J. Nannoplankton Res. 29 (2), 2007, pp.88-91 © 2007 International Nannoplankton Association
ISSN 1210-8049 Printed by Cambridge University Press, UK88

Taxonomic note: A new Coccolithus species that thrived
during the Paleocene/Eocene Thermal Maximum
Shijun Jiang*, Sherwood W. Wise, Jr
Department of Geological Sciences, Florida State University, Tallahassee, FL 32310, USA; *jiang@gly.fsu.edu
Manuscript received 19th July, 2007; revised manuscript accepted 15th September, 2007

Abstract A calcareous nannofossil study of the Paleocene/Eocene Thermal Maximum (PETM) sequence fromOcean Drilling Program Site 1259 on Demerara Rise (western equatorial Atlantic) has revealed a new species,
Coccolithus bownii, that peaks just above the boundary. This species thrived in the PETM-related stressed environment and is considered a significant environmental indicator. Based on its ultrastructural characteristics, which arestrongly reminiscent of those of the modern Coccolithus pelagicus, the new species is assigned to the genus
Coccolithus, instead of Ericsonia, the latter of which is here considered a junior synonym. Two new combinations(Coccolithus insolitus and Coccolithus occidentalis) are validated that were originally published only in electronicmedia.
Keywords PETM, calcareous nannofossils, Coccolithus bownii, new species, new combinations
1. Introduction
A high-resolution, quantitative calcareous nannofossil
biostratigraphic study of clay-rich sediments from aroundthe Paleocene/Eocene boundary in Hole 1259B, Ocean
Drilling Program (ODP) Leg 207 to the Demerara Rise,
south-western equatorial Atlantic (Jiang & Wise, 2006)
revealed a new species (referred to as Markalius cf. M.
apertus by Jiang & Wise, 2006), which we here describe
as Coccolithus bownii sp. nov. Based on similar peaks inabundance to those of the so-called Paleocene/Eocene
Thermal Maximum (PETM) excursion taxa (e.g.
Discoaster araneus), this new species is considered to be
an opportunistic species that took advantage of theextreme environmental changes associated with this interval and thrived in these stressed environments. Similarabundance acmes have been observed in forms attributed
to Coccolithus subpertusus in several Egyptian PETM
sections (e.g. Dupuis et al., 2003; Knox et al., 2003).
These may be equivalent to C. bownii, which has a similar, although quite distinct appearance. If so, then C.
bownii may prove to be a significant, widespread ecological indicator of PETM-related stressed environments.
2. Material and methods
The sediments examined were sampled with a U-channel
through the archive halves of ODP Sections 1259B-8R-2
through 8R-4. Sections 8R-2 and -3 consist primarily oflight greenish nannofossil chalk with foraminifers, whereas Section 8R-4 contains a dark yellowish brown claystone, interbedded within the nannofossil chalk(Shipboard Scientific Party, 2004).
Preparation of smear-slides followed standard techniques (Bown & Young, 1998), using Norland 61 opticaladhesive as a permanent mounting medium. Slides wereanalysed using a Zeiss Axioskop II microscope undercross-polarised light (XPL), transmitted light (TL), andphase-contrast light (PC) at 1000x magnification.

An FEI Nova 400 Nano scanning electron microscope(SEM) was employed to examine fine-scale structures. A
settling technique (Bukry, 1969) was used in stub preparation to remove large particles and fine clays.
Additionally, a freshly-broken surface was also coated toprovide clean, clay-free specimens.
All materials are archived in the collections of the
Calcareous Nannofossil Laboratory at the Department ofGeological Sciences, Florida State University (FSU),Tallahassee, Florida, USA.
3. Systematic palaeontology
Family COCCOLITHACEAE Kamptner, 1928
Genus Coccolithus Schwarz, 1894
Coccolithus bownii sp. nov.
Pl.1, figs 1-21
2006 Markalius sp. cf. M. apertus Jiang & Wise: pp.236-237,
pl.1, figs 6-9, 22-26.

Derivation of name: After Dr. Paul Bown (UniversityCollege London) in honour of his many valuable contributions to this subdiscipline of micropalaeontology.
Diagnosis: A broadly elliptical to subcircular Coccolithus
with a large central opening.
Description: The subcircular placolith consists of two relatively widely separated shields (Pl.1, figs 3-5), eachcomposed of ~44-48 imbricated elements (Pl.1, figs 3, 4,14, 15). In distal view, the distal shield is dextrogyre with
its inner margin covered by a shingling of thin centralarea laths (Pl.1, figs 14-16). The proximal shield consistsof two closely-appressed and superimposed cycles of elements that both extend out to its margin, the proximalmost being strongly dextrogyre in proximal view (Pl.1,figs 1, 4, 5). This structure of upper and lower tiers of theproximal shield, though somewhat difficult to discern inour specimens, is strongly reminiscent of that shown in

