GEOLOGIJA 45/1, 91–96, Ljubljana 2002 Bournonia excavata (D’Orbigny) from the Campanian-Maastrichtian of Stranice (north-east of Slovenia) Bournonia excavata (D’Orbigny) iz kampanija in maastrichtija pri Stranicah (severovzhodna Slovenija) Mauro CAFFAU Dipartimento di Scienze Geologiche, Ambientali e Marine. Università di Trieste. Via E. Weiss 2. E-mail: caffau@univ.trieste.it Key words: Campanian-Maastrichtian, carbonate platform, rudists, Bournonia excavata, Slovenia Klju~ne besede: campanij-maastrichtij, karbonatna platforma, rudisti, Bournonia exca-vata, Slovenija Abstract The rudist fauna of Stranice, in the north-east of Slovenia, has been studied for a long time thanks to the good preservation-state of the specimens found in the calcareous breccias from Campanian-Maastrichtian. The presence of Bournonia excavata (d’Orbigny) at Stranice is reported for the first time in this work. The specimen described in this paper is compared with other specimens from other carbonate platform deposits, previously described by different authors. In addition, a complete individual with both valves of Radiolites angeiodes (Lapeirouse) is described. Kratka vsebina Rudistno favno pri Stranicah v severovzhodni Sloveniji so raziskovali `e dolgo ~asa zaradi dobre ohranjenosti primerkov, ki so bili najdeni v campanijsko-maastrichtijskih apnen~evih bre~ah. Prisotnost vrste Bournonia excavata (d’Orbigny) pri Stranicah je v tej razpravi prvi~ omenjena. Primerek, omenjen v tem ~lanku, je primerjan z drugimi primerki z drugih nahajali{~ na karbonatni platformi, ki so jih `e prej opisali razli~ni avtorji. Razen tega je opisan popoln primerek z obema loputama vrste Radiolites angeiodes (Lapeirouse). Introduction The rudist fauna of Stranice, in the northeast of Slovenia (fig. 1) has been studied by different authors (Pleni~ar , 1971; P l e ni -~ar & Šribar, 1992; P l e n i ~ a r , 1993, 1994 and Caffau, 2000). The rudist association includes the following species: Hippurites conicus (Kühn), H. (Batolites) organisans de Monfort, Hippuritella castroi (Vidal), H. colli-ciatus (Woodward), H. variabilis (Munier-Chalmas), H. lapeirousei (Goldfuss), H. he- ritschi (Kühn), Vaccinites sulcatus (Defrance), Radiolites angeiodes (Lapeirouse), R. cf. au-rigerensis Muniers-Chalmas, Biradiolites ley-chertensis Toucas, B. radix Astre, Sauvagesia meneghiniana (Pirona), Praelapeirouseia bjelusensis Sli{kovi}, P. kossmati Wiontzek, P. wiontzeki Sli{kovi}, P. pajtleri Pleni~ar, Lapeirouseia jouanneti (Des Moulins), L. las-karevi Milovanovi}, L. plana Milovanovic, L. pervinquieri (Toucas) and L. zitteli Douvill~. This fauna is mostly composed of well-preserved individuals, which allowed to de- 08-91-96.p65 17. 09. 02, 8:41 91 Black 92 Mauro Caffau Fig.1. Location map of the rudist deposits of Stranice. Sl.1. Lega nahajali{~ rudistov pri Stranicah. scribe in detail their taxonomic characters (Caffau, 2000). The association of bentho-nic foraminifers allowed to assign the rudist-containing breccia to Campanian-Maastrich-tian (Pleni~ar & Šribar, 1992). Pleni~ar (pers. comm., 2001) and C a f -fau (2000) consider that the rudist association of Stranice has been subjected to a certain degree of reworking. The presence of Bournonia excavata (d’Orbigny) at Stranice is reported for the first time in this work. Besides, a complete individual with both valves of R. angeiodes is described. Systematic palaentology The morphological characters of B. exca-vata are described on the basis of a right valve of a limestone-embedded specimen and therefore, the morphology of the outer ornamentations can only be partially described. For R. angeiodes, we are able to describe all the outer morphological characters of both valves. All specimens found at Stranice that were used for this study are deposesited at the University of Ljubljana. Bournonia Fischer, 1887 Bournonia excavata (d’Orbigny, 1847) Fig. 2 in text. 1907 Bournonia excavata (d’Orbigny); T o u c a s , p. 26, pl. 2, figs. 11-13a. 1912 Bournonia excavata (d’Orbigny); P a r o n a , p. 285, fig. 4 in text. 1968 Bournonia excavata (d’Orbigny); P e j o v i } , pl. 5, fig.2. 1987 Bournonia excavata (d’Orbigny); Ce stari & Sirna, p.145, fig.3. 1989 Bournonia excavata (d’Orbigny); Ce stari & Sirna, p. 717, fig. 11. 1995 Bournonia excavata (d’Orbigny); C a f f a u & P l e n i ~ a r , p. 230; pl. 7, figs. 2, 2a; pl. 12, fig.3. 1995 Bournonia excavata (d’Orbigny); Ce stari & Sartori, p.136. Diagnosis The most evident morphological characters of the attached valve are the anterior band (ab) and posterior band (pb). Although the shell, 1 to 2 mm thick, is partially embedded in the limestone, two ribs (a and b) at the dorsal side can be seen. The recrys-tallization of the shell doesn’t allow to dis- 08-91-96.p65 17. 