Strictocostella, Patterson, 1987

Vénec-Peyré, Marie-Thérèse & Poignant, Armelle, 2010, Status of foraminiferal collections from the Tertiary Basin of Vienna, and revision of Dentalina spinosa d’Orbigny, 1846 and Nonionina boueana d’Orbigny, 1846, Geodiversitas 32 (3), pp. 479-491 : 483-484

Strictocostella ? spinosa (d’Orbigny, 1846) ( Fig. 3 A-H)

Dentalina spinosa d’Orbigny, 1846: 55 , pl. 2, figs 36, 37. — Cushman 1929: 86, pl. 13, figs 7, 8. — Amato 1974: 84, pl. 1, figs 9, 23.

Dentalina spinosa – Papp & Schmid 1985: 34, pl. 17, figs 1, 2. Non d’Orbigny, 1846.

TYPE MATERIAL. — The lectotype here designated and 4 paralectotypes ( MNHN FO 45, d’Orbigny collection).

TYPE LOCALITY. — Baden ( Austria).

OTHER MATERIAL EXAMINED. — Several topotypes, among them topotypes MNHN F62163 and MNHN F62164 . — 5 specimens from Saubrigues (Aquitaine Basin, France).

DIAGNOSIS

“Coquille allongée, mince, fragile, peu arquée, ornée en long de six côtes non interrompues, saillantes, très élargies et mucronées en arrière, formée de loges ovales séparées les unes des autres par un très fort étranglement, dont la dernière est un peu acuminée en avant. Cette charmante espèce, l’une des plus remarquables du genre, se distingue de toutes les autres par ses côtes peu nombreuses, qu’une pointe termine en arrière” (d’Orbigny 1846).

FIXATION AND DESCRIPTION OF THE LECTOTYPE This species was described from the locality of Baden. The d’Orbigny Vienna Basin collection at the MNHN includes a mount (MNHN FO 45) containing five specimens labelled “ Dentalina spinosa, Baden ”. These specimens correspond well with d’Orbigny’s original description of Dentalina spinosa . Four of the specimens possess three chambers, one has four chambers which are highly fissured. The last chamber in all the specimens is broken. We designate the best preserved specimen, third from the left (marked with a black dot), as lectotype of Dentalina spinosa d’Orbigny ( Fig. 3C ).

Description

Test elongate (774 µm in length), straight, uniserial, composed of 3 chambers equal in size, the first ones missing; sutures horizontal; intercameral foramen at the end of a small neck and bordered by a small lip; surface with prominent and translucent costae (6 or 8 by chamber) which seem to be discontinuous and ended in a spine.

ADDITIONAL OBSERVATIONS

The topotypes, selected by M. Lys when he revised the d’Orbigny collection ( Lys & Sigal 1947), were examined with SEM ( Fig. 3A, B ). The proloculus possesses elongate, protruding basal spines ( Fig. 3F ). Several different (6 or 8) longitudinal plate-like costae form a thin peripheral flange. Some of these costae run from a part of a chamber to another part of either the next or the previous one, crossing the sutures ( Fig. 3G, H ). They are more or less alternating around the same chamber. Other costae do not cross the sutural area and end in short spines at the chamber base. A few spines, independent from the costae, are also observed at the base of the chambers ( Fig. 3E ). A round aperture, with a bordering lip, is placed on a small, slightly flaring neck ( Fig. 3D ). The neck is set in a small depression. No tooth or tooth-like projections are visible.

In their revision of the Austrian collection, Papp & Schmid synonymized Dentalina spinosa with Dentalina elegantissima under the current valid name Nodosaria elegantissima . They incorrectly fixed the lectotype of Dentalina elegantissima in vial 36; it is registered under the number GBA 1981/03/64. The d’Orbigny collection of the MNHN also includes 3 syntypes of Dentalina elegantissima mounted in MNHN FO 38. A comparison of these specimens with the Dentalina spinosa material and the original illustrations by d’Orbigny shows that the two species clearly differ. Dentalina elegantissima has a slender test, more chambers, and a sutural area that is less constricted. Its costae are less prominent, fewer in number and extend the entire length of the test. In addition, Dentalina elegantissima has no spines at the base of chambers and a longer neck. The aperture is difficult to observe. We designate here the best preserved specimen, underlined by a dot on the slide, as the lectotype of Dentalina elegantissima .

STRATIGRAPHICAL DISTRIBUTION

D’Orbigny pointed out that Dentalina spinosa is rare, whereas D. elegantissima is frequent at Baden. Dentalina spinosa has been little mentionned in the literature. Cushman (1929) reported it from the late Tertiary of Venezuela, Amato (1974) indicated that this species is abundant in the Upper Oligocene of SW France (Chattian of Saint-Étienne-d’Orthe, Aquitaine Basin) and Cahuzac & Poignant (2004) mentionned that it is very rare in the upper Burdigalian of the SW France (Saubrigues, Aquitaine Basin).

GENERIC ATTRIBUTION OF DENTALINA SPINOSA Since d’Orbigny’s initial description, the genera Dentalina and Nodosaria have been divided into several different taxa ( Loeblich & Tappan 1987). The assignment of d’Orbigny’s species to one of these taxa is difficult because the apertural characters are not obvious on the type specimens. Due to the rarity of this species, we only examined a few specimens by SEM. Based on the general morphology and ornamentation, this species could be related to Strictocostella Patterson, 1987 . Due to the absence of the last chamber, the SEM photographs are not conclusive regarding the presence or absence of the tooth which is diagnostic of Strictocostella .

Figures

FIG. 3. — A-H, Strictocostella? spinosa (d’Orbigny, 1846); A, topotype (Baden) (MNHN F62163); B, topotype (Baden) (MNHN F62164); C, lectotype (MNHN FO 45); D, E, enlargements of A; F, enlargement of A showing the chamber basal spines; G, H, enlargements of B showing (arrows) the alternating costae running from a part of a chamber to another part of the next chamber; I, J, Nonion commune (d’Orbigny,1846),specimen from Baden (MNHN F62166); K-M, Nonion boueanum (d’Orbigny, 1846); K, specimen from Baden (MNHN F62165); M, lectotype (MNHN FO 94). Scale bars: 100 μm.