Morphometric analyses of well-preserved specimens of Crassostrea gryphoides (Schlotheim, 1813) housed at the Croatian Natural History Museum (CNHM) were performed using two different measurement methods. Shell height (H), curved shell height (H’), shell length (L), curved shell length (L’), ligament height (HLig), curved ligament height (H’Lig), ligament length (LLig), curved ligament length (L’Lig) and shell width (W) were measured by a digital calliper and by an elastic ribbon. Their relations were tested in order to select the best methods to distinguish the morphotypes. The obtained results represent a solid base for future studies of oyster ecology.

Pliocene fossil megaflora from the locality Cabuna in Podravina comprises 26 Dicotyledonae taxa, represented with 45 samples of leaves, leaf fragments and fruits. Leaves are of variable sizes, sometimes fragmented, but often well preserved in silty clay, pointing to a sheltered environment such as an oxbow marsh. Approximately 15% of the determined taxa have “entire” leaf margins, while the rest have serrated/toothed leaves. Paleotemperatures were calculated using the Leaf Margin Analyses (LMA) improved for the wet habitats and compared with results obtained by Coexistence Approach (CA), i.e. comparison of optimal temperature and humidity of the determined taxa. Mathematically calculated Mean Annual Temperature (MAT) of 7.806 °C significantly differs from CA results, presuming the MAT of 15 °C and humidity of around 60%. Such a discrepancy might be the consequence of delayed reaction of land flora to rather abrupt cooling, typical for the end of the Pliocene.

Bivalves are nowadays represented by several thousand species of variable sizes and shapes. Additionally, thousands more species occurred during their 500-million-year long evolution. Present on Earth since the Cambrian, the class Bivalvia experienced periods of gradual evolution, interspersed with periods of rapid changes. Some groups of bivalves, namely clams, oysters, scallops, and marine mussels, managed to survive a series of extinctions, and their descendants still thrive in modern oceans and seas. Other groups, such as the rudists, completely disappeared from marine environments, after undergoing successful evolutionary radiation. In this study, we consider the possible reasons for the longevity of some bivalve orders and discuss the possible causes of demise of several once-successful clades. As expected, a small body size, large number of specimens, infaunal mode of life, motility, and long-living planktonic larvae proved to be evolutionary advantages during stress periods. The ability to harbor chemosymbionts could be an additional benefit during biotic crises.

Polymictic gravels exploited in the vicinity of Rugvica, SE from Zagreb, comprise clasts of various lithology, colour, shape, and size. Pebbles are composed of sedimentary, volcanic and, sporadically, metamorphic rocks. During the field work we recognized fossils in the abundant carbonate pebbles. Most of the carbonate clasts are rounded, discoidal in shape, varying in colour from white to dark grey, almost black. Pebbles were measured by a calliper and petrographic thin sections were prepared from fossiliferous pebbles. Numerical analyses pointed to some minor differences in their shape and size, but micropaleontological analyses revealed clasts of Carboniferous, Permian, Triassic, Jurassic, Cretaceous, Paleogene and Neogene age. Most of the Mesozoic and Cenozoic clasts originate from the two local mountain areas (Medvednica Mt. and Samobor Hills), with part of the Jurassic-Cretaceous pebbles possibly derived from SW Slovenia. Irregularly shaped and sometimes poorly rounded clasts of the Paleogene/Neogene ages seem to be abruptly transported to short distances by torrents or streams. The most enigmatic were the clasts of Carboniferous-Permian age. The nearest Palaeozoic outcrops occur upstream in Central Slovenia, but some fossils point to the even longer transport route, from the Karavanks in the upper flow of the Sava River. Gravels are overlain by fine-grained lake sediments and peat coal. Peat comprises significant amount of pine pollen, pointing to the warming period within the Late Pleistocene, which was additionally confirmed by the radiocarbon dating.

Chemosymbiotic bivalves are rare and specialized biota, able to survive in hostile environments. We recorded their presence in the Middle Miocene (Badenian—Langhian/Serravallian) deposits of Northern Croatia. Bivalve specimens, representatives of the families Solemyidae (11 specimens) and Lucinidae (998 specimens), are in most cases preserved as casts and molds. Newly collected specimens (10 lucinids and 2 solemyids) were cleaned up, determined, and housed at the Croatian Natural History Museum and the University of Zagreb, Faculty of Science. Lucinid bivalves are widely dispersed and comprise several taxa, including the most numerous Lucinoma borealis (Linnaeus, 1767), particularly common Lucina (Eomiltha) polymorpha Kochansky, 1944 and Megaxinus ellipticus (Borson, 1825). They were found in deposits of different lithologies, varying from argillaceous marls to limestones. Lucinids are generally considered the most diverse among the chemosymbiotic bivalves, and are widely distributed in various habitats. Some of the collected lucinids lived in the shallower marine, oxygen-depleted environments. We also recorded solemyids and lucinids together with planktic molluscs (pteropods) pointing to the deeper marine environments. The age of the deposits comprising these findings coincides with the Langhian opening of the marine corridors between the Paratethys and the Mediterranean during the highstands, a major faunal turnover event in the Central Paratethys and Miocene Climatic Optimum. Records of chemosymbiotic bivalves and accompanied fauna in the investigated area could point to the further diversification of the Badenian marine environments in this part of the Central Paratethys and their correlation with similar contemporaneous environments and fauna in the Mediterranean.

