GC 57-2.indb 1. INTRODUCTION In the Lower Cretaceous of Croatia, notwithstanding the remarkable stratigraphic development of shallow water carbonate platforms, rudist bearing sediments are rare and/or poorly documented. Rudist faunas have been hitherto mentioned from the following localities: – in Istria, in the Kanfanar–Dvigrad area, where Touca- sia rich beds from the Kanfanar Formation, of early Aptian age, were acknowledged (TIŠLJAR, 1978; VLAHOVIĆ et al., 2002, among others). The Veli Brijun Island also exposes a remarkable requie- niid rich locality of Aptian–Albian age (VELIĆ & TIŠLJAR, 1987), – in the Lika region, near Korenica, “Offneria rhod- anica” PAQUIER was collected by POLŠAK (1970) in Aptian limestones, – Tounj, near Ogulin where the presence of requieniids was indicated by VELIĆ & SOKAČ (1978, 1979) in Aptian limestones, Lower Aptian Rudist Faunas (Bivalvia, Hippuritoidea) from Croatia Jean-Pierre MASSE1, Mukerrem FENERCI-MASSE1, Tvrtko KORBAR2 and Ivo VELIĆ2 – from Svilaja Mt., in the hinterland of Split, caprinid facies including a few Offneria sp. and Glossomyo- phorus costatus MASSE, SKELTON & SLIŠKOVIĆ of Early Aptian age was reported by CVETKO- TEŠOVIĆ et al. (2003). The foregoing shows that the Aptian is a key stage for Lower Cretaceous rudist studies in Croatia, as well as in adjacent regions: in Slovenia, where Aptian caprinids have been described by PLENIČAR & BUS- ER (1967) and TURNŠEK et al. (1992), and in Bosnia, where caprinids and caprotinids have been studied by MASSE et al. (1984). The objective of the present paper is to specify the taxonomic position of Lower Aptian rudists found in the Kanfanar area of Istria, and the Tounj area of central Croatia (Fig. 1). This study is based on material col- lected from these two areas and includes the taxonomic reappraisal of caprinids figured from the Lika region, Slovenia and Bosnia. The present contribution includes a description of the regional stratigraphy followed by a systematic palaeontological study of the rudist material. The faunal assemblages are subsequently discussed in terms of biostratigraphy, palaeoecology, palaeogeogra- phy and palaeobiogeography. 2. STRATIGRAPHIC SETTING Lower Aptian shallow water carbonates are widely dis- tributed along the Croatian part of the Karst Dinarides, i.e. within deposits of an ancient Adriatic Carbonate Platform (AdCP). The carbonates were deposited within different platform environments, most frequently within extensive lagoons and protected shallow peritidal set- tings, rarely within bioconstructed bodies. Orbitolinid- bearing limestones are widespread. Rudists appear as the coarsest bioclasts within floatstones intercalated in orbitolinid-bearing limestones or within skeletal car- bonate bodies. There are two well investigated areas in Croatia that are characterized by relatively rudist-rich limestones – western Istria and an area surrounding the town of Ogulin in central Croatia (Fig. 1). 2.1. Kanfanar area in western Istria – – western Croatia The stratigraphic succession of Jurassic and Cretaceous platform carbonates in western Istria is divided into Geologia Croatica 57/2 117–137 13 Figs. 3 Pls. ZAGREB 2004 Key words: Rudist faunas, Lower Aptian, Lower Cre- taceous, Adriatic Carbonate Platform, Croatia. 1 Centre de Sédimentologie et Paléontologie, Université de Provence, UMR 6019–CNRS, F-13331 Marseille, Cedex 3, France; e-mail: jpmasse@up.univ-mrs.fr 2 Institute of Geology, P.O. Box 268, Sachsova 2, P.O. Box 268, HR-10000 Zagreb, Croatia. Abstract Lower Aptian rudist faunas from Croatia consist of Requienia? zla- tarskii PAQUIER, Toucasia sp., Agriopleura sp., Glossomyophorus costatus MASSE, SKELTON & SLIŠKOVIĆ, Himeraelites sp. and Offneria sp. This assemblage has a clear Southern Tethyan (Arabo– African) significance and typifies the Early Aptian. Faunas from the interior of the Adriatic Carbonate Platform in Istria are dominated by Requieniidae while those from the northeastern area in the vicinity of Tounj–Ogulin, close to the platform margin, exhibit a higher diversity and include, beside requieniids, Caprinidae, Caprotinidae and Mono- pleuridae, in conjunction with evidence of open marine conditions. 118 Geologia Croatica 57/2 119Masse et al.: Lower Aptian Rudist Faunas (Bivalvia, Hippuritoidea) from Croatia three megasequences (VELIĆ et al., 1995) bounded by major discontinuities – emersion surfaces represent- ing time periods of subaerial exposure characterized by scattered accumulation of bauxite laterites. The megasequences are of the following chronostratigraphi- cal ranges (VELIĆ et al., 2002): Bathonian–Lower Kimmeridgian (I), Upper Tithonian–Upper Aptian (II) and Upper Albian–Upper Santonian (III). The best outcrops of Aptian carbonates of west- ern Istria are exposed in the Kanfanar area (Fig. 2). They represent the uppermost part of the second mega- sequence. Relatively uniform lithologies imply that the carbonates were deposited within a generally stable lagoonal environment. As a result of Late Aptian–Early Albian subaerial exposure and subsequent erosion, the thickness of Lower Aptian carbonates is highly vari- able, i.e. they are locally absent (see fig. 1 in VELIĆ et al., 1989). Owing to its commercial value, Lower Aptian lime- stones with rudists in Istria are relatively well inves- tigated from a stratigraphic and palaeoenvironmental point of view. The commercial name of the deposits is “Istrian Yellow” (VELIĆ & HVALA, 2002). The limestones have been studied in detail along sections in the Lim valley and Kanfanar quarry (Fig. 3; VELIĆ et al., 1995; TIŠLJAR et al., 1995; VLAHOVIĆ, 1999; Fig. 1 Location map. Fig. 2 Geological sketch-map of the Kanfanar area. 118 Geologia Croatica 57/2 119Masse et al.: Lower Aptian Rudist Faunas (Bivalvia, Hippuritoidea) from Croatia VLAHOVIĆ, et al., 2002). Bacinella-rich beds are the dominant facies, and these include scattered rudists (Fig. 3). The succession of Aptian carbonates around Kanfa- nar has been described in detail by VELIĆ et al. (1995) and VLAHOVIĆ (1999). Underlying Barremian gastro- pod grainstones (bed a in Fig. 3), are overlain by a mas- sive and compact 19.5 m thick interval of oncoid-bear- ing Lower Aptian limestones (Figs. 4 and 5). VLAHOVIĆ (1999) assigned these Aptian carbon- ates to a unique informal Kanfanar Fm. consisting of a lower Sv. Petar Mb. (Lower Aptian massive oncoid- bearing limestones), and an upper Begovac Mb. (top- most Lower Aptian and Upper Aptian limestones). The Sv. Petar Mb. shows a basal interval (2 m thick) composed of rhythmic alternations of Bacinella-oncoid floatstones and mudstones (interval b in Fig. 3). The interval is overlain by an approximately 2.50 m thick Bacinella-oncoid floatstone containing rudists (beds c in Fig. 3) described in Section 3. Overlying the main rudist bed, the main mass of Bacinella-oncoid float- stones containing rare requieniid shells is approximately 15 m thick (interval b’ in Fig. 3). Besides Bacinella irregularis RADOIČIĆ, the lime- stones are characterized by a typical Lower Aptian microfossil association, including: Salpingoporella dina- rica RADOIČIĆ, Palorbitolina lenticularis (BLUMEN- BACH), Sabaudia briacensis ARNAUD-VANNEAU, Fig. 3 Stratigraphic column of Aptian carbonates in the Kanfanar area (modified after VELIĆ et al., 1995). 