Me-Cretaciclavulina gusici n . gen . , n . sp . ( ? family Valvulinidae BERTHELIN , 1880 ) , a new larger benthic foraminifer from the lower Campanian of Brač Island , Croatia

The larger benthic foraminifera Cretaciclavulina gusici n. gen., n. sp. is described from the lower Campanian Pučišća Formation of the Island of Brač, Croatia. With its elongate test, trochospiral to uniserial coiling, simple chambers, paraporous wall structure, and areal aperture provided with a cribrate apertural plate, Cretaciclavulina is tentatively placed into the family Valvulinidae BERTHELIN, 1880. Besides Neobalkhania bignoti CHERCHI, RADOIČIĆ & SCHROEDER, 1991, Fleuryana adriatica DE CASTRO, DROBNE & GUŠIĆ, 1994, and Reticulinella fleuryi CVETKO, GUŠIĆ & SCHROEDER, 1997, Cretaciclavulina gusici represents the fourth benthic foraminifera newly described from the Upper Cretaceous shallow-water carbonates of Brač Island. Article history: Manuscript received August 19, 2015 Revised manuscript accepted March 30, 2016 Available online June 1, 2016


GEOLOGICAL SETTING 2.1. Lithostratigraphy
On the Island of Brač, situated along the central part of the Croatian Adriatic coast (Fig. 1), an almost complete, relatively undis- ŠIĆ & JELASKA, 1990), ranging in age from Cenomanian to Maastrichtian (Fig. 2): -The Milna Formation (Cenomanian) comprises bioclastic (including foraminifera, rudists and other mollusca) wackestones to grainstones alternate with microbial laminites, occasional slump features, and rare intraformational breccias (GUŠIĆ & JELASKA, 1990;KORBAR et al., 2012).-The Sveti Duh Formation (uppermost Cenomanian-Lower Turonian) comprises pelagic skeletal wackestones with planktonic foraminifera and calcispheres indicate drown-turbed, and well-exposed Upper Cretaceous succession of the ADCP is exposed.This succession has served as a representative example for the Upper Cretaceous shallow-water carbonate development of the ADCP (Figs. 1, 2).Palaeogene deposits are also present along the northwestern and, as scattered outcrops, along the southeastern coast of the island (Fig. 1).
ing of the ADCP (JENKYNS, 1991;GUŠIĆ & JELASKA, 1990;DAVEY & JENKYNS, 1999;KORBAR et al., 2012 -The Sumartin Formation (Upper Campanian-Maastrichtian) represents the regressive cycles of the Maastrichtian, above the Late Campanian emersion, which were deposited in peritidal environments.The new benthic foraminifer described in the present paper was observed in the Campanian deposits of the uppermost part of the Gornji Humac and are more frequent in the Pučišća Formation (Rasotica and Lovrečina members).PEJOVIĆ & RADOIČIĆ (1987) subdivided the Upper Cretaceous deposits into six formations mainly based on benthic foraminifera and rudists.Six formations were also recognized by GU ŠIĆ & JELASKA (1990), but their litho-and chronostratigraphic interpretation differs from that of PEJOVIĆ & RADOIČIĆ (1987).They emphasized the diachronous character of some formation boundaries (Fig. 2) and subdivided some of them into smaller units.Rudist bivalves and benthic microfossils have been studied comprehensively as biostratigraphic markers for the upper Cretaceous succession of Brač (POLŠAK et al., 1982;GUŠIĆ & JELASKA, 1990;CVETKO TEŠOVIĆ et al., 2001, KORBAR, 2003;STEUBER et al., 2005 and references therein) and the type localities of several taxa are located on the island.

