ARCHAEORADIOLITES. A NEW GENUS FROM THE UPPER APTIAN OF THE MEDITERRANEAN REGION AND THE ORIGIN OF THE RUDIST FAMILY RADIOLITIDAE by MUKERREM FENERCI-MASSE*, JEAN-PIERRE MASSE*, CONSUELO ARIASt and LORENZO VILASt *Centre de sedimentologie-pal.eontologie, laboratoire associe au CNRS, Universite de Provence, 13331 Marseille Cedex 03, France;e-mails: [email protected]; [email protected] tDepartamento de Estratigrafia, Instituto de Geologia Economica (CSIC-UCM), Facultad de c.c. Geologicas, Universidad Complutense, 28040 Madrid, Spain; e-mails:[email protected];[email protected] Typescript received 7 June 2004; accepted in revised form 7 June 2005 Abstract: Archaeoradiolites gen. novo (Radiolitidae), mainly suggested to be the direct ancestor of Archaeoradiolites, characterized by radially arranged branching walls structur­ which in turn is considered as the progenitor of Eoradio­ ing the outer shell layer, includes two species, Archaeoradio­ lites. The onset of the Radiolitidae is associated with global lites primitivus gen. et sp. novo and Archaeoradiolites oceanic changes that favoured calcite as opposed to aragon­ hispanicus gen. et sp. novo (type species), the distinction of ite biomineralization. The acquisition of a porous shell which is based on size, shell habit and development of the microstructure appears, in many respects, biologically radially branching microstructure. Their geographical distri­ advantageous and may account for gaining a rapid bution is restricted to south-east Spain and south-west « 1 myr) ecological ability for efficient colonization and France, i.e. the Western European Tethyan margin, whereas occupation of space of the family in the earlier phase of its data from the Black Sea coast of Turkey suggest a possible radiation. extension to the Eastern European Tethyan margin. Each species has a distinct biostratigraphic distribution within Key words: rudist bivalves, Upper Aptian, new genus, bios­ the Upper Aptian (mainly the Gargasian). Agriopleura is tratigraphy, evolution. THE Late Aptian-Albian marked the onset of the radi­ shell habit, and the radial plates, muri or walls, that are ation of Radiolitidae, which followed the mid-Aptian orthogonal to the plates, here labelled walls. Walls repre­ crisis that affected shallow water, carbonate platform sent salient infoldings of the plates. This organizational biotas, including rudists (Masse 1989; Masse and mode is found, for instance, in Eoradiolites davidsoni Gallo-Maresca 1997). This family is characterized by (Hill) and other, relatively advanced, forms of the genus specific attributes regarding: (I) shell structure: the cal­ Eoradiolites, and also in some species of Praeradiolites citic outer shell layer tends to exhibit a cellular micro­ and Bournonia, forms in which the resulting, cellular structure, with various geometrical patterns; (2) pattern is mainly quadrangnlar (Amico 1977). The poly­ myocardinal features: myophores of the left valve (LV) gonal cell geometry of the Sauvagesiinae relates to the are represented by vertical, downward-projecting plates same process (Milovanovic 1935) whereas this group into the right valve (RV), teeth are nearly equal and has been considered as a division of the Radiolitidae also project deeply in sockets or gutters of the opposite (Douville 1902). valve. Cellular structures belonging to the foregoing categor­ The so-called cellular structure has been attributed by ies are not observed in all Radiolitidae. For instance, a earlier workers (Palmer 1928; Boggild 1930; Douville radial irregular pattern tends to characterize the genus 1935; Milovanovic 1935; Masse and Philip 1972; Strum Katzeria Sliskovic (Sliskovic 1966; Caffau et al. 1992; and Perkins 1975; Amico 1977) to the association of two Pejovic 2002), while in Rajka Milovanovic walls are rep­ distinct sets of laminae or plates: the funnel plates, here resented by minute columns (Grubic 2002). Moreover, labelled plates, conforming with the overall conical outer some Radiolitidae lack any type of cellular porous microstructures, as m Gorjanovicia Polsak (Polsak 1967), 1993, 1996; Masse et al. 1992, 1998; Gallo-Maresca 1993, which has a compact outer shell, similar to that of the in press) (Text-fig. 1B). The following will focus on Late Monopleuridae. Aptian radiolitid-bearing beds where specimens of The objective of the present paper is to describe a Archaeoradiolites have been collected, mainly the AI­ new genus, Archaeoradiolites, found in the Upper Aptian mansa-Jumilla region, including the Carche (Masse et al. of south-east Spain, characterized by a radially branching 1992), Sopalmo (Arias et al. 1996), Sierra Larga, La Oliva, outer shell microstructure, which departs from that Caroch series, where the stratigraphic distribution of