J. Nannoplankton Res., 42(1), 2024, pp. 1–5 https://doi.org/10.58998/jnr3470© 2024 The Authors ISSN 1210-8049 Printed by The Sheridan Press, USA

1Proposal for the Ericiolaceae (Prymnesiophyceae, Haptophyta)fam. nov.
Odysseas A. Archontikis*

Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK; odysseas.archontikis@univ.ox.ac.uk
Department of Earth Sciences, The Natural History Museum, Cromwell Road, London SW7 5BD, UK

Helge A. Thomsen

Technical University of Denmark, National Institute of Aquatic Resources (DTU Aqua), Kemitorvet, Building 201, DK-2800 Kgs. Lyngby, Denmark

K. J. Sebastian MeierInstitut für Geowissenschaften, Christian-Albrechts-Universität zu Kiel, Ludewig-Meyn-Str. 10, 24118 Kiel, Germany

Jeremy R. Young

Department of Earth Sciences, University College London, London WC1E 6BT, UK*Corresponding author
Manuscript received 13 July 2023; revised manuscript accepted 24 October 2023
Available online 16 February 2024
DOI: 10.58998/jnr3470
This is an open access article licensed under the Creative Commons Attribution 4.0 International (CC BY 4.0) license(https://creativecommons.org/licenses/by/4.0/).

Abstract The extant nannolith-bearing genera Ericiolus and Pileolosphaera are distinguished by the possessionof triradiate nannoliths with a very similar and highly distinctive structural pattern. The nannoliths display three symmetrically arranged rays that develop from a nannolith center but show no obvious affinities to any other currently
known extant coccolithophore. On this basis, we propose the establishment of a new family, Ericiolaceae fam. nov.,to accommodate Ericiolus and Pileolosphaera.

Keywords Coccolithophore, Ericiolus, Pileolosphaera, systematics
1. Introduction
The nannolith-bearing genera Ericiolus Thomsen emend.
Archontikis & Young and Pileolosphaera Meier, Kinkel,& Young are taxonomically ambiguous and, at present, informally classified as ‘nannolith incertae sedis’ (Archontikis et al., 2023; Young et al., 2023). Both genera include
species with monomorphic and monothecate coccospheresshowing one type of triradiate nannoliths. Ericiolus, as
recently revised by Archontikis et al. (2023), is used asa broad but coherent taxonomic group of at least eightmorphologically different species: Ericiolus spiculigerThomsen, E. frigidus Thomsen, E. aspiphorus (Thomsen & Østergaard) Archontikis & Young, E. multistellatus (Thomsen & Østergaard) Archontikis & Young, E.
pusillus (Thomsen & Østergaard) Archontikis & Young,E. bendifii Archontikis, Millán, Winter, & Young, E. mattioliae Archontikis, Millán, Winter, & Young, and E. sheldoniae Archontikis, Millán, Winter, & Young (Figure 1),
with a wide biogeographical range, having been recordedin polar surface waters and the lower photic zone of sub-tropical environments (Thomsen et al., 1995; Thomsen &Østergaard, 2015; Archontikis et al., 2023). Conversely,Pileolosphaera is a monospecific genus. Its type species, P.
longistirpes Meier, Kinkel, & Young, was described fromthe surface waters of the southwestern Baltic Sea (Meieret al., 2014), whilst occurrences of the species are also reported from the northwestern Pacific Ocean, the Irish andNorth Seas (Tanimoto et al., 2003; Meier et al., 2014), and
the Adriatic Sea (Cerino et al., 2017; Godrijan et al., 2023).
2. Discussion
As discussed in Archontikis et al. (2023), nannoliths ofEriciolus and Pileolosphaera are structurally closely related showing three-fold symmetry and a radial growth ofelements (Figure 1) developing from the nannolith center
rather than a rim. In Ericiolus, the nannoliths are remarkably small and can have either a) three radiating elements
arranged parallel to the cell surface; b) four radiate elements with three of them parallel to the cell surface andone perpendicular to it; or c) three radiating units that

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Archontikis, Thomsen, Meier, Young

Pileolosphaera
longistirpes

Ericiolus
spiculiger

Central spine
made bythree blades

Ericiolus
aspiphorus

Ericiolus
frigidusTerminal
Round tipEriciolus
multistellatus

TerminalKnob

Ericiolus
pusillus

Central pore

Ericiolus
bendiﬁi

Ericiolus
mattioliae

Knob

Lath-made calyx

Ericiolus
sheldoniae

Lath-made calyx

Figure 1: Schematic representation (not to the same scale) and diagnostic morphological features (three-fold symmetry, radial growth of elements) for
all currently known members within the Ericiolaceae fam. nov.

