W Wei:New calcareous nannofossil speci es... .... .. p. I 07 - 115 .

Joumal of Natmoplankton Research, 20, 2, 1998.

NEW CALCAREOUS NANNOFOSSIL SPECIES AND
STRATIGRAPHIC MARKERS FROM THE UPPER PALEOCENE
Wuchang Wei, Scripps Institution of Oceanography, University ofCa/ifornia, San Diego, CA 92093-0215, USA

Abstract: A new speci es , Discoas ter protonmltiradiatu s, is desc ribed from the Upper Pal eo cene. The
stratigraphic distributi ons of thi s and a poorl y known species, Ericsonia rob ust a, are documented fromseven DSDP/ODP sites from low through high latitudes . D . protomu ltiradiatu s generally ranges fr om
slightly below to slightly above the first occurrence of Discoaster multiradiatu s (NP8/N P9 zonal boundary)and correl ates with the middl e part of magneti c chron C2 5n. E. rob usta ~ 11 ~m has a longer ra nge andgenerally occurs from near the bottom of magneti c chron C2 5n to the top of chron C25n. These datums
pro vide four potenti all y useful stratigraphic markers for low through high latitude correlati ons in theUpper Paleocene .

Introduction
Since publication of the calcareous nannofossil zonationsof Martini (1971) and Bukry (1973a), nannofossils havebeen used extensively for stratigraphic correlation of
Cenozoic marine sediments. However, improvements in thestratigraphic resolution of the Upper Paleocene have beenfew, partly due to only a limited number of high-resolution
studies of this stratigraphic interval (e.g. Romein, 1979;
Varo1, 1989; Bybell & Self-Trail, 1995). In tltis paper, a new
species, Discoaster protomultiradiatus, is described . The
stratigraphic distributions of this and a poorly known
species, Ericsonia robusta (Bramlette & Sullivan) PerchNielsen, are documented from seven DSDP/ODP sites
ranging from low through high latitudes, and their firstand last occurrences are shown to be useful stratigraphic
markers in the Upper Paleocene.
Material and methods
Samples were taken from DSDP/ODP Sites 524, 528, 577,
605, 690 and 752 (Figure 1). These are basically all the
DSDP/ODP sites that have moderate to goodmagnetostratigraphies
that
allow
detailedmagnetobiostratigraphic correlations for the Upper
Paleocene. In addition, Site 245, which does not havemagnetostratigraphy, was studied in order to further test
the stratigraphic distributions of Discoaster
protomultiradiatus n. sp. and Ericsonia robusta within abiostratigraphic framework. References for detailed
information about these DSDP/ODP sites are provided inTable 1. Previous nannofossil studies of these sites havebeen made by MacKenzie & Wise ( 1983) for Site 245,
Percival (1984) for Site 524, Backman (1986) for Site 528,
Monechi ( 1985) and Backman (1986) for Site 577, Lang &Wise ( 1987) for Site 605, Pospichal & Wise ( 1990) for Site
690, and Pospichal et al. ( 1991) for Site 752 . However, E.
robusta was either not recorded , or its stratigraphic
distribution was generally misrecorded, due to problematic
species concepts . There appears to be no correct
publication of SEM micrographs of this species to date.
Misidentification of tl1e species is eo nunon in the literature,
as can be seen from the synonymy list in the ' Systematic
descriptions ' (below).
Besides using standard smear-slides, mobile
mounts were made so that the nannofossil specimens could
be turned and observed in different orientations using alight microscope. This was very helpful in examining the
thicknesses of D. protomultiradiatus and E. robusta. In
addition, the new species was examined using a slightly

• 577

0

•

:'752
0

690•

Figure 1: Locations of DSDP/ODP sites investigated in this study. Palaeopositi ons of Sites 577 and 752 were significantly
different from current positions and are shown as open circles.

107===========================

Journal of Nannoplankton Research, 20 ,2, 199 8.

Hole

Location\Vaterdepth (m)W Wei:New calcareous nannofossil species.

