Rivista Italiana di Paleontologia e Stratigrafia volume 1Ol

NOTA BREVE - SHORT NOTE

DESCRIPTION OF AN EARLY ONTOGENETIC EVOLUTIONARY STEP
IN ZEPID O RB I T O I D E S : LEP I D O R B I T O I D E S B I S AM BER GENSIS

ASYMMETRICA SUBSP N., EARLY MAASTRICHTIAN (CENTRAL TURKEY)

E,RCAN OZCAN'I & SEVINQ OZKAN-ALTINER'I'*

Receited April 16, 1999; accepted JanuatT 10, 2001

Ke1'ruords: Foramjnifera, Nepionic arrangenent) Lepidor-
bitoides, Early Maastrichtian, Anatolia (Turkey)

Riassunto. Lepidorbitoides bisambergensis è caratterizzrto per
ayere una camcra embrionale quadrìserìale senz-a nessuna cameretta
che si origini dircttamentc dalla deuterocor.". È r.r. specre comune e
molto diagnostica nelle successioni fl-vscioidi del Maestrichti:rno infe-
riore dell'Anatolia. Alcune popolaz-ioni dr questa specre presentano
una disposizione marcatamente asimmetrictr della prima c:mcrr, in
visjone orizzontale, nei primi stadi ontogenetìci. Tale asjmmetria è

."^ ,1" ..-" marcata differenza neila dimensione dellc
canlerette ausiliaric chc si trovano sia nella protoconca che nella deute-
roconc? e sono anche enfatizz,ate dallo sviluppo dispari di camerette
nella serie che si origina da queste camerette ausiljarje sul lato della
protoconca. Questc popolazioni asirnmetrjche a c:rusa della compars;r
cli un;r nuova camerette trusiliaria si trovano comlÌnemente rr orrzzon-
ti stratigrafici sottostanti quelli a disposizione simmetrica, che le sos-
titniscono progressivamente. Gli esemplari asimmetrici "quadriseriali"

rappresentano lo stadio filogenetico iniziale de L. biambergensis e sr
troyàno negli orizzonti stratigrafjci corrispondenti alle zone t G. ha"r,a-
nensís and G. aeg'ptiaca (?). Si ritiene meritino uno stàtus tassonomi-
co sottospecifico e vengono descritti con il nome dr Lepidorbìtoides
bisambergensis asymmetrica subsp. n.

Abstract. Lepidorbitoides bísambergertsis is characterìsed by hev-
ing a 'quadriserial' enrbrl-o without any chamberlet directly arisine
from the deuteroconch and is a very diagnostic and common specìes in
Lor.er Maastrichtian flvsch successions in Anatolia. Some populations
of this species present iìn earlv ontogenetic morphologic feature which
js characterised bv distinctly asl.mmetric early chamber arrangement
recognised jn the horizontal sections. This asymmetry is mrinly
caused by the pronounced djfference in the size of auxiliary chamber-
lets which rest on both, protoconch and deuteroconch and also
enhanced by the dcvclopmcnt of uncqu.rl rumbcr of chamberlets in
the series arising fron.r these auriliary chamberlets on the protoconchal
side. These asymmetric specimens are commonlv identified in strati-
graphic horizons belor. the svmmetric ones after the introductìon of a
new ruxiìia11- ch:mberlet and proeressivell' replaced by symn.retric
ones ìn the vounger popuÌations. Asymmetric 'quedriserial' specirlens

representìng thc c:rly phl,logenetic stage of L. bisambergensis
described ìn the stratigraphic horizons corresponding to G. ha'oanen-

sls and G. deg)pt;dca (?) zones are thought to deserue a particlrlar tax-
onomìc status and are attributed rc Lepidorbitoides bkambergensis
asymmetrica subsp. n.

lntroduction.

