Neomeris mokragorensis sp. nov. (Calcareous alga, Dasycladales) from the Cretaceous of Serbia, Montenegro and the Northern Calcareous Alps, (Gosau Group, Austria)

The new species of the genus Neomeris – Neomeris mokragorensis sp. nov. described in this paper from western Serbia originates: from the Albian of Mokra Gora (the succession transgrading on the serpentinite) and from the Turonian of the Skrape`–Kosjeri} area (the succession transgrading on the Carboniferous). The presence of this species has been noted in the Turonian of the Kukes and in the Santonian of the Metohija Cretaceous Unit (Mirdita Zone). In the surrounding of Podgorica (Dinaric Carbonate Platform, Montenegro), the same species previously was presented as Neomeris cf cretacea STEINMANN. Well preserved Neomeris specimens from the Turonian to the Santonian strata of the Northern Calcareous Alps (Gosau Group, Austria) previously described as Neomeris circularis BADVE & NAYAK, is assigned to Neomeris mokragorensis sp. nov. Neomeris mokragorensis is characterized by a thin loosed skeleton formed only around ampullae, by which, besides the form of the ampullae, this species is clearly distinct from Neomeris cretacea (Steinmann).


Geological setting Western Serbia
In western Serbia, Neomeris mokragorensis sp.nov.has been found in two regions: in the Albian sediments of Mokra Gora (Figs. 1,1) and in the Turonian of the Skrape` Valley (Figs. 1,2).

Mokra Gora (cf. Mirdita Zone)
The Cretaceous succession of Mokra Gora is part of the Drina Cretaceous Unit (RADOI^i] 1995).In western Serbia, this unit crops out in the Zlatibor-Tara-Zvijezda Belt, from where it stretches further to the area of Vi-{egrad in eastern Bosnia (Fig. 1, dotted line).Large ophiolite massifs, basinal Diabase-chert Formation and shallow water Triassic carbonates are transgressively and diachronously overlain by Albian to Turonian-Lower Senonian sediments.The Albian, Early-Middle Cenomanian, Middle Turonian and Early Senonian ages of Mokra Gora successions were documented by rich micro and macrofossil associations (@IVKOVI] 1905; LÓCZY 1924; MILOVANOVI] 1934; PEJOVI] & RADOI^I] 1971; BANJAC 1994) and also by Albian-Cenomanian palynolospectra (DULI] 1994).Precise stratigraphic data on the interval between the Early-Middle Cenomanian and the Middle Turonian limestone with rudists (on the Ogra|enica marly sequence, respectively) are lacking.The Ogra|enica marly sequence (Fig. 5) represents a peculiar feature in the paleogeography of the Drina Cretaceous Unit, occurring in the Mokra Gora area only, as a result of Mid-Cretaceous tectonic events.Early Cenomanian slump breccia (Fig. 6), observed in the western periphery of Mokra Gora, was the first announcement of these events.
In the eastern part of the Mokra Gora (Fig. 2), Cretaceous sediments, represented by some tens of metres of marls and marly limestones, overlying serpentinites with weathering crust, outcropped at places.These freshwater? to brackish deposits without noted microfossils, but in some beds with molluscs (Glauconia, Acteonella, Natica, Cerithium, other different gastropods; Lucina, Cirena, Lopha, Gryphaea, ostreid coquinas at places and other bivalvies) were ascribed to the Albian, although a latest Aptian age of the lowermost beds cannot be excluded.These sediments gradually pass into a sequence of alternating marls and marly-silty, peloidal or bioclastic limestone (Fig. 4), some of them containing benthic foraminifera, Charophyta gyrogonites and small molluscs.Within the beds about 10-12 metres below the outcrop in Fig. 4, the presence of Hemicyclammina sigali MAYNC indicated an age not older than middle Albian.The hand sample 011541 containing Neomeris mokragorensis sp.nov.and marls with Atopochara trivolvis PECK (011541a; see LJUBOVI]-OBRADOVI] 1995) are from the base of this outcrop.Wackestone -p.p. packstone with Neomeris contains frequent annelids (prevail- ing fragments), rare Charophyta gyrogonites, micromolluscs and few foraminifera (last occurrence of Hemicyclammina sigali in this sequence!)In the sample 011545, only few a Charophyta gyrogonites were detected (Pl. 3,Figs. 9,10).Very rare Ovalveolina maccagnoae DE CASTRO, associated with minute molluscs and rare ostracods, were found in samples 011546, 011549 and 011551.They became abundant in the topmost beds (Pl. 3,Figs. 7,8).This sequence is ascribed to the Late Albian-Earliest Cenomanian (Vraconian).
Upward, badly exposed Early-Middle Cenomanian limestone with orbitolinids, Pseudorhapydionina laurinensis (DE CASTRO), Charentia cuvillieri NEUMANN, Cuneolina, nezzatidae and ostracods is present.Further, followed friable deposits, some of them rich in molluscs (e.g.ostreids coquina, those with different gastropods), corresponding to the lower part of the Ogra-|enica marly sequence (Fig. 5).The succession continues in friable hemipelagic marly limestone with rare and badly preserved ammonites, echinoderms and rare planktonic microfossils (minute Pithonella, "Hedbergella").In this part of the sequence, olistostromatic beds and some bioclastic limestone with debris of rudists and other molluscs, halimedacean algae and rare foraminifera were noted.Based on the ammonites, LOCZY (1924) considered a Cenomanian-Turonian age for this deposit, a view accepted by later researches.The Ogra-|enica marly sequence is discontinuously overlain by Middle Turonian to Early Senonian limestone with rudists (Fig. 5, on the top-arrow).The presence of the Santonian species Vaccinites oppeli (DOUVILLE) was mentioned by MILOVANOVI], 1934, probably from the upper part of this limestone sequence.Younger beds of the Santonian are not documented.
It should be mentioned at this point that the Albian sequence of the same Cretaceous Unit at Vardi{te, westward of Mokra Gora (Fig. 1, 3), have been studied by BORTOLOTTI et al. (1971).According these authors "the fossils indicate an Late Jurassic age and an environment of shallow water and anomalous salinity".Between the illustrated microfossils shown in Fig. 6, the specimen "L", assigned with reserve to Haplophragmoides sp. is recognized as Hemicyclammina sigali MAYNC, a species widely distributed in the Albian of Mokra Gora.
In the basal part of the Drina Cretaceous Unit, fossils are rare and badly preserved.In addition, Albian shallow water facies in this area are different from those in the Albian of the Periadriatic Carbonate Platforms, therefore these deposits were not recognized, by our Italian colleagues, as Albian.

