Bolboforma (Phytoplankton Incertae Sedis), Bachmayerella and other Calciodinelloidea (Phytoplankton) from the Middle Miocene of the Alpine–Carpathian Foredeep (Central Paratethys)

Bolboforma is a microfossil of uncertain origin with affinities to protophytic algae. It generally occurs at high latitudes and/or in cool and temperate waters and has a high stratigraphic potential especially for the Miocene. Calcareous cysts of dinoflagellates represent the ‘benthic cyst stage’ of unicellular organisms belonging to the marine phytoplankton. The occurrence of Bolboforma, Bachmayerella is documented here and, for the first time, some calcareous cysts of dinoflagellates tentatively attributed to Alasphaera and Pithonella from Badenian (Langhian–Middle Miocene) sediments in Austrian and Moravian localities. Alasphaera and Pithonella were previously described from Cretaceous and Danian sediments only, therefore, their range has been extended into the Paratethyan Middle Miocene. Correlation of Bolboforma bioevents with standard geological time-scales allows confirmation, and in some cases refinement, of age assignments based on other microfossil groups, such as foraminifera and calcareous nannofossils, in Paratethyan areas. In particular, this paper presents a case study of the biostratigraphy of the Grund Formation outcropping at its type locality in Lower Austria. Age attribution of the Grund Formation has been uncertain for some time. The recovery of Praeorbulina glomerosa circularis and Uvigerina macrocarinata, associated with Bolboforma reticulata, allows the correlation of the Grund Formation with the Early Badenian (Middle Miocene). As planktonic foraminifera are generally very rare or absent in shelf deposits of many other Austrian and Moravian Middle Miocene sedimentary sequences, Bolboforma, and in particular B. reticulata, remains an important biomarker to identify lower Badenian sediments. Additionally, the new species Bolboforma gneixendorfensis Spezzaferri & Rögl is described. It is generally double-chambered with a weakly reticulate wall texture and is associated with Bolboforma reticulata, B. bireticulata and/or B. moravica.


INTRODUCTION
Bolboforma comprises a group of marine calcareous microfossils of uncertain origin with affinities to protophytic algae. Bolboforma specimens are monocrystalline, calcitic hollowshaped and consist of a spheroidal or subspheroidal single chamber. In some cases the wall may be built of at least three layers (Poag & Karowe, 1987). They may encapsulate a smaller chamber and produce cysts. Cysts are smooth or weakly ornamented and their function is still unknown (Spiegler, 1987;Spiegler & Daniels, 1991). Rare double-chambered Bolboforma specimens/species display a septum separating a large chamber from a smaller terminal aperture-bearing chamber (Daniels et al., 1981). The wall texture is smooth or strongly ornamented with a short neck or collar generally bordering the aperture. Specimens range in size from 50-250 µm, but their diameter is usually less than 150 µm.
Although recent studies have shown that the isotopic composition of Bolboforma is typical of tychoplancton (Spiegler & Erlenkauser, 2001), which include organisms occasionally carried into the plankton by chance factors such as turbulence, the taxonomic position and the life strategy of Bolboforma is still poorly known. However, a strong resistance to dissolution and the high stratigraphic potential, especially for the Miocene, make the Bolboforma an important and exceptional microfossil group for interpreting the stratigraphy and palaeoceanography of sediments from cool and temperate regions (Spezzaferri & Spiegler, 1998a;Spezzaferri et al., 2001;Cooke et al., 2002). In many cases Bolboforma biostratigraphy may improve upon and, in some cases, supplement the standard zonations based on other microfossil groups from Early Eocene to Early Pliocene sediments (Spiegler & Daniels, 1991).