Bivalves of the genus Neopycnodonte Stenzel, 1971 (Ostreida: Gryphaeidae) are known as common bioconstructors from the mesophotic marine environments of the Cenozoic era. Along with mussels, they are among the first taxa to colonize natural and artificial hard substrates, but they live somewhat deeper, being most common between 50 and 150 m.More than eighty specimens of fossil Neopycnodonte from the Neogene deposits of Mt. Medvednica, the Samoborsko gorje Hills, the Glinsko Pokuplje area and Siena (Italy) are housed in the Croatian Natural History Museum (CNHM) under the names: Ostrea cochlear Poli, 1795, Picnodonta cochlear (Poli, 1795) and Picnodonta (Ostrea) cochlear (Poli, 1795) var. navicularis (Brocchi, 1814). The presence of the Pycnodonteinae subfamily was also recorded from several areas in Croatia during the preparation of the Basic Geological Maps. Like many other oysters, pycnodonteins are highly variable in shape and there have been some doubts concerning their taxonomy. The authors support one of the previously suggested taxonomical schemes (Freneix, 1975), assigning the fossil specimens from CNHM to the species Neopycnodonte navicularis (Brocchi, 1814), which is considered a direct ancestor of the recent N. cochlear (Poli, 1795).

The Croatian Natural History Museum (CNHM) houses rich fossil collections from the Neogene deposits of Northern Croatia, comprising numerous scallops (Bivalvia: Pectinidae). During the Middle Miocene (Badenian = Langhian and early Serravallian), this region was located at the southwestern margin of the Central Paratethys. The value of the CNHM’s historical collections has been presented through taxonomic revisions and biostratigraphic, paleoenvironmental and paleogeographic study. Methods included the cross-checking of specimens from museum boxes with all available published data, systematic revision of scallops, recording the abundance of each taxon, defining the preservation state of the specimens, measuring the morphometric elements and taking photographs of each specimen. After the conducted revision of 624 specimens, the number of registered taxa in the collections was reduced from 52 to 33, and their stratigraphic distribution has been updated. The species Lissochlamys excisa (Bronn, 1831) has been recorded for the first time at the southwestern part of the Central Paratethys. The southernmost Badenian record of Delectopecten vitreus (Gmelin, 1791) known so far has been described. Six types of pectinid habitats have been distinguished, based on the provided paleontological and lithological data, also estimating the scallops’ abundance in each of them. Bioerosion and encrustation traces on scallops’ shells represent an additional contribution to paleoecological studies.

The present paper deals with holoplanktonic gastropods (Pteropoda) from the Middle Miocene (Badenian) deposits of Serbia. The material for the present study comes from three localities at the southern margin of the Pannonian Basin (Central Paratethys): Konjarnik (greater center of Belgra de), Sumijevac stream near Koceljeva (western Serbia), and Radljevo (Kolubara Basin, central Serbia). A total of four taxa were recorded and their stratigraphic value is discussed. Two taxa were identified to species level: Vaginella austriaca KITTL, 1886, belonging to the family Cavoliniidae GRAY, 1850 (1815), and Limacina valvatina (REUSS, 1867)?, from the family Limacinidae GRAY, 1847. Four specimens could only be identified to genus level (Vaginella sp. indet. and Clio? sp. indet.). The specimen of Clio? sp. indet. is possibly the first find of the genus Clio in Serbia. Here presented records of the genera Vaginella and Clio? from the late Badenian (NN6 nannozone) modify the insight into their paleogeographical distribution in the Middle Miocene of the Central Paratethys.