Lepidorbitoides bisambergensis ís an Early Maas-
trichtian species characterised by a 'quadriserial' nepi-
onic chamber arrangement (specimens having two auxil-
iary chamberlets of Van Gorsel 1975 and 1928 and with-
out any chamberlets arising directly from deutero-
conch). Although Papp (1954, 1956) considered this
species late Campanian in age, same horizons which bear
Sìderolites calcitrapoides above L. campaniensis popula-
tions were dated as early Maastrichtian by Van Gorsel
(1975). Caus (1988) rnd Òzcen & Ózkan-Altiner
(1999a) also considered this species Eariy Maastrichtian
in age. L. bisambergezsis, which possesses two auxiliary
chamberlets, has both symmetric and asymmetric vari-
ants as recognised in horizontal sections. Asymmetric Z.
bisambergensls is distinguished from the symmetric ones
basically by having an auxiliary chamberlet comparative-
ly smaller than the other. The e.ìrly ontogenetic a5ym-
metrv in some specimens of L. bisambergensis and its
stratigraphic position below the symmetric ones were
first recognised by Van Gorsel (1975, 1978). This author
illustrated the embryos with tl.o auxiliary chamberlets;
one Ì/ith the dimensions smaller than the other and
from which only few and small subsequent chamberlets
are formed. Although these asymmetric specimens were
considered as the primitive stages of development of Z.
bisambergensls, the variation in early chamber arrange-
ment, their biometric aspects and stratigraphic position
have not been fully discussed.

' Department of Geological Engineering, Akdeniz University, 07200 Topqular, Antall'a, Turke,v.
''r Marìne Micropaleontology Research Unìt, Department of Geological Engineering, Middle East Technical Universìty, 06531 Ankara,

Turkev



5'ìì.ìi.ì.-;t/)--- IHAN]
BARTIN

138 E. ózcan & S. Òzkan Altiner

Fig. 1 Location of the sarnplìng sites (top) and generalized colurn-
nar sections of the measured sections Han and Hay-\fi/
(below). Stars indicate the Lepidorbitoiles and other
orbitoidal foramìnifera bearing horizons.

Anatolian L. bisambergensis malnly represented by
symmetric specimens have been identified in numerous
horizontal secrions and its early ontogenetic biometric
aspects we.re previously described by Òtr^n (1995),
Ozcan & Ozkan-AItiner ( 1997) and ó.crn & ózkan-
Altiner (1999a, b). The analysis of early onrogeneric fea-
tures of Lepidorbitoides specimens from secrions FIan
and Hay-V measured in northwest central Anatolia has
revealed the different developmental stages of asymmet-
ric and symmetric L. bisambergensis. .NlI the specimens
in the lower part of the secrion Han have invariably
asymmetric nepionts. These specimens have been attrib-
uted.to L. bisambergensis asymmerrlca subsp. n. (ózcan
Ec Ozkan-Akiner, 1999a). However, rhe complete
description of the new raxon is here presented for the
first time. Lepidorbitoirles specimens secrioned in the
stratigraphically lowermost orbitoidal foraminifera
bearing horizon below the asymmetric ones have only
one auxiliary chamberlet ('biserial' nepionrs of Van
Gorsel 1975, 1978\ and were attributed to L. cam-
paniensis. Asymmerric specimens which are replaced by
symmetric ones in the younger horizons seem to repre-
sent an important evolutionary step after the introduc-
tion of a second auxiiiary chamberlet during Early Maas-
trichtian and thought ro deserve an independenr subspe-

cific status. Asymmetric and
symmetric L. bisambergensis
populations are diagnostic for
Gl. bar.,anensis and G. deg/ptirt-
ca zones. Chamberlets which
arises directly from deutero-
conch (adauxiliary chambers of
Van Gorsel, 1975 and 1978) are
first observed in the popula-
tions consisring of asymmetric
L. bisambergensis.

Material and age of the sam-
ples.

Asymmetric L. bisamber-
gensis specimens have been
identified in sections Han and
Hey-V rneasured in the r icinity
of town of Hanònù (Kasta-
monu) near the Black Sea coast
and near the town of Haymana
(Ankara) in northwest Central
Anatolia respectively (Fig. t).