The existing literature documenting Bolboforma is generally restricted to sediments recovered during deep-sea drillings (DSDP and ODP Holes, at latitudes between 30( and 70( (Rögl & Hochuli, 1976;Kennett & Kennett, 1990;Qvale & Spiegler, Dinoflagellates belong to the marine phytoplankton. Within their life cycle they can produce benthic cysts composed of silica or carbonate during 'resting stages' related to environmental conditions. These cysts can be preserved in the fossil record. Specimens, which may belong to the calc-dinocyst group, Bachmayerella tenuis and Bachmayerella laqueata, were first described by Rögl & Franz (1979) from Middle Miocene sediments in the Central Paratethys. In the eastern Mediterranean these microfossils characterize Pliocene and Pleistocene sediments. Their last occurrence has a high stratigraphic potential, especially within the Globigerina cariacoensis-Truncorotalia truncatulinoides Zone in the Pleistocene (Spezzaferri & Spiegler, 1998b). Other spherical calcareous dinoflagellate cysts belong, for example, to Pithonella and Alasphaera genera.
The aims of this study are: (1) to document the occurrence of Bolboforma in Middle Miocene inner shelf to upper bathyal facies from Austrian and Moravian sequences; (2) to refine and confirm an age attribution of the sediments using the distribution of Bolboforma; (3) to document for the first time the presence of calcareous cysts of dinoflagellates in these areas.
Bolboforma and calcareous cysts of dinoflagellates are documented in Plates 1-3. The figured material is deposited in the Naturhistorisches Museum Wien, Micropalaeontological Collection, nos. 2003z0047/0001 to 0039.

STRATIGRAPHY AND GEOLOGICAL SETTING
The rising mountain chain extending from the Alps to the Kopet Dag, between Iran and Turkmenistan, triggered the isolation of the northern Mediterranean Tethys margin in the Early Oligocene forming a new palaeogeographical unit termed Paratethys (e.g. Rögl, 1999). From its formation to its closure in the Late Miocene, this area experienced an evolution that was different from that of the Mediterranean region. The development of floras and faunas in the Paratethys was related to palaeogeographical settings and, therefore, separate studies on Paratethyan faunas and floras and their endemism have been produced (Steininger et al., 1990;Cicha et al., 1998 for an overview). In particular, regional stratigraphic stages were introduced for the Oligocene-Miocene interval (Fig. 1).
The Alpine-Carpathian Foredeep, which is part of the central Paratethys, follows the outline of the Bohemian Massif and turns from a west-east-trending basin to northeast, toward Moravia north of the Danube River (Fig. 2). In the investigated part of this basin, marine sedimentation started in Late Oligocene (Egerian z Chattian to Aquitanian). Older Cenozoic sediments are preserved in graben structures in Southern Moravia. Early Miocene (Eggenburgian to Karpatian = Burdigalian) sediments are conformable and extend northeastward in the Carpathian Foredeep. In the Late Ottnangian, brackish conditions prevailed (Rzehakia = Oncophora Beds) and ended the first Early Miocene marine cycle. The basin was strongly narrowed by the overthrust of Alpine-Carpathian nappes (Kovac et al., 1998).
A late Early Miocene transgression produced the deposition of the Karpatian 'Schlier' (silty-sandy calcareous shales of the Laa Formation) on the Carpathian nappes and the foredeep sediments. A successive regression-transgression cycle triggered the formation of the Middle Miocene Badenian Sea in the whole basin, as described by Jiricek & Seifert (1990), Kovac et al. (1998), Stranik & Brzobohaty (2000) and Jiricek (2001). The basin evolution and the geological setting of the Austrian part of the foredeep (Molasse Basin) is described in detail by Roetzel et al. (1999a).
Lower Badenian sediments in Austria belong to the Grund and Gaindorf Formation, and consist of marly silts, silts, sands and gravels. The Mailberg Formation consists of corallinacean limestone with some marly intercalations.
In the Moravian part of the foredeep the Lower Badenian started with coarse clastic sediments, followed by the shallow Brno Sands and basinal sediments from the Brno Marl ('Brünner Tegel'). The sea transgressed on the Bohemian Massif, where deeper-water sediments were preserved in graben and valley structures (Brzobohaty et al., 1983;Brzak, 2001;Petrova et al., 2001).