~

Reference
~

~~

245
524
528
577
605
6908

31 °32.02 ' S; 52 ° 18.11 ' E
29 °29 .055 'S; 3°30.74 ' E
28 °31.49 ' S; 2° 19.44 'E
32 °26.51 ' N; 157°43.40'E
38 °44.53 'N; 72°36.55 'E
65 °9.692 ' S; l 0 12.296' E

4857
4796
3800
2675
2194
2914

752A 30°53.475 'S ; 93 °34 .652 'E

1086

p. 107- 115.

Hole 524
Sample~"" ""~ ~ 'A
~

V

g ~
~ 12"
:=:::
::1
corN<>-

Simpson et al. (1974)
Hsli et al. ( 1984)
Moore et al. (1984)
Heath e t al. (1985)
van Hinte et al. (1987)
Barker et al. ( 1988,
1990)
Peirce e t al. (1989,
1991)

s s

" :::!. :::!.

'S

tl ·a

.E .E

Depth
(mbsf)
48.29
49.77
51.30
52.29
57.43

0

"'
§;:E

le

ci.

~

-">

-">

~

" "''
~c ~8 c § "'·~

12 12.>; .>; :§
~

tl

~

Zc Q" Q '-l '-l ..::
.~

.~

•t:

·~:

A
A
A

NP9

R
R

A
A
A
A
A

Table l: DSDP/ODP hole locations. water depths and references
for background information
63.41
66.83
68.33

modified technique ofMoshkovitz ( 1978), which facilitatesobservation of the same nannofossil specimens under thelight microscope and in the SEM. This is particularly
important because D . protomultiradiatus closely
resembles Discoaster multiradiatus in the SEM, but thetwo species are quite distinct in polarised light.
As E. robusta has a relatively large size-range, andthe larger specimens appeared to have a shorter
stratigraphic range, about 40 specimens of this species
were measured per sample on a monitor screen connected
to a video camera mounted on the microscope. The accuracyof measurement using this system is about 0.31J.m, which is
sufficient for the problems to be addressed in this study.
Besides the stratigraphic distributions of D.
protomultiradiatus and E. robusta, the first occurrence(FO) of D. multiradiatus and the last occurrence (LO) of
Fasciculi thus spp. were documented in order to show thestratigraphic relationships of D. protomultiradiatus andE. robusta in nannofossil zones NP8-NP9 . Abundances ofindividual species were estimated semiquantitatively at amagnification of xlOOO, using the following categories(each successive category is five times the preceding
category.
A= abundant: more than one specimen per field ofview(FOV)
C = common: 1 specimen in 1-5 FOV
F= few: 1 specimen in 6-30 FOV
R = rare: 1 specimen in 31 -150 FOV
1, 2: 1 or 2 specimens in over 150 FOV, probably
reworked.
The magnetic polarity time-scale and chron
terminology of Cande & Kent ( 1995) are used here.
Comparison of the numerical ages given here with those in
the polarity time scale of Berggren et al. ( 1985) can bedone using the age conversion formula ofWei ( 1994 ).

Results and discussion
The stratigraphic distributions of D. protomultiradiatusn. sp. and E. robusta in Sites 524, 528, 577,605,690 and 752
are presented in Figures 2 through 7, respectively. Thosein Site 245, which does not have magnetostratigraphies,
are presented in Figure 8. Light and SEM micrographs ofthe two species are shown in Plate 1.

NP8

A
A

Figu•·e 2: Stratigraphic distribution of selected nannofoss il species,
DSDP Hole 524 . A=abundant , C = common, F=few, R= rare.
Magnetostratigraphic data are fr o m Tauxe e t al. (1983). Black
indicates !lorrnal polarit y, white indicates reverse d polarity, andhatched pattern indicates polarity uncertain.