Section Han which com-
mences with condensed, plank-
tonic foraminiferal clayey lime-
stone or shale lithologies at the
base consists of thick, coarsely
turbiditic horizons of mainly

Studied
sections HAN HAY.W
=uJ
o
o

ag
tu
o

uJ

I
a

É=
oF
L

Thick.
(m)

Lithology Samp.
no.

IJJ

f
o

*=
AF
L

Thick.
(m)

Lithology Samp.
no.

U'
f
o
IJJ
o
É
uJ
E
o

É
lrJ
o-
f]-
f

z
F
T
o
fr
Fo

=
z
Szf
o

e7

=1
;3

Y
,o
a
îr
(5

ÉB
<o
:< fD

40*
37 tc

275

248

146

132
130
123
'118

35*

34*
31 *

28 tc
27 lc
25*
23*

16*
14

Y

1

z
F
+
9
fr
Fo

I

z
z
o-

=
O

KAVAK

770
758
755

732

tzó

105

98

95*
94

91*

85

84

82*

60

JY

170

0

z

=
I



Ontogeny in Lepidorbitoides r39

sandstone, pebbly sandstone and olistostromal con-
glomerate horizons (Gùrsókù Formation). Except for
the lower part, this section is almost devoid of fine sili-
ciclastic and carbonate levels. Ten horizons (Han-16, 23,
25, 27, 28, 31., 31, 35, 37, 40) with orbitoidal foraminifer;r
have been sampled. Asymmetric L. bisambergensis popu-
lations have been identified in samples Han-23,25,27,
28 and 31. Although sporadic, asymmetric specimens
may also be encountered in Han-34, 35 and 32. Three
successive clayey limestone horizon, Han-17, 18, 19,
below asymmetric L. bisambergensls and above L. cam-
paniensis bearing levels (Han-16) yielded planktonic
foraminifera in three meters interval. Han-1,7 bears Con-
tusotruncana plummerae, Globotruncana ArcA,
Globotruncana bulloicles, Globotruncana /inneiana and
Globotruncana orientalis. Han-18 yielded Globotrun-
canita eleoata, GÌobotruncanita stuartformìs, Globotrun
cAnA Arcrl, Globotrwncana linneiana and G/obotruncdnd
rosett,t. Han-19 contains Globotruncana aeg/ptidcd (?),
Globotruncana arca and GlobotruncdnA linneìana. Htn-
16 with L. campaniensis and PseurlosirJerolites cidali just
three meters below Han-18 is of possibly R. calcarata
zone age. In the absence of planktonic foraminifera in
the upper part of the succession, Han-23, 25,27,28 and
31 containing asymmetric 'quadriserial' specimens and
the overlying Han-3'{, 35, 37 and 4O containing mosrly
symmetric 'quadriserial' specimens are possibly of G.
hapanensis (?)- G aeglptittcd (?) zone age.

Section Hay-\f consists of deep- marine plank-
tonic foraminiferal clayey limestone, marl/shale and tur-
biditic sandstone and olistostromal horizons (Òzcrn
and Òzkan-Altiner, 1997). Lower part of the section
which is mainly composed of siliciclastic levels is almost
devoid of orbitoidal foraminifera. Higher up in the sec-
tion, coarse turbiditic horizons intercalated with fine
siliciclastic levels dominate in the succession. In this part
of flysch succession, three horizons (Hay-W-S2,91, and
95) have been analysed. Asymmetnc Lepidorbitoideshas
k..- ;1.--;{;.,1 ^-r-, in Hay_\í_91 and sporadically in
Hay-V-95. Hay-W-S2 bears invariably the specimens
with one auxiliary chamber ('biserial') (L. campaniensis)
and Hay-W-95 bears mostly symmetric L. bisambergen-
sis specimens. Hay-W-91 with l. bisambergensis asym
metrica and primitive stage of development of
Orbitoides megaloformis is of G. havanensis zone age.
Hay-W-S2 with Z. campaniensis specimens 34 meters
beiorv G. ventricosa/ R. calcarata- G. hapanensis zonal
boundary is possibly o{ R. calcarata zone age (Òzcan Er
Ózken-AlLiner 1999a;.