Skrape` Valley (The Cretaceous of Kosjeri}, western belt of the Vardar Zone)
The Late Cretaceous deposits of Skrape` occur in the most eastern part of the Kosjeri} Cretaceous area (Fig. 3).The oldest known sediments are Cenomanian in age transgrading over Early Carboniferous strata.The shallow water Cenomanian and p.p. Turonian deposits gradually pass into a basinal succession.
In the Skrape` Vallley, Neomeris mokrogorensis sp.nov.was found in two localities.In both cases in the sequences between the Cisalveolina fraasi Zone and sediments with hippuritids.In the locality Gradnja (sampled in 1966, the outcrop was 14 m thick), the Neomeris was found in the 4 m thick marly limestone (samples in the base and on the top, 07504, 07505) associated with barrel-shaped segments of Halimeda, Terquemella, Nezzazatinella picardi (HENSON), Gendrotella rugorensis (MAYNC), remains of gastropods and rare coral debris.About 10 metres upward (marly limestone, sandy marls and sandstones), Turonian hippuritids where discovered within a conglomeratic bed (data of D. PEJOVI] 1966).The other locality with Neomeris mokragorensis sp.nov. is on the opposite riverside to Gradnja.
Limestone with Neomeris mokragorensis sp.nov. in the Skrape` area was deposited in a low energy, shallow-water, lower?-middle ramp environment.

Other localities Mirdita Zone and Montenegro
Neomeris mokragorensis sp.nov.has been recognized in the Turonian and Santonian limestone of the Mirdita Zone, and in the Albian (revised) of the Dinaric Carbonate Platform (Montenegro).
Dinaric Carbonate Platform Montenegro.From the Albian marly limestone in the surroundings of Podgorica (SE segment of the DCP), previously ascribed   to the Cenomanian, this species was presented as Neomeris cf.cretacea STEINMANN (RADOI^I] 1976; Pl. 5, Figs.1-2).The limestone with Neomeris mokragorensis sp.nov.was deposited in a very shallow protected inner platform area, characterized by the presence of beds with Atopochara trivolvis.

