene (Zones NP17-NP19/20), and reminiscent of
the older D. lodoensis and D. sublodoensis species.
Discoaster saipanensis Bramlette and Riedel, 1954 var. 1
Pl. 9, figs 30-32
Discoaster saipanensis Bramlette and Riedel, 1954 var. 2
Pl. 9, figs 33-36
Discoaster spinescens Bown, 2005
Pl. 9, fig. 15
Discoaster wemmelensis Achuthan and Stradner, 1969
Pl. 9, figs 7-12
6.6.4. Other discoasters
Discoaster lodoensis Bramlette & Riedel, 1954
Pl. 9, figs 37-38
Discoaster sublodoensis Bramlette & Sullivan, 1961
Pl. 9, figs 24, 39
Family SPHENOLITHACEAE Deflandre, 1952
Plates 10-13
Remarks: Sphenoliths are common to dominant components of certain Exp. 320 assemblages, especially in the
Oligocene to lower Miocene interval. The group is morphologically highly variable and similar morphologicalfeatures and trends occur repeatedly through their history(Fig. 4). The intergrading morphologies within species
plexi result in problematic taxonomy and likely explaininconsistent stratigraphic placement of some datums. Thisis particularly the case for Oligocene to lower Miocene
sphenoliths that have been used in standard nannofossil
zonation schemes (S. ciperoensis, S. distentus) and manytaxonomic names are rather poorly constrained (e.g. S.

Pl. 10, figs 1-49
Remarks: Sphenolith base typically has four distinct
quadrants and is square or tapering. In older forms thespines are compound, becoming duo- or monocrystalline
in later-appearing forms, and are usually visible but dim
at 0° and brightest when at 45° to the polarizing directions; S. furcatolithoides spines behave slightly differently. Species are differentiated based on overall heightand shape, spine size and degree of taper. Sphenolithus
furcatolithoides, S. perpendicularis, S. kempii and S.
cuniculus form a distinct subgroup with first three/four
spines then two separate spines that bifurcate directly
above the base. S. strigosus has a duocrystalline spine,
a higher spine bifurcation point and is dark at 45°. The
group contains predominantly Eocene forms, namely: S.
arthuri, S. conspicuus, S. editus, S. orphanknollensis, S.
pseudoradians, S. radians, S. spiniger, S. villae; and in
the S. furcatolithoides subgroup: S. cuniculus, S. furcatolithoides, S. perpendicularis, S. kempii, S. strigosus and,tentatively, S. runus. The species are defined as follows:
1. Sphenolithus arthuri Bown, 2005b (not figured here) like S. radians but larger and more coarsely constructed, with blockier spine and base;
2. Sphenolithus conspicuus - narrow with a tall spine(dark at 0°, conspicuously bright at 45°) and tall basewith long upper quadrants;
3. Sphenolithus editus – tapering triangular outline withlarge and wide lower basal quadrants with sharply tapering spine;
4. Sphenolithus orphanknollensis – small, with narrow,tapering spine;
5. Sphenolithus pseudoradians – like S. radians but larger, more irregular outline and apical cycles that extend
laterally beyond the base of the apical spine;
6. Sphenolithus radians – square base with equidimensional quadrants and compound tapering spine that
may have terminal bifurcations;
7. Sphenolithus spiniger – tapering triangular outline
with larger lower basal quadrants and a birefringent
structure that passes between the basal quadrants at
45° to polarising direction;
8. Sphenolithus villae Bown, 2005 (not figured here) –relatively tall base with spine that indents deeply into
the upper quadrants;
Sphenolithus furcatolithoides Subgroup
9. Sphenolithus cuniculus (not figured here) – like S. furcatolithoides but with very short lower quadrants;
10.Sphenolithus furcatolithoides – small with two longspines that are bright at 0° (dark at 45°) extending fromthe upper quadrants;
11. Sphenolithus perpendicularis – like S. furcatolithoides

32

Bown, Dunkley Jones

Figure 4. Stratigraphic distribution of Paleogene and early Neogene sphenoliths. The timescale is from Pälike et al. (2010). Dotted vertical lines arequestionable stratigraphic ranges, horizontal bars indicate well constrained range base or top. Informal groups are indicated and phylogentic inferences are indicated with sloping dotted lines.

but the two spines are more divergent;12.		 Sphenolithus kempii – like S. perpendicularis butwith three or possibly four spines;
13.		 Sphenolithus strigosus – like S. furcatolithoides but
the spine bifurcates at a higher level.
14.		 Sphenolithus runus – narrow with large, lower basal
quadrants and spine distinctly bright at 45°.