The stratigraphic age of basal Badenian sediments in the foredeep has been dated by calcareous nannoplankton as Zone NN4, and in the Grund Formation as Zone NN5, and by the occurrence of Praeorbulina glomerosa circularis as Zone M5b (Rögl & Spezzaferri, 2003;Coric & Rögl, 2004;Spezzaferri, 2004). This contrasts with the interpretation of Cicha (1999) and Svabenicka & Ctyroka (1999) who placed the lower part of the Grund Formation in the Early Miocene Karpatian stage. Therefore, the stratigraphic potential of Bolboforma for Miocene sediments is relevant to this study, to clarify the age attribution of the Grund Formation and solve the debate.

MATERIAL AND METHODS
Samples were washed using standard techniques for foraminiferal preparation. For each sample, 200 g of sediment were soaked in hydrogen peroxide for several hours, then soaked in warm water and washed under running water through >250 µm, >125 µm and >63 µm mesh sieves. Bolboforma and calc-dinocyst specimens were analysed under a binocular microscope, identified and picked from the >125 µm and >63 µm size fractions. Selected specimens were also observed using a scanning electronic microscope (SEM).

THE LOCALITIES
Bolboforma species were previously documented in sediments from several Austrian sections (Spiegler & Rögl, 1992). Bachmayerella species were described for the first time from an Austrian section (Rögl & Franz, 1979). Calciodinelloidea were unknown from the Paratethys Miocene. Occurrence of these organisms is restricted to isolated samples only and a continuous record is unavailable. Therefore, only a short description of the localities (Fig. 1) and sediments in which they occur -and not complete lithological logs -is given below.  (Roetzel et al., 1999b;Pervesler & Roetzel, 2002). The Grund Formation at the type locality shows a sequence of bedded fine sands and pelites which are cut by channels with coarse clastic infilling, mainly comprising mollusc shells. These sediments are attributed to the Lower Badenian based on Praeorbulina glomerosa circularis, planktonic foraminiferal Zone M5b (Berggren et al., 1995) and nannoplankton Zone NN5 of Martini (1971) as in Rögl et al. (2002). + Locality Windmühlberg is 2 km NW of Grund, near the main road B2, between the villages of Grund and Guntersdorf. Sediments consist of yellowish fine sands and pelitic layers and belong to the Grund Formation, Lower Badenian. + Locality Kalladorf is 9 km north of Hollabrunn, Lower Austria. An excavation was carried out in 1987 for a gas pipeline by NIOGAS Comp. at the wine cellars about 100 m east of the village. Sediments consist of alternating yellowish fine sands and grey-brown pelites with incised small channels filled with coarse sand and mollusc shells and belong to the Grund Formation. They are attributed to the Lower Badenian based on P. glomerosa circularis and Orbulina suturalis (basal Zone M6). + Roggendorf 1 is a deep drilling of OMV AG SSW of Maria Roggendorf, 7 km NE of Hollabrunn (Coric & Rögl, 2004). Two metres of Quaternary sediments cover 270 m of clayey silty marls and sands of the Grund Formation (Zone NN5, basal Zone M6). These sediments overlay a sequence of Lower Badenian (Zone NN4 to NN5) sand, gravels and conglomerates, which are transgressive on the Laa Formation (Early Miocene, Karpatian, Zone NN4). + Locality Locatelliwald is 3 km NNW of Immendorf, NNE of Hollabrunn, in an old quarry (Spiegler & Rögl, 1992). Sediments consist of a corallinacean limestone with intercalated yellowish brown marl layers and belong to the Mailberg Formation (Lower Badenian). + Locality