Austria
The Gosau Group of the Northern Calcareous Alps uncoformably overlies the already deformed sediments of the Upper Austroalpine nappe complex.The remants of the neritic Lower Gosau Subgroup comprise different facies associations (continental to shallow marine), which altogether cover a range from the Late Turonian to the Early Campanian (e.g.WAGREICH & FAUPL 1994;SANDERS 1998).The occurring lithologies (marls, limestones, sandstones) comprise a wide range of nearly pure silicoclastic, mixed clastic carbonate and pure carbonate lithologies, including also diverse types of bioconstructions Neomeris mokragorensis sp.nov.Origin of name.The species name refers to the type area Mokra Gora in Western Serbia.
Diagnosis.Representative of Neomeris with an elongated cylindrical thallus and densely set whorls with laterals set in quincunxes.Calcification formed in distal part of the whorls around fertile ampullae only, resulting in a wide central cavity.Primary laterals, basal parts of the secondaries and their distal swellings (cortex) unknown (not calcified); fertile ampullae ovoidalsubspherical in shape and individually calcified including the membrane and thin sheath around the ampulla, usually overgrown during diagenesis.
Dimensions.Data from western Serbia and the Northern Calcareous Alps show good accordance.Minimum values (D, d) from the Alps correspond to a tiny specimen (SCHLAGINTWEIT & EBLI 1995: pl. 1, fig. 5).
According the specimen Neomeris mokragorensis sp.nov.from the Kukes Cretaceous Unit, Mirdita Zone (Fig. 7) the main stem of this species is about one third of the diameter.
Description.The variably preserved, simple, thin, loosely connected skeletons (Pl. 1, Figs. 1-6) consist of individually calcified laterally fussed ampullae, alternating in whorls.The skeleton of the primary carbonate sheaths, due to recrysallization and overgrowth sometimes becomes better preserved ( Pl. 1, Fig. 3; Pl. 2, Fig. 2; Pl. 3, Fig. 4) The primary calcified ampullae were preserved in both the studied material -from the Alps (SCHLAGINTWEIT & EBLI 1995, pl. 1, figs. 4, 8, 9) and from Western Serbia (Pl.1,Fig 11).The ampullae have an ovoidal-subspheric form.Usually, in random sections in thin slides, have a circular form because the axial sections of the ampullae, as those in the fragment shown in Pl. 1,Fig. 11, are extremely rare.In the same fragment (and in some others similarly preserved) are clearly distinct a primary calcified membrane (up to 0.01 mm thick) and a sheath around it (up to 0.02 mm thick).Dimensions of ampullae, in the axial sections (according Pl. 1, Fig. 12): internal diameter 0.1 mm, external with calcareous sheath 0,16 mm Axial dimensions, internal 0.13 mm, external, with primary sheath, about 0.2 mm.Some specimens or a part of them consist only of orthosparite internal moulds of ampullae (about 0.1 mm in diameter) or of subspheric to irregular sparite units, mending both internal moulds and sheaths (Pl. 1, Figs. 2, 6, partly Fig. 1).
The particularly preserved, unique specimen of this species is shown in Pl. 1, Fig. 4. It has a netlike skeleton of fused individual calcified ampullae with micrite filling.Similarly preserved are the oblique sections in Pl. 1, Figs. 5, and 10, both with mixed individually calcified and completely recrystallized ampullae.
The middle part of the secondary laterals, visible in the tangential sections, usually appears as micritic pores (Pl. 1, Fig. 8, d is about 0.025 mm) somewhat in a displaced position.
Relations.Neomeris mokragorensis sp.nov.differs greatly from Neomeris cretacea (STEINMANN) by the skeletal structure and by the form of the reproductive organs (ampullae).The calcareous skeleton of Neomeris cretacea is compact and relatively massive, the ampullae are elongated-ellipsoidal in form.The biometric differences between the two species were given by SCHLAGINTWEIT & EBLI (1995).

Fig. 4 .
Fig. 4. Outcrop of a part of the Albian (Vraconian) deposits (about 15 metres) in the eastern part of Mokra Gora, at the crossing of the road and the railway (Photo: 1970).