Cribratina hoeverensis Steffahn & Helm sp. nov.: a new ‘larger’ agglutinated foraminiferal species from the Upper Cretaceous (Lower Campanian) of Hannover, NW Germany

A new species, Cribratina hoeverensis sp. nov., is erected to accommodate the youngest known species of the larger agglutinated foraminiferal genus Cribratina Sample, 1932, recovered from Upper Cretaceous beds (Lower Campanian, lingualquadrata Zone and lowermost pilula Zone) east of Hannover, NW Germany.


INTRODUCTION
Several species of free larger agglutinated foraminifera have been found in Upper Cretaceous beds of north-western Germany in the last few years (e.g. Rodriguez, 1987;König, 1994;Riegraf, 1995aRiegraf, , b, 1998. Showing remarkable sizes up to 1 cm, these foraminifera can be easily recognized even in the field. Field work at a well-known locality near Hannover has revealed a previously unknown species of such foraminifera.
In the Höver quarry 'Alemannia' (Fig. 1) these quarrying operations have revealed a substantial exposure of an undisturbed stratigraphic succession from the lowest Lower Campanian (lingua/quadrata Zone) to the lowest Upper Campanian (gracilis/mucronata Zone). The beds have a general dip of 10( towards ENE. Recent findings originating from the lingua/quadrata Zone and lowermost pilula Zone, which crop out extensively on gently inclined slopes in the southwestern part of the quarry 'Alemannia' (Fig. 1), have revealed several free 'larger' calcareous and agglutinated foraminifera (Helm & Steffahn, 1999). The foraminiferal assemblage yields species of Neoflabellina (most abundant N. elliptica), Nodosaria (e.g. N. vertebralis gr.) and different agglutinated species of the well known genus Lituola; these are not further considered in this paper.
Conspicuous is the presence of numerous uniserial, agglutinated specimens which are thought to belong to Cribratina Sample, 1932 a genus previously not known from the Upper Cretaceous of NW Germany. These specimens are here proposed to represent a new species.

MATERIAL AND METHODS
The specimens were obtained by simply collecting them individually from the surface of slightly weathered marl beds and the erosional slopes of the Lower Campanian lingua/quadrata Zone and lowermost pilula Zone (Fig. 2). The bulk of the material was collected between 1995 and 1999. The overall preservation of the Cribratina specimens is good even though the proloculus is broken in most of the tests. The tests were cleansed by ultrasonic treatment and examined with a binocular microscope; ten well preserved specimens were prepared as thin sections (longitudinal and cross-sections); four tests were analysed by SEM.
The specimens are stored in the collection of the 'Niedersächsisches Landesmuseum' (NLM), 'Abteilung Naturkunde', Hannover, Germany (catalogue numbers: Holotype NLM 102.392; Paratypes NLM 102.393 to NLM 102.397). Cribratina Sample, 1932 would be the most suitable genus to describe the species under discussion because of its prominent cribrate aperture and true twofold alveolar wall structure.

GENERIC DETERMINATION
Referring to Arnaud-Vanneau & Prestat (1984), Loeblich & Tappan (1988) and Hart (1995) the assignment of the species to other external similar appearing genera within the Textulariina (the characteristics of these genera are listed in Table 1) can be excluded.
• Atactolituola Loeblich & Tappan, 1984 is about the right size but can be excluded because its wall is always of simple (pseudolabyrinthic) structure and it possesses an initial coil. • Coscinophragma Thalmann, 1951 is a very large genus with a cribrate aperture but is generally branching and possesses a canaliculate wall structure.
• Labyrinthidoma Adams, Knight & Hodgkinson, 1973 is also a very large genus and can be excluded because of its initial trocho-or streptospiral coil. • Polychasmina Loeblich & Tappan, 1946 is very similar in size but its aperture possesses just a single row of slits. • Thomasinella Schlumberger in Peron, 1893 can be excluded because of the simple nature of its aperture and arborescent growth form.
The species under discussion belongs almost unquestionably to Cribratina because it best fits the initial description of the genus from Sample (1932) which is as follows: Test free, nodosarian in shape; chambers numerous, overlapping; apertural chamber larger and better rounded in microspheric than in megaspheric form; proloculum small in microspheric form, large in megaspheric form; sutures depressed; wall medium to finely arenaceous, cement calcareous or ferruginous; aperture terminal, cribrate, composed of numerous subangular openings within an oval area, better developed in microspheric form; size, up to 10 mm.
A more recent diagnosis of the genus from Loeblich & Tappan (1987) is: Test free, large, up to 10 mm in length, elongate, uniserial and rectilinear, chambers closely appressed, sutures straight, horizontal and constricted; wall thick, agglutinated, of medium-to coarse-grained quartz and other mineral particles, with subepidermal alveolar layer; aperture terminal, cribrate, with many irregular and subangular openings on a produced area of the final chamber face.
However, the specimens do not fit entirely the description of the known species of this genus (there is only one recorded species -Cribratina texana) and therefore a new species is proposed here:

Derivation of name.
With reference to the region of origin: sampling locality Höver, NW Germany.

Diagnosis.
A species of Cribratina with several, scarcely overlapping, sturdy chambers -very gradually increasing in breadth and height -bordered by straight occasionally slight oblique sutures giving the chambers a strongly flattened respectively a shallow wedge-like shape. Final chamber is also sturdy, but presents a slightly vaulted apertural face with a terminal, multiple aperture comprising numerous rimmed openings.
Holotype. NLM 102.392 (Pl. 1, figs 1 and 2). Description. Test free, uniserial, rectilinear, sub-cylindrical. Neither coiled or biserial stages nor branching have been observed. Proloculus globular to bulbous. Chambers numerous (23 to 31), distinctly sturdy to closely appressed; all chambers wider than high, very gradually but slightly increasing in size, giving the test a slender conical appearance; intercameral septa are predominantly planar especially in the first two thirds of the test; chambers just scarcely overlapping (Pl. 2, figs 1, 5); the well defined sutures are mostly straight; occasionally oblique sutures giving a wedge-like shape to some chambers; in extreme cases these chambers pinch out, i.e. grow progressively thinner on one side up to total disappearance; last chamber sturdy, having a slightly vaulted apertural face and possessing a multiple 'cribrate' aperture with 21 to 27 rounded to subangular rimmed openings randomly arranged within a round to oval area; the exoskeleton is build up of true alveolar layers which display no polygonal subepidermal network and endoskeletal differentiation like beams and rafters; wall is twofold: (1) an outer thin epidermal layer of agglutinated medium to fine-grained diverse calcareous particles, e.g. bioclastic debris and coccoliths (Pl. 1, figs 3 and 4) and subordinate quartz; (2) an inner thick alveolar subepidermal layer of calciticcemented fine-grained detritus. The alveoli are developed as more or less regular multiple branching blind ending cavities (Pl. 2, figs 1 to 7).  described as being agglutinated of medium-to coarse-grained commonly quartz particles. Nevertheless, it must be admitted that the size and nature of the agglutinated grains alone are not an adequate specific differentiator, as this can reflect environmental conditions rather than specific preferences (see also variations).  are known only from the Comanchean (Upper Aptian to Lower Cenomanian) of Texas and Oklahoma (e.g. Conrad in Emory, 1857:Cribratina texana); the Cenomanian of Tunisia (Arnaud-Vanneau & Prestat, 1984: Cribratina sp.); and Morocco (Butt, 1982: Cribratina texana). Our discovery of Cribratina near Hannover extends the stratigraphical occurrence of the genus up to the late Upper Cretaceous and its geographical distribution into the Boreal Realm of central Europe.