09. 02, 8:41 92 Black Bournonia excavata (D’Orbigny) from the Champanian-Maastrichtian of Stranice 93 tinguish the pseudo-polygonal structure that characterises the Bournonia genus. Biometrical parameters Morphometrical parameters are indicated in fig.2: Sa (Shell area), Ia (Inner area) and ab^pb (angle formed between the anterior and the posterior radial bands). These parameters were previously used in other studies of radiolitids, for example: Cestari (1992), C a f f a u & P l e n i ~ a r (1996), C a f -fau & Protopsalti (1999) and Caffau (2000). Measures were done on a transversal section of the specimen of Stranice and on the photographs of the other specimens, published by the authors listed in table 1. Ventral side. ab and pb are separated by an interband, a concave region with smooth shell surface. The angle ab^pb is 56° (tab. 1). ab and pb are 2.5 and 3.5 mm wide respectively at the proximal part of the shell, being pb wider and longer than ab. Both radial bands present sharp ends ab is perfectly straight, whereas pb is slightly twisted. Dorsal side. The thickness of the shell varies from 0.3 to 1.5 mm in this side. Two longitudinal ribs a and b (fig. 2) encompass this area giving a pseudo-polygonal shape to the transverse section of the shell. The shell is 1.5mm thick at the ribs, being the mayor thickness of the shell. Comparative analysis of B. excavata specimens from different origins. Some morphometric parameters such as the angle ab^pb, the area of the inner cavity Ia and the area of the shell Sa (fig. 3) were measured on the specimen of B.excavata described in this work. Other rudist associations that include B. excavata, similar to that of Stranice, from the western Peritethyan Upper Cretaceous carbonate platform deposits were described or mentioned, for example, by Pol{ak (1979), Pol{ak et al. (1982), Caffau & Pleni~ar (1995), Cestari & Sirna (1987), Pejovi} (1968), Sirna & Cestari (1989). The same morphometrical parameters were measured on specimens of the same species described by the mentioned authors. Morphometrical values, chronological distribution, localities of origin and bibliographic information are summarised on table 1. (X nribs Sa/la abApb (degree«) locality age this study 2 0,61 56 Stranice north-east Slovenia Campanian-Maastrichtlan CAFFAU & PLENICAR (1995) pi. 7; fig. 2a 2 1,8 50 Trieste Karst north-east Italy Santonian-Campanian CESTARI & SlRNA (1987) pi. 145; fig. 3 2 0,96 55 Southern Salento southern Italy Campanian-Maastrichtlan CESTARI & SARTORI (1995) p. 136 2 1,45 53 Esperia, Latium Central Italy Coniacian-Santonian PARONA(1912) p. 285, fig. 4 2 1,9 56 Central Apennines Italy Santonian PEJOVIC (1968) Pi. 5; fig. 2 2 1,7 55 Jugoslavia Maastrichtian SlRNA & CESTARI (1989) P. 717, fig 11 2 1,1 58 Latium-Abruzzi Central Apennines Santonian-Campanian TOUCAS (1907) p.26, fig. 11a 2 0,97 60 France early Santonian Tab.1. Sa/Ia and abApb values of the specimen of Stranice and of other specimens reported in the literature, coming from different carbonate platform deposits. Tab.1. Vrednosti Sa/Ia in abApb primerka iz Stranic in drugih primerkov z razli~nih nahajali{~ na karbonatni platformi, o katerih poro~ajo v literaturi. 08-91-96.p65 17. 09. 02, 8:41 93 Black 94 Mauro Caffau Fig.2, Bournonia excavata. The thin shell of the specimen is well visible in this figure. The small shell area Sa leads to the low rate Sa/Ia for this specimen. x3. Sl.2. Bournonia excavata. Tenka lupina primerka je na tej sliki dobro vidna. Mala povr{ina Sa na lupini povzro~a za ta primerek nizko razmerje Sa/Ia. x3. The morphometrical values Sa/Ia show a considerable difference between the specimen of Stranice (Sa/Ia = 0.61) and those from other origins (Sa/Ia = 0.96-1.9). These Fig.3 Transverse section of a right valve of Bournonia excavata where the measured parameters are indicated. Sl.3. Pre~ni presek desne lopute vrste Bournonia excavata, na katerem so prikazani merjeni parametri. data strongly suggest that the shell of the specimen under study was subjected to erosion due to transportation, giving a lower rate Sa/Ia than the other specimens of the same species. The values of the angle ab^pb, that do not depend on erosion due to transportation, are in the same range for all the specimens, between 50 and 60 degrees. Stratigraphic distribution. This species is found in France, Italy (Central Apennins, Karst of Trieste, Puglia), Croatia and Spain. Radiolites Lamark, 1801 Radiolites angeiodes (Lapeirouse, 1781) Figs. 4,5,6 in text. 1908 Radiolites angeiodes (Lapeirouse); T o u c a s , p.77, pl.15, figs. 10-15. 