This research is a continuation of the previous biometrical study of the Eocene macroids in Dalmatia (southern Croatia), with the aim to determine the principal bioconstructors and reveal the composition and distribution patterns of macroids during the Paleogene Period. We randomly collected 322 samples of extracted macroids and 12 samples of host rocks, from the beaches between Omiš and Mimice in Dalmatia. Thin sections were prepared at the University of Zagreb/Faculty of Science, studied and photographed using a light microscope with camera. Macroids occur within the Eocene "Nummulitic" packstones, floatstones to rudstones, dominated by the large benthic foraminifera, a common facies of ramp crests, deposited along the coasts of the Tethys Ocean. Algal-dominant genera are Sporolithon and Lithoporella. Among the encrusting foraminifera, Acervulina and Solenomeris prevail. Serpulids, corals, bryozoans, echinoids, crinoids, and other biota also occur as bioclasts, but they are less abundant. Regularly shaped macroids can be classified as rhodoliths, as they are dominated by the genus Sporolithon. Irregularly shaped macroids were formed by the intercalation of red algal and encrusting foraminiferal layers, pointing to the slightly deeper depositional environment. The subsequent demise of green and then red algae, and their replacement with encrusting foraminifera during the Paleogene can be correlated with the basin subsidence and/or increased turbidity, a scenario related to the Alpine tectonics in this area.

The multicoloured ‘Košna’ conglomerates are investigated in the area of the Košna Voda spring, in the Brušane area of Velebit Mt., Croatia. The studied conglomerates consist of red-coloured matrix and clasts of various lithologies (sandstones, limestones, chert and quartz pebbles) and sizes, suggesting provenance from different areas. Average clast size and their percentage was determined by the Udden-Wentworth classification with estimation of the matrix content. Clasts and matrix lithological and mineralogical characteristics were determined using petrographic, ore microscopy, and X-ray diffraction analysis. Sandstone clasts in the studied conglomerates are classified as lithic arenites, subarkoses and arkoses. Limestone clasts are mostly wackestones to packstones with foraminifera, ostracods, echinoid and bryozoan fragments that derive from late Carboniferous/early Permian shallow-marine limestones. Calcispheres and incipient growth forms of Microcodium are also present, suggesting different sediment sources and resedimentation processes. Fragments of fusulinid foraminifera were identified in the matrix of the ‘Košna’ conglomerates. Based on the analyses performed, and field observations, the ‘Košna’ conglomerates are described as early Permian (Cisuralian) polymictic clast-supported to matrix-supported conglomerates and breccia-conglomerates that share structural and textural similarities with conglomerates from other areas in the Dinarides, as well as in the Eastern and Southern Alps. The ‘Košna’ conglomerates are younger than the Sakmarian and are comparable with the Trogkofel limestones of the Carnic Alps and the Karavanke Mts. in Slovenia. We suggest that the studied deposits originated from the uplifted Variscan Mountains during the Variscan and Saalian orogenic movements, and were finally deposited from tractive flows and occasional debris flows in a shallow marine environment of the Palaeo-Tethys, possibly in fan deltas.

Microorganisms have inhabited the oceans since the dawn of Earth. Some of them have organic walls and some produce mineral tests that are usually composed of carbonate minerals or silica. They can therefore be preserved with original parts during sedimentary deposition or fossilized through permineralization or carbonization processes. The most common marine fossil groups studied by micropaleontologists are cyanobacteria, coccolithophores, dinoflagellates, diatoms, silicoflagellates, radiolarians, foraminifers, red and green algae, ostracods, and pteropods. Dormant or reproductive cysts can also be used for determinations of the fossil microbiota. Microfossils can be studied in petrographic slides prepared from rocks or separated from loosely consolidated rocks by disaggregation or dissolution and wet sieving. Their presence is sometimes recognized by biomarkers. Transmitted light microscopy and reflected light stereomicroscopy are necessary for micropaleontological studies whereas scanning electronic microscopy (SEM) aids research on the tiniest fossils and reveals fine skeletal details. Microorganisms have influenced the oxygenation of water and the atmosphere, as well as Earth's carbon cycle and have contributed to the formation of sedimentary rocks. By studying microfossils, paleontologists depict the age of the rock and identify depositional environments. Such studies help us recognize periods of stress in Earth's history and understand their influence on living organisms. Biogenic rocks, made of microfossils, can be used as raw materials, such as fossil fuels, building stone, or additives for the food industry, agricultural, or cosmetic purposes.