120 Geologia Croatica 57/2 121Masse et al.: Lower Aptian Rudist Faunas (Bivalvia, Hippuritoidea) from Croatia S. minuta (HOFKER), Vercorsella scarsellai (DE CAS- TRO), V. laurentii (SARTONI & CRESCENTI), Novale- sia distorta ARNAUD-VANNEAU, Praechrysalidina infracretacea LUPERTO-SINNI, Debarina hahouner- ensis FOURCADE et al., Mayncina bulgarica LAUG et al., Voloshinoides murgensis LUPERTO-SINNI & MASSE, Archaealveolina sp. and very rare, but biostra- tigraphically very important, Praeorbitolina cormyi SCHROEDER. Above the Bacinella-oncoid floatstones an approxi- mately 2.7 m thick interval of bioclastic–skeletal grainstones occurs (interval d in Fig. 3) containing Pal- orbitolina lenticularis and other orbitolinids (mostly broken), primitive alveolinids, Pseudonummoloculina aurigerica CALVEZ and rare Pseudolituonella conica LUPERTO-SINNI & MASSE. The interval previously described as Bacinella- oncoid beds is biostratigraphically assigned to the Palorbitolina lenticularis taxon-range zone (VELIĆ et al., 1995). The aforementioned deposits are followed by a 1.5 m thick interval of bioclastic grainstones containing rudist bioclasts (bed e in Fig. 3) that repre- sent a transitional interval between Lower and Upper Aptian deposits in Istria. It is continuously overlain by a thin Upper Aptian sequence consisting of a 0.5 to 1.5 m thick bivalve coquina containing Salpingoporella dinarica and Praechrysalidina infracretacea (bed f in Fig. 3), and by 0.7 to 2.5 m thick biomicrite with abun- dant S. dinarica, frequent P. infracretacea and miliolids (interval g in Fig. 3). These Upper Aptian deposits were assigned by VELIĆ et al. (1995) to the Salpingoporella dinarica abundance zone. The overlying emersion breccia and conglomera- tes, 1.0 to 2.5 m thick, were deposited during the emersion phase from the early Late Aptian to the early Late Albian. They are followed by wackestones to packstone/grainstones containing the following Late Albian orbitolinid and other foraminiferal association: “Valdanchella” dercourti DECROUEZ & MOULLA- DE, Neoiraquia insolita (DECROUEZ & MOULLA- DE), Paracoskinolina fleuryi DECROUEZ & MOUL- LADE, Pseudonummoloculina aurigerica CALVEZ, P. heimi (BONET), Cuneolina pavonia (D’ORBIGNY), C. parva HENSON, Sabaudia auruncensis (CHIOCCHINI & DI NAPOLI), S. minuta (HOFKER), Vercorsella scar- sellai (DE CASTRO), V. laurentii (SARTONI & CRES- CENTI), Mayncina bulgarica LAUG, etc. Finally, it could be concluded that frequent rudist occurrences are limited to the Lower Aptian Bacinella- oncoid floatstones – within interval c in Fig. 3, and the bioclastic grainstones representing the transition from the Lower to the Upper Aptian – bed e in Fig. 3. Rudists occur sporadically within the Bacinella-oncoid intervals b and b’ in Fig. 3. 2.2. Tounj and Ogulin area – central Croatia Lower Aptian platform carbonates in the vicinity of Ogulin (Fig. 6) are characterized by Palorbitolina-lime- stones (“Lower orbitolinid limestones” sensu VELIĆ & SOKAČ, 1978) comprising intercalations of kilometre- long bioclastic–skeletal bodies containing rudists. In contrast to sections in Istria, it is impossible to measure and to describe in detail the Lower Aptian deposits in the area of Ogulin–Tounj due to tectonic disturbance and widespread Neogene and Quaternary cover (Figs. 6 and 8). Therefore, the overall facies char- acteristics of the deposits will be described in a general manner. According to facies characteristics, the Lower Aptian carbonate platform succession of the Tounj area can be subdivided into two parts (Fig. 7). The lower part is represented by orbitolinid-rich (Palorbitolina and Praeorbitolina) wackestones characterized by the presence of calcisphaeres and scattered pelagic micro- fossils – Hedbergella sp., Saccocoma sp. and some lageniids, suggesting an influence from the open sea (VELIĆ & SOKAČ, 1978). Fig 4 Panoramic view of the northern slope of Lim valley (north of Kanfanar) showing the undisturbed Lower Cretaceous well-bed- ded carbonate succession. The massive bed of Lower Aptian Bacinella oncolite (upper third of the succession) is 19.5 m thick. Fig. 5 Polished slab of massive Lower Aptian Bacinella oncolite from Kanfanar quarry containing requieniid shells. These lime- stones are the well-known architectural-building stone named “Istrian Yellow”. 120 Geologia Croatica 57/2 121Masse et al.: Lower Aptian Rudist Faunas (Bivalvia, Hippuritoidea) from Croatia In the upper part of the Lower Aptian deposits, upwardly and laterally to the aforementioned orbito- linid limestones, there are massive, coarse-grained bioclastic–skeletal floatstones to rudstones and skeletal bodies that also contain benthic foraminifera, mainly orbitolinids. Rudists (see Section 3) are associated with corals and gastropods, and fragments of bryozoans, stromatoporoids and other encrusting organisms. Terminal beds of the Lower Aptian, deposited in subtidal–lagoon environments, also belong to the orbitolinid limestones and open marine influences are recorded. Upper Aptian deposits are in normal, continu- ous succession and are characterized by an alternation of algal (Salpingoporella dinarica) wackestones and orbitolinid-rich (Mesorbitolina parva–texana group) packstones/grainstones. They were deposited in shal- low, low current-energy subtidal to higher current-ener- gy peritidal environments during shallowing upward cycles. The overall thickness of the Lower Aptian deposits in the Tounj area can be estimated as more than 300 m (Fig. 7), three times the average thickness in the sur- rounding terrain of central Croatia where it is less than 100 m. This is due to high bioclastic–skeletal produc- tion in coral/rudist environments coupled with the pro- vision of a lot of accommodation space. Biostratigraphically, Aptian deposits are character- ized by development of Palorbitolina-limestones dur- ing the Early Aptian (“Lower orbitolinid limestones” sensu VELIĆ & SOKAČ, 1978, and VELIĆ, 1988), and Fig. 6 Geological sketch map of the Ogulin–Tounj area (after VELIĆ & SOKAČ, 1981). 