GEOLOGIJA 39, 91-95 (1996), Ljubljana
Pironaea buseri n. sp. from olistostromal breccia
of Paleocene flysch by Anhovo
Desanka Pejović
Simina 19, 11000 Beograd, Yugoslavia
Key words: Hippuritidae, Pironaea, taxonomy, chaotic breccia, Soča Valley,
Slovenia
Abstract
A new species, Pironaea buseri, found in chaotic breccia in Paleocene flysch
beds in the wider region of the Soča valley, is ascribed to the genus Pironaea
Meneghini. The large L-S distance and equal L-S and E-S spacings distinguish
the new species from any known pironaea species. The species was found with
Vaccinites giordani (Pirona) and Hippuritella cornucopiae (Defranee).
Introduction
In the chaotic limestone breccia of the Podbrdo cyclotheme within the Paleocene
flysch Jože Fekonja years ago found in the Rodez quarry at Anhovo (Fig. 1) a well
preserved sample of sorted out incomplete right valve of a pironaea that was stored
by Miklavž Fajgelj in the collection of rocks from the quarry. Shortly afterwards Dr.
Stanko Buser found in a similar chaotic breccia in flysch not far from the pironaea
find on the crest between the quarries Lastivnica and Deskle the rudists Vaccinites
giordani (Pirona) and Hippuritella cornucopia (Defranee). The mentioned rudist
fauna was ceded to me by Stanko Buser for paleontologie examination for which I
am very grateful to him.
The rudists were redeposited during the forming of Paleocene flysch as isolated
specimens into the flysch basin from the southerly lying Dinaric carbonate platform.
Owing to their position within the impermeable flysch marls, the isolated rudists
were not lithified in the chaotic breccia nor firmly glued to its limestone fragments,
and were therefore well suited for palaeontologic study. It is interesting to note that
previously nowhere in Slovenia pironaeas and the species Vaccinites giordani were
found in primary position in the Upper Cretaceous limestone, but only redeposited in
younger flysch beds. This permits the supposition that these rudist species were asso-
ciated with a narrow living environment on the northern rim of the Dinaric carbon-
ate platform that was redeposited into the flysch basin during the time of its disinte-
gration (B u s e r et al., 1988; В u s e r et al., in press).
92
Desanka Pejovid
Fig. 1. Location map of Pironaea buseri n. sp.
Owing to the extremely well preserved internal characteristics, and owing to the
fact that the pironaea found in Anhovo in the Soča valley differs from all pironaeas
found so far, the fossil was attributed to the new species Pironaea buseri.
Systematic palaeontology
Hippuritidae Gray, 1848
Pironaea Meneghini, 1868
Pironaea buseri n. sp.
PI. 1, Fig. 1
Derivation of name: The species is dedicated to Professor Stanko Buser, Uni-
versity in Ljubljana.
Holotype: Transverse section of the right valve shown in PI. 1, Fig. 1, sample no
158, author's collection of rudists, Belgrade.
Type locality and stratigraphie position: The quarry of Rodez near
Anhovo; redeposited in Paleocene flysch.
Material studied: Only one incomplete specimen of the right valve.
Pironaea buseri n. sp. from olistostromal breccia of Paleocene flysch by Anhovo_93
Diagnosis: Right valve externally ribbed longitudinally, ribs separated by a
narrow furrow. Outer shell layer thin. Ligamental ridge and pillars radially posi-
tioned to each other. Ligamental ridge and the second pillar almost equal in length.
L-E distance takes approximately one-third of valve circumference; L-S and S-E dis-
tance equal. Secondary folds of the first cycle well developed and narrower at base;
secondary folds of the second cycle distinctly marked, nonuniform in shape.
Description: The found fragment of a right valve is 5cm long; its anterior-pos-
terior and dorsal-ventral diameters are 10.5 cm and 11cm, respectively. The part of
the right valve to which the fragment belonged is impossible to identify, but seems to
be the central part. It shows externally large longitudinal ribs 1 cm wide, separated
by narrow furrows equivalent to internal folds. Each rib shows two or three secon-
dary ribs. Plicated growth lines are distinct. Internal features are not distinguishable
in the three successive transverse sections, i.e. ontogenetic changes are not
detectable.
The outer shell layer is relatively thin (about 3 mm) in relation to the valve size.