Other spinose Eocene sphenoliths15.		 Sphenolithus richteri – small and narrow with spine
dark at 0° and distinctly bright at 45°.
16.		 Sphenolithus obtusus
Sphenolithus conspicuous Martini 1976
Pl. 10, figs 16-18

Calcareous nannofossils from the Paleogene equatorial PacificSphenolithus editus
Perch-Nielsen in Perch-Nielsen et al. 1978
Pl. 10, figs 3-4
Sphenolithus orphanknollensis Perch-Nielsen, 1971
Pl. 10, figs 19-24
Sphenolithus pseudoradians Bramlette & Wilcoxon 1967
Pl. 10, figs 1-2
Sphenolithus radians Deflandre in Grassé 1952
Pl. 10, fig. 31
Sphenolithus runus Bown & Dunkley Jones 2006
Pl. 10, figs 48-49
Sphenolithus spiniger Bukry 1971
Pl. 10, figs 5-6
Sphenolithus cf. S. spiniger
Perch-Nielsen in Perch-Nielsen et al. 1978
Pl. 10, figs 7-15
Remarks: Similar to S. spiniger but large and coarsely
constructed. Occurrence: Zones NP17-19/20; IODP
Sites U1331-1333.
6.6.6. Sphenolithus furcatolithoides
Subgroup
Sphenolithus furcatolithoides Locker 1967
Pl. 10, figs 42-43
Sphenolithus perpendicularis Shamrock, 2010
Pl. 10, figs 38-41
Sphenolithus kempii sp. nov.
Pl. 10, figs 25-30, 32-35
Derivation of name: Named after David Kemp (University College London), stratigrapher and palaeoceanographer. Diagnosis: Medium sized sphenoliths with three (orpossibly four) long spines and square base. At 0° the twoouter spines are bright, the middle spine is dark and thebase is bright. At 45° the middle spine is bright, the twoouter spines are dark and the base is darker and crossed by
X-shaped extinction lines. Remarks: S. kempii has a morphology intermediate between the single spined S. radians
and the two-spined S. perpendicularis and S. furcatolithoides, and may be ancestral to these forms. Differentiation:
Distinguished from most other Eocene sphenoliths by thepresence of three discrete spines: otherwise, similar to S.
furcatolithoides, which has just two outer spines, S. perpendicularis, which has two widely divergent outer spines
and to S. radians, which has just one central spine. Dimensions: L = 5.3µm (Paratypes L = 5.0µm). Holotype:Pl.10, fig.25. Paratype: Pl.10, fig.29. Type locality: IODP
Hole U1333A, Pacific Ocean. Type level: Middle Eocene,
Sample U1333A-20-2, 50 cm (Zone NP15). Occurrence:
Lower Zone NP15; IODP Sites U1333.
Sphenolithus cf. S. kempii sp. nov.
Pl. 10, figs 36-37
Remarks: Sphenolith seen in top view with four spinesarranged as two orthogonal pairs. May represent S. kempii
specimens, indicating the presence of an additional spinethat cannot be seen in more typical side views.
Sphenolithus strigosus Bown & Dunkley Jones 2006
Pl. 10, figs 44-47

