MILIOLIDAE - Acta Palaeontologica Polonica

MILIOLIDAE FROM MIOCENE OF POLAND 65
1968. Quitiqueloculina triangularis d'Orbigny; J. P. Margerel, p. 16, PI. 5, Figs 21-22
(non PI. 6, Fig. 1).
1969b. Quinqueloculina akneriana akneriana d'Orbigny; A. K. Bogdanowich, p. 86,
PI. 2, Fig. 8a, b.
Material. - Over 1000 QS and 20 MS (CoIl. No. F-115, Sec. No.139­
142,315,317-319,346,347,349-351).
Dimensions. QS - L 0.8-1.25; B 0.5-1.05; T 0.5-0.8; MS - L 1.65-3.5;
B. 0.8-1.25; T 0.4-0.8.
Description. - QS broadly oval, thick, high-triangular in cross-section,
periphery subacute; chambers broad, flat on one side and slightly inflated
on the other; middle chamber large, broad, prominent; juvenile stage
may be triloculine; MS large, flat, with broadly rounded periphery and
indistinct middle chambers; sutures slightly depressed, indistinct; wall
thin in QS, thick in MS; surface smooth, polished; aperture oval, not
large, with a simple, bifid tooth.
Variability. The shape of massiline forms varies from circular to
broadly oval, whereas the quinqueloculine and triloculine forms are always
the same shape. A distinctive feature of the massiline forms is their
rounded periphery, while the quinqueloculine forms show a particular
deformation of chambers. which are increasingly more inflated on th9
front side than on the back side. This is well seen in cross-sections (Textfig.
23).
Dimorphism. Massiline forms belong generally to the micro generation
(Text-fig. 23/1), quinqueloculine forms to the micro and mega I generations
(Text-fig. 23/2-6) and triloculine forms to the mega II generation
(Text-fig. 2317-11). The morphological differentiation of generations is
not marked except for the size of the proloculus and the number of
chambers. PD: micro - 20-30 ~l, mega I - 100-110 fl, mega II ­
200-300 fl.
Remarks. - Massiline forms show the same shape and internal
structure as Miliolina podolica Didkovsky, 1959 does. It is clearly seen
from the cross-section of this species given by its author (op. cit.,
Text-fig. 2) and from those of our specimens, that the juvenile stage has
its internal structure identical with that of Quinqueloculina triangularis
d'Orbigny. The only difference betwen them is the thicker wall in the
juvenile stage of the massiline forms of Q. triangularis which indicates
that there is a possibility for calcium carbonate to accumulate on the
chamber walls of the juvenile stage while successive massiline chambers
are being built. The quinqueloculine stage removed from the inside of the
massiline form corresponds morphologically to Q. triangularis (Textfig.
24). It should be mentioned that both the species have been described
from strata of the same age, namely Q. triangularis from the lithothamnian
facies of the Upper Tortonian of Nussdorf in the Vienna Basin,
and M. podolica from the clay facies of the Upper Tortonian in Podolia.
5 Acta Palaeontologica nr 1/74