bifurcate and a distally oriented fourth element that develops into a central elongate spine with a terminal knob
or a calyx (see Archontikis et al., 2023 for extended discussion). The nannoliths in Pileolosphaera similarly show
three radiating elements that are parallel to the cell surface, and a central spine formed of three blades (Meieret al., 2014). Meier et al. (2014) showed via light microscopy observations that nannoliths of Pileolosphaera arecomposed exclusively of V-units and, therefore, have
similar crystallographic properties to the nannoliths of theextinct genus Discoaster (Discoasteraceae, Discoasterales). Archontikis et al. (2023) further suggested potential
affinities of both Pileolosphaera and Ericiolus with thegenus Discoaster on the grounds of all being characterisedby a similar pattern of ray development and by similarmorphology. Discoaster is an extinct genus; however, itslast representatives only disappeared in the early Quaternary, ~1.8 million years ago. Although we do not have afossil record for Ericiolus, given the current diversity
within the genus, it would be reasonable to predict thatit evolved some time ago. Therefore, evolution from thegenus Discoaster is not inconceivable.
While nannoliths of Pileolosphaera are noticeably
larger than those of Ericiolus (~3.0–4.0 µm versus 0.2–1.3µm) and there are considerably fewer of them (6–8 versus
30–70) on the coccosphere (Meier et al., 2014; Archontikis
et al., 2023), the similarity in nannolith structure and raydevelopment (Plates 1 and 2) is notable and suggestive ofa close taxonomic relationship between the two genera.
This feature is also highly distinctive and further suggests
a clear separation of Ericiolus and Pileolosphaera fromall other groups of living coccolithophores. As a result,
we propose the establishment of a new family, Ericiolaceae fam. nov., to accommodate Ericiolus and Pileolosphaera. This principle has previously been followed byJordan & Young (1990) and Andruleit & Young (2010)

Proposal for the Ericiolaceae (Prymnesiophyceae, Haptophyta) fam. nov.

3

Plate 1

Plate 1: Scanning electron microscope images of Ericiolus (1) and Pileolosphaera (2) coccosphere types. Scale bars = 1 μm. 1. Ericiolus bendifii(image code: 199–21, Station 69–11, MATER-II cruise, northwestern Mediterranean & Alboran Seas, R/V Hesperides, October 1999). 2. Pileolosphaera longistirpes (image code: 93856-2, Station W3, Kieler Förde, R/V Polarfuchs, 11 September 2009).

who, respectively, erected and expanded the family Papposphaeraceae Jordan & Young (1990) emend. Andruleit& Young (2010) for the analogous cases of the genera
Papposphaera and Pappomonas, as well as Picarola, Vexillarius, and Kataspinifera based on a set of shared morphological features. However, molecular genetic analyses
are currently unavailable for the Ericiolaceae to help elucidate familial-level phylogenetic relationships; therefore,
we suspend taxonomic treatment at an ordinal level.

Genus Ericiolus Thomsen in Thomsen et al. (1995)
emend. Archontikis & Young in Archontikis et al. (2023)
Type species: Ericiolus spiculiger Thomsen in Thomsenet al. (1995)

3. Systematic Taxonomy: Proposal ofa new family

Ericiolus aspiphorus (Thomsen & Østergaard, 2015)
Archontikis & Young in Archontikis et al. (2023)
Plate 2, fig. 4

Family ERICIOLACEAE fam. nov.
Plates 1, 2
Diagnosis: Coccosphere monothecate and monomorphic
consisting of nannoliths with three-fold symmetry. Thenannoliths show three radiating elements that develop
from the nannolith center.
Type genus: Ericiolus Thomsen in Thomsen et al. (1995,p. 30) emend. Archontikis & Young in Archontikis et al.
(2023, p. 184)
Type species: Ericiolus spiculiger Thomsen in Thomsenet al. (1995, pp. 30–31)
3.1. Taxonomic Appendix
No new formal taxonomy is proposed. Here we include
the recommended terminology for all currently known extant taxa within the Ericiolaceae.