Description.

Lepidorbitoides bisambergensis asymmetrica

suDsp. n.

Pl. 1

1.951 Lepidorbitoides bisambergensis (Jaeger, 191,t), Papp, pl.. 1, figs.
7, 8.

1.975 Lepídorbitoides bìsambergensis (Jaegea 191't), Van Gorsel, Pl.
VII, figs. a and b; PI. VIII, figs. b end c.
Lepidorbitoídes bisambergensis (Jaeger, 1914), Van Gorsel, Fig.
1 6-d.

1997 Lepidorbìtoides bisambergensis (Jacgcr, 1914), Ozcan rnd
Ozkan-Altiner, Pl. 1, figs. 11-14; PI.2, fìg.1.

1999a Lepidorbitoides bisambergensis asymmetrlca subsp. r.. Ò....rt
and Òzkan-Altiner, Pl. 2, figs. 13, 15-22.

1999b Asymmetric l. bisambergensìs (Jaeger, 1914), Ozcan and
Ózkan-Altiner, Fig. 3, 9-13.

Ózcan and Ózkan-Altiner )n 1999a, illustratcd the neu. taron
(pl. 2, figs. 15-22), but did'nt described it. According to ICZN, art. 13
the name is not velid. A full description is provided only herc.

Etimology. Narled considering the aslrmrìtric peri-embryonic
charnber àrrangerncnt (having auxiliary chamberlets of unequal size) as
recognised in horizontal sectrons.

Holotype. Specincn l{n-27-21, illustrated on Plate 1, fìgure
1Z is designated as tvpe specimen. The asymmetric specimens fìgured
on Plate 1 (Figures 6-1 6 and 1 8-24, 27) are designatcd as peratvpes. All
materiàl h:rs been filed in the collection oi Department of Geological
Engineering, Akdeniz Univcrsit,r', Antalya.

Type locality. Northeast of Kastamonu, loceted about 4 krn
north of town of Hanònii (Fig. t).

Type horìzon. C. ha-aanensis zrtzie and:rlso possibl1. e part of G.
aegtptiaca zone.

Assocìated fauna. Different dcr-elopmental stases of
Orbitoi des megalofttrmk ;rnd primitive Orbitoides gruenbacbensis pc:pt-
lations have been identified based on the biorretric specìes definition
oÍ O rb itct icle s proposed by Van Gorsel ( 197 8 

1 
. O rbit o irJes'pec imcns in

Han-25 have a range of embryo size (Li+li) benveen 410 and 1025
microns u.ith an averase o[ 7A3.4 microns. The number of epi-embry-
onic chambers (E) varies between 4 and 12 n-ith an averrge of 2.09.
Tlris popuiation is attributed rc O. megaloforrnis. The Orbitoides pop-
ulation in sample Han-2l has: range of Li+li b(rwecr 515 and 915
rnicrons with.rn aler:ge of /55 n.ricrons, and is attributed to
"advanced" O. megaloformisl "primitive" O, gruenbachensis. Orbitoides
specimens in Han-31 have a range of Li+li bet-een 525 and 875
microns with an average of ltt.t microns, :rnd E varics between 5 and
9 r.ith an average of 7.16. This population is attributed to advanced O.
megaloformk.

External and internal features. The well preserved
specimens are lenticular, discoidai and circular in out-
line, having usually slightly undulating periphery. Test
diameter is up to 4.5 mm, but usually less than 4mm. At
the surface of the test pillars with the diameter up to 150
microns are observed at the central part. These pillars are
smaller near the peripheral part of the test and are usu-
aIIy 35-75 microns in diameter as measured in vertical
sections. Internal features are described mainly consid-
ering the peri-embryonic chamber arrangement n hich is
the most diagnostic morphological element of the new
taxon. The values of size of the protoconch (P) and
deuteroconch (D) and deuteroconch/ protoconch ratio
(D/P) of the asymmetrtc Lepidorbitoides populations
are presented in Table 1.