33

6.6.7. Other spinose Eocene sphenoliths
Sphenolithus richteri sp. nov.
Pl. 11, figs 7-12
Derivation of name: Named after Carl Richter (University of Louisiana, USA), Exp. 320 shipboard scientist
and palaeomagnetist. Diagnosis: Small narrow sphenolith with square base, comprising equidimensional quadrants, and tapering monocrystalline spine that is dark
at 0° and bright at 45°. Differentiation: Quite distinct
from other Eocene sphenoliths, but somewhat similar
to Miocene S. heteromorphus but the base is square. Dimensions: L = 4.3µm (Paratype L = 3.3µm). Holotype:
Pl.11, fig.7. Paratype: Pl.11, fig.11. Type locality: IODP
Hole U1331A, Pacific Ocean. Type level: Middle Eocene, Sample U1331A-11H-CC (Zone NP16). Occurrence: Zone upper NP15-Zone NP16; IODP Sites U1331(NP16), U1332 (one upper NP16 sample), U1333.
Sphenolithus obtusus Bukry 1971
Pl. 11, figs 1-6
Occurrence: Zone upper NP16-17; IODP Sites U1331,
U1332, U1334.
6.6.8. Sphenolithus predistentus GroupPl. 11, figs 13-48; Pl. 12, figs 1-16
Remarks: A plexus of late Eocene to Oligocene spinose
sphenoliths that have been widely used in biostratigraphic
zonal schemes (e.g. S. distentus and S. ciperoensis). The
plexus displays great variability, homeomorphic trends
and the common occurrence of intergradational forms,
which hinders their use as marker species and has been
the focus of considerable discussion (e.g., Olaffson andVilla, 1992; Blaj et al., 2010). The morphology is characterised by a base with two, low quadrants (or ‘feet’) that
increase in size in younger forms. Spines are tall, duoor monocrystalline, and taper, with terminal bifurcations
that may be very long. Older representatives of the group(S. predistentus, S. akropodus) have duocrystalline spinesand low basal ‘feet’ and later forms have relatively larger
feet that encroach up the spine, which may appear monocrystalline. The sphenolith basal-width to proximal-cycleheight ratio was considered a useful diagnostic characterby Blaj et al. (2010), but they did not consider S. akropodus or S. peartiae, which have ratios identical to S. distentus. Nevertheless, generally, S. predistentus has basal
width/height (W/H) ratios of >2.5, S. distentus 1.7-2.5
and S. ciperoensis <1.7 (see Table 3). The species herein
are defined as follows:
1. Sphenolithus akropodus – large with tall, narrow, tapering spine (may appear monocrystalline) and basal‘feet’ that encroach on the spine; the angle between the
top and bottom surface of the feet is up to 90° and thebasal W/H ratio is like S. distentus (Table 3).
2. Sphenolithus calyculus – like S. ciperoensis but thebase shows four quadrants at 0°.
3. Sphenolithus celsus – like S. predistentus but with avery tall and narrow spine.
4. Sphenolithus ciperoensis – small with relatively large
basal ‘feet’ (~half the height of the sphenolith and bas-34

Bown, Dunkley Jonesal W/H <1.7; Table 3) with low spine that typically appears monocrystalline, and at 45° a birefringent structure passes between the ‘feet’.
5. Sphenolithus distentus – like S. akropodus but smallerwith shorter spine that typically appears monocrystalline.
6. Sphenolithus intercalaris – small, only the spine ispresent, most likely due to preservation but probably
also reflecting the small size and fragility of the base.
7. Sphenolithus peartiae – like S. predistentus but whenat 45° to the polarising directions a birefringent structure passes between the basal ‘feet’.
8. Sphenolithus predistentus – small to medium sized,
spine with very low base that meets the spine alonghorizontal or near horizontal sutures.
9. Sphenolithus tribulosus - the spine is broadest at thebase and tapers sharply, giving an inverted T-shaped
outline; the basal ‘feet’ are small and inconspicuous orabsent.

Sphenolithus akropodus de Kaenel & Villa, 1996
Pl. 11, figs 29-38
Remarks: Morphologically similar to S. distentus (Table3), but larger and with a discrete stratigraphic range in thelower Oligocene. Occurrence: Zone NP21-Zone NP22;IODP Sites U1332-1334.
Sphenolithus calyculus Bukry, 1985
Pl. 12, figs 11-16
Sphenolithus celsus Haq, 1971
Pl. 11, figs 24-26
Sphenolithus ciperoensis Bramlette and Wilcoxon, 1967
Pl. 12, figs 5-10
Sphenolithus distentus(Martini, 1965) Bramlette and Wilcoxon, 1967
Pl. 11, figs 45-48; Pl. 12, figs 1-4
Sphenolithus intercalaris Martini, 1976
Pl. 11, fig. 13

Sphenolithus peartiae sp. nov.
Pl. 11, figs 39-44
Derivation of name: Named after Leslie Peart (Consortium for Ocean Leadership, Washington), Exp. 320 shipboard staff educator. Diagnosis: Small to medium sizedsphenolith with low base that meets the spine along horizontal or near horizontal sutures but when at 45° to polarising direction a birefringent structure passes between
the basal ‘feet’. Differentiation: Like S. predistentus butwith a basal birefringent structure between the feet, andsimilar to S. ciperoensis but with lower feet that do notinsert into the spine and greater base height to width ratio.
Similar basal W/H ratio as S. distentus (1.74-1.95; Table3) but has basal birefringent structure. Dimensions: Holotype H = 6.20µm, W = 3.65µm (Paratype H = 7.20 µm,
W = 4.80 µm). Holotype: Pl.11, fig.42. Paratype: Pl.11,
fig.44. Type locality: IODP Hole U1334A, Pacific Ocean.
Type level: Oligocene, Sample U1334A-19H-CC (Zone
NP23). Occurrence: Zone NP23-Zone NP24; IODP Sites
U1331-1334.
Sphenolithus predistentus Bramlette & Wilcoxon 1967
Pl. 11, figs 17-23, 27-28