Buchberg is in an old quarry 1.5 km SW of Mailberg, NE of Hollabrun, in Lower Austria (Spiegler & Rögl, 1992). Sediments of the Mailberg Formation consist of corallinacean limestone with intercalated yellowish brown marl layers and are attributed to the Lower Badenian, based on P. glomerosa circularis and O. suturalis (basal Zone M6). + Locality Kautendorf near Staatz, Lower Austria, building site at lot no. Pz-1966/11. Light grey to yellowish marl with rich foraminiferal fauna of deeper water ('Badener Tegel'), in front of the Jurassic klippen of Staatz, Waschberg Unit (Grill, 1968). Sediments are attributed to the Lower Badenian, Lower Lagenidae Zone based on P. glomerosa circularis and O. suturalis (basal Zone M6). + Locality Gneixendorf, exploration well NÖ-06 by GKB (1987), Krems embayment, Lower Austria (Spiegler & Rögl, 1992 (Redinger, 1992). Sediments consist of alternating calcareous clays, marls and detrital limestones. The occurrence of Orbulina suturalis indicates a Lower Badenian age (Zone M6). + Locality Zidlochovice is an old brickyard north of the town in Southern Moravia, the facies stratotype of the Lower Badenian (Moravian Substage). Sediments consist of grey to blue-grey and greenish marl to clayey and silty-sandy marls, topped by corallinacean limestone (Cicha in Papp et al., 1978). They contain P. glomerosa circularis, O. suturalis and Globigerinoides bisphericus and are attributed to the basal part of Zone M6. Spiegler, 1987Genus Bolboforma Spiegler & Daniels, 1974 Bolboforma gneixendorfensis n. sp. (Pl. 1, figs 5, 7-9, 11-14; Pl. 3, figs 1-2, 5-7)
Explanation of Plate 1. fig. 1. Bolboforma bireticulata Spiegler, sample W-3, Windmühlberg, 500. figs 2a-b. Bolboforma bireticulata Spiegler, sample 104.7-104.8 m, Gneixendorf, 500: 2a, this specimen displays evidence of slight corrosion in the wall texture. However, the less marked reticulation where the wall texture is well preserved should also be noted. This specimen seems to be transitional to those in figs 5, 7, 8, 9, 11, 12 and 13; 2b, detail of the wall texture -the edges are still well preserved, while the wall texture in the depressions is corroded. fig. 3. Bolboforma bireticulata Spiegler, sample 104.7-104.8 m, Gneixendorf, 500. This specimen resembles that of fig. 2; the wall texture is, however, better preserved and displays almost no evidence of corrosion. fig. 4. Bolboforma bireticulata Spiegler, sample 104.7-104.8 m, Gneixendorf, 500. This specimen resembles that of figs 2, 3 -the wall texture is strongly corroded, although the edges are still evident and seems to be better preserved. Diagnosis. Tests are spherical, double-, very rarely singlechambered. The wall texture is very weakly ornamented with widely spaced reticulations. The aperture is circular, bordered by a collar placed in a polygonal depression and surrounded by a smoother area. The encapsulated cysts are single-chambered and smooth to very weakly ornamented (Pl. 3, figs 1-2). Remarks. This species has also been found in the Mediterranean Sea DSDP Leg 42A-372, 9-13 m (Spiegler & Rögl, 1992).
Bolboforma gneixendorfensis differs from B. reticulata, B. bireticulata and B. moravica in having a remarkably weaker ornamented wall texture. Under the light microscope it appears nearly smooth. Spiegler & Rögl (1992) have described this form as a possible cyst and not as a species. However, several specimens (Pl. 1, figs 9 and 11a-b) show the presence of encapsulated cysts inside the test. This indicates that B. gneixendorfensis is a species able to produce cysts and is not a cyst itself.