122 Geologia Croatica 57/2 123Masse et al.: Lower Aptian Rudist Faunas (Bivalvia, Hippuritoidea) from Croatia both maximal development of the alga Salpingoporella dinarica RADOIČIĆ and the first appearance of large Mesorbitolina during the Late Aptian. The complete succession of the “Lower orbitolinid limestones” corresponds to the stratigraphic range of Palorbitolina lenticularis (BLUMENBACH). They contain other Early Aptian index-fossils including Praeorbitolina cormyi SCHROEDER, P. wienandsi SCHROEDER, Orbitolina (Mesorbitolina) lotzei SCHROEDER, Sabaudia briacensis ARNAUD-VAN- NEAU, Neotrocholina friburgensis GUILLAUME & REICHEL, N. aptiensis JOVČEVA, Derventina filipes- cui NEAGU associated with foraminifera of wider stratigraphic range as well as with rare occurrences of Salpingoporella dinarica RADOIČIĆ. Biostratigraphi- cally, these deposits could be assigned to the Palorbi- tolina lenticularis taxon-range zone. Fig. 7 Stratigraphic column of the Upper Baremian–Lower Aptian in the Ogu- lin–Tounj area. 122 Geologia Croatica 57/2 123Masse et al.: Lower Aptian Rudist Faunas (Bivalvia, Hippuritoidea) from Croatia The stratigraphic position of the rudist-containing bodies in the wider area of Tounj, i.e. in central Croatia, is within the upper part of the Bedoulian. It corresponds to the range of P. wienandsi and O. (M.) lotzei, in asso- ciation with other aforementioned benthic foraminifera. Limestones characterized by the mass appear- ance of the alga Salpingoporella dinarica (S. dinarica abundance zone) overlie the described Lower Aptian deposits in the area of Tounj, similar to the precisely described Aptian facies development in Istria (see Sec- tion 2.1.). Upwardly, the first appearance of the large Mesorbitolina indicates the presence of Gargasian deposits. 3. SYSTEMATIC PALAEONTOLOGY The repository of rudist specimens described in the present paper is at the Centre de Sédimentologie–Palé- ontologie, Université de Provence, Marseille. Neverthe- less, owing to the fact that most of the studied mate- rial was observed on natural outcrops of more or less compact and massive limestones, the corresponding specimens are expected to be still “in situ”. The sym- bols used for descriptions are as follows: UV – upper valve; LV – lower valve; D – dorsal side; V – ventral side; A – anterior side; P – posterior side; pmp – poste- rior myophoral plate; pmc – posterior myophoral cav- ity; pm – posterior myophore; am – anterior myophore; at – anterior tooth; as – anterior socket; ct – central tooth; pt – posterior tooth; ps – posterior socket; bc – body cavity; cp – cardinal platform; L – ligament crest/dorso-ventral axis; com – commissure; ab – ante- rior band; pb – posterior band; ib – interband; cl – outer calcitic shell layer; hcp – horizontal concave partitions; tab – body cavity tabulae. Order Hippuritoida NEWELL, 1965 Superfamily Hippuritoidea GRAY, 1848 Family Requieniidae DOUVILLE, 1915 Genus Requienia MATHERON, 1842 Requienia? zlatarskii PAQUIER, 1903 Pl. I, Figs. 1–7 At Kanfanar quarry, besides Toucasia as formerly men- tioned by various authors (see in VLAHOVIĆ et al., 2002), requieniids are represented by numerous sec- tions showing: – a lower valve with a lamellar anterior side, a smooth posterior side, a pronounced, acute, ventral carina, and lacking a myophoral plate (PI. I, Figs. 1, 3, 4, 7), – a moderately convex upper valve with a well-defined body cavity (PI. I, Figs. 1, 2, 4, 5), – on both valves, a cardinal platform extending over nearly 1/3 of the dorso-ventral axis (PI. I, Figs. 4, 5). The apparent absence of myophoral processes in both valves and the relatively wide development of the cardinal platform suggest muscle attachment onto this platform. Assuming that this interpretation is cor- rect, this leads us to exclude the present material from Requienia, because the genus is characterized by a pos- terior myophoral plate in the upper valve (DOUVILLE, 1915). Similarly Matheronia seems inadequate because in the representatives of this genus (especially Math- eronia virginiae GRAS, the type species) the cardinal Fig. 8 Tounj quarry. Fault contact (in the centre of the photograph) of well-bedded Albian limestones (K1 6, on the left) and thick-bedded to massive Lower Aptian rudist limestones (bK1 5, on the right). Elevation from the bottom to the top of the quarry is approx. 80 m, comprising an approximately equally thick part of the Lower Aptian succession. 124 Geologia Croatica 57/2 125Masse et al.: Lower Aptian Rudist Faunas (Bivalvia, Hippuritoidea) from Croatia platform is poorly developed and muscle attachment is on the walls of both valves (PAQUIER, 1903; DOU- VILLE, 1915). Lovetchenia possesses a wide cardinal platform on both valves but muscles are attached on the widened and thickened commissural edges (MASSE, 1993). Notwithstanding the foregoing difficulties to find a genus for housing our material we tentatively place it close to Requienia zlatarskii PAQUIER (PAQUIER, 1903). This form and Requienia petersi TOULA as well (TOULA, 1902) posses a lower valve with a lamellar anterior side, a smooth posterior side, an acute ventral carina, while the upper valve is slightly convex. Where- as R. zlatarskii displays a small myophoral plate on the posterior side of the upper valve the internal characters of Requienia petersi are nearly unknown. Because the later was poorly described R. zlatarskii appears more appropriate for our material. Genus Toucasia MUNIER CHALMAS, 1873 Toucasia sp. PI. II, Figs. 1–6 In the Kanfanar area this genus is represented by numerous randomly oriented sections of isolated lower valves or bivalve specimens, with several whorls (PI. II, Figs. 2, 3). The lower valve shows a rounded posterior side and a nearly flat