observed in other Radiolitidae, especially the subcontem­ rudists has been calibrated to benthic foraminifera, essen­ poraneous Eoradiolites. The form here described has been tially Orbitolinidae, having potential for distinguishing formerly ascribed to Eoradiolites, essentially Eoradiolites the lower and upper part of the Gargasian, and the plicatus (Hill) (Gallo-Maresca 1993; Masse 1995; Masse Clansayesian. et al. 1998). Identical or closely related forms have also The synthetic stratigraphic section of the Sierra del been reported from south-west France (Masse 1995) Carche (Aptian-Albian) (Text-fig. 2) illustrates the strati­ (Text-fig. lA) and the western Black Sea region of Tur­ graphic distribution of the two species of Archaeoradiolites key (Masse et al. 2002). Because the new taxon is the and also Eoradiolites, in the Gargasian-Clansayesian inter­ oldest Radiolitidae documented until now and has val. The biostratigraphic interpretation that conforms to potential to be the root of the family, we discuss its the Masse et al. (1992) former dating can be summarized relationships with both the progenitor of the Radioliti­ as follows: (1) Orbitolina (Mesorbitolina) pervia Douglass dae, the genus Agriopleura Ktihn, and the genus Eoradio­ and Dictyoconus? pachymarginalis Schroeder mark the lites Douville, formerly regarded as the origin of the Lower Gargasian; (2) Orbitolinopsis? aquitanica Schroeder family. and Poignant and Orbitolinopsis reticulata Moullade and Peybernes identify the Upper Gargasian; (3) Pseudochoffa­ tella cuvillieri Deloffre marks the Clansayesian. STRATIGRAPHY OF THE The tripartite division of the Upper Aptian, based on RUDIST-BEARING BEDS FROM specific micro palaeontological assemblages, is well docu­ SOUTH-EAST SPAIN mented on a regional scale (Arias et al. 1993, 1996) and is corroborated by sequence analysis. The Lower/Upper Radiolitidae have a significant record in the Late Aptian­ Gargasian boundary is marked by a major sedimentary Albian of south-east Spain where they have been reported discontinuity: a subaerial truncation surface followed by from various localities distributed in the Alicante, Valen­ marginal marine or continental sands and sandstones (the cia, Albacete and Murcia provinces (Arias et al. 1989, so-called Montemayor sands), with a wide regional extent. aroch , 200 km I * • , •N • x N I exATIVA I PKOVINC..: ATLANTIC OCEAN .,.J " FRANCE I ALBACETE )(/<:��:;; , PROVIKCE .....+-+- ( '\ X�'><�"''''K (' /x) ..... -1-_-1-\ ,) "t'-"}(/l('...... x t�LCOY ........... , ,... ALIC�"HE PROVI'IlCE ..J MURCIA PROVINCE MEDITERRANEAN SEA 1-__',-0 _......;,20. Km A TEXT -F I G. 1. A, radiolitid-bearing locations in south-west France and south-east Spain. B, radiolitid sites in the Valencia-Albacete and Murcia provinces in south-east Spain (stars indicate fossil-bearing localities). T EX T -FIG. 2. Stratigraphic section of the Aptian-Albian of the Sierra del AGE � " Carche showing the position of Archaeoradiolites species and the FO (first occurrence) of Eoradiolites. 0:: ID 2 w � a. a.I-- I-'-r.r- :::> 4 700 � rw...J Z ·0 « 0 - :2: I- m ri:. ...J LO W 3 « � � 0 ...J I- z « iii 2 w :;: . I- (f) z « 1 .J 0 0:: W 500 .;...;.�.� 3 D... D... ::J zf- I- « - en « (!) 0:: «0:: (!)w S 2 0 ...J � 300 Z V « - � I- -� l- D.. « z « - ...J I :::) 1 limeslones 0 I\i Radiolitids B C \l Polyconitids rudist sandslones W 100 F.=F. D m b::::, Requienids types o Caprinids J 1= I marls @ Solitary corals " oblique & Stromatoporoids b" I bedding � Orbitolinids i 0 0 00ids � ���i� �/��_LithocOdium 1 1 � � Oysters I Chondrodonts T Bioturbation Aside from Archaeoradiolites these stratigraphic sist of Pseudotoucasia santanderensis (Douville), Horio­ sections also document the FO (first occurrence) of pleura gr. almerae Paquier and Polyconites verneuili Eoradiolites sp. sensu stricto. Associated rudists con- (Bayle). SYSTEMATIC PALAEONTOLOGY Archaeoradiolites hispanicus gen. et sp. novo Text-figures 3A, 4-16 The symbols used in the descriptions are as fo llows: LV, left valve; RV, right valve; D, dorsal side; V, ventral side; A, anterior side; P, 1992 Eoradiolites sp.; Masse et aI., pp. 209-201, pI. 4, posterior side; AV c, anteroventral carina; amp, anterior myoph­ fig. 7. oral plate; pmp, posterior myophoral plate; mp, myophoral plate; 1993 Eoradiolites katzeri Sliskovic; Gallo-Maresca, p. 34, at, anterior tooth; pt, posterior tooth; as, anterior socket; et, cen­ pI. 2, figs 2, 4. tral tooth; ps, posterior socket; L, ligament ridge; Ab, anterior 1993 Eoradiolites plicatus (Conrad); Gallo-Maresca, pp. 55- band; Pb, posterior band; Ib, interband. 56, pI. 7, fig. I. Size estimates include dDV, the dorsal-ventral diameter, and 1998 Eoradiolites plicatus (Conrad); Masse et aI., p. 206, clAP, the antero-posterior