Nannoplankton (AGENG)

Mikropaleontologi Lanjut

Tugas Nannoplankton

AGENG WARASTA

12011072

PALEOGEN DAN NEOGEN

1. Family COCCOLITHACEAE Poche, 1913 emend Young & Bown 1997

Description: Coccoliths are placoliths with rim structure similar to Coccolithus: V-unit forms

both distal shield and lower cycle of central-area; R-unit forms both proximal shield and

upper cycle of central-area.

Genera included:

Coccolithus - dominant genus, with central area open, spanned by a

disjunct bar, or delicate axial cross (separation

from Cruciplacolithus is tenuous)

Clausicoccus - central area covered by perforate plate, common in

the Palaeogene, and extends into Early Miocene

Coronocyclus - open ring-like coccolith

without shields, elements of rim complexly intergrown, apparently

with

outer V-unit and inner R-unit

Cruciplacolithus - with disjunct axial cross in central area

Hughesius - with central plate formed of 4 or fewer disjunct

elements

Solidopons - with narrow rim spanned by oblique disjunct bridge

 Chiasmolithus, Sullivania - Palaeogene genra with diagonal cross

in central area

2. Family CALCIDISCACEAE Young and Bown, 1997

Description: Coccoliths are placoliths with rim structure similar to Calcidiscus, i.e. the V-

unit forms distal shield and central-area/tube; R-unit forms proximal shield only. As in the

Coccolithaceae, growth occurs downward from the proto-coccolith ring which becomes

embedded within the structure so that alternating V- and R-units are only visible on

specimens where the proximal shield has broken off.

Distal shield sutures usually show laevogyral curvature. The proximal shield is usually

formed of a single layer of elements with sub-radial sutures; sometimes a lower layer is

developed, with elements showing strong dextral obliquity (in proximal view). The

connection between the proximal and distal shields is weak and they frequently separate.

Genera included:

Calcidiscus Circular to broadly elliptical with

closed central area or narrow opening

Paleocene

-Recent

UmbilicosphaeraCircular to broadly elliptical with wide

central opening

Paleocene

-Recent

OolithotusSub-circular with proximal shield off-

centre

Pliocene

to Recent

HayasterNearly flat, with few elements and

small proximal shield

Eocene-

Recent

Cryptococcolithu

sEllptical with grill in central area Miocene

Ceratolithus HE

T

(old

nam

eNeosphaera)

Only one shield, circular. These do

NOT belong in the Calcidiscaceae, but

they do look rather similar

Pliocene-

Recent

3. Family NOELAERHABDACEAE Jerkovic 1970 emend. Young & Bown 1997

Coccolith structure: Coccoliths are placoliths with Reticulofenestra-type structure, i.e. V-

unit vestigial, R-unit forms proximal shield, distal shield, inner and outer tube-cycles, grill

and any central-area structures; strongly birefringent. In the SEM characteristic features

include; grill in central area, anti-clockwise imbrication of inner tube elements, and

monocyclic proximal shield. References: Young (1989), Young et al. (1994).

Genera included:

Typical

specimenGenus Range Distinguishing features

Reticulofenestr

a

Eocene-

RecentElliptical, central area open or closed

Cyclicargolithu

sEocene-NN8 Circular with narrow central area

Pseudoemiliani

aNN14-19 Numerous slits in distal shield

Gephyrocapsa NN14-21 Bridge over central area

Emiliania NN21 Slits between all distal shield elements

Noelaerhabdus NN10-11 Paratethyan endemic with large spine

Bekelithella NN10-11 Paratethyan endemic with circlet of

spines

4. Family PONTOSPHAERACEAE Lemmerman, 1908

Description: Coccospheres sub-spherical, without flagellar opening (although flagellae have

occasionally been observed). Monomorphic (Pontosphaera) or dimorphic with strongly-

modified equatorial coccoliths (Scyphosphaera). Coccoliths are muroliths, central area with

variable number of perforations. V-units form narrow outer rim-cycle with anti-clockwise

imbrication. R-units form inner rim, with weak clockwise imbrication, baseplate and blanket.

Genera:

Pontosphaera - monomorphic

Scyphosphaera - dimorphic. NB In the fossl record only the

equatorial coccoliths can be confidently assigned

to Scyphosphaera.

5. Genus Alveosphaera Jordan & Young 1990

Description: Coccosphere with elongate oblong muroliths, with central area floored by

transverse laths.