anterior side. The dorso–ventral axis (DV) ranges from 5 to 8 cm, while the antero–pos- terior one (AP) fluctuates from 4 to 6 cm. The cor- responding ratio (AP/DV) is therefore 0.8 to 0.75, a value close to those of Toucasia carinata MATHERON (MASSE et al., 1998a). On juvenile specimens and/or sections of the juvenile part of the shell the junction between the posterior and the anterior site is character- ized by an acute ventral carina (PI. II, Fig. 4) which tends to disappear in adults (PI. II, Figs. 2, 3, 5, 6). The posterior myophoral plate of the lower valve, a diagnos- tic attribute of the genus, corresponds externally to a dark line and/or a small groove. The transverse section of the myophoral plate has a low triangular shape on both valves (PI. II, Figs. 2, 3, 5, 6). At Tounj Toucasia is also present. In both localities the absence of complete, isolated specimens, precludes a precise identification of the species. Family Monopleuridae MUNIER CHALMAS, 1873 Genus Agriopleura KÜHN, 1932 Fig. 9 (A–B) At Tounj, longitudinal sections ascribed to this genus are characterised by a triangular shaped lower valve indicating a conical morphology and a depressed, con- cave upward, upper valve (Fig. 9). The lower valve has a smooth outer surface. Sections with elongated slender teeth and myophoral bulges connected to the inner side of the upper valve are also present. Thin sections, cut in the rock bearing Agriopleura specimens, show the acel- lular outer shell (calcitic) layer with an oblique, some- times wavy growth banding (Fig. 9B). The absence of well preserved transverse sections preclude observation of the radial bands and the overall configuration of the myocardinal apparatus, especially the ligamental crest and surrounding cavities, all characters with strong taxonomic implications at the species level. Fig. 9 Agriopleura sp., Tounj. (A) field photograph showing a bouquet-like aggregation of mainly upward oriented (life position) shells. The typical attributes of the genus are: a) concave upper valve, b) sub-triangular outline of the lower valve, c) elongated teeth. (B) Longitudinal oblique thin section showing a compact shell structure with growth banding. 124 Geologia Croatica 57/2 125Masse et al.: Lower Aptian Rudist Faunas (Bivalvia, Hippuritoidea) from Croatia Family Caprotinidae (GRAY, 1848) SKELTON, 1978 Genus Glossomyophorus MASSE, SKELTON & SLIŠKOVIĆ, 1984 Glossomyophorus costatus MASSE, SKELTON & SLIŠKOVIĆ, 1984 Fig. 10 (A–B) Our material was collected at Tounj and is mainly rep- resented by transverse sections of the lower valve with an elliptical outline (linked to a dorso–ventral com- pression) and a well defined (dark coloured), strongly ribbed, outer shell layer. The ventral zone shows a relatively wide slightly elevated anterior band and a narrow, ribbed and salient, posterior band. The inter- band corresponds to a narrow acute groove. Notice that in sections close to the apex the shell outline is nearly circular with some antero–posterior compression and the outer shell ornamentation less vigorous especially on the dorsal side. Internal characters consist of a row of three holes: two sockets and a myophoral cavity for the teeth and the myophoral plate of the opposite valve, respectively. All these attributes conform to the defini- tion of Glossomyophorus costatus MASSE, SKELTON & SLIŠKOVIĆ (1984). Family indet. Genus Himeraelites DI STEFANO, 1889 Himeraelites sp. PI. III, Figs. 1–4 We ascribe to this genus a set of transverse sections of the lower valve found at Tounj. The outline is rounded with a slightly antero–dorsal–postero–ventral com- pression. The dorso–ventral axis (DV) is 3.2 to 4 cm in long, while the antero–posterior one (AP) is 2.5 to 3 cm. The corresponding ratio (AP/DV) is therefore 0.75 to 0.85. Nevertheless, it is about 1 close to the apex. The outer shell layer is very thin (about 1 mm) with fine costulation which is frequently missing (due to micritization) while the inner (originally aragonitic) shell layer is thick (1.6–1.8 cm) on the dorsal side and thinner on the ventral side (0.3–0.4 cm). Owing to the sparitisation of the dorsal side, the cardinal elements are poorly defined, nevertheless the acute central tooth and the adjacent anterior socket are frequently detectable through the paramorphic preser- vation of antecedent aragonitic structures (PI. III, Figs. 2–4). The thin ligamental cavity is bent towards the anterior side and deeply penetrates into the dorsal side until the central tooth. There is an anterior inner thickening corresponding to the anterior myophore, the posterior one is assumed to be located on the thickened posterior side. Family Caprinidae D’ORBIGNY, 1847 Genus Offneria PAQUIER, 1905 Fig. 11 (A–B) From central Croatia, POLŠAK (1970) described Off- neria rhodanica PAQUIER represented by a portion of the upper valve showing the diagnostic attributes of the genus Offneria. Whether the figured specimen (POLŠAK, 1970, fig. 2, p. 147) belongs to O. rhodanica or O. murgensis MASSE (MASSE, 1992) is not clear. In contrast, figures of rudist specimens from southwest- ern Slovenia (Trnovski Gozd), provided by PLENIČAR & BUSER (1967), identified as Caprina cf. douvillei PAQUIER and Offneria rhodanica PAQUIER, clearly belong to Offneria murgensis MASSE. This assignment is based on the complex canal network observed on specimens from plate II, figs. 1 and 2 of PLENIČAR & BUSER (1967), whereas fig. 2 illustrates a lower valve with a well developed canal system (a feature unknown in Caprina douvillei ), while the canal organisation of Offneria rhodanica is more simple, especially at the Fig. 10 Glossomyophorus costatus, Tounj. (A) Transverse section of a lower valve showing the main attributes of the species: ornamenta- tion, radial bands and internal myocardinal characters. (B) Interpretation of A. 126 Geologia Croatica 57/2 127Masse et al.: Lower Aptian Rudist Faunas (Bivalvia, Hippuritoidea) from Croatia articulation between the ventral and posterior sides of the shell. On plate V, fig. 2 in PLENIČAR & BUSER (1967) a similar configuration is shown. Offneria rhodanica collected in the Kladanj area (Bosnia) and mentioned by MASSE et al. (1984) has not been described nor illustrated hitherto. A reappraisal of this material (lower valve housed in Masse collec- tion) shows the following characters (Fig. 11): – the ventral side bears a continuous row of canals and is slightly depressed; canal walls are bifurcated at the posterior/ventral junction, – on the posterior side the inner row of wide canals flanking the myophoral plate is surrounded externally by a row of numerous small canals, – on the anterior side there are several rows of polygo- nal or rounded canals, the size of which decreases outward, – the body cavity possesses tabulae, – horizontal concave partitions are present locally in canals having a relatively large size, – vertical walls dividing canals are common, – the thin calcitic outer shell layer is preserved near the articulation between the anterior and ventral sides. This set of characters typifies Offneria murgensis MASSE (MASSE, 1992; CHARTROUSSE, 1998). 