Biostratigraphy
The Pučišća Formation contains especially rich assemblages of larger benthic foraminifera dominated by various imperforate taxa in the Rasotica and Lovrečina members and hyaline foraminifera in the Brač "Marble" Member.These assemblages were used for the interpretation of stratigraphic and palaeoenvironmental features (GUŠIĆ & JELASKA, 1990; CVETKO TE ŠO-VIĆ et al., 2001).CVETKO TEŠOVIĆ et al. ( 2001) described these assemblages in detail including taxonomic, phylogenetic, stratigraphic and palaeoecologic aspects.The Late (but not latest) Campanian age of the Pučišća Formation is largely based on the age determination of the Brač "Marble" Member.GUŠIĆ & JELASKA (1990) gave stratigraphic priority to the relevant and well-studied larger benthic foraminifera (orbitoidids and siderolitids).Based on numeric ages derived from strontium-isotope stratigraphy (SIS) of low-Mg calcite of rudist shells, STEUBER et al. (2005) revised the chronostratigraphy of the Coniacian-Maastrichtian platform carbonates of the island of Brač.According to the strontium-isotope stratigraphy, the Pučišća Formation is mid-Santonian to late Middle Campanian in age.Based on benthic foraminifera, especially Calveziconus lecalvezae CAUS & CORNELLA, the samples containing Cretaciclavulina gusici n. gen.n. sp.can be assigned to the lower Campanian (see revised ranges of FRIJIA et al., 2015).

MATERIAL AND REPOSITORY
The micropalaeontological analysis of samples from the Pučišća Formation was performed on about 200 thin sections.Sections of Cretaciclavulina gusici n. gen, n. sp. were only observed in 15 of them.The investigated samples are the property of the Croatian Geological Survey and their repository (inventory numbers: 10807−10815) is currently in the Geological-Palaeontological Department of the Croatian Natural History Museum, Demetrova 1, Zagreb, Croatia.Diagnosis: Test elongate, trochospiral (most likely triserial) to uniserial, with a short intermediate biserial stage between these.Chambers simple, broad low, enlarging in the triserial stage and of nearly constant width in the uniserial stage.Wall thick agglutinating, and canaliculate (paraporous), possibly with an inner calcareous (?aragonitic) layer.Foramen single interiomarginal in the trochospiral and areal in the uniserial part.Aperture areal, provided with a cribrate apertural plate.
Remarks: The wall structure combined with the elongate test and its trochospiral to uniserial chamber arrangement allow a comparison of Cretaciclavulina with some representatives of the family Palaeotextulariidae GALLOWAY, 1933, Valvulinidae BERTHELIN, 1880, and partly also the Ataxophragmiidae SCHWAGER, 1877, Verneuilinidae CUSHMAN, 1911 as well as Pseudogaudryinidae LOEBLICH & TAPPAN, 1985 (Fig. 3A).
The wall of Cretaciclavulina displays closely spaced, fine and more or less parallel, more rarely bifurcating canaliculi or parapores that are not open to the exterior, but end blindly shortly before the outer test surface (see BANNER et al., 1991;HOT-TINGER et al., 1990;HOTTINGER, 2006, for details) (Fig. 3A).This thin outer "pavement" is commonly eroded.Canaliculi appear scarcer to absent in the septa.The phylogentic relationship concerned with the appearance of such "false keriothecae" (VA-CHARD et al., 2004) is still poorly understood and requires further study (see also RIGAUD et al., 2015).
In the adult chambers of some Cretaciclavulina the outline of an inner calcareous layer, morphologically close to that of the Palaeotextulariidae (Fig. 3B), is preserved.In Palaeotextulariidae, however, the inner layer is clearly yellowish and fibrous whereas that observed in Cretaciclavulina is recrystallized into sparite (?originally aragonitic).It is worth mentioning here that a yellowish inner fibrous calcitic layer was reported recently from the Upper Cretaceous (Coniacian) genus Siphodinarella (SCHLAGINT- WEIT et al., 2014).Axial sections (that usually do not allow bi se rial to be distinguished from the triserial forms) of Cretaci clavulina show morphological resemblance to large-sized palaeozoic Palaeotextulariid genera such as Climacammina BRADY (Fig. 4A), Deckerella CUSHMAN & WATERS (Fig. 4B), and Palaeobiginerina GALLOWAY.These taxa are biserial becoming uniserial in the adult part.The wall structure is originally described as "calcareous, microgranular, commonly with an inner radial fibrous layer" (LOEBLICH & TAPPAN, 1987, p. 218).This view was corrected by PILLER (1990)    shows an early biserial stage, later becoming abruptly uniserial, and an agglutinating, canaliculate wall (Fig. 4H).
It is worth mentioning here that the Mesozoic-Cenozoic taxa that were compared with Cretaciclavulina were all described from isolated specimens recovered from deeper water marly litho logies.Cretaciclavulina instead is reported from typical shallow-water platform carbonates.