~

.>;

~ ]

,

. ~

cor-

N"'
:::::..
~ ·c..8 ·-eHole528
SampleDepth(mbsf)
3 10.50
3 12.55
313.97
3 15.47321.97323 .47325.03326.53331.53341.03342.53350.53

0 "'
§;:E

Z<o

NPIO

NP9

~

::: -i\ ""v~.g E s s
1; s ::1 ::1
12

-">

ci.
~

"' e -e!:;"' ' .>;c .>; ~"8 ~ tl §" -~"
E

~

~

~

.~

Q

A
A
A
A
A
A
A
A

F

NP8

Ei s
:::!. :::!.
q~ '-l '-l•t: ..::
·~::

2

F

c
c
c
c
R c
c c c
F
F
F

R

c
c
c

Figure 3: Stratigraphic distributi on of se lected nanno foss il species,
DSDP Hole 528. Magnetostratigraphic data are trom Shackleton etal. ( 1984 ). See Figure 2 caption for additional information.

D. protomultiradiatus n. sp. closely resembles D.
multiradiatus Bramlette & Riedel in SEM micrographs. The
difference is that D. protomu/tiradiatus contains twocycles of elements in the centre, whereas D. multiradiatusshows only one central cycle (Plate 1, Figures 1-3; compare
witl1 Plate ofRomein, 1979; Plate I ofWei, 1992; and Plate
34 ofBybell & Self-Trail, 1995). The i1mermost cycle ofD.
protomultiradiatus is birefringent in polarised light (Plate
I, Figures 5, 7 and 13), which differentiates it from D.
multiradiatus. The ray number of D. protomu/tiradiatus
COimnonly ranges from 33 to 38, simil-ar to early specimensof D. multiradiatus, but significantly more than later
specimens of D. multiradiatus (Romein, 1979; Wei, 1992).
More importantly, the stratigraphic range of D.
protomultiradiatus is very short and significantly different108p. 107- 115 .

W We i:New calcareous nannofoss il species

Joumal of Namwplankton Research, 20, 2, 1998.

Hole 577
SampleHole690B
Depth(mbsf)
80.83

A

150
R
82.93
83.33
84.03
84.63
85.23
85.53
85.83

F F
A
A
A
NP9A

c c
c c

A
A

F A
C C A

Depth
(mbsf)IS 3 28
18:3: 13018-4 28160.48161.50161.98

V

NP IO

C

2

C
C

I
I

C A
C

C
C

87.33
87.63
88.23
89.t3

~I

Sample

A

A

A

A
A

R A A
R A A
A A

NP8

C

A

F A

Figure -t: Stratigraphic distributi on of selected 11annofossil species,
DSDP Hole 577. Magnetostratigraphic data are from Bleil ( 19 85 ).
See Figure 2 caption for additional information.

Figure 6: Stratigraphic distribution of se lected nannofoss il species,
ODP Hole 6908. Magnetostratigraphic data are from Spiell ( 1990).
See Figure 2 caption for additional information.

E ::1.
E

::1.
~

q

Hole 605
Depth(mbsf)
560

557.80559.50Hole 752A
SamplecNPtO

ct61.55163. 15c
569.70578.70583.00584.50586.80588.30594.30597.00597.90

A
A
A
A

c
c

NP9

c
c
c
c
c
c

174.t4175.60180.65t 82. t5
t90.85
t92.35

A

R
R
R
R R

Depth
(mbsf)

A
A
A
A

NPJO

c

c

c
c

NP9

c
c
c
C
R

R
R

R
C

R
C

A
A
A
A
A
A
A

F C C A
605.70606.60607.20609.006t0.606 tl.20

F
NP8

F
F
F
R

2t0.25
2 11.45

A
A
A
A
A
A

Figure 5: Stratigraphic distribution of se lected nannofoss il speci es,
DSDP Hol e 605. Magnetostratigraphi c data are from van Hinte etal. ( 19 87 ). See Fi gure 2 caption for additional information.