4. DISCUSSION 4.1. Biostratigraphy Toucasia is documented from the Upper Hauteriv- ian (MASSE et al., 1998d) to the Albian (DOUVILLE, 1915; MASSE, 1996). Agriopleura is also known to appear in the Upper Hauterivian (MASSE, 1996; MASSE et al., 1998b) and became extinct in the mid- Aptian. Himeraelites was originally described from the Albian–Cenomanian (DI STEFANO, 1889) and possesses a significant record in the Albian from Italy (MASSE et al., 1998c). It was also documented from the Upper Aptian of Algeria (CHIKHI AOUIMEUR, 1983), from the mid-Aptian of Saudi Arabia (HUGHES, 1998), and the Lower Aptian of southern Italy (MASSE, 1992). There is no clear taxonomic framework for pre- Albian species, the detailed biostratigraphic distribution of which is therefore unknown. Requienia zlatarskii was found by PAQUIER (1903) in Bulgaria, in beds ascribed to the Barremian. Closely related forms were also mentioned by PAQUIER (1908) from Serbia in orbitolinid limestones consid- ered Barremian to Lower Aptian in age. R. cf. zlatarskii was identified by one of the present authors (JPM) in the Lower Aptian of Bosnia and in southern Dobrodja (Romania), too. A closely related form was figured from the Zonguldak area (Western Pontids – Turkey, MASSE et al., in press) and from Algeria (FLIERT, 1952), but in the latter case figures are lacking. Glossomyophorus costatus and Offneria are typical Lower Aptian species (MASSE et al., 1984; MASSE, Fig. 11 Offneria murgensis, Kladanj, Bosnia. (A) Transverse section of the lower valve showing the canal architecture and myocardinal ele- ments. (B) Interpretation of A. 126 Geologia Croatica 57/2 127Masse et al.: Lower Aptian Rudist Faunas (Bivalvia, Hippuritoidea) from Croatia 1992; BARON-SZABO & STEUBER, 1996; MASSE et al., 1998b; SKELTON & MASSE, 2000). In conclusion, notwithstanding taxonomic uncertain- ties concerning the species of Toucasia, Agriopleura, and Himeraelites, the presence of Requienia? zlatarskii, Glossomyophorus costatus and Offneria murgensis sug- gests an early Aptian age for the Croatian faunas. This is also in accord with the micropalaeontological data. 4.2. Palaeoecology and palaeogeographic setting Early Aptian times represented a significant change in platform settings, relative to antecedent Valangin- ian–Barremian conditions. While pre-Aptian platforms in the region were dominated by intertidal or restricted subtidal conditions without rudists, the Aptian was marked by the onset of more open conditions with the dominance of subtidal settings where rudists have a sig- nificant record. This trend is also documented on neigh- bouring Periadriatic platforms where the Early Aptian appears to have been a golden age for rudist develop- ment (SARTORIO, 1986, 1987; MASSE, 1992). Oligospecific associations of Toucasia and Requie- nia? zlatarskii found at Kanfanar in a muddy substrate document the proximal zone of the inner platform rud- ist bearing domain, excluding severely restricted subti- dal and intertidal settings. More diverse rudist faunas including Glossomyophorus, and Himeraelites, as well as corals, stromatoporoids, hydrozoans, bryozoans, etc., with a tendency for shell aggregation, found at Tounj, tend to indicate the distal zone of the inner platform rudist-bearing domain, i.e. more open setting than those at Kanfanar. Rudists and other organisms flourished within a high energy belt where skeletal remains accu- mulated or were transported locally, either basinward into a relatively deeper subtidal or backward – into a restricted lagoon, behind prograding bioclastic–skeletal bodies. Similar settings may be expected for the Offne- ria-bearing sediments from central Croatia, by compari- son with palaeoecological models from the Middle East (MASSE et al., 1998b; BORGOMANO et al., 2002). The recent extent of the Adriatic carbonate platform (AdCP) deposits and position of the discussed Aptian Fig. 12 Recent extent of Adriatic Carbonate Platform deposits (1) and surrounding domains, showing the position of Lower Aptian rudist-rich skeletal limestones (2). 128 Geologia Croatica 57/2 129Masse et al.: Lower Aptian Rudist Faunas (Bivalvia, Hippuritoidea) from Croatia deposits (Fig. 12; DRAGIČEVIĆ & VELIĆ, 2002), provide a clue for understanding the palaeoenviron- mental settings. Kanfanar was located in the inner part of the platform, possibly 50 km from the platform edge, facing the Belluno basin. In contrast, Tounj was situated close to the platform edge facing the Slovenian–Bos- nian basin. These locations may also explain the vertical development of rudist-rich limestones in the two areas. The Kanfanar area may be regarded as a relatively sta- ble, i.e. low or moderately subsiding, platform interior. However, the platform edge facing the Slovenian–Bos- nian basin is known as a dynamic, unstable and tec- tonized margin (e.g. CHARVET, 1970; COUSIN, 1973; BLANCHET, 1975; JELASKA, 1987; BUSER, 1989; PAMIĆ et al., 1998; DRAGIČEVIĆ & VELIĆ, 2002, etc.), expected to promote strongly subsiding blocks and possibly an outer platform escarpment. 