It has also been concluded that the weak reticulation shown by B. gneixendorfensis is not an artefact due to corrosion and/or Within the same sample, B. gneixendorfensis has been observed with different degrees of dissolution and corrosion of the wall texture; from well preserved (Pl. 1,figs 5,7,11,12) to strongly corroded (Pl. 1,figs 9,13,14). In addition, B. reticulata, B. bireticulata and B. moravica occurring in the same assemblage show a typical marked reticulated pattern even when strongly corroded (Pl. 1, figs 2a-b, 4, 6, 10). This indicates that the wall texture pattern of B. gneixendorfensis is real, typical of this species and not due to secondary processes.
Although small and juveniles specimens are generally less markedly ornamented than adult and large specimens (Spiegler & Spezzaferri, 2004), it has been concluded that B. gneixendorfensis does not represent a juvenile or small and less ornamented variant in a large population of more strongly reticulate forms (e.g. B. reticulata or B. bireticulata). In fact the size of most specimens of B. gneixendorfensis identified in the material in this study is comparable with the size of well-developed and adult B. reticulata (e.g. Pl. 1, fig. 7; Pl. 2, fig. 9) and, therefore, these specimens can be considered as adult.
Most of the specimens in the material possess a doublechambered test. Daniels et al. (1981) also observed abundant double-chambered specimens (over 100 specimens) of B. reticulata and B. laevis from the Reinbekian stage (Nannofossil Zone NN5, Middle Miocene) in a single sample from drill site Wursterheide. These authors observed that the two chambers are slightly elongated and subdivided by a septum with a round opening.

Diagnosis.
Tests are spherical and single-chambered. The wall texture is strongly ornamented with widely spaced reticulations. The aperture is circular, bordered by a thick collar placed in a polygonal depression and surrounded by a smooth area. Often the collar is broken. The encapsulated cysts are single-chambered, ornamented by weaker, but still marked, reticulations corresponding in arrangement to those of the outer test (Pl. 2, fig. 10).

Remarks. This species is relatively well documented in Middle
Miocene sediments from the North Atlantic to the Southern Oceans (e.g. Spezzaferri & Spiegler, 1998a;Cooke et al., 2002). Its presence in Middle Miocene sediments from the Mediterranean Basin is reported in Spiegler & Daniels (1991) and Spiegler & Rögl (1992). The distribution in the Paratethys and northern Germany is reported in Spiegler & Rögl (1992) and Spiegler (2002)  Diagnosis. Tests are double-chambered and elongated, chambers are spheroidal. The wall texture is strongly ornamented with widely spaced reticulations. The aperture is circular, bordered by a thick collar placed in a polygonal depression and surrounded by a smooth area. Often the collar is broken. Encapsulated cysts are single-chambered, ornamented by weaker but still marked reticulations corresponding in arrangements to those of the outer test.
Remarks. This species differs from B. reticulata only in having a double-chambered test and sharper ridges of reticulation.
The specimen in Plate 1 ( fig. 1) displays a strongly reticulate texture and evidence of weak corrosion. The specimens of Plate 1 (figs 2a-b, 3) show a well-preserved wall texture with a less marked reticulate texture and very weak corrosion. The specimen in Plate 1 (fig. 4) displays a weakly ornamented texture and heavier corrosion. Redinger, 1992 (Pl. 1, fig. 10 Diagnosis. Tests may be single-or double-chambered. The wall texture is strongly ornamented by reticulations. The edges of the reticulations bear a little spine-like projection not present in B. reticulata. The aperture is circular, sometimes bordered by a thick collar situated in a polygonal depression.

Bolboforma moravica
Remarks. This species is documented from the Central Paratethys as well as in the North Atlantic (Voering Plateau) and North America (Spiegler & Rögl, 1992). Its distribution spans the Badenian-Middle Miocene (Nannofossil Zones NN5 and NN6).
