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Main text - terms applicable to any coccoliths

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1. GENERAL TERMS
2 COCCOSPHERE RELATED TERMS
3 TERMS FOR ENTIRE COCCOLITHS
4 ULTRASTRUCTURE RELATED TERMS
5 TERMS FOR DESCRIBING COCCOLITH RIMS
6 CENTRAL-AREA STRUCTURES
7 CRYSTALLOGRAPHY
8 INTRA-SPECIFIC VARIATION
9. NANNOLITH SHAPES
10. TERMS FOR PARTICULAR GROUPS
APPENDICES

1. GENERAL TERMS

Nannoplankton plankton 2-63 µm in diameter. (Alternative spelling nanoplankton, see appendix). Informal grouping including coccolithophores, Thoracosphaera, chrysophytes, etc., but excluding the bacterial picoplankton. {Lohmann 1909}
Calcareous nannoplankton nannoplankton with calcareous tests.{?Stradner 1961}
Nannofossil fossil <63 µm in diameter, excluding fragments and juveniles of larger fossils.
Calcareous nannofossil nannofossil formed of calcium carbonate.
Coccolithophore noun, calcareous nannoplankton belonging to the division Haptophyta {Lohmann 1902}
Coccolithophorid adjective, e.g. Coccolithophorid algae.
Coccosphere test of coccolithophore (not necessarily spherical). An extracellular cover made up of numerous coccoliths. {Wallich 1860}
Coccolith calcareous structure formed by coccolithophore. {Huxley 1868}
Haptophyte unicellular alga belonging to the division Haptophyta, includes all coccolithophores, and also related non-calcifying forms, e.g. Prymnesium, Phaeocystis, Pavlova, Chrysochromulina (Alternative term Prymnesiophyte, see appendix).
Nannolith calcareous nannofossil lacking the typical features of calcareous dinophytes, heterococcoliths or holococcoliths and so of uncertain affinity, see also Young (1992a), Young et al. (1994, 1999). The division between coccoliths and nannoliths varies between authors and is liable to revision as new data becomes available. N.B. This rather restricted definition of the term has little etymological justification, but has been widely used, e.g. Perch-Nielsen (1985a, 1985b), Bown (1987), Aubry (1989). (The terms heliolith and ortholith provide an alternative basis for sub-dividing the calcareous nannofossils, see appendix). {?Perch-Nielsen 1985a}
Heterococcolith coccolith formed of crystal-units of variable shape and size. Crystal units typically arranged in cycles with radial symmetry. {Braarud et al. 1955a, 1955b}
Heterococcolithophore cell bearing coccosphere of heterococcoliths.
Holococcolith coccolith formed of numerous minute (<0.1 µm) crystallites all of similar shape and size (N.B. Many of the terms below are not applicable to holococcoliths, and there is a separate section for specific holococcolith terms). {Braarud et al. 1955a, 1955b}
Holococcolithophore cell bearing coccosphere of holococcoliths.
Combination coccosphere coccosphere with both hetero- and holococcoliths. N.B. These are thought to represent a transitional state between heterococcolithophorid and holococcolithophorid phases of the life cycle. (The alternative term combination cell is less precise so is not now recommended). {Thomsen et al. 1991, Cros et al. 2000}
Xenosphere anomalous coccosphere containing coccoliths normally regarded as forming on quite discrete species (e.g. Emiliania huxleyi and Gephyrocapsa oceanica; Winter et al. 1979). N.B. These are very probably artefacts, the term is suggested specifically to suggest the abnormal nature of these structures. See also Young & Geisen (2002). {Young et al. 1997, from Greek xenos, stranger}

2 COCCOSPHERE RELATED TERMS

2.1 Descriptive Terms

(largely based on Okada and McIntyre 1977)
Monomorphic all coccoliths of similar type (e.g. Coccolithus).
Dimorphic coccoliths of two discrete types (e.g. Scyphosphaera).
Polymorphic coccoliths of more than two discrete types (e.g. Syracosphaera pulchra).
Varimorphic coccosphere with coccoliths whose size and/or morphology varies according to position on the coccosphere (e.g. Helicosphaera). {Young et al. 1997}
Dithecate with two discrete layers of coccoliths of different types (e.g. Syracosphaera pulchra).
Endotheca inner layer of coccoliths of dithecate coccosphere.
Exotheca outer layer of coccoliths of dithecate coccosphere.
Monothecate with a single layer of coccoliths (e.g. Scyphosphaera).
Multilayered with two or more layers of coccoliths but no differentiation into endo- and exotheca (e.g. Emiliania, Florisphaera, Coccolithus pelagicus phase hyalinus).
Shape coccospheres are three-dimensional so their shape should be described using appropriate terms for solid objects. Useful terms include: cylindrical, ellipsoidal, fusiform (elongate with tapering ends), obpyriform (inverse pear-shaped), ovoid (egg-shaped, i.e. one end broader than the other), spherical. See also Heimdal (1993), Jordan et al. (1995).

2.2 Orientation

Apical pole end of coccosphere with flagellar opening.
Antapical pole opposite end of coccosphere.
Antapical coccoliths (abb. AAC)
 coccoliths occurring at antapical pole.
Body coccoliths (abb. BC)
 coccoliths other than polar coccoliths and exothecal coccoliths.
Circum-flagellar coccoliths / apical coccoliths (abb. CFC)
 coccoliths occurring around flagellar opening. (Alternative term stomatal coccoliths, see appendix).
Exothecal coccoliths (abb. XC)
 coccoliths of the exotheca
Flagellar opening opening in coccosphere through which the flagella and haptonema pass.
Polar coccoliths coccoliths occurring at poles of coccospheres. {Kamptner 1937}

2.3 Coccolith arrangement

Overlapping adjacent coccoliths overlap.
Non-overlapping adjacent coccoliths arranged with edges directly butting rather than overlapping.
Interlocking adjacent coccoliths interlock.
Non-interlocking adjacent coccoliths do not interlock.
N.B. Interlock and overlap are separate phenomena, and can occur in any combination (see Fig. 1).

2.4 Informal taxon-based terms

As with coccoliths (see below), various terms have been coined to refer to coccospheres of particular taxonomic groups. These do not need any special definition, beyond noting the taxonomic groups included. E.g.; Braarudosphere Braarudosphaeraceae, Helicosphere Helicosphaeraceae.

3 TERMS FOR ENTIRE COCCOLITHS

3.1 Orientation

Proximal directed toward centre of coccosphere/cell. On nannofossils this is usually assumed to be the concave side, but cannot always be determined.
Distal directed toward outer surface of coccosphere/cell.
Horizontal perpendicular to proximo-distal direction.
Vertical proximo-distal direction.
Internal/inner/inward toward centre of coccolith.
External/outer/outward away from centre of coccolith.
Longitudinal direction parallel to long axis of an elliptical / elongated coccolith.
Transverse direction parallel to short axis of an elliptical / elongated coccolith.
End edge of coccolith parallel to short axis.
Side edge of coccolith parallel to long axis.
Length/width/height maximum dimensions of coccoliths in the longitudinal, transverse and vertical directions respectively.

3.2 Parts

In the vast majority of heterococcoliths there is an outer part which is somewhat higher than the inner part of the coccolith. This provides a convenient basis for starting any description of the shape and structure of coccoliths. It also is in large part a reflection of the coccolithogenesis process; growth outward and upward from the proto-coccolith ring forms the rim whilst growth inward forms the central-area .
Central-area Inner part of coccolith, enclosed by the rim. Usually characterised by less regularly cyclical elements than the rim and by inward element growth. May be entirely closed, or include a central opening. N.B. We recommend hyphenating central-area since it has a special meaning.
Rim Outer part of coccolith, usually characterised by regular cycles, some vertically directed structures and outward element growth (alternative term marginal area, see appendix). N.B. Use of this term was agreed after considerable discussion at the workshops.