Diagnosis: Being monospecific see diagnosis of genus.Description: Test elongate, trochospiral to uniserial.The early stage, rounded triangular (with concave sides), is most likely triserial as visible in transverse sections (Pl.1B) becoming increasingly rounded.In the specimen shown in Pl. 1A, this stage amounts about ~40 % of the total test.The rounded void at the  apex of the holotype specimen possibly refers to the proloculus (Fig. Pl. 1G).Altogether, the information on the initial stage is poor as most random sections are beyond the uniserial stage.Further towards the following uniserial stage, transverse sections of the test become more and more rounded in outline (Pl.1B-E, G).
A short biserial part occurs between the triserial and uniserial stages (Pl.1D).
The adult stage is represented by a series of at least six uniserial chambers.This stage is roughly cylindrical, rectilinear to slightly bent, with chambers that only slightly increase in breadth and height.This accounts for the slender, sometimes slightly bent cylindroconical test morphology.Transverse sections are either circular or slightly elliptical in outline.The solid septa are almost planar (so that the chambers are not overlapping) and pierced by a single foramen in a central to slightly eccentric position.In axial sections, the appressed chambers have a low rectangular shape with rounded margins.Wall agglutinating, with a large amount of microgranular or microagglutinated calcareous material, thick and canaliculate (or paraporous) with fine pores (or canaliculi) ending blindly shortly before the outer test surface (Fig. 3A).This thin outer layer (or "pavement", see HOTTINGER, 2006) is most ly eroded.The pores are straight and more or less parallel (radial arrangement), but may branch in the outer part.In the adult uniserial chambers of the holotype specimen, remnants of an inner calcitic layer are discernible.The thickness of this layer is about 0.04 mm at the lateral walls and is decreasing/tapering upon the septa towards the foramina (Fig. 3B).Foramen single interiomarginal in the trochospiral and areal in the uniserial part.Aperture (last chamber) areal, provided with a cribrate apertural plate (Pl.1I).
Dimensions:  JELASKA (1990, pl. 15, figs. 8, 9) as an "unidentified or unknown foraminifera".The two illustrations presented are a longitudinal section of the uniserial final part cutting nine chambers (op. cit.,pl. 15,fig. 8,refigured here on Pl. 1A,and detail in G).The other one represents an oblique transverse section of the triserial early portion (op.cit.Pl. 15, fig.9, refigured here on Pl. 1C).Based on these sections GUŠIĆ & JELASKA (1990) summarized the characteristics of this taxon comprising "a well-developed keriothecal wall structure, in addition to a comparatively simple morphology and lack of endoskeleton".In fact, this material was insufficient for recognizing the new character of the form based on the combination of the different coiling modes in the early and late test portions.
Transverse sections of the chrysalidinid Praechrysalidina infracreatcea LUPERTO SINNI, 1979 (Aptian of south Italy) (e.g., LUPERTO SINNI, 1985, pl. 6, fig. 5-6) are very similar to those of Cretaciclavulina gusici.P. infracretacea differs from the latter mostly by having a triserially coiled test throughout.Moreover, the early part of the test with its foramina are said to be most likely simple with broad apertural flaps situated at the inner margin, later becoming pierced by numerous areal pores (cribrate) opposed to the single areal foramina in Cretacicla vulina (see also BANNER et al., 1991).
The species Gerochella cylindrica NEAGU (Lower Valanginian of Romania, Fig. 4C) can be considered homeomorphic to Cretaciclavulina gusici, but is more slender (test length up to 1.4 mm; width between 0.24 to 0.29 mm).As already remarked, the wall of G. cylindrical is compact, finely agglutinated, whereas in Cretaciclavulina the wall is canaliculate (paraporous).
With its elongate test, trochospiral later becoming uniserial, the simple chambers, a paraporous wall structure, and probable cribrate apertural plate, Cretaciclavulina is tentatively placed into the family Valvulinidae BERTHELIN, 1880.According to LOEBLICH & TAPPAN (1987, p. 181), the Valvulinidae range in age from the Palaeocene to the Holocene.Cretaciclavulina n. gen.Type species: Cretaciclavulina gusici n. gen., n. sp.Origin of the name: Composite name referring to the Cretaceous and the genus Clavulina D'ORBIGNY.