Ligamental ridge is long, wide at the top and narrow at base and slightly bent away
from the first pillar. The first pillar is droplike, narrow at base like a stem. The sec-
ond pillar is longer than the first pillar and insignificantly longer than the ligamental
ridge, almost uniform in thickness through the length, radially positioned and very
slightly curved at top to the first pillar. It clearly shows facing sheets of the outer
shell layer. L-E distance is large, greater than in any known pironaea species; it takes
almost a third of the valve circumference. L-S and S-E distances are equal. Secon-
dary folds of the first cycle, 11 in number, are well developed and equally long,
widening distally and narrow at base, they look like drops. They distinctly show the
facing line of two outer shell layer sheets. Secondary folds of the second cycle are
well marked, 12 in number, unequal in size, mostly half shorter than those of the first
cycle. They also show the facing line of the outer shell layer sheets. Three secondary
folds between ligamental ridge and the first pillar, and three between the first and
the second pillars, are arranged so that the first cycle fold is in the middle and a sec-
ondary fold of the second cycle on its either side.
Remarks: The large L-E distance and equal L-S and E-S spacings, and the
shapes of pillars and ligamental ridge, distinguish sufficiently Pironaea buseri n. sp.
from any known pironaea species. The new species resembles Pironaea machnitschi
Wiontzek (Wiontzek, 1933, p. 10, Fig. 1) in having larger siphonal zone, or the L-S
spacing, and in certain similarities of shape and position of E and S pillars and the
ligamental ridge. However, L-S distance in the latter species is half that of S-E,
whereas L-S and S-E distances are equal in the new species. Also, the shape and
number of secondary folds of the first and second cycles clearly differ in the two
species. Secondary folds of the first cycle are forking in the proximal end in Pironaea
machnitschi, and are simple in the new species. Besides, the configuration of secon-
dary folds is also different: it is regular in Pironaea buseri, i.e. one fold of the first
cycle between two folds of the secondary cycle, and in Pironaea machnitschi two
folds of the first cycle are next to each other.
In the shape of ligamental ridge, and in the shape but not the number of secon-
dary folds of the first and second cycles, the new species has some resemblance to the
species Pironaea fruscagorensis Milovanović, Sladic, Grubić. However, the L-E dis-
tance in P. fruscagorensis is even smaller than that of L-S or S-E in the new species;
moreover, secondary folds are lacking in the siphonal zone.
If the moniliform nature of folds in Barrettia, and not only this genus because it
94_Desanka Pejović
was also noted in some pironaeas {Pironaea milovanovici Kühn, P. postdalmatinica
Pamouktchiev, P. milovanovici quatretondaensis Philip), was a secondary phenome-
non, as I suggested as a possibility (Pejović, 1988; Pejović, in press) and con-
firmed on some caprinids (Pejović, 1972, p. 367-368, Figs, a-d), the new species
would be also comparable with Barrettia monilifera Woodward from Flor de Alba
Limestone, Puertorico (Van Dommelen, 1971, p. 113, PI. X, Fig. 1). The L-S dis-
tance in this specimen is almost identical with that of the new species Pironaea
buseri. Also, the number and distribution of secondary folds between L and S, and S
and E, which are not even moniliform, neither the first and second pillars are identi-
cal with respective folds of the new species.
References
Buser, S., Pejović, D. & Radoičić, R. 1988: Redeposited Rudists in Senonian and Pale-
ocene Flysch Beds in the wider Region of the Soča Valley. - First International Conference on
Rudists, October 1988, Abstracts, p. 3, Belgrade.
Buser, S., Pejović,D. & Radoičić, R. 19 : Redeposited Rudists in Senonian and Pale-
ocene Flysch Beds in the wider Region of the Soča Valley. - Proc. Intern. Conf. on Rudists
(Belgrade, October 1988), Serb. Geol. Soc, Spec. Pubi, (in press).
Pejović, D. 1972: On the Phenomenon of "Rosary" in the external Layer of the Caprinidae
Shell. - Bulletin scientifique. Sect. A, Tome 17, No 11-12, Zagreb.
Pejović, D. 1988: On Radiolitidae and Hippuritidae Shell Structure. - First International
Conference on Rudists, October 1988, Abstracts, p. 18, Belgrade.
Pejović, D.: Sur la structure du test des Radiolitidae et Hippuritidae. - Proc. 1®* Intern.
Conf. on Rudists (Belgrade, October 1988), Serb. Geol. Soc, Spec. Pubi, (in press).
Van Dommelen, H. 1971: Ontogenetic, Phylogenetic and Taxonomic Studies of the Amer-
ican Species of Pseudovaccinites and of Torreites and the Multiple-fold Hippuritids. - Thesis,
University of Amsterdam, 1-125, Amsterdam.
Wiontzek, H. 1933: Rudisten aus Oberen Kreide des Mittleren Isonzogebietes. - Palaeon-
tographica, 80, A, Stuttgart.
Pironaea buseri n. sp. from olistostromal breccia of Paleocene flysch by Anhovo
95
Plate 1
1 Pironaea buseri n. sp., Rodež by Anhovo
Holotype, transverse section of right valve, sample no 158, natural size