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Holococcoliths

HOLOCOCCOLITHS

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.

holococcolith terms

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}

holococcolith types
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