Basinal Middle Triassic successions of the Samobor and Žumberak Mts. (north-western Croatia) have historically produced fossils of ammonoids. These finds have, however, largely been neglected in the later literature. This paper describes and redescribes a large collection of ammonoids, most of which were collected by previous researchers throughout the 20th century. Aside from the detailed taxonomic descriptions and revisions, several taxa previously unknown from these localities were identified. Of the species whose holotypes were designated at the Gregruć Breg locality, some are found to be dubious, with validity of other remaining inconclusive and a single taxon, Eoprotrachyceras dorae comb. nov., being treated as valid. Certain Middle Triassic ammonoid genera may also require future comprehensive revisions. A preliminary, modified ammonoid zonal/sub-zonal scheme for the Ladinian of the Tethyan province is proposed, to be inclusive of most of the data from the literature. The need for improvement of the subdivision of this stage is recognized. Based on ammonoids, condensed red nodular limestones of the Gregurić Breg locality (Samobor Mts.) most likely span the Avisianum subzone (upper Illyrian) – Longobardicum subzone (“middle” Longobardian), indicating that subsidence began in the earlier part of the Illyrian. At Mt. Žumberak, scant ammonoid remains indicate that the upper, limestone-rich portion of this succession spans at least the Avisianum subzone (upper Illyrian) – Longobardicum subzone (“middle” Longobardian), but additional data is needed for drawing more robust conclusions. Overall, the timing of basinal deposition is well correlated between Gregurić Breg and Žumberak localities (lower Illyrian – upper Longobardian).

(1) The ancient Paratethys Sea was a spacious inland salt-water basin, extending from the Alps, over Central Europe, to Central Asia. The southwestern part of its central area, the Croatian part of the Pannonian Basin System (CPBS), is generally known for shallow-water deposition and biota. The main purpose of this paper is to emphasize the significance of its less widespread deeper-water deposits in environmental and applied geology. (2) The authors consulted the previously published data, combined with their own results, obtained from the paleontological and sedimentological research, seismic stratigraphy and well-log analyses. (3) During our research in the CPBS, we noticed the connection between the tectonic structures and deep marine canyons and depressions within the Paratethyan shallows. Such structures can be recognized on well-logs and seismic or surface outcrops. They are situated along the faults, and deposits are characterized by the domination of pelagic over the benthic biota, sometimes with visible selective dissolution of aragonite/calcite tests. (4) Studied sedimentary sequences from these structures proved to be a precious source of data on the transgressive-regressive cycles, ancient migrations, modes of deposition and hydrocarbon formation during the Miocene Epoch in the CPBS.

ABSTRACT The Lower Triassic of the Muć-Ogorje area in Central Dalmatia (southern Croatia) is characterized by clastic and carbonate deposits which are investigated through a 230 m thick succession. The fossil associations identified point to a Dienerian age for the lower, and a Spathian age for the upper part of the studied profile, while trace fossils suggest deposits of Smithian age in the middle part, enabling comparisons with other successions in the region. Changes in sedimentology and associated biota throughout the succession, and environmental conditions are reconstructed for seven facies associations, the distribution of which suggests multiple oscillations in relative sea level. Sedimentary structures point to the influence of high environmental energy, possible storms, with signs of tectonic influence in the studied area. The study deposits lack ooid limestone intervals, which are well represented in other Lower Triassic sections in Croatia, Slovenia, Italy, and Hungary. Moreover, the study section exhibits changes in biota abundance, presence of organic-rich laminae and pyrite, as well as changes in siliciclastic input and transgressive-regressive cycles, especially within the upper, Olenekian, part of the succession studied. The results confirm that environmental stress was persistent throughout the Early Triassic, and contribute to our better understanding of the aftermath of the end Permian extinction and the environmental conditions of the western Tethys epicontinental shelf area.