3.3 Profile - coccolith shape in vertical cross-section

Although there is a very wide range of coccolith shapes the three types listed below recur frequently in disparate groups, see also Young (1992a). They are probably homoeomorphic adaptations for organising coccoliths on the cell. Intermediates between the types occur and any of them can occur with or without processes. These terms have no taxonomic implications.
Planolith rim not elevated (e.g. Rhabdosphaera, Discoaster). {Young 1992a, from Latin planus flat}
Murolith rim elevated but without well developed shields (e.g. Zeugrhabdotus, Pontosphaera). (Discolith has been used in this sense, see appendix). {Young 1992a, from Latin murus wall}
Placolith rim has two, or more, well developed shields (e.g. Coccolithus). {Lohmann 1902}

3.4 Outline - coccolith shape in plan view

Axial Ratio (abb. AR) ratio of length to width. Suggested descriptive terms, for elliptical coccoliths, are: Circular ; Sub-circular; Broadly elliptical; Normally elliptical; Strongly elliptical..
Asymmetrical without bilateral symmetry due to a wing or similar structure.
Elliptical continuously curved with two axes of symmetry. Close to, but not necessarily an exact, mathematical ellipse (alternative terms oval, ovoid, see appendix).
Irregularly elliptical with an approximately elliptical shape but departing noticeably from regular form.
Lenticular symmetrical form intermediate between a rhombus and ellipse, i.e. with pointed ends (e.g. Syracosphaera prolongata, Stradnerlithus).
Oblong symmetrical form intermediate between a rectangle and ellipse, i.e. with curved ends but sub-parallel sides (e.g. Calciopappus caudatus, Ellipsolithus macellus). N.B. This is recommended botanical use (Stearn 1983).
Polygonal with straight sides (triangular, pentagonal etc., e.g. scapholiths, Corollithion). (alternative term geometric, see appendix).
Reniform concavo-convex, kidney-shaped (e.g. Nephrolithus).
Ring-shaped circular or elliptical with narrow rim and open central-area (e.g. Cricosphaera, Manivitella).
Wing local extension of rim (e.g. Helicosphaera, Kamptnerius).

3.5 Coccolith size

Coccolith size is normally given as maximum dimension in plan view, i.e. length. The following sequence of terms are suggestions, based primarily on appearance in the light microscope. Minuscule (<1 µm), Very small, 1-3 µm; Small 3-5 µm; Medium 5-8 µm; Large 8-12 µm; Very large >12 µm.

3.6 Informal taxon-based terms for entire coccoliths

Many terms, originally defined as descriptive morphological terms, have become, restricted taxonomically. For instance most authors would agree that the term helicolith should be restricted to coccoliths of the Helicosphaeraceae, and not to any unrelated homoeomorphs. These terms are useful in many contexts, for example where it is important to distinguish between the organism and the coccolith/nannolith, or for describing polymorphic coccospheres. In general these terms are more widely used by workers on living coccolithophores than by palaeontologists. Comprehensive reviews are given by Tappan (1980), Chretiennot-Dinet (1990), Heimdal (1993), Siesser and Winter (1994), Jordan et al.(1995).
We do not give detailed definitions here, since essentially they are defined by the characteristic morphology of the taxa on which they are based. New terms of this sort can be formed by adding to an appropriate generic root either (1) the suffix -lith (e.g. sphenolith) or (2) the suffix -id + coccolith, murolith, planolith, or placolith (e.g. reticulofenestrid coccoliths).
Only modern usage is given here and many terms have undergone a complex evolution of meaning so that literature usage needs to be interpreted with caution - this applies particularly to the terms cricolith, cyrtolith, discolith, rhabdolith, and tremalith.
Caneolith Syracosphaeraceae, endothecal coccolith. (N.B. The terms complete/incomplete caneoliths have been used, see appendix). {Braarud et al. 1955a, 1955b}
Cricolith Pleurochrysidaceae, placolith with narrow rim and open central-area . {Braarud et al. 1955a, 1955b}
Cyrtolith Syracosphaeraceae, exothecal coccolith. {Braarud et al. 1955a, 1955b}
Discolith Pontosphaeraceae, murolith without flanges. {Huxley 1868}
Helicolith Helicosphaeraceae, coccoliths with helical flange.
Lopadolith high rimmed equatorial murolith of Scyphosphaera. {Lohmann 1902}
Osteolith whorl coccoliths of Ophiaster. {Halldal and Markali 1955}
Pappolith Papposphaeraceae.
Podorhabdid coccolith Podorhabdaceae.
Protolith Stephanolithaceae, Parhabdolithaceae (cf. Bown 1987).
Rhabdolith Rhabdosphaeraceae, planoliths +/- spines. {Schmidt 1870}
Scapholith Calciosolenia, Anoplosolenia. (Alternative term rhombolith). {Deflandre and Fert 1954}
Tremalith Hymenomonadaceae, vase-shaped murolith. {Lohmann 1913}
Reticulofenestrid coccolith Reticulofenestra and descendants. {Young 1989}
Coccolithid placolith Coccolithaceae. {Jordan et al. 1995}
(N.B. See also the sections on nannoliths and holococcoliths, and the appendix, for related terms).

4 ULTRASTRUCTURE RELATED TERMS

4.1 Types of ultrastructural component

(largely based on Young and Bown, 1991).
Element Apparently discrete component of a coccolith. This is an observational term, several elements may unite to form a crystal-unit.
Crystal unit A group of elements from different cycles in crystallographic continuity. These are the fundamental components of coccoliths and their identification is a key objective of ultrastructural research.
Segment one symmetrically repeated part of the coccolith, including elements from each cycle, consisting of one or more crystal-units.
Lamina platy sub-structure within a crystal-unit (e.g. Braarudosphaera).
Contact-surface plane of contact between two elements. (alternative term attachment surface, see appendix).
Suture trace of contact-surface on surface of coccolith.
Cycle ring of elements or crystal-units.
Tier one of a set of vertically superposed cycles (e.g. Arkhangelskiella, Lapideacassis).

4.2 Element shapes

(N.B. a,b,c three orthogonal axes, with any orientation)
Block nearly equidimensional element (a≈b≈c).
Tile broad and thin element (a≈b>c) N.B. Plate has been used in this sense but we prefer to use it for larger structures, not for single elements).
Lath elongate and wide element(a>b>c).
Rod elongate and narrow element (a>b≈c)
Wedge tapering nearly equidimensional element.
Petal/petaloid element tapering broad and thin element.
Ray tapering elongate and wide element.
Spine tapering elongate and narrow element.
Granule small and irregular or variable-shaped element (e.g. blanket elements of Helicosphaera, spine-forming elements of Cretarhabdus). N.B. Crystallite has been used in this sense but we prefer to only use it for holococcolith elements.

4.3 Element modifications

Curvature curving of elements. Laevogyre - elements curve to the left when traced radially outward. Dextrogyre - elements curve to the right when traced radially outward. Straight - elements not curved.
Node block-shaped projection from element.
Keel lath-shaped projection from element.
Ridge rod-shaped projection running along element.
Tooth rod or wedge-shaped projection from element.
Kink angular bend in element.
Offset displacement of an element from radial growth due to a double kink.

4.4 Special structures

Scissor-structure crystal-unit structure formed of two elements growing at only slightly different angles, and forming a two-layered shield (e.g. Coccolithus upper and lower proximal shield elements, Fig. 6) or tube (e.g. Toweius inner and outer tube elements, Fig. 6). {Young 1992b}
Cross-over zone belt around which two cycles of crystal-units cross (this usually corresponds to the proto-coccolith ring, e.g. Coccolithus, Fig. 6). {Young 1992b}

4.5 Openings

Canal narrow elongate opening within a coccolith or nannolith (Fig.s. 10, 14).
Cavity broad opening within a coccolith or nannolith (Fig.s. 10, 14).
Common opening opening formed by several individuals; i.e. the space within a coccosphere or group of associated nannoliths.
Depression pit on the surface of a coccolith or nannolith.
Hole opening running through one element (e.g. Pemma basquensis). {Farinacci et al. 1971}
Opening general term for any space not filled by elements.
Perforation small opening between two or more elements. {Farinacci et al. 1971}
Slit elongate perforation (e.g. Emiliania).