The equatorial layer consists of a bilocular embryo
(protoconch and deuteroconch) and surrounding rings
of almost arcuate equatorial chamberlets. The almost

1978



140 E. Ózcan & S. Ozkan-Altìner

Samples

LEPIDORBITOIDES ORBITOIDES
N P p) D F) D/P Ad ps ds N Li+li (p) E

Range Mean Range Mean Mean Mean Mean Mean Range Mean Range Mear
HAY.W.82 70-110 88.0 95-1 50 118.2 aaÀ 0.00 7.09 6.18 32 440-1025 ooz. I 4-9 6.20
HAY.W.91 2 1 10-120 1150 1 50-1 75 162.5 140 0.00 zo 430-775 604.4 4-B 4.86
HAY.W.95 53 85-1 55 108 9 120-210 161 .8 148 0.02 34 J/C-tUO: ovz.3 4-12 7.51

HAN.16 3 65-75 71.7 70-110 YJ,J 1.30 0.00 8.50 O.UU

HAN.23 11 90-1 20 100 9 1 20-1 65 139.0 1.37 0.00

HAN.25 30 7 5-1 40 108.3 85-1 80 145.3 4 aA U.UO 19 410-1025 703.4 4-12 7.09
HAN.27 z.+ 85-r 40 113.3 1 05-205 tct./ I 2' 0.00 tt 515-915 7EE N 7-11 9.66
HAN.28 z 1 00-1 05 102.5 145-170 157.5 1.54 0.00

HAN.31 to 1 05-1 60 123.4 1 20-1 90 160.0 129 0.00 9 525-875 711.1 5-9 /. to
HAN.34 28 90-1 45 112.3 125-220 165.7 0.1 1 540-1210 786.9 5-14 9.00
HAN.35 24 85-1 75 125.2 125-275 179.4 0.00 t3 660-1 1 55 914.0 6-'11 9.25
HAN.37 27 90-1 55 118.3 140-205 1Aq A 1.44 0.00
HAN.4O 17 75-200 132.9 1 05-250 187.6 4 ^4 0,12 10 545-1 1 55 898.0 o-tl 9.50

Tab. 1 Values of size of the protoconh (P) and deuteroconch (D)
b i t o ide s (.Hav -'ù'l-9 1, Han r23 -3 1 ), symmetric Le p id o rb ir o ìde s
Han-16) populations.

and deuterocon.h/p.oto.orch
(Ha1-Y-9t, Han-34-'t0) and

ratìo (D/P) of the asvmmettc Lepidor
Lepidorbitoides cdmp,lniensis (Hay-V-82,

globular protoconch is followed by slightly larger deute-
roconch which is invariably the progressive chamber in
'quadriserial' Lepidorbitoides.It was observed in the ver-
tical sections that protoconch- deuteroconch axis (P/D
axis) is not necessarily aligned in accordance with the
equatorial plane and may show a small deviation. Two
auxiliary chamberlets of unequal dimensions, which are
very diagnostic for this taxon, arise from the protoconch
and deuteroconch. Considering the size of auxìliary
chamberlets along P/D axis, one of them is invariably
very small and may be as small as one-third of the size of
the larger auxiliary chamberlet.

Chamberlets developing from each of the auxiliary
chamberlets close on the protoconchal and deuterocon-
chal wall. The position of the closing chamberlet on rhe
deuteroconchal wall (dc) is usually symmetric with
respect to protoconch- deuteroconch (P-D) axis. FIow-
ever, a slightly pronounced asyrnmetrv of the deutero-
conchal closing chamber in some specimens is also
observed. The number of the chamberlets arising from
the auxiliarl. chamberlets on tfie deuteroconchal side rnay