6. Calciosolenia Gran 1912 emend. Young et al. 2003

Description: Coccosphere with rhombic muroliths with central area floored by transverse

laths (scapholiths); monomorphic or dimorphic.

7. Genus Acanthoica Lohmann 1903 emend. Schiller 1913 and Kleijne 1992

Description: Coccosphere polymorphic with characteristic set of apical and antapical spines

shown by all species, though some individual specimens may depart from standard pattern.

8. Genus Algirosphaera Schlauder 1945 emend. Norris 1984

Coccosphere: monomorphic or with differentated CFCs.

Coccoliths: Rim and radial cycle show typical Rhabdosphaeraceae structure, but lamellar

cycle is modified into/replaced by an elongate domal or double-lipped (labiatiform)

protrusion, which is filled by fine rod-like elements. The species were often placed

in Anthosphaera in the older literature (see Aubry 1999 for full discussion).

9. Genus Discosphaera Haeckel 1894

Coccosphere: Monomorphic, non-motile.

Coccoliths: With large trumpet-like (salpingiform) spines. Coccolith bases are broadly

elliptical, with normal rhabdosphaeraceae-type rim, radial and lamellar cycles. Spine circular

in cross section, weakly attached to base above narrow pore in centre of the base

10. Genus Rhabdosphaera Haeckel, 1894

Coccosphere: Dimorphic with inner spine-bearing and outer non spine-bearing coccoliths,

distributed around coccosphere. Usually non-motile and no differentiation of circum-flagella

coccoliths but occasional cells with flagella have been observed (Lohmann 1902, Probert

pers. comm.).

Coccoliths: Radial cycle absent, lamellar cycle fills central area and forms spine.

11. Coronosphaera Gaarder in Gaarder & Heimdal 1977

Description: Coccospheres - Monothecate, dimorphic, motile. Body coccoliths flangeless

muroliths; rims formed of an outer cycle of strongly imbricate (anticlockwise) elements and

an inner cycle of vertical elements. Central area with two radial laths per rim element and

central plaque formed of two plates. Circum Flagellar Coccoliths similar but slightly smaller,

with low spine.

Remarks: Coronosphaera is usually placed in the family Syracosphaeraceae, but has also

been considered a genus incertae sedis within the order Syracosphaerales. It is distinguished

from Syracosphaera by

the strong imbrication of the rim elements

the occurrence of two laths per rim

Absence of flanges

Absence of exothecal coccoliths

12. Syracosphaera Lohmann 1902

Description: Coccospheres usually dithecate, Exothecal coccoliths (XCs) highly variable.

Endothecal coccoliths are muroliths with 1, 2 or 3 flanges, (the forms with 2 flanges are often

placolith-like), these are often differentiated into body coccoliths (BCs), circum-flagellar

coccoliths (CFCs) and antapical coccoliths (AACs).

Fossil record: About 60 modern species of Syracosphaera are known (Young et al. 2003)

and their coccolith morphology is well established (see examples above). Most Pleistocene

specimens of Syracosphaera can be asigned to modern taxa, e.g. S. pulchra and S. lamina. 

However, in older sediments the occasionalSyracosphaera specimens often appear to belong

to different species. A few examples are shown below.

13. Genus Braarudosphaera Deflandre 1947 [Pontosphaera]

Description: Pentaliths approximately pentagonal, sutures go to edges of pentagon. NB

In Micrantholithus sutures go to vertices of the pentagon.

14. Genus Micrantholithus Deflandre in Deflandre and Fert, 1954

Description: Similar to Braarudosphaera but sutures emerge through corners of pentalith

and edge often indented.

Remarks: Most of the common Eocene species have been recorded in the Miocene but only

sporadically and not in open-ocean deposits.

15. Genus Amaurolithus Gartner and Bukry, 1975

Description: Ceratoliths non-birefringent or only weakly birefringent. The c-axis is

perpendicular to the plane of horseshoe, but spines on the surface may result it in being tilted

from the horizontal and so showing some birefringence, but birefringence is lower than

in Ceratolithus and extinction is rarely exactly in line with axis of the ceratolth.

In the SEM Amaurolithus ceratoliths (sometimes termed amauroliths) usually come to rest

with the more ornamented surface upward, in this orientation the left hand arm is distinctly

curved whilst the right hand arm is relatively straight, but more heavily ornamented.

Remarks: Raffi et al. (1998) documented likely evolutionary relationships

between Ceratolithus and the fossil genera Amaurolithus and Triquetrorhabdulus. They

presented evidence that A. delicatus, A. amplificus and C. acutus all independently evolved

from Triquetrorhabdulus. Since this indicated that Amaurolithus was polypyhletic they

proposed dividing the genus in two; Amaurolithus and Nicklithus.

