Terms for specific heterococcolith and nannolith groups

For most groups, the general terminology provides all the terms needed. Some groups, however, have special features which require additional terms, as outlined below.
Lapideacassid nannoliths are not covered here: their morphology and systematics are reviewed by Perch-Nielsen and Franz (1977), and Perch-Nielsen (1985b). Terminology for Rhabdolithaceae is mainly covered above, but see also Kleijne (1992). Aubry (1984 et seq.) reviews terminology for many Cenozoic groups.


Jurassic - Living, Text-fig. 11
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, e.g. 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.


Late Miocene - Living, Text-fig. 11
Informal taxon-based term: Ceratolith - dibrachiate nannoliths formed by the Ceratolithaceae. Includes Amaurolithus nannofossils; does not include the ring-shaped exothecal heterococcoliths.

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).


Palaeocene - Pliocene, Text-fig. 11.
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).

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

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).

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.


Palaeocene - Early Eocene, Text-fig. 12
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.


Eocene - Living, Text-fig. 12
Informal taxon-based term: Helicolith - nannolith formed by the Helicosphaeraceae.
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.

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 ubiquitous 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).


Cretaceous, Text-fig. 12
Informal taxon-based term: Polycyclolith nannolith formed by the Polycyclolithaceae. Varol (1992) gives a recent review of the group.
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).


Palaeocene - Pliocene, Text-fig. 12
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.
Compoundformed 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.


Oligocene - Pliocene, Text-fig. 12.
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.


1. Terms for parts of holococcoliths

(Text-fig. 13)
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

(Text-fig. 13)
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

(Text-fig. 13) 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}


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

(Text-fig. 14) 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

(Text-fig. 14)
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

(Text-fig. 14)
Central Opening opening running longitudinally through the nannoconid. Types:
Canal narrow, <1 Ám;
cavity - wide, >1 Ám;
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

(Text-fig. 14) 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 a to the horizontal. These are birefringent in longitudinal view (Perch-Nielsen 1988). {van Niel1992}
Type B-cycle cycle of plates inclined at a higher angle (angle b) 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 D 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 D, i.e. combined thickness of A and B cycles.


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

(Text-fig. 15). 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

(Text-fig. 15).
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 Ám) with their c-axes tangential to the wall, and randomly aligned.

3. Wall types

(Text-fig. 15).
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

(Text-fig. 15).
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

(Text-fig. 15).
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.

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