be equal in number and in size, if not, it is observed that
larger chamberlets arise from the larger auxiliary cham-
berlet. In some of the specimens, the number of the
chamberlets arising from each of the auxiliary chamber-
lets before the closing chamberlet (pc) on the protocon-
chal side are not equal (Fig. 2, Han-25-15,28, 5; Htn-27 -
1.,21, 8, 13; Han-31-1 5,3, 12; Han-35-24) and chamber-
lets usually close at 5th budding stage. Howeveq in the
lower part of section Han, the closing chamberlet on rhe
protoconchai side (pc) may even rest on the smaller aux-
iiiary chamberlet and the last chamberlet arising from the
larger auxiliary chamberlet (Fig. 2, Han-25-15, Han-27-
1, 21, 8). This indicates the retardation of the develop-
ment of chamberlets from the small second auxiliary
chamberlet on the protoconchal side. Thus, the position
of protoconchal closing chamberiet is strongly asymrncr-
ric with rcspect to the P/D axis. The sizes of the cham-
berlets on the protoconchal side are npt also equal. Larg-
er chamberlets arise from the larger and smaller ones
from the smaller auxiliary chamberlets. This also
enhances the asymmetry of the perì-embryonic chamber

flg.1-5

Ptg. 6-24,27

PLATE 1

Lepidorbitoides campaniensis van Gorsel, 1973, All X75. (1 - Han-16-1; 2 -lHan-16-2;3 - Hay-\X/-g2-1l; ,l - Hav-v/-g2-9;5 -
Hav-\W-82-Z).

Lepidorbitoìdes bisambergensis asyntnetrica subsp. n. All X75. (6 - Han-23-3; 7 -iHa,n-23-11;8 - Han-25-29; 9 - Han-25-28; 1O
-Han-25-9; 11 -Han-25-5;12-Han-25-15;13-Han-25-18; 14-Han-25-12;15-Han-27-ir;16-Han-27-22;17-Han-27-
21; 18 - Hn-27-14; 19 - Han-2/-18; 20 - Han-31-9; 21 - Han-31-1.5;22 - Han-31-10; 23 -Han-37-7;21 -Han-31-2; 27-
Hav-W-91-16).

Ftg.25-26,284a - Lepidorbitoides bisambergensr (Jaeger, 1914) (Svmrnetric L. bianbergezsls), All X75. (2.5 - Han-34-21;26 - Han-3,1-5; 2E
Han-37-21 29 - Hay-V-95-8; 30 - Hav-W-95-21).



() nto geny i n Lep i d orbito i d e s 141



E. Ozcan & S. Ozkan Alttruer

arrangement and asymmetric position of protoconchal
closing chamberlet. Specimens with auxiliary chamber-
lets, almost equal in size, replace the asymmerric ones ìn
the younger stratigraphic horizons. Asymmetric speci-
mens are very rare in Han-35 and 37.In Han-40, the
specimens which are unquestionably asymmetrrc were
not identified. In section Han, although the majority of
the specimens are without adauxiliary chamberlets, two
specimens having one adauxiliary chamberlet in Han-25,
one specimen with one and one specimen with two
adauxiliary chamberlets in Han-34 and one specimen
with two adauxiliary chamberlets in Han-40 were also
sectioned (Fig. 2, Han-34-5, Han-40-9) . One "biserial"
specimen having only one auxiliary chamber (Lepidor-
bitoides campaniensis type ) was also encountere d in Han-
35 (Fig. 2, Han-35-10). These 'biserial' specimens have
been mainly identified in the lower stratigraphic hori-
zons (Hay-V-S2 and Han-16). The ernbryo and peri-
embryonic biometric aspects of asymmetric LEidor-
bitoides populations are given as follows:

Han-23: The diameter of the protoconch varies
from 90 to 120 microns, with a sample average of tOO.9;
that of the deuteroconch from 12a to 165 microns, with
a sample average of t:9.0. All specimens are invariably
asymmetric'quadriserial' without any chamberlets
directly arising from deuteroconch.

Han-25: The diameter of the protoconch varies
from 75 to 140 microns, with a sample average of tOg.:;
that of the deuteroconch from 85 to 180 microns, with
a sample average of t+S.3. A1l specìmens are invariably
asymmetric'quadriserial'. Only two'quadriserial' speci-
mens, out of 30, with one charnberlet, which arises from
the deuteroconch, were also sectioned.