4.3. Palaeobiogeography In Aptian times Toucasia had a wide extent in the Mediterranean and outside the Mediterranean regions (MASSE, 1985). Agriopleura had also a wide extent in the Mediter- ranean region and occurred on African and European Tethyan margins (MASSE, 1985). In France and Swit- zerland, Agriopleura species are recorded in the Upper Hauterivian–Barremian and are missing in the Lower Aptian. In contrast in the Arabo–African domain, Agriopleura is mainly documented from the Lower Aptian (MASSE, 1992; HUGHES, 1998; SKELTON & MASSE, 2000). This contrasting palaeobiogeographical distribution through time suggests an African affinity for the Croatian Agriopleura. Requienia zlatarskii (see biostratigraphy) seems to be a Balkan element present on both European and Afri- can margins, but with a restricted palaeobiogeographi- cal distribution, running from the Pontides to Serbia and Bosnia through Moesia. Croatia is the southernmost location of this species (Fig. 13). Glossomyophorus costatus was firstly recognized from Saudi Arabia, Southern Italy and Bosnia (MASSE et al., 1984). It has currently been widely observed in other regions of the eastern Mediterranean and Middle East (Oman, United Arab Emirates, Somalia, Northern Italy, Greece and North Africa – SKELTON & MASSE, 2000; Fig. 13). This species is therefore a south Tethyan (Arabo–African) palaeobiogeographical marker. Offneria murgensis, the presence of which is highly suspected in Central Croatia but well established in Slovenia and Bosnia, is also an Arabo–African form (MASSE, 1992; HUGHES, 1998; MASSE et al., 1998b). 5. CONCLUSION Lower Aptian rudist faunas investigated at Kanfanar (Istria) and Tounj (central Croatia) consist of Requie- niidae: Requienia? zlatarskii, Toucasia sp. (close to T. carinata), Monopleuridae: Himeraelites sp. and Agrio- Fig. 13 Palaeogeographic reconstruction of the Mediterranean and Middle East Tethyan domain during the Early Aptian (modi- fied, after MASSE et al., 1993) showing the distribution of Glos- somyophorus costatus in the Arabo–African margin, and Requienia zlatarskii restricted to the Balkans and Black Sea region of Turkey. 128 Geologia Croatica 57/2 129Masse et al.: Lower Aptian Rudist Faunas (Bivalvia, Hippuritoidea) from Croatia pleura sp., Caprotinidae: Glossomyophorus costatus, and Caprinidae: Offneria sp., probably O. murgensis. Besides the typical Early Aptian species (Offneria murgensis and Glossomyophorus costatus), poorly defined species of Himeraelites and Agriopleura, also have Lower Aptian affinities. The associated benthic foraminifera, mainly the Palorbitolina–Praeorbitolina doublet, corroborates the foregoing age assignment. The Croatian rudist assemblage closely resembles the Italian one although some elements (Glossomyo- phorus, Offneria) have been reported from neighbour- ing areas of Slovenia and Bosnia. Notwithstanding its South Tethyan (Arabo–African) palaeobiogeographic significance this assemblage also shows Balkan forms (Requienia? zlatarskii). Faunas from Kanfanar are dominated by low diver- sity (Requienia? zlatarskii, Toucasia) and low den- sity assemblages associated with Bacinella dominated biotopes, in relatively restricted settings of the Adriatic Carbonate Platform interior. In contrast, faunas from Tounj are more diverse (Toucasia, Glossomyophorus, Himeraelites and Agriopleura) and consist of densely packed assemblages associated with corals and other encrusting organisms. The corresponding thick congre- gations mark the proximity to an outer margin of the Adriatic Carbonate Platform, facing the Slovenian–Bos- nian basin, and open marine conditions. Acknowledgements This paper has benefited from the careful review of Th. STEUBER (Bochum, Germany) and P.W. SKELTON (Milton Keynes, United Kingdom) who helped to improve our manuscript. This paper resulted from the projects UMR 6019–CNRS (Centre de Sédimentologie et Paléontologie, Université de Provence, Marseille, France), and No. 0181001 and 0181009 supported by Ministry of Science, Education and Sport of the Republic of Croatia. 6. REFERENCES BARON-SZABO, R.C. & STEUBER, T. (1996): Korallen und Rudisten aus dem Apt im tertiären Flysch des Parnass- Gebirges bei Delphi–Arachowa (Mittelgriechenland) [Aptian Corals and Rudists in Tertiary flysch of Parnass Mountains near Delphi–Arachowa (Central Greece) – in German].– Berliner Geowiss. Abhandl., E18, 3–75. BLANCHET, R. (1975): De l’Adriatique au bassin Pannoni- que – essai d’un modèle de chaîne alpine [From Adriatic to Pannonian – a proposed model for the Alpine chain – in French].– Mém. Soc. géol. France, 53 (120), 1–172. BORGOMANO, J., MASSE, J.-P. & AL MASKIRY, S. (2002): The lower Aptian Shuaiba carbonate outcrops in Jebel Akhdar, northern Oman: Impact on static modeling for Shuaiba petroleum reservoirs.– Am. Assoc. Petrol. Geol. Bull., 86/9, 1513–1529. BUSER, S. (1989): Development of the Dinaric and the Julian Carbonate platforms and of the intermediate Slovenian basin (NW Yugoslavia).– Mem. Soc. Geol. Ital., 40 (1987), 313–320. CHARVET, J. (1970): Aperçu géologique des Dinarides aux environs du méridien de Sarajevo [Geological outline of Dinarides in the area south of Sarajevo – in French].– Bull. Soc. Géol. de France (7), 12/6, 986–1002. CHIKHI AOUIMEUR, F. (1983): Etude paléontologique de quelques rudistes de l’Aptien supérieur du Djebel Ouenza (Algerie nord-orientale) [Palaeontological study of some Upper Aptian rudists of Djebel Ouenza (Northeastern Algeria) – in French].– Géologie méditerranéenne, 10, 33–48. CHARTROUSSE, A. (1998): Les Caprinidae (Rudistes) du Cretace inférieur [Lower Cretaceous Caprinidae (Rudists) – in French].– Unpubl. PhD Thesis, Université de Provence, Marseille, 289 p. COUSIN, M. (1973): Le sillon slovène: les formation triasi- ques, jurassique et neocomiennes au Nord-Est de Tolmin (Slovénie occidentale, Alpes meridionales) et leur affinites dinariques [The Slovenian Trough: Triassic, Jurassic and Neocomian formations northeast of Tolmin (western Slovenia, southern Alps) and their Dinaric affinities – in French].– Bull. Soc. Géol. France (7), 15, 326–339. CVETKO-TEŠOVIĆ, B., BUCKOVIĆ, D., JELASKA, V., GUŠIĆ, I. & KORBAR, T. (2003): Lower Cretaceous platform deposits of Mt. Svilaja.– In: VLAHOVIĆ, I. & TIŠLJAR, J. (eds.): Evolution of Depositional Environ- ments from the Palaeozoic to the Quaternary in the Karst Dinarides and the Pannonian basin. Excursion Guide- book, 22nd IAS Meeting of sedimentology – Opatija, Cro- atia, 83–92, Zagreb. DI STEFANO, G. (1889): Studi stratigrafici e paleontologici sui sistema Cretaceo della Sicilia. 1. Gli strati con Capro- tina di Termini-imerese [Stratigraphical and palaeontolo- gical study of the Cretaceous system of Sicily. 1. Deposits with Caprotina of Tremini-imerese – in Italian].