5 TERMS FOR DESCRIBING COCCOLITH RIMS

5.1 Parts of rims

Each of these parts may be formed of a single cycle of elements, part of a cycle or several cycles.
Shield broad (sub-)horizontal structure (placoliths).
Tube (sub-vertical structure between two shields (placoliths).
Wall (sub-)vertical structure not associated with shields (muroliths).
Flange (sub-)horizontal protrusion from rim.
Collar (sub-)vertical protrusion from rim (may occur on proximal or distal surface).
Crown discontinuous/beaded collar.

5.2 Directions on the rim

(largely based on Black 1972)
Radial direction in the surface of the baseplate perpendicular to its margin: Inward-outward - toward-away from centre.
Tangential direction in the surface of the baseplate parallel to its margin: Clockwise/dextral/right, anticlockwise/sinistral/left senses of direction as seen in distal view. We recommend: use of clockwise/anticlockwise as the clearest of these terms for general purposes. Use of dextral/sinistral when it is wished to particularly emphasise that this is the orientation as seen in distal view.
Vertical direction perpendicular to the baseplate: Up/down distal-proximal directions.
Flare and taper divergence of orientation from horizontal/vertical in the radial direction. Flare surfaces diverge upward, producing obconical/funnel-shaped bodies. Taper surfaces converge upward, producing conical bodies.

5.3 Element arrangement as seen in side view

Imbrication/inclination divergence from horizontal in the tangential direction. Imbrication is applicable to a cycle of elements, inclination to individual elements.
Clockwise/anticlockwise
imbrication		 offset of upper part of element from lower.
Imbrication angle angle of contact-surface from the horizontal. High-angle - sub-vertical contact-surfaces. Low-angle - sub-horizontal contact-surfaces.
Zeugoid rim rim with high-angle imbrication, and without distinct shields. (Alternative terms loxolith rim, zygodiscid rim, see appendix).

5.4 Element arrangement as seen in plan view

Obliquity horizontal divergence from radial direction. (Alternative term precession, see appendix).
Dextral/sinistral obliquity deflection from radial of outer part of element relative to inner part, as seen in distal view. Note that elements will show opposite apparent senses of obliquity in distal and proximal view. This can be described as follows: a dextrally oblique cycle displays clockwise obliquity in distal view but anti-clockwise obliquity in proximal view.
Butting elements with simple (sub-)radial sutures.
Interlocking elements with complex sutures.
Overlapping elements with low angle oblique sutures (N.B. This pattern has occasionally been described as imbrication, but we prefer to use imbrication for description of vertical structures).

5.5 Identification of elements

For description and discussion, the various elements/cycles of elements need to be identified. This is best done by reference to the location of the elements using the set of orientation and structure terms given above. Examples are given in Figure 8. Element shape is not recommended as an alternative since it is easily altered - by diagenesis, intra-specific variation and evolution.

6 CENTRAL-AREA STRUCTURES

6.1 Structural types

Conjunct formed from crystal-units of the rim structure. E.g. Gephyrocapsa (bridge and grill), Helicosphaera sellii (bar), Kamptnerius (plate), Watznaueria biporta (bar). (Alternative term optically continuous structure, see appendix). {Young 1992a}
Disjunct formed from crystal-units discrete from the rim structure. E.g. Arkhangelskiella (plate), Coccolithus pelagicus (bar), Helicosphaera seminulum (bar), Watznaueria britannica (bar). (Alternative term optically discontinuous structure, see appendix). {Young 1992a}

6.2 Orientation in profile

Basal occurring on the proximal surface.
Elevated occurring above the proximal surface.
Vaulted cone-shaped, rising from the rim toward the centre.
Longitudinal parallel with long axis of (elliptical) coccolith.
Planar flat, not vaulted.

6.3 Orientation in plan view

Transverse parallel with short axis of (elliptical) coccolith.
Diagonal inclined relative to axes. Angle should be measured from transverse direction (but some authors use opposite convention, i.e. measure angle from longitudinal direction):
Low angle near to transverse direction;
High angle near to longitudinal direction.
Dextral/sinistral inclined to the right/left of the long-axis as seen in distal view. N.B. As with element obliquity the terms dextral/sinistral are preferred for describing orientations which appear different in proximal and distal view.
Relative width width of central-area relative to rim width:
Wide central-area width >2x rim width;
Normal central-area width 1-2x rim width;
Narrow central-area width <1x rim width.

6.4 Structures spanning central-area

Arm part of crossbar, bridge or cross running from centre of coccolith to edge of central-area. (alternative terms limb, spoke, see appendix).
Bar any elongate central-area structure. N.B. This is a general term. When it is useful to be more specific terms such as longitudinal bar, cross-bar, and arm can be used. (Alternative term jugum, see appendix).
Blanket covering of small elements on distal side of central-area (e.g. Helicosphaera, Coccolithus).
Bridge elevated bar spanning the central-area (e.g. Gephyrocapsa).
Cross-bar bar spanning the central-area.
Cross pair of cross-bars meeting in centre.
Axial cross (abb. +), cross-bars longitudinal and transverse.
Diagonal cross (abb. X) cross-bars diagonal - may be symmetrical or asymmetrical relative to the axes.
Offset cross cross with an offset between the arms of one, or both, of the crossbars (e.g. Chiasmolithus).
Foot broadening of bar as it meets the rim (e.g. Cruciplacolithus tenuis).
Lateral bar bar running from rim to a cross bar (e.g. Retecapsa).

6.5 Structures closing central-area

Central opening opening at centre of coccolith, may be spanned by bars or other central-area structures, but not by a continuous structure such as a grill or plate.
Closed central-area central-area without a central opening.
Grill system of bars closing central-area (e.g. Emiliania).
Net mesh-like structure closing central-area (e.g. Reticulofenestra, Cribrosphaerella). (Alternative term cribrate central-area, see appendix).
Open central-area central-area without any structures.
Plate continuous or nearly continuous structure closing central-area.
Perforated plate plate with perforations (e.g. Arkhangelskiella).

6.6 Processes

Calyx flaring structure at tip of process (e.g. Podorhabdus, Papposphaera).
Boss low process, height similar to or less than width (alternative term knob, see appendix).
Process general term for any structure rising from the central-area.
Protrusion broad low process, with height similar to width, and width near that of entire central-area. Types:
Conical cone-shaped protrusion (e.g. Acanthoica);
Sacculiform sac-like protrusion with more or less rounded upper part (e.g. Algirosphaera). (N.B. labiatiform has been used for the elongate double-lipped sacculiform protrusions, see appendix).
Spine elongated process, height greater than width. (Alternative term column, see appendix). Types:
Styliform {Halldal and Markali 1955} - spine tapers toward the distal end;
Claviform {Halldal and Markali 1955} - spine has blunt end, without calyx. (N.B. helatoform has been used for nail-shaped processes, see appendix);
Calicate spine is surmountd by a calyx.
Salpingiform {Braarud et al. 1955a, 1955b} - spine (or protrusion) trumpet-shaped (e.g. Discosphaera).
Stem part of process below calyx.
Cavity wide opening within process (e.g. Podorhabdus grassei, Algirosphaera robusta).
Canal narrow opening running along length of process.
Proximal pore opening of canal, on proximal side of central-area.