Han-27: The diameter of the protoconch varies
frorn 85 to 140 microns, with a sample average of tt:.3;
that of deuteroconch from 105 to 205 microns, with a
sample average of 151.7. All specimens are invariably a-
synmetric,'quadriserial' without adauxiliary chamber-

Han-28: The diameter of the protoconch varies
from 100 to 105 microns, with a sample average of 102.5;
that of deuteroconch from 145 to 170 microns, with a
sample average of t5l .5. Specimens are invariably asym-
metric 'quadriserial' without any chamberlets directly
arising from deuteroconch.

Han-31: The diameter of the proroconch varies
from 105 to 160 microns, with a sample average oî tZZ.+;
that of deureroconch from l2O and 190 microns, with a
sarnple average of 160.0. The majority of the specimens
are asymmetric 'quadriserial' without any chamberlets
arising directly from deuteroconch.

Hay-\X/-91: The diameter of the protoconch varies
from 1 10 to 120 microns, with a sample average of t t S.O;
that of deuteroconch from 150 to 125 microns, with a
sample average o[ 162.5. Specimens are asymmerrlc

'quadriserial' without any chamberlets arising directìy
from deuteroconch.

Stratigraphic remarks and Conclusions.

The study of early ontogenesis of Anatolian Lepì-
dorbitoides bisambergensis characrerize d bv having
'quadriserial' nepionts without any chamberlet arising
from deuteroconch has revealed two distinct tvpes with
different peri-embryonic configurations. These arrange-
ments differentiated mainly on rhe basis of the differ-
ence in size of auxiliary chamberlets and consequenr dif-
ference in size and the number of the chamberlets sur-
rounding the embryo have been categorized into two
groups as stratigraphically older 'asymmetric' and
younger'symmetric' ones. Asymmetric Lepidorbitoides
forms a transitional stage between 'biserial' L. cam
paniensis with only one auxiliary chamber and symmer-
ric Lepìdorbitoides bisambergensis with two auxiliary
chamberlets of equal sizes. Asymmetric and symmetric
variants were previously re cognised by Van Gorsel (1925
and 1978) and stratigraphic position of asymmetric ones
was tentat;vely mentioned as Early Maastrichtian. In
this study, transitional stages from 'biserial' Lepidor-
bitoides campaniensis ro asymmetric and symm etric Lep-
idorbitoides bisambergensis nepionts have been docu-
mented and described by their biometric characte ristics.
L. bìsambergensis asymmetrica was erected on the fol-
lowing arguments. 1) The specimens are distinctly
asymmetric by having two auxiliary chamberlets of
unequal size. All specimens in samples Han-23,25,27,
28, Hay-W-91 and majority of the specimens in Han-31
are invariably asymmetric, representing distinct popula-
tions as recognised in horizontal sections. The size of
auxiliary chamberlets progressively becomes equal in
successive populations. 2) In most of the asynmerric
specimens, the number of chamberlets arising from two
of the auxiliary chamberlers on rhe protoconchal side are
not equal. This also enhances the asymmetry of peri-
embryonic chamber arrangemenr. 3) Asymmetric speci-
mens are identified in the lower stratigraphic horizons
below the symmetric ones with the introduction of a
second auxiliary chamberlet during phylogeny. This
indicates the stratigraphic importance of asymmetric
Lepidorbitoides specin-rens. Planktonic foraminifera
identified in some levels of studied secrions indicate that
these populations are of Gl. hatanensis and possibly G.
aegtptiaca zone age (Òzcan & Òzkan-Altiner 1999a and
b). Van Gorsel (1975) introduced asymmerric L. bisam-
bergensis in three populations from Pemberger of Aus-
tria and indicated that asymmetric forms are older than
the symmetric ones. These populations, 1961A\q
19614G and 1961Y2 have the mean D and D/P values of
1,15.6 microns, 1.36; 162.2 microns, 1.43; 159.0 microns,



Han.40
rffiffiffiffiffi
rffi@ffiffiffiffi

Han.37

wffiffi
ffi,m
Han.3l m,ffi

ffiffi
ffiffi

ffiffiffim
@ffim

ffiffi.Han.23
Deutcroconchal closing chamberlet

Auxiliarl
chamberlel

Photoconchal closing
charnberlet (pc)