– Atti della Reale Accademia di Scienze, Lettere e Belle Arte di Paler- mo, 10, 44 p. D’ORBIGNY, C. (1847): Considérations zoologiques et géolo- giques sur les Brachiopodes ou Palliobranches [Zoological and geological considerations on Brachiopods and Pallio- branches – in French].– Compt. Rend. Hebd. Séanc. Acad. Scien., 25/7, 266–269. DOUVILLE, H. (1915): Les Requieniides et leur evolution [Requieniiids and their evolution – in French].– Bull. Soc. Géol. France, 4/14, 383–389. DRAGIČEVIĆ, I. & VELIĆ, I. (2002): The northeastern mar- gin of the Adriatic Carbonate Platform.– Geol. Croat., 55/2, 185–232. FLIERT, J. VAN DE (1952): Liste des rudistes du Crétacé du Constantinois [List of Cretaceous rudists of the Con- stantine area – in French].– In: DELEAU, P. (ed.): Les pays Constantinois. XIXeme Congrès Géologique Interna- tional Alger, Monographies Regionales, 13, 47–52. GRAY, J.E. (1848): On the arrangement of the Brachiopoda.– Annals and Magazine of Natural History, 2, 435–440. 130 Geologia Croatica 57/2 131Masse et al.: Lower Aptian Rudist Faunas (Bivalvia, Hippuritoidea) from Croatia HUGHES, G.W. (1998): Middle East Aptian rudist–forami- niferal–algal associations and their possible modern Arabi- an Gulf analogue.– Geobios, Mem. spec., 22,147–158. JELASKA, V. (1987): Paleoambijentalna dinamika sjevero- istočnog rubnog prostora Vanjskih Dinarida u juri i kredi (Jurassic and Cretaceous paleoenvironmental dynamics of the northeastern margin of the Outer Dinarides).– Geol. vjesnik, 40, 195–216. KÜHN, O. (1932): Rudistae. Fossilium Catalogus, I: Animalia [Rudistae. Fossil Catalogue, I: Animals – in German].– Pars 54. Gustav Feller, Neubrandenburg, 200 p. MASSE, J.P. (1985): Paléobiogeographie des rudistes du domaine peri-méditerranéen a l’Aptien inférieur [Palaeobiogeography of Early Aptian rudists in the peri- Mediterranean domain – in French].– Bull. Soc. Géol. France, 8/5, 715–721. MASSE, J.P. (1992): Les rudistes de l’Aptien inférieur d’italie continentale: aspects systematiques, stratigraphiques et paléobiogeographiques [Lower Aptian rudists of continental Italy: systematic, stratigraphic and palaeo- biogeographic aspects – in French].– Geol. Romana, 28, 243–260. MASSE, J.P. (1993): Systematique, stratigraphie et paléogeo- graphie du genre Lovetchenia (Requieniidae) du Crétacé inférieur méditerranéen [Taxonomy, stratigraphy and palaeogeography of the genus Lovetchenia (Requieniidae) of the Mediterranean Lower Cretaceous – in French].– Geobios, 26/6, 699–708. MASSE, J.P. (1996): Lower Cretaceous rudist biostratigraphy of southern France, a reference for Mesogean correla- tions.– Revista Mexicana Ciencias geologicas, 12/2, 236–256. MASSE, J.P., BELLION, Y., BENKHELIL, J., BOULIN, J., CORNEE, J.J., DECOURT, J., GUIRAUD, R., MASCLE, G., POISSON, A., RICOU, L.E. & SANDULESCU, M. (1993): Lower Aptian 114–112 Ma.– In: DERCOURT, J., RICOU, L.E. & VRIELYNCK, B. (eds.): Atlas Tethys, Palaeoenvironmental Maps, Maps. BEICIP–FRANLAB, Rueil Malmaison. MASSE, J.P., ARIAS, C. & VILAS, L. (1998a): Lower Creta- ceous rudist faunas of southeast Spain: an overview.– Geo- bios, Mem. spec., 22, 193–210. MASSE, J.P., CHARTROUSSE, A. & BORGOMANO, J. (1998b): The lower Cretaceous (Upper Barremian–Lower Aptian) caprinid rudists from Northern Oman.– Geobios, Mem. spec., 22 , 211–223. MASSE, J.P., GALLO MARESCA, M. & LUPERTO-SINNI, E. (1998c): Albian rudist faunas from southern Italy: taxonomic, biostratigraphic and palaeobiogeographic aspects.– Geobios, 31, 47–59. MASSE, J.P., GOURRAT, C., ORBETTE, D. & SCHMUCK, D. (1998d): Hauterivian rudist faunas of southern Jura (France).– Geobios, Mem. spec., 22, 225–233. MASSE, J.P., ÖZER, S. & FENERCI, M. (in press): Upper Barremian–Lower Aptian rudist faunas from the western Black Sea region (Turkey).– Cour. Forsch. Inst. Secken- berg. MASSE, J.P., SKELTON, P.W. & SLIŠKOVIĆ, T. (1984): Glossomyophorus costatus nov.gen. nov.sp., rudiste (Caprotinidae) nouveau de l’Aptien du domaine médi- terranéen central et oriental [Glossomyophorus costatus nov.gen. nov.sp., new Aptian rudist (Caprotinidae) of central and eastern Mediterranean – in French].– Geo- bios, 17, 723–732. MATHERON, P. (1842): Catalogue méthodique et descriptif des corps organisés fossiles du Département des Bouches- du-Rhone et lieux circonvoisins [Catalogue of fossil orga- nisms of the Bouches-du-Rhone and neighbouring areas – in French].– Carnaud Fils, Marseille, 269 p. MUNIER CHALMAS, H. (1873): Prodrome d’une classifica- tion des rudistes [Introduction to rudist classification – in French].– Journal de Conchyliologie, 3, 71–75. NEWELL, N.D. (1965): Classification of the Bivalvia.– Ameri- can Museum Novitates, 2006, 1–25. PAMIĆ, J., GUŠIĆ, I. & JELASKA, V. (1998): Geodynamic evolution of the Central Dinarides.– Tectonophysics, 297, 251–268. PAQUIER, V. (1903): Les rudistes urgoniens. Premiere partie [Urgonian rudists. Part one. – in French].– Mém. Soc. Géol. France, Paléontologie, 11, 1–46. PAQUIER, V. (1905): Les rudistes urgoniens. II Serie inverse [Urgonian rudists. II “Serie inverse” – in French].– Mém. Soc. Géol. France, 29/13, 47–102. PAQUIER, V. (1908): Sur les rudistes de l’Urgonien de Serbie [On Urgonian rudists of Serbia – in French].– Mém. Soc. Géol. France, 8, 1–108. PLENIČAR, M. & BUSER, S. (1967): The Cretaceous macro- fauna in the Western part of the Trnovski Gozd.– Geolo- gija, 10, 147–159, Ljubljana. POLŠAK, A. (1970): Offneria rhodanica du Cretace inferieur de la Lika en Croatie [Offneria rhodanica from the Lower Cretaceous of Lika in Croatia – in French].– Geol. vjesnik, 23, 145–149. SARTORIO, D. (1986): Caprinid patch reef in the Cansiglio inner platform carbonate sequence (Southern Alps): a record of the Earliest Aptian transgression.– Riv. Ital. Paleont. Strat., 92, 383–400. SARTORIO, D. (1987): Reef and open episodes on a carbona- te platform margin from Malm to Cenomanian: the Can- siglio example (southern Alps).– Mem. Soc. Geol. Ital., 40, 91–97. SKELTON, P.W. (1978): The evolution of functional design in rudists (Hippuritacea) and its taxonomic implications.– In: YONGE, C.M. & THOMPSON, T.E. (eds.): Evolutionary Systematics of Bivalve Molluscs. Philosophical Transacti- ons Royal Society, London, B248, 305–318. SKELTON, P.W. & MASSE, J.P. (2000): Synoptic guide to Lower Cretaceous rudist bivalves of Arabia. Middle East Models of Jurassic–Cretaceous carbonate systems.– Soc. Econ. Paleont. Miner., Spec. Publ., 69, 89–99. TIŠLJAR, J. (1978): Oncolites and stromatolites in Lower Cretaceous carbonate sediments in Istria (Croatia, Yugosla- via).