Velleditsiella felicitaszae, 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

Velleditsiella felicitaszae sp. nov.

Fig. 2.

Etymology: In honor of Felicitász Velledits (Institute of Mineralogy and Geology, University of Miskolc, Hungary) for her paleontological contributions.

Type material: Holotype: MHNG-75631-1, fully recrystallized adult test in subaxial section partly impregnated by Fe-Mn solutions (Fig. 2B). Paratypes: few hundreds of specimens from the type locality (mainly in MHNG-7563; others in MHNG-2011-1; e.g., Figs. 2A, C–P).

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 non-ornamented Velleditsiella forming up to 6–7 predominantly triserially arranged whorls.

Description.—The test is smooth, conic elongate, with a rounded outline. The proloculus is globular (Fig. 2C, O), followed by about three trochospirally arranged pear-shaped chambers per whorl (Fig. 2G–K). Moderately enlarging on up to six-seven whorls, chambers are connected by a single interiomarginal opening (foramina in Fig. 2C, F, H–L) and separated by slightly curved, oblique septa. Loosely coiled, chambers delimit a straight, median siphon, roughly rounded tubular in shape (Fig. 2A, B, G–N, P). The narrow end of each chamber is directly open on the siphon (Fig. 2B, G, P, N). This additional opening, probable secondary aperture, is related to a small hook, local inner wall deformation of the siphon edge (Fig. 2J). The siphon is secondarily laminar (i.e., lined by umbilical lateral laminar extensions of the wall of each additional chamber; Fig. 2A, B). On the spiral side, the suture is covered by thick but short lateral outer laminar extensions of the wall (Fig. 2A, B, E). In our material, tests are entirely recrystallized into calcisparite. The original wall structure, primarily bilamellar, finely laminated and very finely perforate (e.g., Fig. 2A), is indirectly preserved in parts finely impregnated by Fe-Mn solutions. This peculiar type of preservation is unique to primarily aragonitic tests and shells ( Rigaud et al. 2013, 2015a). The primary aperture is simple, interiomarginal.

Dimensions.—The observed specimens of Velleditsiella felicitaszae gen. et sp. nov. reach a maximum of 300 μm in height and 220 μm in width. The spiral angle varies around 60º. The siphon is about 20–25 μm in width.

Remarks.—On account of strong morphological similarities, the Triassic species Trochosiphonia stanleyi Rigaud, Martini, and Vachard, 2015b can be regarded as a solid direct ancestor for Velleditsiella felicitaszae gen. et sp. nov. ( Fig. 5 ). Externally, Velleditsiella felicitaszae gen. et sp. nov. and Trochosiphonia stanleyi are homeomorphic. Internally, however, the two species strongly differ in the chamber– siphon relationship (chambers are slightly appressed, not connected to the siphon and ovoid in Trochosiphonia stanleyi ). The species occurs with representatives of the aragonitic orders Involutinida (i.e., Coronaserra , Coronipora , Frentzenella , Involutina , Kristantollmanna , Licispirella , Papillaconus , Semiinvoluta , Trocholina ) ( Rigaud et al. 2013) and Robertinida (i.e., Velleditsiella spinaferra gen. et sp. nov., Rossanella martinii gen. et sp. nov., Oberhauserella ). Other foraminifers are calcitic nodosariids and miliolids. Involutinida dominate the association, mainly with representatives of the genus Involutina ( Rigaud et al. 2015a) .

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

Figures

Fig. 5. Triassic–Early Jurassic evolution of the order Robertinida at the genus level (partly based on Rigaud et al. 2015b, with new data). Dashed lines indicate uncertain stratigraphic distribution, dotted lines indicate uncertain phyletic relationship.