C) n to geny in LE i d ctrb tto ide s

Initial chamber arrangeme nt of symmetrìc and asymmetric (L. bisambergensìs asymmetrica) Lepidorbitoides and L. campdntensrs in sec-
tion Han. Numbers refer to the specimen numbers. Auxiliary chamberlets are hatched. Protoconchal and deuteroconchal closing cham-
berlets in 'quadriserial' specimens and closing chamberlet rn L campaníensls are finel1' stippled. Chamberlets directly arisìng from the
deuteroconch are coarsely stippled. Ali X65.

113

Fig. 2



t44 E. Òzcan & S. Òzlean Altiner

1.45 respectively. Z. bisambergensis asymmetrica popula-
tions in Han-23, Han-25, Han-27, Han-31 have mean
D/P values varying between 1.29 and 1.32 which all are
in the biometric limits of L. campaniensis.proposed by
Van Gorsel (1978). According ro the mean D and D/P
data presented in Table l, L bisambergensis asymmetrica
can be tentatively defined as 140 microns <D< 160
microns and 1.3 <D/P< 1.4.

REFERE

Caus E. (1988) - Reevaluation of Lepidorbitolles evolution as
a function of the age relations between species as estab-
lished with nannoplankton biostratigraphy. Reztue
Paléobiol., 7 : 421 - 428, Genève.

GorseÌ J.T. van (1,973) - Lepidorbitoides from the Campanirn
type region. Proc. K. Neclerl. Alead.'Wetensch.,B, 76: 26a-
222 , Amsterdam.

Gorsel J.T. van (1975) - Evolutionary trends and stratigraphic
significance of the Late Cretaceous Helicorbitoides-
Lepidorbìtoides lineage. Lltrecht Micropaleont. Bull. tZ:
1-99, Utrecht.

Gorsel J.T. van (1978) - Late Creraceous orbitoidal
foraminifera. Academic press, London, 3: 1-12A.

Jaeger R. (1914) - Grundzùge einer stratigraphischen
Gliederung der flyschbildungen des \ffienerwaldes.,4llr.

Geol Ges. \Yien, 122-1.72.
Ózcan E. (1995) - Evaluatìon of the nepionic chamber

arrangement in Lep idorbitoides bisambergensis (Jaegeq
1914), Early Maastrichtian, SE Turkey. Ret,ue Paléobiol.,
14 (1): 195-208, Genève.

Acknouleclgements.

This paper is fìnancially supported by the Scientific and Tech-
nical Council of Turkey (Project no: TúBITAK-YDABeAG-69). Spe-
cial appreciatìon is extended to Research assistant of METU, Òmer
Yìlmaz for hìs help during the field work and in drawings.

NCES

ÓzcanE. & Òzkan-Altiner S. (1997) - Late Campanian Maas-
trichtian evolution of orbitoidal foraminifera in Hry-
mana Basin succession (Ankara, Central Turkey). Ret,ue
Paléobiol.,1 6 (1) : 2t 1 -29 0, Genève.

Òzcan E. & Ózkan-Altiner S. (1999a) - The genus Lepidor-
bitoides: Evolution and stratigraphic significance in
some Anatolian Basins (Turkey). Reawe Micropaléont.,
42: 111-131, Paris.

Ózcan E. & Ózkan-Altiner S. (1999b) - The genera Lepidor-
bitoides and C)rbitoides: Evolution and srratigraphic sig-
nificanc in some Anatolian Basins. Geol. Journ., 34:
275-286, London.

Papp A. (1951) - Ùber die Entwicklung von Pseudorbitoides
und Lepidorbiroides in Europa. Verhandl. Geol. Bunde-
sanst., vo\.: 162-1 70, Vien.

Papp A. (1956) - Orbitoiden aus dern C)berkreideflysch des
tVienerwaldes. Verhandl. Geol. Bundesanst., vol. ,: 133-
143, Vien.