7 CRYSTALLOGRAPHY

7. 1 Crystallographic orientation

(Fig. 8) Calcite c-axis orientation can be, summarised with the following terms. Based on Young and Bown (1991), Young et al. (1992). N.B. Actual orientations depart significantly (up to 30û) from true vertical and radial.
V-unit crystal-unit with sub-vertical orientation of c-axis. {Young and Bown 1991}
R-unit crystal-unit with sub-radial orientation of c-axis, relative to its point of origin (nucleation) on the proto-coccolith ring. {Young and Bown 1991}
T-unit crystal-unit with sub-tangential orientation of c-axis (e.g. Braarudosphaeraceae, Polycyclolithaceae). {Young et al. 1997}
Compound formed of several crystal-units. E.g. Micula, Discoaster.
Pseudo-monocrystalline formed of several crystal-units with parallel c-axes, but non-parallel a-axes. E.g. Discoaster. These behave optically as single crystals, but will not fuse into a single crystal during overgrowth.
Monocrystalline formed of a single crystal-unit, and so all elements have identical crystallographic orientation of c- and a-axes and overgrow as one unit, e.g. apical spine of Sphenolithus heteromorphosus, entire nannoliths of Florisphaera, Marthasterites, Minylitha, Ceratolithus.

7.2 Graphical conventions for indicating crystallographic orientation

Symbols A single symbol per element can indicate c-axis direction, see Fig.ure 8.
Shading To directly illustrate observations made with a gypsum plate hatching can be used - vertical and horizontal for parts in extinction (purple). Diagonal for birefringent parts (blue and yellow). The direction of diagonal hatching should of course be based on the c-axis orientation and since the gypsum plate orientation varies between microscopes the relationship between observed colour (blue, yellow) and c-axis direction has to be determined for each microscope.
Unit type shading For illustrating structure it is convenient to apply the same shading to all the elements of one crystal-unit cycle in all views of the nannolith. For this the following scheme is recommended: V-units stippled; R-units blank; T-units dashes.

7.3 Light microscopy based terms

Birefringent/non-birefringent appearing bright/dark between cross-polars. N.B. A coccolith or part of a coccolith can only appear non-birefringent in one orientation (when the c-axis is vertical), so these terms should not be used without explicit description of specimen orientation; e.g. "discoasters are non-birefringent in plan view".
Extinction-figure appearance of a specimen in cross-polarized light, particularly pattern of isogyres.
Isogyre dark line in cross-polarized light caused by elements in extinction.
North/South, East/West orientations relative to the microscope body.

8 INTRA-SPECIFIC VARIATION

8.1 Primary coccolith variation

As a general principle styles of variation should be described without reference to inferred causal factors - e.g. heavily calcified E. huxleyi is preferable to cold-water morphotype. Terms used here are largely based on Young and Westbroek (1991), Young (1994).
Normally formed with typical form.
Abnormally formed departing from normal form in some way, includes all the categories below.
A. Degree of completion / ontogenetic variation variation in degree to which the coccolith has grown. (N.B. terms such as juvenile and mature are not recommended for use in this context).
Coccolithogenesis process of coccolith development and growth {Outka and Williams 1971}
Proto-coccolith ring earliest stage of coccolith growth, crystal-units simple without differentiation of elements. {Young 1989}
Incomplete coccolith elements differentiated but incompletely grown.
Complete coccolith all elements fully grown.
B. Teratological Malformation abnormal form developed as result of irregular growth. N.B. The use of the term malformation to describe other types of variation (e.g. degree of calcification, or growth) is not recommended.

C. Degree of calcification primary variation in amount of biogenic calcite incorporated in a coccolith.
Under-calcified coccolith with elements markedly thinner than normal for the species.
Normally calcified coccolith with elements of normal thickness for the species.
Over-calcified coccolith with elements markedly thicker than normal for the species.

8.2 Secondary alteration of coccoliths - diagenetic and water-column effects

Overgrowth secondary inorganic growth of calcite on elements.
Etching secondary inorganic dissolution of calcite from elements.
Descriptive scheme, {from Roth and Thierstein 1972, Roth 1983}.
X Excellent preservation coccoliths appear pristine.
E1 Slight etching serrate outlines, partial dissolution of delicate structures.
E2 Moderate etching irregular outlines, dissolution of most delicate structures and species.
E3 Strong etching much material fragmented, only resistant species left.
O1 Slight overgrowth overgrowth of shield and central-area elements noticeable but does not obscure details.
O2 Moderate overgrowth many elements with large overgrowths, many details obscured.
O3 Strong overgrowth only overgrown elements, identifications very limited.
N.B. Overgrowth and etching commonly both occur in the same sample, this can be shown by codes such as E1-O2. This scheme is primarily for light microscopy, successful electron microscopy requires preservation grades E1, X or O1.

9. NANNOLITH SHAPES

Nannoliths display a wide range of shapes, including the following types which all occur independently in more than one group. These shape terms are independent of structure, e.g. tetraradiate nannoliths may be formed of one, four or many crystal units.
Dibrachiate consisting of two sub-parallel arms joined at one end. Includes horseshoe, arrow-head, and arcuate shapes (e.g. Ceratolithus, Amaurolithus, Ceratolithina, Ceratolithoides - except C. verbeekii).
Compact more or less equidimensional nannoliths. Includes conical (e.g. Sphenolithus), obconical (i.e. inverted cone-shaped, e.g. Conusphaera), cylindrical (e.g. Fasciculithus) and cubic (e.g. Micula) shapes.
Rod-shaped elongate, and apparently without a basal disc. Includes bladed (e.g. Lithraphidites quadratus, Triquetrorhabdulus carinatus) and (sub-)cylindrical (e.g. Microrhabdulus) shapes.
Radiate with radial symmetry. N.B. the number of crystal-units may be larger or smaller than the number of rays.
Triradiate threefold radial symmetry (e.g. Marthasterites, Trochasterites).
Tetraradiate fourfold radial symmetry (e.g. Micula, Quadrum, Nannotetrina).
Pentaradiate fivefold radial symmetry (e.g. Goniolithus, Braarudosphaera).
Multiradiate more than fivefold radial symmetry (e.g. many Discoaster spp.).
Central body core part of radiate nannolith where elements are in contact.
Free rays parts of radiate nannolith extending beyond central body.
Short free rays length of free rays is less than radius of central body, resulting in a rosette-shaped outline.
Long free rays length of free rays is greater than radius of central body, resulting in a star-shaped outline.
Convex outline without free rays (e.g. Braarudosphaera). Including e.g. triangular, square, and pentagonal shapes.
Stellate with free rays (e.g. Micrantholithus, Discoaster). Including rosette and star-shaped.

10. TERMS FOR GROUPS

Braarudosphaeraceae

The Braarudosphaeraceae are an enigmatic group of nannoliths ranging from the Early Cretaceous to the present day. Despite being extant they have never been succesfully cultured and so their affinities are uncertain (they may be Haptophytes, Dinophytes or belong to another group). They are of minimal biostratigraphic value but occasionally occur in enormous abundance, most notably in the Early Danian just after the K/T boundary and in the Oligocene of the South Atlantic.
Update: Although Braarudosphaera has still not been succesfully cultured, despite repeated attempts, Takano et al. (2006) have obtained DNA sequences from single-cell isolations. These showed that Braarudosphaera is a haptophyte and falls inside the coccolithophore clade.

Informal taxon-based term: Pentalith {Gran and Braarud 1935} - nannolith formed by the Braarudosphaeraceae (N.B. does not include other nannoliths formed of five elements, such as Discoaster pentaradiatus).
Lamina plate-like sub-element of segments.
Segment one of the five component parts of a pentalith. They appear to be single crystal-units, with tangential c-axis orientation.

