Nannoplankton (AGENG)
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Transcript of 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.