Remarks: Along with S. moriformis, this is the mostcommon and consistently occurring sphenolith throughthe Oligocene section. It is highly variable in size and intergrades with S. akropodus, S. distentus and S. peartiae.
Sphenolithus tribulosus Roth, 1970
Pl. 11, fig. 14
6.6.9. Other sphenoliths
Sphenolithus belemnos Bramlette and Wilcoxon, 1967
Pl. 12, figs 45-46
Sphenolithus delphix Bukry, 1973
Pl. 12, figs 23-28
Sphenolithus cf. S. delphix Bukry, 1973
Pl. 12, figs 17-22
Remarks: Like S. delphix but more coarsely constructed
and with a relatively lower, broader spine.
Sphenolithus disbelemnos Fornaciari and Rio, 1996
Pl. 12, figs 37-44
Sphenolithus heteromorphus Deflandre, 1953
Pl. 12, figs 47-48
Sphenolithus procerus? Maiorano & Monechi, 1997
Pl. 12, figs 29-36
Remarks: Low basal quadrants are wider than the upper
quadrants and the spine is duocrystalline, gently taperingand brightest at 45°. First described from Zone NN2 but
occurs slightly earlier here (Zones NP25 and NN1). Occurrence: Zones NP25-NN2, Sites U1333-1334; Zone
NN2, DSDP Site 563, N. Atlantic (Maiorano and Monechi, 1997)
6.6.10. Sphenolithus moriformis Group
Sphenolithus conicus Bukry 1971 sensu stricto
Pl. 13, figs 13-18
Remarks: Described by Bukry (1971) as a ‘large’, ‘tall’‘triangular’ species (7-12 µm) but applied more broadly
in the literature to include smaller, triangular forms.
The name is applied here to large forms only (>7 µm inheight), which are particularly conspicuous in the Oligocene/Miocene boundary interval. These sphenoliths arecoarsely constructed with a high, gently tapering base anda short tapering spine. The base is typically longer than
the spine, with the lower quadrants slightly larger thanthe upper. The spine is composite, dark at 0° and brightat 45°. In XPL the sphenolith shows high birefringencecolours of yellow, orange and blue. Similar sphenoliths
that are smaller were differentiated as Sphenolithus cf. S.
conicus ‘small variety’ in this study. Occurrence: Zone
NP25-NN2; IODP Sites U1333, U1334.
Sphenolithus cf. S. conicus Bukry 1971 small variety
Pl. 13, figs 1-12
Remarks: Medium sized sphenoliths with a gently tapering base and short tapering spine. The base has four
quadrants and is typically taller than or similar in length
to the spine, with the lower quadrants slightly larger thanthe upper. Specimens with slightly taller spines were informally differentiated. The spine is composite, dark at 0°

Calcareous nannofossils from the Paleogene equatorial Pacificand bright at 45°. Differentiation: A somewhat generalized sphenolith morphology but the spine is taller thanS. moriformis and it is smaller than S. conicus s.s. May
intergrade with Sphenolithus abies Deflandre in Deflandre& Fert, 1954. Occurrence: Zone NP22-NN15; IODP Sites
U1331-U1334.
Sphenolithus cf. S. conicus Bukry 1971 large variety
Pl. 13, figs 19-28
Remarks: A large (~>7 µm), coarsely constructed sphenolith with a high, parallel-sided base and a short spine.
Similar to S. conicus s.s. but the base is typically longer
than the spine, with the lower quadrants larger than theupper. The spine is composite, dark at 0° and bright at 45°.
In XPL the sphenolith shows high birefringence coloursof yellow, orange and blue. Occurrence: Zone NN2;
IODP Sites U1334.
Sphenolithus sp. 1
Pl. 13, figs 29-36
Remarks: Large, coarsely constructed sphenolith withlower basal quadrants that are larger than the upper quadrants and the spine is duocrystalline with near parallelsides and a blunt termination. Similar in general morphology to S. procerus. Occurrence. Not well constrained,
but Zones NP21-23 and possibly younger occurrences up
to NN2; Sites U1332-1334.
Sphenolithus moriformis (Brönnimann & Stradner, 1960)
Bramlette & Wilcoxon, 1967
Pl. 13, fig. 37
Sphenolithus grandis Haq and Berggren, 1978
Pl. 13, fig. 38-41
Remarks: Used here for large (>7 µm) S. moriformis-likesphenoliths.
6.6.11. Incertae Sedis Nannoliths
Lapideacassis Black 1971 sp.
Pl. 13, fig. 45
Remarks: Very rare (middle Eocene, Site U1331).
Nannotetrina Achuthan and Stradner, 1969
Pl. 14, figs 6-46
Remarks: These cruciform nannoliths form conspicuouscomponents of the Exp. 320 middle Eocene sections andare divided herein as follows:
1. Nannotetrina sp. 1 – small, with broadly square outline;
2. Nannotetrina cf. N. alata – small, short arms withblunt terminations;
3. Nannotetrina alata – long arms with blunt terminations;
4. Nannotetrina fulgens – long tapering arms with pointed terminations;
5. Nannotetrina cristata – three dimensional with curving arms and inter-arm fill;
6. Nannotetrina spinosa – broadly square with elongations from the corners and shorter spines from thesides resulting in an stellate (eight-pointed) symmetri-35