16. Genus Ceratolithus Kamptner, 1950

Description: Ceratoliths strongly birefringent, c-axis lies in plane of horseshoe,

perpendicular to length.

Remarks:

Ceratolith morphology: The ceratoliths usually come to rest with the more ornamented side

upward, in this orientation the right arm is usually shorter than the left arm, and more

strongly curved, forming most of the arch. Both arms have keels on both surfaces. Those on

the lower surface are more or less smooth, whereas those on the upper surface have a rodded

structure. This rodding is most strongly developed on the right arm, and the rods are more

nearly vertical on this arm. The asymmetry of structure makes the two surfaces easy to

distinguish, in the light electron microscope and with care they can also be distinguished in

the LM.

Life-cycle phases: The extant species C. cristatus also produces hoop-shaped coccoliths and

"Neosphaera" planoliths. See species description for details.

17. Genus Discoaster Tan, 1927

Overview: Radiate nannoliths with each ray formed of a discrete crystal-unit, with the c-axes

perpendicular to the nannolith surface. Includes >100 species. The most obvious sub-division

is into rosette-shaped species with >8 rays and star-shaped species with <10 rays, and a

number of other features parallel this sub-division. Formal classification as proposed by

Theodoridis (1984) into the genera Heliodiscoaster and Eudiscoaster has not, however,

proven popular (see discussion below).

18. Catinaster Martini and Bramlette, 1963

Description: Catinasters are rather curious sub-cylindrical or cup-shaped nannofossils. They

have six-fold radial symmetry and the same crystallographic orientation as discoasters. There

are two main species, C. coalitus which has septae-like radial structures confined to the cup,

and C. calyculus in which radial structures extend beyond the cup. The cup was probably

formed by fusion of the bifurcations of a small discoaster (Martini & Worsley 1971, Peleo-

Alampay et al., 1988).

19. Genus Alisphaera Heimdal 1973

Description: Coccosphere monothecate, ellipsoidal with apical opening. Coccoliths arranged

on coccosphere with long axis aligned equatorially and broader flange directed toward apical

opening.

Coccoliths placolith-like, with asymmetrical distal flange, one side broader with a variable

extension, other side narrow and in many species with 8-10 teeth projecting into central area.

Plate in central area formed by extension of tube elements inward, usually with irregular

central fissure. No discrete circumflagellar coccoliths.

20. Genus Florisphaera Okada & Honjo 1973

Monospecific genus of deep-photic coccolihophores - see species for notes.

21. Genus Gladiolithus Jordan & Chamberlain 1993

Description: Dimorphic deep photic zone coccolithophores. 

MESOZOIC

1. Acaenolithus Black 1973

2. Goniolithus Deflandre, 1957

Diagnosis: 

Small to medium size pentagonal liths, with narrow rim and granular central area plate. Dark

image in LM.

3. Arkhangelskiella Vekshina 1959

Diagnosis: 

Arkhangelskiellid coccoliths with 1 or 2 distal shield cycles. Bright, unicyclic light microsope

image, although darker towards outer edge; central-area has perforate plate with axial sutures.

Remarks: 

The most common genus and a characteristic component of Maastrichtian nannofossil

assemblages. The central area structure is described in detail by Moshkovitz and Erhlich

(1988).

4. Broinsonia Bukry 1969

5. Thiersteinia Wise & Watkins in Wise 1983

6. Ahmuellerella Reinhardt 1964

7. Amphizygus Bukry 1969

8. Braloweria Crux, 1991

Diagnosis: 

Loxoliths with central area filled with a tall, columnar to bulbous boss borne on a plate. Seen

in side view. Spine has a thick wall, narrow axial canal and is formed from two

crystallographically distinct units.

9. Bukrylithus Black, 1971

Diagnosis: 

Loxolith coccoliths with narrow unicyclic rim and central area spanned by a plate

incorporating broad, fibrous, tapering axial-cross-bars. Dark overall image in XPL.

10. Monomarginatus Wind & Wise in Wise & Wind 19

12. Campylosphaera Kamptner, 1963

Description: Like Cruciplacolithus but the coccoliths are longitudinally arched and typically

near parallel sided, and so appear oblong in outline.

13. Chiasmolithus Hay et al., 1966

Diagnosis: Placolith coccoliths with Coccolithus-type shields and tube, but with disjunct

diagonal cross bars spanning the central area.