from that of D. multiradiatus (Figures 2-8). Previous studies
most likely included D. protomultiradiatus in D.
multiradiatus, as the FO of D. multiradiatus reported here
for Site 524 is younger than that reported by Percival (1984),
who placed it at the level of the FO of D.
protomultiradiatus as recorded herein. Romein (1979)

NP8

A
A
A

Figur·e 7: Stratigraphic distribution of se lected na nnofossil species,
ODP Hole 752A. Ma gneto stratigraphi c data are from Gee et al.
( 199 1). See Figure 2 caption for additi onal information.

included in D. multiradiatus specimens that have abirefringent central column. He considered the two central
cycles as remnants ofthe (extended) column and the distal
cycle in Helio!ithus, although the outer central cycle is
now more clearly related to the middle cycle rather thanthe distal cycle in Heliolithus. Perch-Nielsen (1985)
considered the birefringent central column as the remnantof another genus, Helio/ithus. In other studies, such as

109

Journal of Nannoplankton Research, 20, 2, \9 98 .

"'

~

.!:;l

"'

~

.Sj
""'::!

V)<l)-'""'

10:---

Sample8-1 , 55
8-2,42
9-1,909-2, 27
9-2,72
9-3,52
9-3, 120
10-1,70
10-1, 122
10-2, 38
10-3,55

~

~

1\

V

·-~ ·c:::... !::). ~...
~~ .!:;l"'<:l0 "'<:l0 ..:0

0 ·<.::.-

283.55284.92311.90312.27313.77314.52315.20320.70321.22321.88323.55

-~ 8

0

....

10:

""

!O:;:;E«:~.._

z 0

NP10

NP9

NP8

:::!

'-'

.::J
Q

E

::t

-~ - ::: .':1 .':1
-~

.!::

'-'

Depth
(mbsf)

E

::t

orNO\

Hole 245""'::!

W Wei:New calcareous nannofossil species ..... , p. 107 - 115.

~"':::!

-t:l"':::!

-t:l

~
.!:;l

ci.

0.

V)

"':::!

~

"''-'
·;:::

0

"''-'
·;:::

~
'-'

'-'

Q

kl

kl

~

-~

..:

"ti

"'

A

c
A
A
A
A
A R

R
R
R

c c
c c

A
A
A
A
A
A
A
A
A

Figure 8: Stratigraphic distribution of selected nannofossil species,
DSDP Hole 245. See Figure 2 caption for additional information.

Pospichal et al. (1991), D. protomultiradiatus wasapparently not included in D. multiradiatus because theyreported the FO of D. multiradiatus between Sample 752A22-2, 45cm and -22-3, 45cm (Pospichal et al., 1991, p.725),
the same stratigraphic level that the datum was recorded
herein (Figure 6). D. protomultiradiatus occurs further
downhole (Figure 6).
Available data suggest that D. protomultiradiatus
is most likely related to, and evolved from, Bomolithus
rather than Heliolithus. The reason is that Bomolithus
has three cycles of elements and only the central part (thecolumn) is birefringent in polarised light, whereas in
Heliolithus, which has three cycles of elements in H.
kleinpellii but only two cycles in its generotype, H.
riedelii , all cycles are birefringent in polarised light (seePerch-Nielsen ( 1985) for justification of the division ofBomolithus from Heliolithus).
No gradational form between D. protomultiradiatus
and D. multiradiatus was found in this study or illustrated
in previous studies. Based on the above discussions, it isconsidered to be practical and useful to separate D.
protomultiradiatus from D. multiradiatus forbiostratigraphic and evolutionary studies.
Size distributions of E. robust a in selected sites arepresented in Figure 9. Although E. robusta has a relatively
large size-range (6.5 to 15.5J.Un), there is no clear pattern ofbimodal size distribution (Figure 9), and thus the species
is not subdivided based on size. However, specimens:2:11 J.Ull appear to have a more restricted strati graphical range
than specimens <llJ.un (Figures 2-8). Specimens <llJ.lm
have a less consistent strati graphical range, which appears
to be longest in the low latitudes (Site 577), shorter in the
middle latitudes (Sites 524, 528, 245 and 605), and shortest