89

Jiang, Wisethe naturally etched specimens of Coccolithus pelagicus
figured by Young (1992, p.4, figs 1-5).
The central opening is large, occupying about 40-50%of the coccolith’s diameter along the minor axis (Pl.1, figs1-21). Only the proximal shield and the distal shield elements appear bright in XPL (Pl.1, figs 17-19), producing
a herringbone birefringence pattern characteristic of thegenus. In etched specimens, the birefringence patterndoes not change, except that the central opening appears
much larger.
Differentiation: Coccolithus bownii resembles, in outline, Coccolithus occidentalis comb. nov. However, thelatter species has a striking chevron-pattern of elements,
formed by the two cycles of elements of the proximal
shield, of which the proximal-most is only half the widthof the underlying cycle. The central-area opening is also
considerably smaller, occupying only a quarter of the total
width, measured along the minor axis (see Black, 1964,pl.52, fig.1). The large central opening and subcircularoutline differentiate C. bownii from other Coccolithus
species, most of which are more elliptical. Coccolithus
formosus, on the other hand, is circular, but has a muchsmaller central opening (about 20% or less of the total
minor-axis diameter; see Black, 1964, pl.50, fig.2, as ‘C.
lusitanicus’).
Remarks: As pointed out above, construction of the proximal shield of C. bownii resembles closely that of themodern C. pelagicus, that is, it consists of two thin, closely-appressed, superimposed layers of near equal width.
The presence of this construction in the Lower Eoceneshows that this feature occurs in the older as well as theyounger parts of the Coccolithus lineage. This construction contrasts with other contemporaneous forms, such as
C. occidentalis comb. nov. and C. muiri (= ‘Ericsoniaovalis’; see Roth, 1970, p.841), which Black (1964)
placed in a separate genus, Ericsonia, based on the much
shorter widths of the proximal-most tier of the proximal
shield. The relative widths of those two tiers, however,vary significantly among species and over time (Wise,1983, p.505). Consequently, it is difficult to draw a nonarbitrary dividing line between the genus Coccolithus andBlack’s Ericsonia. Following the lead of Bukry (1973)
and Wise (1973, 1983), we continue to place all suchspecies in the genus Coccolithus.
Occurrence: C. bownii is common to abundant within
Zone NP10 of Martini (1971) in ODP Hole 1256B.
Specifically, it shows an acme within the PETM interval,and decreases in abundance thereafter, upsection (Jiang &Wise, 2006, fig.2). Should the acmes of C. subpertusus in
Egypt actually be of C. bownii, then this new species
would have at least a low-latitude distribution.
Dimensions: 6-8µm diameter (holotype = 6.2µm).
Holotype: Pl.1, fig.1.
Paratypes: Pl.1, figs 3, 4, 8, 10, 14, 15.
Type locality: ODP Hole 1259B, Demerara Rise, offSouth America (9˚18.0485’N, 54˚11.9448’W), Sample
1259B-8R-4, 57-58cm.

Coccolithus insolitus (Perch-Nielsen, 1971) Jiang,Ladner & Wise comb. nov.
Basionym: Ericsonia insolita Perch-Nielsen, 1971, p.13,
pl.1, fig.1; pl.7, figs 4, 6; pl.61, figs 14, 15; Elektronenmikroskopische Untersuchungen an Coccolithen und verwandten Formen aus dem Eozän von Dänemark. Det
Kongelige Danske Videnskabernes Selskab Biologiske
Skrifter, 18: 1-76.
Remarks: See remarks under C. bownii. This combination was previously made by Ladner & Wise in Wise et al.
(2002), in a publication distributed via CD-ROM only.
New combinations published in electronic media areinvalid under provisions of the International Code ofBotanical Nomenclature published in 2000 (Article 29.1;
Greuter et al., 2000).
Coccolithus occidentalis (Black, 1964) Jiang, Ladner &Wise comb. nov.
Basionym: Ericsonia occidentalis Black, 1964, pp.311312, pl.52, figs 1, 2: Cretaceous and Tertiary coccoliths
from Atlantic seamounts; Palaeontology, 7(2), pl.52, figs
1, 2.
Remarks: See remarks under C. bownii. This combination was previously made by Ladner & Wise in Wise et al.
(2002) and is invalid (see remarks under C. insolitus).
Acknowledgements
We thank Kim Riddle and Thomas Fellers of the FSU Biology
Unit 1 SEM laboratory for helpful assistance and instruction on
the operation of the newly-installed FEI Nova 400 Nano SEM,
which was purchased through a grant from the US National
Science Foundation (NSF Grant 0520950). We are grateful toOsman Varol, Jeremy Young and Paul Bown for constructive
and helpful comments that greatly improved this manuscript.
The samples were provided by the ODP. ODP is sponsored by
the US NSF and participating countries under management of
Joint Oceanographic Institutions (JOI), Inc. General support for
the Calcareous Nannofossil Laboratory in the FSU Departmentof Geological Sciences was provided by NSFOPP Grants
0125526 and 0230469 to SWW.

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Plate 1
Coccolithus bownii
Sample ODP 206-1256B-6H-2, 115-117cm. Scale-bar = 2µm

Holotype, SEM, partial proximal view SEM, proximal (upper) and oblique(lower) views

Paratype, SEM, oblique view (same as Paratype, SEM, oblique viewfig.2)

SEM, proximal-oblique view

SEM, proximal view

SEM, proximal view

Paratype, SEM, proximal view

SEM, proximal view

Paratype, SEM, proximal view

SEM, proximal view

SEM, proximal view

SEM, distal (upper) and proximal(lower) views

Paratype, SEM, distal view (same asfig.13)

SEM, distal view

SEM, distal view

XPL, plan view

XPL, plan view

Paratype, XPL (19), TL (20), PC (21) plan view