Velleditsiella spinaferra, Rigaud & Blau, 2016

Rigaud, Sylvain & Blau, Joachim, 2016, New robertinid foraminifers from the Early Jurassic of Adnet, Austria and their evolutionary importance, Acta Palaeontologica Polonica 61 (4), pp. 721-734 : 725-727

Velleditsiella spinaferra sp. nov.

Fig. 3.

Etymology: From the Latin spina, spine and ferre, to carry; for the spiny external morphology displayed by the new species.

Type material: Holotype: MHNG-75631-2, fully recrystallized adult test in subaxial section, slightly impregnated by Fe-Mn solutions (Fig. 3E). Paratypes: dozens of specimens from the type locality (MHNG-75631 and MHNG-2011-1; e.g., Fig. 3A–D, F–Q).

Type locality: Rot-Grau Schnöll Bruch , Adnet, Austria (see Fig. 1) .

Type horizon: Hettangian–Sinemurian (Lower Jurassic) of the Schnöll Formation and the marmorea crust (see Fig. 1D–F) .

Material.— Type material only.

Diagnosis.—A spiny, high trochospiral Velleditsiella with 2–3 bulged chambers per whorl.

Description.—The test is spiny, high conic elongate, with two to three bulged chambers per whorl (Fig. 3I, O, P). The proloculus is globular (Fig. 3L), followed by trochospirally arranged pear-shaped chambers, moderately enlarging on up to seven whorls. Chambers, loosely coiled and separated

→ Fig. 2. Robertinid foraminifer Velleditsiella felicitaszae gen. et sp. nov., uppermost Hettangian–lowermost Sinemurian, Adnet, Austria. Holotype (B), paratypes (A, C–P). A. MHNG-75631-1, subaxial section. B. MHNG-75631-1, subaxial section. C. MHNG-75631-1, oblique centered section. D. 4a1(2), subaxial, slighty oblique section. E. 1620(2), oblique section. F. 1620(1), oblique section. G. 4a2(8), transverse section. H. 4a2(5), transverse section. I. 1620 (2), transverse section. J. AU1P, transverse section. K. AU1E, transverse section. L. 4a2(6), oblique section. M. 4a1(2), oblique section. N. 4a2(8), subaxial section. O. 4a2(7), centered, slightly oblique section. P. 4a2(5), oblique section. Abbreviations: Ch, chamber; F, foramen; iH, inner hook; L, lamellae; NP, narrowest part of the chambers (open on the siphon); P, perforations; Pr, proloculus; S, siphon; SO, secondary opening.

by slightly curved oblique septa, are connected by a single interiomarginal opening (foramina in Fig. 3A, G, I, L) and delimit a median siphon (Fig. 3B, D–I, K–P). The narrow end of each chamber is directly open on the siphon (e.g., Fig. 3B, E, G, O–P). This additional opening, probable secondary aperture, is related to a small hook, local inner wall deformation of the siphon edge (Fig. 3B, L, O). The siphon is secondarily laminar (Fig. 3H, M). On the spiral side, the suture is slightly overlapped by dorsal extensions of the wall (see Fig. 3H, M). In our material, tests are entirely recrystallized into calcisparite but easily recognizable thanks to the distinctive spines, even when tests are non-impregnated. The original wall structure, primarily bilamellar, finely laminated and very finely perforate, is indirectly preserved in parts finely impregnated by Fe-Mn solutions (e.g., Fig. 3B, E, H, M). This peculiar state of preservation is unique to primarily aragonitic tests and shells ( Rigaud et al. 2013, 2015a). The primary aperture is simple, interiomarginal (Fig. 3B, K).

Dimensions.—The observed specimens of Velleditsiella spinaferra gen. et sp. nov. reach a maximum of about 400 μm in height and 250 μm in width. The spiral angle varies around 40º. The siphon is about 20–25 μm in width. In section, spines commonly reach 10–40 μm in length.

Remarks.— Velleditsiella spinaferra gen. et sp. nov. differs from V. felicitaszae gen. et sp. nov. in its bulged chambers, more irregular coiling, spiny ornamentation and more acute apical angle. It is the only known Duostominoidea with a spiny test.

Thanks to its distinctive spines, which may have played a role of protection, Velleditsiella spinaferra gen. et sp. nov. is easily recognizable in thin section and thus possesses a high biostratigraphic potential. The foraminiferal association is identical to that of V. felicitaszae .

Stratigraphic and geographic range.—Only known from the uppermost Hettangian–lowermost Sinemurian (Lower Jurassic) of Adnet ( Austria).