Calcispheres

Palaeozoic calcispheres are of uncertain affinity and are not discussed here. Most Mesozoic and Cenozoic calcispheres are now believed to be dinoflagellate cysts. Keupp (1991) gives an English-language synthesis of this group, Janofske and Keupp (1992) give a brief overview, these workers regard wall structures as the primary basis for classification. Williams et al. (1978), Sergeant (1982) and Evitt (1985) summarise the terminology for describing organic-walled cysts, much of which can be directly applied to calcispheres. Only the most important, relevant terms are included here.

1. Orientation

Dinoflagellates have clearly differentiated ends, shown by shape, flagellar disposition, behaviour, etc. Swimming direction is conventionally used to determine front and rear.
Apex/anterior end front of dinoflagellate when swimming, usually pointed. Almost always contains the archaeopyle.
Antapex/posterior end rear of dinoflagellate when swimming, usually flaring.
Ventral side side of dinoflagellate with longitudinal flagellum and sulcus.
Dorsal side side opposite longitudinal flagellum and sulcus.

2. General terms

Calcisphere hollow, typically spherical, calcareous nannofossil. Whereas coccospheres are composite structures formed of numerous coccoliths calcispheres possess a continuous wall.
Cyst wall formed around dinoflagellate during non-motile, non-vegetative, stage. These often show paratabulation but are continuous structures, except for the archaeopyle if present. Most calcispheres are thought to be cysts, however, the thoracosphere of Thoracosphaera heimii is formed during the vegetative stage and so is not a cyst.
Dinoflagellate informal taxon-based term for member of the phylum Dinophyta.
Theca non-resistant organic wall of motile vegetative stage of dinoflagellates, composite structures formed of plates.
Thoracosphere informal taxon-based term for calcisphere formed by Thoracosphaera. N.B. T. heimii has a wall structure of large elements (ca. 1 µm) with their c-axes tangential to the wall, and randomly aligned.

3. Wall types

Oblique/Obliquipithonelloid formed of elements with their c-axes oblique to the wall and variably aligned relative to each other (e.g. Obliquipithonella multistrata).
Pithonelloid formed of elements with their c-axes oblique to the wall and sub-parallel to each other (e.g. Pithonella sphaerica, P.ovalis).
Radial/Orthopithonelloid formed of elements with their c-axes perpendicular to the wall (e.g. Calciodinellum, Rhabdothorax).
Tangential formed of elements with their c-axes tangential to the wall (e.g. Fuetterella conforma, Thoracosphaera heimii).

4. Paratabulation features

Archaeopyle opening for excystment.
Operculum plate covering the archaeopyle.
Paratabulation structures on the cyst of a dinoflagellate reflecting the tabulation of the theca. Paratabulation may be developed on the inner or the outer surface of calcispheres.
Cingulum sub-equatorial channel occupied by the transverse flagellum.
Sulcus furrow occupied by longitudinal flagellum.
Horn protrusion from either end of dinoflagellate.

5. Paratabulation types

Holotabulate paratabulation of ridges or edges on the cyst corresponding to plate boundaries on the theca.
Intratabulate paratabulation of processes on the cyst corresponding to plates on the theca.
Cingulotabulate paratabulation confined to cingulum and archaeopyle.
Cryptotabulate paratabulation confined to archaeopyle.

Ceratolithaceae and Triquetrorhabdulaceae

The Ceratolithaceae and Triquetrorhabdulaceae are a rather rare but biostratigraphically valuable pair of nannolith families (see also Neogene range chart). Relationships between them were postulated by several authors and demonstrated by Raffi et al. (1999). The Triquetrorhabdulaceae are extinct (range - Late Oligocene to early Pliocene) but the Ceratolithaceae are extant (range - Late Miocene to Recent). Combination coccospheres indicate that the Ceratolithaceae have a complex life cycle producing in addition to Ceratoliths (horseshoe-shaped nannoliths) two types of heterococcolith - hoop coccoliths and planoliths (formerly assigned to the genus Neosphaera). References Alcober and Jordan 1997, Young et al. (1998), Sprengel and Young (2000).

CERATOLITHACEAE

Informal taxon-based term: Ceratolith - dibrachiate nannoliths formed by the Ceratolithaceae. Includes Amaurolithus nannofossils; does not include the hoop-shaped exothecal heterococcoliths, or the planoliths formed during the alternate life-cycle phase.

1. Orientation

Upper / lower The more-ornamented surface is designated upper. This division is arbitrary, but it is useful since there is a consistent polarity to structures. With careful through-focussing it is quite possible to distinguish the two sides by light microscopy. N.B. The terms distal/proximal should not be used since ceratoliths appear to be either intracellular or wrapped around the cell (Norris 1965).
Anterior / posterior Closed end is designated anterior.
Left /right Based on upper view, looking toward anterior end.

2. Parts

Apical region anterior end of ceratolith, hence terms such as apical node.
Arch part of apical region connecting the two arms.
Arm rod-like extension back from apical region.
Rod rod-shaped structure attached to the nannolith, (e.g. Amaurolithus bizarrus).
Spur projection from apical region.
Keel lath-like structure running along an arm. Types:
Dentate keel - keel formed of sub-parallel teeth.
Smooth keel - keel without teeth.
Tooth rod-like sub-element of a keel.
Wing plate-like extension from main body of nannolith (e.g. Amaurolithus ninae).

TRIQUETRORHABDULACEAE

Orientation: There is no obvious proximal/distal differentiation.
Longitudinal parallel to length of nannolith.
Transverse perpendicular to length of nannolith.
Blade one of the three main sub-parts of the nannolith.
Dentate blade blade with transverse sub-structure of rod-shaped teeth.
Lateral blade one of two broader blades nearly in the same plane (e.g. T. rugosus)
Median blade narrowest of three blades.
Ridge subsidiary longitudinal structure on a blade. E.g. T. challengeri.
Wing blade greatly extended in transverse direction. E.g. T. finifer.
Tooth rod-like part of a dentate blade.

Discoasters

Dicoasters are the most important single group of Cenozoic nannoliths, ranging from the Palaeocene to the Pliocene. The numerous species are of great biostratigraphic value (see also Neogene range chart)

Informal taxon-based terms:
Discoaster nannolith formed by Discoasteraceae.
Eu-discoaster typically Neogene and usually star-shaped discoasters, with planar contact surfaces between elements.
Helio-discoaster typically Palaeogene and usually rosette-shaped discoasters, with curved contact surfaces.
N.B. These terms are useful even if formal taxonomic division into the genera Eu-discoaster and Helio-discoaster is not made. The differences between them are given in Theodoridis (1984) and Aubry (1984).

1. Orientation

In virtually all discoasters, there are consistent differences between the two faces (Stradner and Papp 1961; Prins 1971; Romein 1979; Aubry 1984; Theodoridis 1984; Self-Trail and Bybell 1995). Many of the Neogene eu-discoasters consistently have one concave and one convex face and, by analogy to coccoliths, these faces have been termed proximal and distal (e.g. Theodoridis 1984). The two sides are also consistently characterised by various other structures, in particular there are usually sutural ridges on the distal side (Text-fig. 11). These structures can be used to separate the proximal and distal faces of planar eu-discoasters.
In helio-discoasters the rays are usually curved, so laevogyral and dextrogyral faces can be distinguished. Moreover, the curvature is usually stronger on the laevogyral surface. It is not, however, certain which of these faces corresponds to the proximal face in eu-discoasters, and they have varying relationships to discoaster concavity. Hence, the terms proximal and distal have been applied rather inconsistently in this group (compare Stradner and Papp 1961, Prins 1971 and Romein 1979) and are, perhaps, better avoided.
Proximal Concave side of eudiscoaster
Distal Convex side of eudiscoaster
Laevogyral face Side of heliodiscoaster showing left-handed curvature of rays
Dextrogyral face Side of heliodiscoaster showing right-handed curvature of rays

2. Ray-related terms

Ray disc element.
Free ray part of ray protruding beyond central-area
Ray tip outermost part of ray.
Bifurcate tip ray tip divides into two bifurcations (e.g. D. variabilis).
Simple tip ray tip without bifurcation or proximal extension.
Proximal extension continuation of the ray downward from the tip (e.g. D. brouweri).