in the high latitudes (Sites 690 and 752). Furthennore, theFO of E. robusta (< llJ.lm) can be difficult to identify at low
latitudes because the species overlaps with Ericsonia
subpertusa Hay & Mohler, and there are transitional forms
between these two species .
The stratigraphic relationships between D.
protomultiradiatus, E. robusta :2: l1J.lm, and D.
multiradiatus, as well as their correlations to the magnetic
polarity time-scale ofCande & Kent ( 1995), are sununarisedin Figure 10, based on data presented in Figures 2-8. As
the stratigraphic range of D. protomultiradiatus, and its
overlap with that of D. multiradiatus, is very short, the FO
of D. protomultiradiatus before that of D. multiradiatus
may not always be seen (as at Site 245, 528 and 577 in tllis
study) due to large sample-spacing or condensation of
the section. The absence of D. protomultiradiatus in Site
690 (Figure 5), however, is probably due to environmental
exclusion from this e:\.1remely high latitude. The southern
limit of this species thus lies between -50°S (palaeolatitudeof Site 752) and 65°S (Site 690). Nevertheless, whenever D.
protomultiradiatus is found, that stratigraphical interval
generally can be placed within the vicinity of the FO of D.
multiradiatus. i.e. the NP8/NP9 zonal boundary aroundthe middle of magnetic chron C2 5n.
The stratigraphic range of E. robusta 2!1Jlm also
overlaps with that of D. multiradiatus, and is longer thanthat of D. protomultiradiatus (Figure 10). The FO of E.
robust a :2:11 J.Un precedes the FO of D. multiradiatus, which
is followed by the LO of E. robusta :2: llJ.lm, at all the sites
investigated here except Site 245. The apparent concurrenceof the FOs of D. multiradiatus and E. robusta :2:l1J.lm at
Site 245 is attributed to poor core recovery in core 9, where
about 5m of sediment was not recovered (Figure 7). The
FO of E. robusta :2:11 J.UTI is located near the bottom of chron
C25n and the LO of E. robusta ::::: llJ.lm is associated withthe top of chron C25n (Figure I 0).
Conclusions
D. protomultiradiatus n. sp. is a distinct species thatgenerally ranges from slightly below to slightly above theFO of D. multiradiatus <md correlates with the middle partof magnetic chron,C25n. E. robusta :::=::11 J.Ull generally ranges
from below the FO of D. protomultiradiatus to above theLO of D. protomultiradiatus, that is, from near the bottomof magnetic chron C25n to the top of chron C25n. These
datums provide four potentially useful stratigraphic
markers within a 0.5m.y. interval for low through highlatitude stratigraphic correlation in the Upper Paleocene.
These markers appear to be particularly useful instratigraphic correlations because they are relatively
cosmopolitan and they appear to be nearly synchronous(within O.l-0.2m.y. resolution) from low through highlatitudes, as revealed by magnetobiostratigraphic
calibrations.
Systematic descriptions
Family Discoasteraceae Tan, 1927
Genus Discoaster Tan, 1927
Discoaster protomultiradiatus n. SJ).
Plate !,Figures 1-7, 13, 14
Derivation of name: Latin, proto = first, primitive;
multiradiatus = many-rayed.

110============================

Journa l of Namwplankton Researc h, 20, 2, 1998.

W Wei:New ca lcareous nam10fossi l species ..... , p. I 07 - 115 .

20

10

8

15

524-5-2, 43 cm

577-10-2, 93 cm

6

10

4
2
0 .,..,

r-: C! "'
00

10

00

0

.,.., 0 .,.., C!

"' "'

0

0

8
6

.,.., C! .,.., 0"' c--i c--i ......

0

«)

.,f

524-5-3, 43 cm

"'·
c: 4
Cl)

....e
(.,1

Cl)

=..

"'0

eo-..