Ericiolus spiculiger Thomsen in Thomsen et al. (1995)
Ericiolus frigidus Thomsen in Thomsen et al. (1995)
Plate 2, fig. 7

Ericiolus multistellatus (Thomsen & Østergaard, 2015)
Archontikis & Young in Archontikis et al. (2023)
Plate 2, fig. 6
Ericiolus pusillus (Thomsen & Østergaard, 2015)
Archontikis & Young in Archontikis et al. (2023)
Plate 2, fig. 8
Ericiolus bendifii Archontikis et al. (2023)
Plate 1, fig. 1; Plate 2, fig. 2
Ericiolus mattioliae Archontikis et al. (2023)
Plate 2, fig. 3
Ericiolus sheldoniae Archontikis et al. (2023)

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Archontikis, Thomsen, Meier, Young

Plate 2

Plate 2: Scanning (1–6) and transmission (7–8) electron microscope images of the nannolith ultrastructure observed in Pileolosphaera (1), Ericiolus(2–4, 6–8), and Discoaster (5). Scale bars = 1 μm (Figs. 1, 5) and 0.25 μm (Figs. 2–4, 6–8). 1. Pileolosphaera longistirpes (image code: 00000, Station
Bellevue pier, Kieler Förde, November 2012). 2. Ericiolus bendifii (image code: 193–76, Station 69–11, MATER-II cruise, northwestern Mediterranean & Alboran Seas, R/V Hesperides, October 1999). 3. Ericiolus mattioliae (image code: 285–31, Station CTD089, AMT18 cruise, R/V James
Clark Ross, South Atlantic Ocean, November 2008). 4. Ericiolus aspiphorus (image code: OA330–404, Station 69–6, MATER-II cruise, northwestern
Mediterranean & Alboran Seas, R/V Hesperides, October 1999). 5. Discoaster triradiatus Tan 1927 (reprinted from Samtleben, 1978, plate 5, fig. 4).
6. Ericiolus multistellatus (image code: 291–49, Station CTD089, AMT18 cruise, South Atlantic Ocean, R/V James Clark Ross, November 2008). 7.
Ericiolus frigidus (image code: 11304b, Station EPOS #159 ANT VII/3 ‘EPOS II’ cruise, R/V Polarstern, Weddell Sea, December 1988; reprintedfrom Thomsen & Østergaard, 2015, fig. 16). 8. Ericiolus pusillus (image code: SC330, Station EPOS #163, ANT VII/3 ‘EPOS II’ cruise, R/V Polarstern, Weddell Sea, December 1988; reprinted from Thomsen & Østergaard, 2015, fig. 12).

Proposal for the Ericiolaceae (Prymnesiophyceae, Haptophyta) fam. nov.

Genus Pileolosphaera Meier et al. (2014)
Type species: Pileolosphaera longistirpes Meier et al.
(2014)
Pileolosphaera longistirpes Meier et al. (2014)
Plate 1, fig. 2; Plate 2, fig. 1

5Jordan, R.W. & Young, J.R. 1990. Proposed changes to the classification system of living Coccolithophorids. International Nannoplankton Association Newsletter, 12(1): 15–18.
https://doi.org/10.58998/nina2136
Meier, K.J.S., Kinkel, H. & Young, J.R. 2014. A note on calcareous nannoplankton from the Kieler Förde (Baltic Sea).
Journal of Nannoplankton Research, 33(1): 29–37. https://Disclosure Statement
At least one of the authors is a member of the editorial
board of Journal of Nannoplankton Research. The peer-review process was guided by an independent editor, and theauthors also have no other competing interests to declare.

doi.org/10.58998/jnr2178Samtleben, C. 1978. Pliocene-Pleistocene coccolith assemblages from Sierra Leone Rise - Site 366, Leg 41. Initial Reports of the Deep Sea Drilling Project, 41: 913–931. https://doi.org/10.2973/dsdp.proc.38394041s.406.1978
Tanimoto, M., Aizawa, C. & Jordan, R.W. 2003. Assem-Acknowledgements
We are thankful to Jon Schueth, Kyoko Hagino, and an
anonymous reviewer for their careful reviews. We also
thank Denise Kulhanek for providing a high resolution
image of Plate 2, Figure 5 and her editorial assistance. The
micrographs illustrated in Plate 2, Figures 7 and 8 havebeen included with the kind permission of Acta Protozoologica and Jagiellonian University, while Plate 2, Figure 5 is reproduced with the permission of the International Ocean Discovery Program. This work was supportedby the UK Natural Environment Research Council [grantnumber NE/S007474/1] to Odysseas A. Archontikis.

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