3. Other terms

Central-area portion of discoaster with rays in contact.
Contact-surface surface between adjacent elements (alternative term attachment surface, see appendix).
Disc main part of discoaster, excluding bosses or stems.
Boss low distal or proximal protrusion from centre of disc (alternative term knob, see appendix).
Rosette-shaped discoaster with short free rays (Text-fig. 10).
Segment ray and associated boss or stem elements.
Stem high distal or proximal protrusion from centre of disc (e.g. Discoaster kuepperi).
Star-shaped discoaster with long free rays (Text-fig. 10).
Sutural ridge ridge running along suture.

Fasciculiths

Fasciculiths are an extinct Palaeogene group of nannoliths, range Palaeocene to Early Eocene. There are about 20 species, all classified in the genus Fasciculithus and Family Fasciculithceae
Informal taxon-based term: Fasciculith - nannolith formed by the Fasciculithaceae.
Orientation: The concave end of the nannolith is assumed to be proximal.

Apical cycle distal cycle of fasciculith. (Alternative term cone, see appendix).
Central body optically distinct body occurring in the centre of fasciculith. {Romein 1979}
Column cycle proximal cycle of fasciculith, usually forms most of the fasciculith.
Fenestra regular depression on fasciculith.
Longitudinal ridge ridge parallel to length of fasciculith.
Proximal surface lower surface of fasciculith.

Helicosphaera

The Helicosphaeraceae constitute an important family of heterococcoliths ranging from the Early Eocene to the present day (extant species H. carteri, H. pavimentum). There is only one genus but numerous fossil species, many of which are of biostratigraphic value, though mainly as secondary markers (see also Neogene range chart). The morphology is unusually complex so some special terminology is needed.

Informal taxon-based term: Helicolith - nannolith formed by the Helicosphaeraceae.

1. Orientation

The asymmetry of helicoliths allows more-precise description of orientation than for most other coccoliths.

Anterior end with origin of flange and usually with broader flange on distal side often with distinct wing or spur. (Alternative term pterygal, see appendix).
Posterior opposite end to anterior. (Alternative term antipterygal, see appendix).
Dextral/sinistral right/left sides of helicolith as seen in distal view with anterior end upwards. As with other uses the terms dextral/sinistral are recommended in place of left/right for terms referring to one particular orientation. The wing, when present is on the sinistral side.

2. Parts

Bar structure crossing central opening. Types;
Conjunct bar developed from rim elements (e.g. H. carteri). (Alternative terms optically continuous bar, bar, bridge, see appendix).
Disjunct bar formed from elements discrete from the rim (e.g. H. intermedia). (Alternative terms optically discontinuous bar, bridge, bar, see appendix).
Normally oriented bar diagonal bar with dextral orientation; i.e. rotated to the right of the long axis in distal view/ anterior end on opposite side to the wing.
Inversely oriented bar diagonal bar with sinistral orientation; i.e. rotated to the left of the long axis in distal view/ anterior end on same side as wing.
N.B. Use of the terms normal/inverse is a ubiquitously adopted convention based on their relative abundances.
Blanket mass of elements forming distal cover. {Theodoridis 1984}
Flange rim structure of helicolith (shield is also used by some workers).
Origin location of first/shortest elements of flange on the proximal side.
Proximal plate inward radiate elements on proximal side of central-area.
Spur spike-like expansion of flange near its termination (e.g. H. recta).
Termination location of last elements of flange on the distal side.
Wing broad expansion of flange near its termination (e.g. H. carteri).

Holococcoliths

1. Terms for parts of holococcoliths

Block zone of holococcolith that behaves in cross-polarized light as one unit.
Cavity open central part of holococcolith, not filled by crystallites (e.g. Calyptrosphaera, Zygosphaera).
Crystallite individual minute crystal (typically ca. 0.1 microns).
Crystallite arrangement pattern of crystallites visible on a surface. Types:
hexagonal - crystallites arranged in hexagonal array (with C-axes directed radially)
hexagonal meshwork - similar but with regular array of perforations due to omission of single crystals (e.g. Calyptrosphaera oblonga).
rhomboid - crystallites arranged in rhombohedral array (c-axes oblique to surface) (e.g. Syracolithus confusus).
Depression pit on surface, not opening into a cavity.
Distal-cover distal layer(s) of crystallites, covering cavity (may merge into rim or be discrete from it).
Perforation opening in wall the size of one crystallite.
Plug distally positioned block (e.g. Lucianorhabdus).
Pore opening in wall larger than one crystallite (e.g. Gliscolithus).
Proximal flange sub-horizontal protrusion from base of rim.
Proximal-plate proximal layer(s) of crystallites (nearly) covering base of coccolith.
Proximal-ring proximal layer(s) of crystallites confined to edge of coccolith.
Rim peripheral zone discrete in cross-polarized light from the main blocks (typically rim elements have radial c-axes).
Septum layer(s) of crystallites forming internal wall.
Wall layer(s) of crystallites forming sub-vertical structure.

2. General terms for description of entire holococcoliths

Cavate with large cavity inside rim (e.g. Calyptrosphaera).
Septate space inside rim is subdivided by septa (e.g. Syracolithus quadriperforatus, Anfractus harrisonii).
Solid coccolith consists essentially of a single mass of crystallites without distinct cavity, or septa, with or without depressions, perforations, or pores (e.g. Syracolithus catilliferus) and possibly many fossil holococcoliths.

3. Morphological types

For holococcoliths, unlike heterococcoliths, we do not have many useful structural characters, and the special shape terms (e.g. calyptrolith, helladolith) describe morphotypes that almost certainly occur independently in different taxa. So these terms are purely descriptive terms and independent from taxonomy. They are not much used by palaeontologists and we do not recommend the creation of new terms for fossil holococcolith types. See also Norris (1985), Kleijne (1991), Jordan et al. (1995).
Calicalith open cavate, without distal cover (e.g. Calicasphaera). {Kleijne 1991}
Calyptrolith domal cavate, with nearly continuous distal-cover (e.g. Calyptrosphaera). {Lohmann 1902}
Crystallolith disc-like solid holococcolith formed of one or two layers of crystallites, with low rim (e.g. Coccolithus pelagicus holococcoliths). {Braarud et al. 1955a}
Flosculolith cavate with distal opening partially closed by a vaulted distal-cover (e.g. Flosculosphaera). {Kleijne et al. 1991}
Fragariolith proximal plate directly surmounted by blade-like process. (e.g. Anthosphaera fragaria). {Kleijne 1991}
Gliscolith cavate with bulbous distal part (e.g. Gliscolithus). {Norris 1985}
Helladolith similar to zygolith but with bridge expanded distally into double-layered leaf-like process (e.g. Helladosphaera). {Heimdal and Gaarder 1980}
Laminolith solid holococcolith formed of several (>2) horizontal layers of crystallites, with or without perforations/pores (e.g. Syracolithus catilliferus). {Heimdal and Gaarder 1980}
Zygolith with bridge-shaped distal-cover (e.g. Corisphaera). {Kamptner 1937}

Nannoconids

The Nannoconaceae are a monogeneric group of rock-forming Late Jurassic - Late Cretaceous, nannoliths of uncertain affinities. The terminology applicable to Nannoconus is reviewed in detail by van Niel (1994), and the following is a list of key terms only.
Informal taxon-based term: nannoconid.