~

1-<

Cl)

~

~

e
:I

524-5-4, 43 cm

e
:I

z

z

10
8
6
4
2

577-10-3, 93 cm

Size (/-!m)

B
10

8

752A-22-2, 45 cm

6

"'c:

4

Cl)

...e

2

(.,1

Cl)

V">OV"lC!VJOV"lC!V"lO

~

Q.

00

NNC"ir..-i~

"' 12
eo-..
0

1-<

10

15 8

6908-22-3, 28 cm

e 6

i ~

0

752-22-3, 45 c m

8642
OL-----'-...-

l001.1"10V)0lf10~

V"lOV"lOV"lOV"lOV"lOV"lOV"lOV"lOV">OV"lr- ociooo\o\ 0 0 _ ;~~~OOOOo\o\~g==~~d~~~~~

Size (/-!m)Size (/-!m)cDFigure 9: Size distribution of Encsonia rob11sta (Bram lette & Sull ivan) Perch-Nielsen. (A) Hole 524; (B ) Hole 577; (C ) Hole 6908; (D)Ho le 752A.

Holotypc: Plate l , Figures l , 4 and 5 (deposited at the
Nannofossil Laboratory, Scripps Institution of
Oceanography, University of California, San Diego).
Diagnosis: A species of Discoasterwith over 30 rays anda birefringent centre.

Description: Medium- to large-sized discoaster with rays
joined throughout their length. Ray numbers commonly
range from 33 to 38.
Remarks : D. protomultiradiatus closely resembles
Discoaster multiradiatus Bramlette & Riedel but differs111

W Wei:New calcareous nam10fossil species ..... ., p. 107- 115.

Journal of Nannoplankton Research, 20, 2, 1998.

Pl.l6, figs 2, 7; Pl.50, fig.23.
19 77 Helio/ithus sp.A Wind & Wise in Wise & Wind: Pl.!3, figs 3,
4; Pl.!4, figs 7-1 0; non P1.13, figs 5, 6 .
1977 Heliolithus sp. Wise & Wind: Pl.l4, figs 4-6 .
1977 He/iolithu s universus Wind & Wise in Wise & Wind: partim. ,Pl.!4, figs 2, 3; non Pl.!2, figs 1-6; non Pl.l3, figs I, 2; non
PI.! 4, fig. !.
1990 He/iolithus sp. cf. H. universus Wind & Wise; Pospichal &Wise: Pl.3 , fi g. l2.

~

C'j

~
...._,
~

0[)

~

~

.......
.......

~

-u
1-1
C'j

0

0

,..c:

1-1

~

r:/)

N annofossil
datums

C24

~

~

0

N

NP9

56
25

;:s;:s""" ......
......
"""\j\j......
......
~~;::: ;:::......
...... ......
......

.........

57

;:s
~

Q

.........

;:s
~
~

~

~

Q

s

:::::L,.....,,.....,
/\I

NP8

s

;:s
"""

....t:::lC)~kiFigure 10: Summary of stratigraphic relationship s between D .
multiradiatus Bramlette & Riedel, D . protomultiradiatus n. sp. ,and E. robusta (Bramlette & Su llivan) Perch-Nielsen based on datafrom Figures 2-8 . The magnetic polarity time-scale of Cand e &Kent (1995) is shown on the left, and the nannofoss il zon es ofMartini ( 1971) are shown on the right.

from the latter in that it has a central cycle of elements thatare birefringent. The species differs from Discoasterbramlettei (Bukry & Percival) Romein by having a larger
size, more rays, and a smaller birefringent centre. D.
protomultiradiatus is considered the predecessor of D.
multiradi atus and it shows a clear link between two genera:
Bomo/ithus and Discoaster.
Size: Commonly l2- l8~l.m in diameter.
Occurrence: D. protomultiradiatus generally occurs from
low through high latitudes and has a very short (--0.2m.y)
stratigraphic range. It generally occurs from slightly below
to slightly above the FO of D. mu/tiradiatus (NP8/NP9
zonal boundary) and correlates with the middle part ofmagnetic chron C25n, with an age-range of about 56.1 to
56.3Ma in the magnetic polarity time scale of Cande &Kent ( 1995).