– Geol. vjesnik, 30/2, 363–382. TIŠLJAR, J., VLAHOVIĆ, I., MATIČEC, D. & VELIĆ, I. (1995): Platformni facijesi od gornjeg titona do gornjega alba u zapadnoj Istri i prijelaz u tempestitne, klinoformne i rudistne biolititne facijese donjega cenomana u južnoj Istri 130 Geologia Croatica 57/2 131Masse et al.: Lower Aptian Rudist Faunas (Bivalvia, Hippuritoidea) from Croatia (ekskurzija B) Platform facies from the Upper Tithonian to Upper Albian in western Istria and transition into tempestite, clinoform and rudist biolithite facies of the Lower Cenomanian in southern Istria (Excursion B).– In: VLAHOVIĆ, I. & VELIĆ, I. (eds.): 1. hrvatski geološki kongres (First Croatian Geological Congress), Vodič ekskurzija (Excursion guide-book), 67–110, Zagreb. TOULA, F. (1902): Geologische Untersuchungen im östli- chen Balkan und in anderen Theilen von Bulgarien und Ostrumelein [Geological investigations in the eastern Balkans and in other parts of Bulgaria and East Romania – in German].– Denkschrifen der Kaiserlichen Akademie der Wissenschaften, Mathematisch-naturwissenschaftliche Klasse, 59, 409–478. TURNŠEK, D., PLENIČAR, M. & ŠRIBAR, Lj. (1992): Lower Cretaceous fauna from Slovenski vrh near Kočevje (south Slovenia).– Razprave IV razreda SAZU, 33, 1–14, Ljubljana. VELIĆ, I. (1988): Lower Cretaceous benthic foraminiferal biostratigraphy of the shallow-water carbonates of the Dinarides.– Revue de Paléobiologie, Vol. Spéc. 2 (Ben- thos ‘86), 467–475, Genève. VELIĆ, I. & HVALA, M. (2002): Istrian rudist limestones as architectural-building stone.– In: VLAHOVIĆ, I. & KOR- BAR, T. (eds.): Abstracts and Excursion Guidebook. 6th International Congress on Rudists, Rovinj, 141, Zagreb. VELIĆ, I. & SOKAČ, B. (1978): Biostratigraphic analysis of the Jurassic and Lower Cretaceous in the wider region of Ogulin, central Croatia.– Geol. vjesnik, 30, 309–337. VELIĆ, I. & SOKAČ, B. (1979): Younger Lower Cretaceous and Lower Cenomanian. Excursion C: Karlovac–Ogulin of central Croatia.– 16th European Micropaleontological colloquium. Ljubljana, 147–156. VELIĆ, I. & SOKAČ, B. (1981): Osnovna geološka karta SFRJ 1:100.000, list Ogulin L 33–103 (Basic geological map of SFRY 1:100.000, Ogulin sheet).– Institut za geološka istraživanja Zagreb (1976), Savezni geološki institut, Beograd. VELIĆ, I. & TIŠLJAR, J. (1987): Biostratigraphic and sedi- mentologic characteristics of the Lower Cretaceous depo- sits of the Veli Brijun Island and comparison with the corresponding deposits in SW Istria (Western Croatia, Yugoslavia).– Geol. vjesnik, 40, 149–168. VELIĆ, I., TIŠLJAR, J. & SOKAČ, B. (1989): The variability of thicknesses of the Barremian, Aptian and Albian carbo- nates as a consequence of changing depositional environ- ments and emersion in western Istria (Croatia, Yugosla- via).– Mem. Soc. Geol. Ital., 40, 209–218. VELIĆ, I., MATIČEC, D., VLAHOVIĆ, I. & TIŠLJAR, J. (1995): Stratigrafski slijed jurskih i donjokrednih kar- bonata (bat–gornji alb) u zapadnoj Istri (ekskurzija A) (Stratigraphic succession of Jurassic and Lower Creta- ceous Carbonates (Bathonian–Upper Albian) in western Istria (Excursion A)).– In: VLAHOVIĆ, I. & VELIĆ, I. (eds.): 1. hrvatski geološki kongres (First Croatian Geological Congress), Vodič ekskurzija (Excursion guide- book), 31–66, Zagreb. VELIĆ, I., TIŠLJAR, J., VLAHOVIĆ, I., MATIČEC, D., KORBAR, T., MORO, A. & ĆOSOVIĆ, V. (2002): Geo- logical evolution of Istria (NW part of the Adriatic Car- bonate Platform, Croatia).– In: VLAHOVIĆ, I. & KOR- BAR, T. (eds.): Abstracts and Excursion Guidebook. 6th International Congress on Rudists, Rovinj, 83–93, Zagreb. VLAHOVIĆ, I. (1999): Karbonatni facijesi plitkovodnih talož- nih sustava od kimeridža do gornjega alba u zapadnoj Istri (Carbonate facies of shallow water depositional systems from Kimmeridgian to the Upper Albian in western Istria – in Croatian with English summary).– Unpubl. PhD Thesis, University of Zagreb, 327 p. VLAHOVIĆ, I., TIŠLJAR, J., VELIĆ, I., MATIČEC, D., SKELTON, P.W., MORO, A. & KORBAR, T. (2002): Apti- an deposits with Requieniids below a Late Aptian–Early Albian regional emersion surface (Kanfanar and Dvigrad, central Istria).– In: VLAHOVIĆ, I. & KORBAR, T. (eds.): Abstracts and Excursion Guidebook. 6th International Congress on Rudists, Rovinj, 95–100, Zagreb. Manuscript received February 17, 2004. Revised manuscript accepted November 08, 2004. 132 Geologia Croatica 57/2 133 PLATE I Requienia? zlatarskii, sections from Kanfanar quarry. 1–2 Anterior–posterior cross sections of bivalve specimens showing the lamellar anterior side, convex upper valve, the body cavity of which is separated from the lower part by a well defined cardinal platform. 3 Ibidem. Upper valve absent. 4–5 Dorso–ventral cross sections of bivalve specimens showing the body cavity of the upper valve and the cardinal platform. 6–7 Field photographs showing the strong anterior–posterior asymmetry and the ventral carina. 132 Geologia Croatica 57/2 133Masse et al. PLATE I p 1 3 6 l cm - A 7 134 Geologia Croatica 57/2 135 PLATE II Toucasia sp., sections from Kanfanar quarry. 1 Dorso–ventral cross section of a bivalve specimen showing the myocardinal characters. 2 Transverse-oblique section showing the spirogyrate organisation of the lower valve and the posterior myophoral plate. 3 Section close to Fig. 2, myophoral elements not preserved. 4 Tranverse oblique section of the lower valve showing the posterior myophoral plate. 5 Transverse section of a lower valve showing the posterior myophoral plate. 6 Transverse section of a lower valve showing the myocardinal elements. 134 Geologia Croatica 57/2 135Masse et al. PLATE II p 1 em - A 136 Geologia Croatica 57/2 137 PLATE III Himeraelites sp., Tounj. 1–2 Transverse section of the lower valve and interpretation of the myocardinal features. 3–4 Ibidem. Notice the development of the inner formerly aragonitic shell, the calcitic, finely ribbed outer shell is partly preserved on specimen 1–2 (arrow). 136 Geologia Croatica 57/2 137Masse et al. PLATE III p p D L ,- , , I ,_ ... ct ....... _ - .... \ I /'" , I pt / l /l '" at I " - I , I mp, I , , \ , , , , be - - , '- , ma , A 2 -----, 1 em / , , ,et ....... - - - 'I ' I I , 1_ .... ,\\ at \ ....... 1 'J \ I I I , Impl , , \ , 4 , , I I' , ... '" I \ ---' rna' , , , , be A v v 138 Geologia Croatica 57/2