Family Calciodinelloidea? Deflandre, 1947Genus Bachmayerella Rögl & Franz, 1979Rögl & Franz (1979 discussed the possibility that these organisms are Tintinnidae or reproduction stages of some marine metazoans. These authors documented a multi-layered wall for the Miocene forms. Successively, the Plio-Pleistocene specimens from ODP Leg 160 were attributed to the group of calcareous cyst of dinoflagellates (Calciodinelloidea) by Spezzaferri & Spiegler (1998b) based on a single-layered wall consisting of elongated calcite microcrystals orientated perpendicular to the surface of the cyst. In contrast to Calciodinelloidea, the wall consists of small polygonal plates. A more precise taxonomic position is still to be clarified. Rögl & Franz, 1979 (Pl. 2, fig. 6 Diagnosis. The calcareous test is sub-spherical with a typical circular archaeophyle of 25-35 µm in diameter. The wall texture is covered by a regular pattern of reticulations. Distinct pores are visible in well-preserved material, irregularly distributed and present on the intersections of the ridges forming the reticulations. A spine-like protruding tube is present in an aboral position.

Bachmayerella tenuis
Remarks. These forms are rare in the Lower Badenian (Langhian, Zone NN5) of the Central Paratethys, but common in some horizons of the Middle to Upper Badenian (Lower Serravallian, Zone NN6). They are also relatively common in the Pliocene and Pleistocene (Spezzaferri & Spiegler, 1998b) and rarer in Miocene (Spezzaferri et al., 2001) sediments from the eastern Mediterranean. Poignant (1997) reports the species from the Burdigalian and Langhian of the Aquitaine Basin.

Diagnosis.
The calcareous test is sub-spherical with a typical circular archaeophyle with diameter sometimes exceeding 50 µm. The wall texture is covered by an irregular pattern of reticulations. Distinct pores are visible in well-preserved material, irregularly distributed and present on the intersections of the ridges forming the reticulations. A small spine-like protruding tube may be present in an aboral position.
Remarks. This species differs from B. tenuis in being generally larger in size and having a more irregular pattern of its strong reticulations. In the Central Paratethys this species has the same stratigraphic distribution as B. tenuis within the Badenian. The only record outside the Paratethys, is from the Upper  Spezzaferri & Spiegler (1998a) Burdigalian and Langhian of the Aquitaine Basin (Poignant, 1997).
Other Calciodinelloidea. By comparison with the species documented in Keupp (1979a) the specimens in Plate 2 (figs 1a-b, 2a-b, 4) have been tentatively attributed to the Family Calciodinelloidea Deflandre (1947) and Genus Alasphaera Keupp (1979b). The presence of individuals of the same species with or without apertures indicates their cyst nature (Keupp, 1979b); however, their taxonomic position remains uncertain.
Alasphaera sp. 1 (Pl. 2, figs 1a-b) The tests are calcareous, rounded, the wall texture is smooth and covered by smooth and regularly distributed pustule-like structures. These specimens differ from Alasphaera caudata Keupp (1979b) in having less pronounced, smaller but more numerous pustules without thickened terminations, and from Alasphaera verrucosa Keupp (1979b) for the smaller, more numerous and smoother pustules. Both A. caudata and A. verrucosa occur in Lower Cretaceous sediments from NW Germany.
Alasphaera sp. 2 (Pl. 2, fig. 5) This form also resembles Alasphaera sp., but differs in having more pronounced pustule-like structures that are more irregularly distributed. Although the specimen is relatively poorly preserved, the pustule terminations seem to be thickened, resembling those of A. caudata, although pustules are less numerous in the latter species.
These specimens are similar to Alasphaera sp. 1, but differ in having a polygonal pattern all over the wall covered with pustule-like structures. The specimen figured by Odrzywolska-Bienkowa (1976) shows the same fine reticulation covering the entire wall.
Similar wall texture and reticulations can also be seen in some radiolarians such as, Conocaryomma universa Pessagno or Praeconocaryomma spp. (Gregory pers. comm.) with the test diagenetically replaced by calcite. Subsequently, the specimen in Plate 2 (figs 2a-b) was sectioned. It displays calcite infilling and, therefore, may be a re-crystallized radiolarian (Rögl, pers. obs.). This specimen demonstrates how difficult it is to distinguish real calcareous cysts of dinoflagellates from incertae sedis and recrystallized radiolarians.