Remarks: It has been traditional to use the genus
Ericsonia rather than Coccolithus for a group ofPaleocene
and Eocene coccoliths (Rmnein, 1979; Perch-Nielsen, 1985),
although Ericsonia ma y be a junior synonym of
Cocco/ithus, as pointed out by a number of authors (e.g.
Bukry, 1973b; Wise , 1983 ). However, the opticalcharacteristics of E. robusta are substantially different fromthose ofCoccolithuspelagicus, i.e. the former appears to
be entirely birefringent whereas in the latter, only the central
area is birefringent under polarised light. Under phasecontrast light, the shield elements in C. pelagicus are dark
and quite visible, whereas tl1ey are not in E. robusta. Basedon these, E. robusta is not placed in the genus Coccolithus.
This species differs from Ericsonia subpertusa in that
virtually the entire placolith is birefringent in E. robusta,
which also lms a larger central opening than E. subpertusa.
There is a transition between the two species, and E.
robusta is believed to have evolved from E. subpertusa,
a~ suggested by Romein (1979).
The synonymy list of E. robusta in this study issimilar to that ofRomein ( 1979). The significant difference
between the two studies stems from different concepts of
Heliolithusuniversus Wind & Wise. Romein (1979) placed
H. universus in tl1e genusEricsonia. However, H. universus
is significantly different from Ericsonia and truly belongs
to the genus Heliolithus, because it consists of two thick,partial cones flaring outwards. This also differs
significantly from E. robusta, which does not have twocones. H. universus resembles Helio/ithus riedelii, butdiffers in having a greater number of elements (ranging
upto about 60) (Wise & Wind, 1977).
Size: 6.5 to l5.5~n in diameter.
Occurrence: Generally conunon from low to high latitudes.
Specimens ~ 11 ~generally occur from below the FO of D.
protomultiradiatus to above the LO of D .
protomultiradiatus, that is, from near the bottom ofmagnetic chron C25n to the top of chron C25n. Specimens< 11 ~m have longer and less consistent age ranges.

Erifsonia robusta (Bramlctte & Sullivan, 1961)
Perch-Niclsen, 1977
Plate 1, Figures 8-12

Acknowledgments
I thank Laurel Bybell and Jeremy Young for constructive
reviews and Jackie Bumett for helpful editorial comments.
Samples were provided by the Ocean Drilling Program.
This research was supported in part by the National Science
Foundation Grant OCE91-l5786. Acknowledgment is also
made to the Donors of the Petroleum Research Fund,
administered by the American Chemical Society, for partial
support of this research.

1961 Cyclolithu s? robustu s Bramlette & Sullivan: Pl.2, fig .7.
1977 Ericsonia cf. E. robusta (Bramlette & Sullivan) Perch-Nielsen:
Pl.l6, figs I , 4, 5, 6; Pl.50, figs 34, 35.
1977 Non Ericsonia robusta (Bramlette & Sullivan) Perch-Nielsen:

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PLATE lAll SEM micrographs have the same magnification , which is given as a scale bar in Fig. I. All light micrographs havethe same magnification, which is given as a scale bar in Fig.4. All specimens are from ODP Sample 752A-22-3, 45 cm.

F!gs 1-7, 13, 14: Discoaster protomultiradiatus n. SJl. 1, 4, 5: same specimen, holotype; 2, 6, 7: same specimen, isotype;13, 14: same specimen, isotype.
Figs 8-12: Ericsonia robusta (Bramlctte & Sullivan) Perch-Nielsen. 11, 12: same specimen.

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Joumal ofannop lankton Re ea rch, 20, 2, 1998.

PLATE 1

2

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spm

9

8

11

7

6

5

4

3

12

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10

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