1912 Radiolites angeiodes (Lapeirouse); Parona, p. 13, fig.9. 08-91-96.p65 17. 09. 02, 8:41 94 Black Bournonia excavata (D’Orbigny) from the Champanian-Maastrichtian of Stranice 95 1984 Radiolites angeiodes (Lapeirouse); P e j o v i } , p.106, fig. 1 in text; pl.2, figs. 1-5; pl. 3, figs. 1,4; pl. 1,3; pl. 5, figs. 1-3. 1993 Radiolites angeiodes (Lapeirouse); P l e n i ~ a r , p. 50, pl.1, figs. 1-5; pl. 2, figs. 1-3. Diagnosis. The attached right valve of R.angeiodes is cone-shaped and has longitudinal robust ribs. Radial bands are well-marked in the shell. The inner structure is constituted by polygonal cells. At the radial bands, a lamellar structure encompass a mesh of small polygonal cells. The free left valve is slightly convex, with radial tiny ribs and two larger ribs at the radial bands ab and pb. The ligamental ridge is present. Attached right valve. This valve is conic in shape (fig. 4, 6), 30mm long and its diameter is 25mm at the commisure. In the ventral area, the anterior radial band ab is well visible along all the shell and is 5mm wide at the commisure. The ab profile is concave and the surface is transversally crossed by tiny lamellae. pb is slightly concave, presents a smooth surface and is less marked than ab. This band is 3mm wide at the com-misure. Radial bands are separated by pronounced ribs, the interband ribs ib. These interband ribs present a triangular profile and are usually more pronounced than the other ribs in the shell. Ornamentations consists of robust, protruding and longitudinal ribs, with a triangular profile. The width of the ribs varies from 1 to 0.5mm at the bases, the larger ribs Fig.4. Radiolites angeiodes. Attached right valve. View of the anterior radial band ab and posterior radial band pb. x2. Sl..4. Radiolites angeiodes. Pritrjena desna loputa. Pogled na prednjo radialno brazdo ab in zadnjo radialno brazdo pb. x2. Fig.5. Radiolites angeiodes. View of the free left valve with both radial bands. x2. Sl.5. Radiolites angeiodes. Pogled na prosto levo loputo z obema radialnima brazdama. x2. Fig.6. Radiolites angeiodes. Attached right valve. View of the morphology of the anterior radial band and the pronounced interband ribs ib, with triangular profile. x2. Sl.6. Radiolites angeiodes. Pritrjena desna loputa. Pogled na morfologijo prednje radialne brazde ab in {trle~a medsifonalna rebra ib s trikotnim profilom.x2. are located at the dorsal area. The thickness of the shell at the commisure varies from 34mm at the dorsal area, 2-3mm at the po-stero-dorsal and postero-ventral side, to 12mm at the ventral side. The inner structure is characterised by the presence of pseudo-pillars at the radial bands ab and pb. The ab pillar is oval and the pb pillar, although similar in shape, is smaller tha the former 08-91-96.p65 17. 09. 02, 8:41 95 Black 96 Mauro Caffau one. The morphology of the ligamental ridge varies from the most ancient to the most recent part of the shell. It shows a triangular profile at the lower part of the shell and ends with a rectangular profile. Free left valve. This valve (fig. 5) is slightly convex and is ornamented by thin concentric growth lines and tiny radial costulae originating from the cardinal area. The radial costulae present a triangular profile, except those at the radial bands that show a rectangular profile. The width of the radial bands increase from the centre of the shell towards the outer side, 2 to 5mm for ab and 1 to 3mm for pb. The angle between both radial bands ab^pb is 61°. Geographic and stratigraphic distribution. This species was found in Algeria, Austria, Bulgaria, France, Italy (Karst of Trieste, central Apennins, Puglia), Romania, Slovenia, Spain, Tunisia, Turkey and Yugoslavia. Final considerations The low frequence of B.excavata at Stranice, testified by the finding of only one specimen and rare small fragments of other individuals, together with the observations on the preservation state of the shell, allow to conclude that the described individual was subjected to reworking, more than other individuals of other species that constitute the rudist assemblage of Stranice. Moreover, the lower rate Sa/Ia confirms that this specimen was subjected to reworking when compared with other individuals of the same species from different origins. Acknowledgements I would like to thank prof. Mario Plenicar from the Palaeontological Chair of the University of Ljubljana who made possible this research, for the cordial and important moments of discussion during the phases that preceded this work. 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