Odrzywolska-Bienkowa's specimen is described from the locality Kikov, Poland, from the Miocene. The presence of B. reticulata (described as B. metzmacheri) in the same locality indicates a possible Badenian age.
The taxonomic position of these specimens is unclear. Their morphology resembles that of Bachmayerella, but their wall texture is irregular, rough, with interspaced spine-like heavy pustules. A subdivision of the wall into polygonal plates is absent. The specimen in Plate 2 (figs 3a-b) shows an irregularly rounded archaeophyle. Similar forms are figured by Szczechura (1986) from the Badenian of Poland.
Pithonella sp. (Pl. 2, This form displays a rounded test with a moderately wide archaeophyle. The genus Pithonella is generally described from Mesozoic and Danian sediments (Bolli, 1974;Rögl, 1976). However, the form documented in Plate 2 (figs 4a-b) and found in Middle Miocene sediments, is tentatively attributed to the Genus Pithonella (Lorenz) based on morphological similarity, a double-layered wall and the nature of the outer layer composed of crystallites. Such forms were also observed in Middle Miocene sediments of the eastern Mediterranean, DSDP Leg 42 (Müller pers. obs.). Pithonella is included here in the Family Calciodinelloidea Deflandre following Keupp (1979a) who demonstrated a systematic relationship between Pithonella and the calcareous cyst of dinoflagellates.

DISCUSSION
Bolboforma is generally not abundant in outcropping sediments in European sections (see Spezzaferri et al., 2001 andSpiegler, 2002 for a review). It has been demonstrated that Bachmayerella spp. is stratigraphically useful in the Pliocene and Pleistocene of the eastern Mediterranean (Spezzaferri & Spiegler, 1998b) although their distribution and ecological preferences are still poorly known. In particular, although, their upper range is well documented (Spezzaferri & Spiegler, 1998b), their first occurrence is still uncertain. The older sediments in which they are found are attributed to the Late Burdigalian from the Aquitaine Basin (Poignant, 1997).
In the Central Paratethys, these organisms are common only in distinct horizons, although the literature available is poor (e.g. Spiegler & Rögl, 1992;Sczcechura, 1986Sczcechura, , 1997. No descriptions are available for other Miocene calcareous cysts of dinoflagellates. Although complete information about their distribution is still missing, this research contributes important data to improve their stratigraphic value. Spiegler (2002) correlated the marine Miocene Bolboforma standard zonation that was calibrated with the Nannoplankton zonation of Martini (1971) and the chronostratigraphy of Berggren et al. (1995) with the regional zonation based on uvigerinids in northern Germany (Fig. 1). Spiegler (2002) reports the presence of B. reticulata in sediments spanning 14.5 Ma to 15.6 Ma, and the range of B. bireticulata from 14.5 Ma to 15.0 Ma. In particular, she recognizes a Lower B. reticulata  and an Upper B. reticulata . The Lower B. reticulata Subzone (Total Range The reference list refers to foraminifera and calcareous nannofossils only, with the exception of Spiegler & Rögl (1992) reporting a preliminary study of Bolboforma.