1. Associations

Groups of associated nannoconid individuals have been found by various workers: Trejo (1960); Colom (1965); Ozkan (pers. comm.). These associations have only a very small common opening and may represent colonial groups of cells (cf. many diatoms) rather than single organisms (cf. typical coccospheres).
Association a group of systematically arranged individuals. {van Niel, 1994}
Rosette association of nannoconids lying side-by-side with their longitudinal-axes radiating from a central point. N.B. It is possible that all rosettes are spherical, but the term sphere is not recommended since this has not been demonstrated, and since nannoconid associations may not be strictly comparable to coccospheres. {Noel 1958}
Twin two nannoconid individuals joined at their ends, with ridges and grooves extending across the contact surface. {van Niel 1995}

2. Orientation

Longitudinal axis axis of rotational symmetry of nannoconid.
Transverse plane plane perpendicular to the longitudinal axis.
Horizontal directions within the transverse plane.
Vertical directions parallel to the longitudinal axis.
Pole end of nannoconid, point of emergence of symmetry axis:
apex pole in N. steinmannii at narrower end of specimen {Bronnimann 1955};
base - pole opposite to apex (broader end in N. steinmannii).{Bronnimann 1955}
Longitudinal view view of nannoconid parallel to longitudinal axis.
Plan view view of nannoconid perpendicular to longitudinal axis.

3. General terms

Central opening opening running longitudinally through the nannoconid. Types:
canal - narrow, <1 µm;
cavity - wide, >1 µm;
aperture - expression of the central opening at the ends of the specimen. {Kamptner 1931}
Bulb a distinct swelling of the outline (e.g. N. borealis - single, N. paskentiensis - double, N. multicadus - triple). {Trejo 1960}
Constriction external indentation of the wall, between bulbs. {Deflandre and Deflandre-Rigaud 1962}
Flange horizontal projection around the end of nannoconid. N.B. Flanges may be symmetrical or asymmetrical in end view, and may be present at one or both ends of the specimen. {Stradner and Grün 1973}
Wall structure enclosing the central opening. {Kamptner 1931}

4. Structure

Nannoconids appear to be formed of two types of plates arranged in alternating cycles (van Niel 1992). These cycles appear to spiral around the wall but the precise geometry is not yet clear.
Plate basic structural element of nannoconid, single sub-triangular platy crystal. (Alternative term wedge, see appendix). {Stradner and Grun 1973}
Type A-cycle cycle of plates inclined at a lower angle (angle α) to the horizontal. These are birefringent in longitudinal view (Perch-Nielsen 1988). {van Niel 1992}
Type B-cycle cycle of plates inclined at a higher angle (angle β) to the horizontal. These cycles are non-birefringent in longitudinal view and form the dark spiral lines observed in cross-polars in longitudinal view (Kamptner 1931, Deflandre and Deflandre-Rigaud 1962, Perch-Nielsen 1988). {van Niel 1992}
Angle Δ angle of the A cycle/B cycle contact to the horizontal. N.B. This is the only angle measurable by light microscopy. {van Niel 1992}
Cycle spacing repeat distance between cycles perpendicular to angle Δ, i.e. combined thickness of A and B cycles.

Polcyclolithaceae

The Polcyclolithaceae are a key group of Cretaceous nannoliths including many biostratigraphic markers. Varol (1992) and Burnett (in Bown 1998) give useful reviews of the group.

Informal taxon-based term: Polycyclolith nannolith formed by the Polycyclolithaceae.
Orientation: clear distal / proximal polarity has not been demonstrated so these terms should be avoided.
Diaphragm plate-like central cycle of elements
Wall outer part of nannolith, typically formed of two superposed cycles of elements.
Reduced cycle smaller of the two wall cycles.
Expanded cyclelarger of the two wall cycles.
Ray, petalloid, block typical shapes of wall elements (cf. section 4.1.2).

Sphenoliths

Sphenoliths are an extinct group of nannoliths. There are numerous species, classified in the single genus Sphenolithus, family Sphenolithaceae (range: Palaeocene - Pliocene). They are of great biostratigraphic value, especially in the Late Oligocene and Early Miocene (See also range chart)

Informal taxon-based term: Sphenolith nannolith formed by the Sphenolithaceae.
Orientation: The concave end of the nannolith is assumed to be proximal/basal.

Apical cycle upper part of sphenolith, formed of most steeply inclined cycle of elements. Types:
Monocrystalline formed of one crystal-unit; e.g. S. heteromorphosus, S. belemnos.
Duocrystalline formed of two crystal-units; e.g. S. distentus, S. furcatulithoides.
Compound formed of several crystal-units; e.g. S. radians, S. abies.
Apical spine elongate extension of apical cycle.
Base all of sphenolith except the apical spine.
Blade one of three sub-parts of an element, only seen in well preserved material.
Core centre of radiation of elements.
Element basic component of sphenoliths, each element appears to be a single crystal-unit.
Lateral cycles cycles between apical and proximal cycles, not always present.
Proximal cycle lowermost cycle of elements.
Upper/lower part part above/below the core.

APPENDICES

Appendix 1 - terms we have not used

The following terms have previously been used in nannoplankton literature but are not used here, for the reasons outlined. In these notes, the term is briefly defined, using our terminology. Then the reason for our not using it is given (see also the introductory section on the choice of terms).
Attachment surface contact-surface between two elements. Superfluous synonym, contact-surface seems more objective.
Bar / Bridge
(sensu Theodoridis 1984)		 synonyms of disjunct and conjunct bar, especially for helicoliths. We consider these terms confusing. Also they are of limited application, whereas the terms disjunct and conjunct can be applied to any central-area structure, not just bars.
Bar / Bridge
(sensu Aubry 1988)		 as per Theodoridis (1984) but with opposite meanings.
Coccocylinder cylindrical coccosphere. Superfluous term (despite being based on a very beautiful specimen), numerous coccospheres are aspherical and there is no utility in coining numerous shape related terms. {Covington 1985}
Column often used as a synonym of spine, which we prefer.
Cone alternative to apical cycle, for fasciculiths. This cycle only forms a conical structure in a few species so we prefer the more neutral term apical cycle.
Complete/incomplete caneoliths endothecal coccoliths of Syracosphaera with, respectively, 3 and 2 flanges. The distinction is useful but there is no real need for these rather obscure special terms. Also, we prefer to use the terms complete and incomplete to describe degree of completion of growth of coccoliths.{Halldal and Markali 1955}
Cribrate central-area obscure alternative to net.
Discolith this term has been widely used for coccoliths with elevated rims but no shields, i.e. muroliths as defined here. We prefer murolith since Discolith has also been used with the different sense of 'a coccolith belonging to the Pontosphaeraceae'. In addition the word discolith is potentially misleading.
Geometric unsuitable alternative of polygonal. Ellipses and circles are just as geometric as triangles or pentagons are.
Heliolith / Ortholith These terms for coccolith types were originally defined on the basis of the crystallographic orientation of the main elements: Ortholiths - dominant elements large with vertical or tangential c-axis orientation (e.g. Discoaster, Braarudosphaera); Helioliths - dominant elements have approximately radial c-axes giving a "sphérolithique" appearance (e.g. Watznaueria, Reticulofenestra). This concept is of limited use since most heterococcoliths are composed of both vertical and radial crystal-units, whilst for many nannoliths the concept of radial and vertical are unclear. As a result there has been only limited agreement between authors who have used these terms as to which taxa should be included in which group - compare Deflandre (1952), Tappan (1980), Aubry (1984 et seq.). {Deflandre 1950}
Jugum synonym of bar. Obscure and superfluous.
Knob synonym of boss, especially for discoasters. We prefer boss, and it has more general application.
Labiatiform elongate double-lipped sacculiform protrusion. Unnecessarily specialised term, applying to only one taxon Algirosphaera robusta.{Halldal and Markali 1955}
Limb / spoke synonym of arm. We prefer arm and it has been more widely applied.
Loxolith rim synonym of zeugoid rim, which we prefer.
Marginal area rim. We prefer rim since it is handier for forming complex terms (e.g. proximal rim element), and because marginal area suggests an unimportant feature whereas this is the most important part of many coccoliths. {many authors}
Nanofossil, Nanoplankton synonyms of nannofossil and nannoplankton. Both nano- and nanno- are etymologically valid prefixes derived from the Greek word nanos (dwarf). We prefer nanno- on the following grounds. A. General usage, as noted by the Oxford English Dictionary (2nd edn 1989), nearly all palaeontologists use nannofossil and many biologists use nannoplankton so this is the de facto "correct" spelling. B. Priority, this was the spelling adopted by Lohmann (1909), when he coined the term nannoplankton. C. Differentiation, the SI use of nano- implies 10-9 (e.g. nanometre).
Optically continuous/
discontinuous structure		 essentially synonyms of conjunct and disjunct. We prefer the latter as they are shorter and less potentially misleading.
Oval, ovoid often used as synonyms of elliptical, but these terms more accurately mean egg-shaped and so are very rarely applicable to coccoliths.
Pterygal, meta-pterygal,
pre-pterygal, anti-pterygal 		orientation terms for helicoliths. Elegant but too obscure for practical use. {Theodoridis 1984}
Precession alternative to obliquity for description of element orientation in plan view. The common scientific use of precession is related to orbital motions which are not analogous to the element orientation. Hence the special use of this term for coccoliths is obscure. {Black 1972}
Prymnesiophyte alternative to Haptophyte. Green and Jordan (1994) showed that Haptophyta, rather than Prymnesiophyta is the correct division level name, it follows that haptophyte is preferable to prymnesiophyte as the informal name for members of the division.
Rhombolith synonym of scapholith. Both are often used, we follow Braarud et al. (1955a, 1955b) in using scapholith. {Halldal 1954}
Stomatal opening,
stomatal coccolith 		circum-flagellar coccoliths. Stomata implies mouth, and so has unwanted functional implications. {Halldal and Markali 1955}
Wedge element of a nannoconid. Bronnimann also used the term plate and this is preferred since it better describes the shape of nannoconid elements as shown by electron microscopy. {Bronnimann 1955}
Zygodiscid rim synonym of zeugoid rim, which we prefer.

