Rossanella martinii, 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 : 727-729

Rossanella martinii sp. nov.

Fig. 4.

Etymology: In honor of Rossana Martini (Department of Earth Sciences, University of Geneva, Switzerland) for her contributions to foraminiferal studies and biostratigraphy.

Type material: Holotype: MHNG-2011-1-716a, fully recrystallized, Fe-Mn impregnated test in subaxial section, showing the scroll-shaped inner-chamber structure (Fig. 4B). Paratypes: dozens of specimens from the type locality (MHNG-75631 and MHNG-2011-1; e.g., Fig. 4A, C–M).

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.—As for the genus, by monotypy.

Description.—The test is involute, low convexoplane to subplanoconcave, circular in outline, with a subrounded margin. The proloculus is globular (Fig. 4A, D, F, H, I 1, L), followed by about six to seven trochospirally coiled chambers per

→ Fig. 3. Robertinid foraminifer Velleditsiella spinaferra gen. et sp. nov., uppermost Hettangian–lowermost Sinemurian, Adnet, Austria. Holotype (E), paratypes (A–D, F–P). A. MHNG-75631-1, subaxial section. B. 1620(2), oblique section. C. 1620(2), oblique section. D. 1620(2), subaxial section. E. MHNG-75631-2, subaxial section. F. 1620(8), subaxial section. G. MHNG-75631-2, oblique section. H. 1620(3), subaxial, slightly oblique section. I. 4a2(8), transverse, slightly oblique section. J. 1620(2), oblique section. K. MHNG-75631-2, oblique section. L. 1620(2), centered, subaxial section. M. 1620(9), oblique section. N. 1620(8), oblique section. O. 1620(3), transverse, slightly oblique section. P. 1620(2), transverse section. Abbreviations: A, aperture; Ch, chamber; F, foramen; iH, inner hook; NP, narrowest part of the chambers; P, perforations; Pr, proloculus; S, siphon; SO, secondary opening; Sp, spine.

whorl on up to three-four whorls. Chambers, ovoid, slightly appressed in the juvenile part, progressively become subrhomboid and more angular. Separated by curved, oblique septa, they gradually increase in size and communicate via a wide, arch-like interiomarginal opening, as the aperture (Fig. 4A, I 1, K–M). Each chamber develops wall extensions that rapidly cover the spiral side of the test and progressively fill the umbilical depression (compare Fig. 4A, B, F, H, L). The test surface, usually not ornamented, may present minor protuberances (bumps) on the spiral side, related to local thickenings of the wall lateral extensions (e.g., Fig. 4L). An inner-chamber, scroll-shaped structure is fused to the aperture floor and extends, in a subvertical to oblique position, to the opposite wall of the chamber (e.g., Fig. 4B, D, I, K, M). Our specimens are all recrystallized into calcisparite. The ghost preservation of fine details of the original wall structure, such as laminae and fine perforations (e.g., in Fig. 4A–C, H) is due to an early Fe-Mn impregnation of walls.

Dimensions.—Specimens of R. martinii reach 280 μm in height and 450 μm in width. The proloculus shows a diameter ranging from 40–60 μm and chambers may attain 170 μm in height. Perforations, very fine, are about 2 μm in diameter.

Remarks.—The new species R. martinii is morphologically close and most likely phylogenetically related to the Upper Triassic species Praereinholdella galei Rigaud, Martini, and Vachard, 2015b . Praereinholdella galei only differs from R. martinii in its round aperture, internally simple chambers, and more angular test periphery. The subfamily Praereinholdellinae is also considered as the probable ancestor of the subfamilies Garantellinae , Epistomininae , and Reinholdellinae (see Rigaud et al. 2015b). As Rossanella gen. nov., the genera Epistomina Terquem, 1883 , Reinholdella Brotzen, 1948 , and Garantella Kaptarenko-Chernousova, 1956 also acquired their inner-chamber structures in the Lower Jurassic. The foraminiferal association is identical to that of V. felicitaszae .

Stratigraphic and geographic range.—The new species is only known from the uppermost Hettangian–lowermost Sinemurian (Lower Jurassic) of Adnet ( Austria).