cal outline;
7. Nannotetrina pappii – broadly square to cruciformwith spinose projections resulting in a stellate (eightpointed) asymmetrical outline.
Other nannofossils with similar appearance include fourrayed discoasters, e.g. Discoaster cruciformis (Plate 14,
figs 4-5) and disarticulated cross-bars of Neococcolithes
protenus (see Plate 14, figs 1-3).
Nannotetrina sp. 1
Pl. 14, figs 6-8
Nannotetrina cf. N. alata(Martini, 1960) Haq and Lohmann, 1976
Pl. 14, figs 9-12
Nannotetrina alata(Martini, 1960) Haq and Lohmann, 1976
Pl. 14, figs 13-18
Nannotetrina cristata(Martini, 1958) Perch-Nielsen, 1971
Pl. 14, figs 19-24
Nannotetrina fulgens (Stradner in Martini & Stradner,
1960) Achuthan & Stradner, 1969
Pl. 14, figs 25-29
Nannotetrina spinosa(Stradner in Martini & Stradner, 1960) Bukry, 1973
Pl. 14, figs 31-42
Nannotetrina pappii(Stradner, 1959) Perch-Nielsen, 1971
Pl. 14, figs 30, 43-46
Tribrachiatus orthostylus Shamrai, 1963
Pl. 14, fig. 47
L-shaped liths Pl. 13, fig. 37-38
Remarks: L-shaped liths of uncertain affinity are occasionally common.
Acknowledgements
Thanks to IODP Expedition 320 operational and technical staff and shipboard science party for facilitating suchan enjoyable and successful drilling expedition. This
research used samples and/or data provided by the Integrated Ocean Drilling Program (IODP). Funding for thisresearch was provided by the Natural Environment Research Council. We very much appreciate the careful andconstructive reviews of Jean Self-Trail, Liam Gallagher
and other reviewers.
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Plate 1
Reticulofenestra umbilicus Group, Reticulofenestra lockeri Group, Reticulofenestra reticulata GroupCalcareous nannofossils from the Paleogene equatorial PacificPlate 2
Reticulofenestra reticulata Group, Cyclicargolithus floridanus Group, Reticulofenestra bisecta Group, Prinsiaceae,
Paleogene calcidiscid Group

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Plate 3
Paleogene calcidiscid Group, Placolith coccoliths incertae sedis, Calcidiscus leptoporus GroupCalcareous nannofossils from the Paleogene equatorial PacificPlate 4
Other calcidiscids, Paleogene calcidiscid Group, Coccolithus pelagicus Group, Chiasmolithus- Cruciplacolithus Groupjafari41

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Plate 5
Chiasmolithus - Cruciplacolithus Group, Clausicoccus GroupCalcareous nannofossils from the Paleogene equatorial PacificPlate 6
Placolith coccoliths incertae sedis, Mesozoic muroliths, Helicosphaera carteri Group,
Helicosphaera compacta-recta Group, Helicosphaera seminulum Group

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Plate 7
Pontosphaeraceae, Rhabdosphaeraceae, Triquetrorhabdulaceae, Discoaster deflandrei GroupCalcareous nannofossils from the Paleogene equatorial PacificPlate 8Discoaster nodifer Group

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Plate 9Rosette discoaster Group, Other discoasters

Calcareous nannofossils from the Paleogene equatorial PacificPlate 10
Sphenolithus radians Group

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Plate 11
Sphenolithus radians Group, other spinose Eocene sphenoliths, Sphenolithus predistentus GroupCalcareous nannofossils from the Paleogene equatorial PacificPlate 12Sphenolithus predistentus Group, other sphenoliths

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Plate 13
Sphenolithus moriformis Group, Incertae sedis nannoliths

Calcareous nannofossils from the Paleogene equatorial PacificPlate 14
Incertae sedis nannoliths

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