Appendix 2 -lith words

The suffix '-lith' has been used to create numerous special terms for particular types of coccoliths. These terms are now used in varying senses, in particular some are used as purely descriptive terms applicable to coccoliths of widely varying structure and taxonomic affinity (e.g. placolith), whilst others are now only used as informal taxon-based terms, i.e. for the characteristic coccoliths from one particular taxon. These terms are, consequently, described in different parts of the main text. For ease of reference, they are all listed here. Only the modern/recommended meaning is given here. Readers should be aware that many of these terms have been used in varying ways in the literature. Terms not used in the main text are given in square brackets, [].

Descriptive terms of wide application
Coccolith plate-like calcareous component of haptophyte cell-covering, homologous with organic scale. {Huxley 1858}
Heterococcolith coccolith formed of crystal-units of complex shape. {Braarud et al. 1955a, 1955b}
Holococcolith coccolith formed of numerous minute (<0.1 µm) crystallites all of similar shape and size. {Braarud et al. 1955a, 1955b}
Murolith any heterococcolith with elevated rim but without well-developed shields. {Young 1992a}
Nannolith calcareous structure lacking the typical features of hetero- or holococcoliths and so of uncertain affinity. {?Perch-Nielsen 1985}
Placolith any heterococcolith with two or more well-developed shields. {Lohmann 1902}
Planolith any planar heterococcolith, rim not elevated. {Young 1992a}

Specialist descritive terms for holococcolith morphologies
Calicalith tube-shaped holococcolith, flaring, open distally. {Kleijne 1991}
Calyptrolith cap-shaped holococcolith. {Lohmann 1902}
Crystallolith planar holococcolith, rim weak. {Braarud et al. 1955a, 1955b}
Flosculolith flaring, tube-shaped holococcolith, with distal opening partially closed by a vaulted roof. {Kleijne et al. 1991}
Fragariolith holococcolith with simple basal ring and leaf like process. {Kleijne et al. 1991}
Gliscolith tube shaped holococcolith with bulbous distal part. {Norris 1985}
Helladolith tube-shaped holococcolith with bridge developed into leaf-like process. {Heimdal and Gaarder 1980}
Laminolith laminated disc-shaped holococcolith +/-pores. {Heimdal and Gaarder 1980}
Zygolith tube-shaped holococcolith with bridge. {Kamptner 1937}

Informal taxon-based descriptive terms
Ceratolith horseshoe shaped nannolith of Ceratolithaceae.
Discoaster stellate nannolith of Discoasteraceae.
Fasciculith compact, top-shaped nannolith of Fasciculithaceae.
Helicolith coccolith with helical flange of Helicosphaeraceae.
Heliolith stellate nannolith with birefringent central-area , of Heliolithus (Palaeogene).
Lepidolith simple planolith, formed of two elements, of Gladiolithus. {Halldal and Markali 1955}
Lopadolith elevated murolith of Scyphosphaera. {Lohmann 1902}
Osteolith femur-shaped circum-flagellar coccolith of Ophiaster and Michaelsarsia. {Halldal and Markali 1955}
Pentalith stellate nannolith with 5 segments of Braarudosphaeraceae. {Gran and Braarud 1935}
Protolith murolith with non-imbricate rim of Stephanolithaceae, Parhabdolithaceae. {Bown 1987}
Rhabdolith planolith (+/- spine) of Rhabdosphaeraceae (also has been for spine bearing coccoliths in general). {Schmidt 1870}
Scapholith rhombic murolith of Calciosoleniaceae. {Deflandre and Fert 1954}
Sphenolith nannolith of Sphenolithaceae. {Deflandre 1952}

Obsolete terms
[Areolith] cap-shaped holococcolith with interior ridges and areolae. {Norris 1985}
[Asterolith] obsolete term for stellate nannoliths. {Sujkowski 1931}
[Caneolith*] endothecal murolith (+/- flanges) of Syracosphaeraceae. {Braarud et al. 1955a, 1955b}.
[Cribrilith] perforate murolith of Pontosphaeraceae; in effect a synonym of discolith and so superfluous. {Halldal and Markali 1955}
[Cricolith*] narrow-rimmed placolith of Pleurochrysidaceae. {Braarud et al. 1955a, 1955b}
[Cyatholith] obsolete, alternative to placolith. {Kamptner 1948}
[Cyclolith] obsolete, circular placolith. {Kamptner 1948}
[Cyrtolith*] exothecal planolith or inverted murolith of Syracosphaeraceae. {Braarud et al. 1955a, 1955b}
[Discolith*] murolith of Pontosphaeraceae (has also been used for muroliths in general). {Huxley 1868}
[Heliolith] heterococcolith with c-axes of main elements radial. {Deflandre 1950, Aubry 1984 et seq.}
[Ortholith] nannolith or holococcolith with c-axes of main elements tangential or parallel{Deflandre 1950; Aubry 1984 et seq.}
[Pappolith*] murolith of Papposphaeraceae. {Norris 1983}
[Pentagolith] Pentagonal coccolith with >5 elements, e.g. Goniolithus. These are so rare that the term is redundant. {Farinacci et al. 1971}
[Porolith] obsolete term for perforate element of Thoracosphaera. {Deflandre 1952}
[Prismatolith] obsolete term for imperforate element of Thoracosphaera.
[Rhombolith] alternative term for scapholith. {Halldal 1954}
[Tremalith*] vase-shaped murolith of Hymenomonadaceae. {Lohmann 1913}
* These terms, have now been moved from the "Informal taxon-based descriptive terms" category to the obsolete category. i.e. they were still in use in 1987 but are now, thankfully, obsolete [JRY 2017]
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