The most numerous and diversified Middle Miocene gastropod collection from Northern Croatia, housed at the Croatian Natural History Museum (CNHM), comes from the Zaprešić Brijeg locality near Zagreb. The gastropod-bearing horizon of the Middle Miocene (Langhian, Badenian) age is today no longer visible on the surface, not only in this area but also in other parts of Northern Croatia. The description of the Zaprešić Brijeg locality and fossil collecting methods can be found in the museum archives and published papers. According to these data, gastropods were collected from "sandstones" during the first half of the 20th century (Gorjanović-Kramberger 1894; Šuklje 1929). Among more than 11000 stored gastropod shells from this locality 45 belong to marine, 2 to marine/brackish and 2 to brackish gastropod families. Some families comprise only one or a few representatives, while other are much more common, such as Potamididae (4459 shells), Nassariidae (2428 shells), Clavatulidae (1813 shells), Turritellidae (1253 shells), and Cerithiidae (508 shells). In previously published papers on the Zaprešić Brijeg gastropod fauna (e.g., Gorjanović-Kramberger 1894; Šuklje 1929; Pavlovsky 1957, 1960) the focus was mostly on the taxonomical aspect. While examining the collection, we observed numerous drilling predation marks in a shape of drill holes on marine gastropod shells and provided numerical analysis of predation marks on some common families (Bošnjak et al., submitted). The aim of this study is to continue the division of gastropod families by their palaeoecology (infauna, epifauna) and feeding type (carnivores, suspension feeders, detritivores and grazers), in order to better understand the palaeoenvironmental conditions during the Middle Miocene (Badenian, Langhian) in this area. Non-marine gastropod taxa indicate the freshwater influx and the vicinity of hinterland. Such a rich museum collection can provide further insight into the palaeoecology of the southwestern margin of the Central Paratethys, even though the original fossiliferous horizon is no more available in the field.References:Bošnjak, M., Sremac, J., Karaica, B., Mađerić, I. & Jarić, A. (submitted): Mollusk mortal kombat: drilled Middle Miocene gastropods from the south-western margin of the Central Paratethys, Croatia.Gorjanović-Kramberger, D. (1894): Geology of Samoborsko gorje Mt. and Žumberak Mt. Rad Yugoslav Academy of Sciences and Arts, 120, 1–82. (in Croatian)Šuklje, F. (1929): Die Mediterranfauna des Zaprešić Brijeg in der Samoborska gora in Kroatien. Bulletin de l'institut geologique de Zagreb, III, 1–52. (in Croatian with German summary)Pavlovsky, M. (1957): Ein Beitrag zur Kenntnis Miozäner Gastropoden von Zaprešić-Brijeg bei Samobor. Geološki vjesnik, 10 (1956), 51–56. (in Croatian with German summary)Pavlovsky, M. (1960): Neue Elemente der Fauna von Zaprešić-Brijeg bei Samobor. Geološki vjesnik, XIII (1959), 213–216. (in Croatian with German summary)

This paper focuses on traces of drilling predation in the middle Miocene gastropod assemblage of the Zaprešić Brijeg locality, Croatia, which provides further insight into the palaeoecology of the south-western margin of the Pannonian Basin System during the Badenian. The analyzed gastropod shells were collected in the first half of the 20th century, and are housed in the Croatian Natural History Museum (CNHM) in Zagreb. The CNHM Zaprešić Brijeg collections contain 11063 gastropod shells, of which 1024 have been identified as drilled (9.3% of the sample), with 633 successfully drilled, 113 unsuccessfully drilled, and 278 multiply drilled shells. The most represented families are Potamididae, Nassariidae, Clavatulidae, Turritellidae, Cerithiidae, Muricidae and Naticidae. The gastropod families Naticidae and Muricidae are recognized as the probable predators based on the shape of the drill holes. Middle Miocene (Badenian) gastropods drilling frequency at Zaprešić Brijeg is 5.72%, which is lower than the recorded Badenian gastropods drilling frequency in the Central Paratethys, while the overall gastropod prey effectiveness from the studied locality (15.15%) is higher than the average of the neighbouring Badenian localities in the Central Paratethys. Among the most represented gastropods at this locality, the highest drilling frequency occurs in the infaunal suspension feeders Turritellidae (14.45%), which mostly show traces of the naticid drilling.

A Journal of Marine Science and Engineering is a widely recognized magazine, published monthly online by MDPI, as an open access and internationally peer-reviewed journal. Its high visibility and rapid publishing, together with well-recognized reviewers make it an interesting choice for a variety of natural scientists, including geologists. Journal statistics and its rapidly increasing rating are the topic of this study.

The basic principles of geological risk calculation through probability of success (PoS) are mostly applied to numerical estimation of additional hydrocarbon existence in proven reservoirs or potential hydrocarbon discoveries in selected geological regional subsurface volumes. It can be adapted and validated for a comprehensive input dataset collected in the selected petroleum province, by dividing up geological events into several probability categories and classes. Such methodology has been widely developed in the last decades in the Croatian subsurface—mostly in the Croatian Pannonian Basin System (CPBS). Through the adaptation of geological categories, it was also applied in hybrid, i.e., stochastic, models developed in the CPBS (Drava Depression), mostly for inclusion of porosity values. As the robustness of this methodology is very high, it was also modified to estimate the influence of water-flooding in increasing oil recovery in some proven Neogene sandstone reservoirs in the CPBS (Sava Depression). This new modification is presented to be applied to geological risk calculation, intending to assess the safety of geological environment storage in deep wells, where spent nuclear fuel (SPN) would be disposed, a subject of great importance. The conceptual study encompassed the magmatic and metamorphic rocks in the pre-Neogene basement of the CPBS, intended to be used for such purpose. Regionally distributed lithologies are considered for nuclear waste disposal purpose, in order to detect the safest ones, considering petrophysical values, water saturation, recent weathering and tectonic activity.