Nannofossils zones
follow Martini (1971 A good example of how Bolboforma can be used in the Paratethys to confirm and improve the stratigraphic resolution based on other microfossil groups and magnetostratigraphy is within the framework of the studies on the Grund Formation. Weinhandl (1957) and Grill (1958) identified in these sediments the typical Early Badenian (Langhian-Middle Miocene) planktonic foraminiferal assemblage consisting of Praeorbulina glomerosa and Orbulina suturalis. In more recent years the lower part of this formation has been dated as Karpatian (Burdigalian-Early Miocene) by Cicha & Rudolsky (1996) and Cicha (1999). The combined effort of different projects focused on the Austrian Miocene contributed new information and insight into this issue. In particular, it was improved by the study of eight profiles (Profiles A-I) previously excavated by the Institute of Paleontology of the University of Vienna in the Grund Formation type locality. The documentation of three specimens of P. glomerosa circularis, in one sample from Profile G, a few specimens of U. macrocarinata identified in Profile F adjacent to Profile G (Spezzaferri, 2004) and Helicosphaera waltrans Coric & Rögl, 2004) enable the correlation of the lower part of the Grund Formation with the Early Badenian (nannofossil Zone NN5 and foraminiferal Zones M5b). The magnetostratigraphy, displaying normal polarity in the Grund type locality, could also be interpreted using biostratigraphic data of calcareous nannofossils and planktonic foraminifera and is tentatively attributed to Chron C5Bn.2n (from 15.034 to 15.155 Ma) as in . The co-occurrence of B. reticulata and Uvigerina macrocarinata, allow the correlation of the investigated sediments with the Lower B. reticulata Zone (14.5-15.6 Ma) and with the U. macrocarinata Subzone (approximately 14.8-15.1 Ma, by comparison with the correlation of Spiegler, 2002). This age is consistent with the age of Chron C5Bn.2n and confirms the age of the sediments of the lower part of the Grund Formation. Spezzaferri (2004) demonstrated that the sediments at the type locality of the Grund Formation can be dated using planktonic foraminifera such as Praeorbulina and Orbulina spp. Although these species are generally very rare and confined in the thin and rare marly layers, their finding in the Grund Formation represents the framework for future studies. However, many outcrops (including some profiles adjacent to Profile G and F, where these specimens were found) do not contain planktonic foraminifera. This formation is characterized by different facies (Harzhauser et al., 1999;Zuschin et al., 2001), which represent environmental conditions such as shallow waters, storm layers and/or coarse sediments, where planktonic foraminifera are absent. Since Bolboforma can also be found in relatively shallow water (neritic) and coarser sediments (such as wackestone and packstone (Spezzaferri et al., 2001), in many cases it remains an important biomarker to identify the Early Badenian (Middle Miocene Nannofossil Zone NN5) in the Grund Formation. Table 2 summarizes the occurrences of planktonic foraminifera, Bolboforma and calcareous cysts of dinoflagellates, compared with the calcareous nannofossil, Bolboforma and Uvigerina zonations. Ages are derived by comparison of foraminifera and Bolboforma bioevents.

CONCLUSIONS
The distribution of Bolboforma and Bachmayerella and, for the first time, the presence of some calcareous cysts of dinoflagellates, such as Alasphaera and Pithonella, are reported here from Badenian (Langhian-Middle Miocene) sediments in Austrian and Moravian localities.
Alasphaera and Pithonella have been previously described in Cretaceous and Palaeocene, but never in Miocene, sediments. Therefore, these new discoveries, allow their range to be extended into the Paratethyan Middle Miocene.
Additionally, the biostratigraphy of the Grund Formation has been investigated in eight profiles excavated at the type locality. Results indicate that, at this site, planktonic foraminifera can be used for biostratigraphy, but are very rare. In particular, three specimens of Praeorbulina glomerosa circularis and a few specimens of the benthic Uvigerina marocarinata have been found in Profiles G and F. Sediments from adjacent profiles and other Middle Miocene sections in Austria and Moravia are barren of planktonic foraminifera, or contain only non-age diagnostic species. In these cases, B. reticulata is an important correlative biomarker, which enables the identification of the Middle Miocene Zone M5b (planktonic foraminifera) and Zone NN5 (calcareous nannoplankton). Therefore, this study demonstrates how the use of Bolboforma may improve stratigraphic resolution in the absence of more precise dating.
Finally, the new species Bolboforma gneixendorfensis is described. This species is similar in size and shape to B. reticulata, B. bireticulata and B. moravica, but differs from them in having a very weakly ornamented wall texture.