Elazigina siderea, Consorti & Rashidi, 2018

Consorti, Lorenzo & Rashidi, Koorosh, 2018, A new evidence of passing the Maastichtian-Paleocene boundary by larger benthic foraminifers: The case of Elazigina from the Maastrichtian Tarbur Formation of Iran, Acta Palaeontologica Polonica 63 (3), pp. 595-605 : 598-601

Elazigina siderea sp. nov.

Figs. 4 , 5 .

1988 Smoutina cruysi Drooger, 1960 ; Inan 1988: 471, pl. 1: 1–9. 2008 indet. Foraminifera at upper left side of the picture; Schlüter et al. 2008: 518, fig. 4g.

2013 Rotalia skourensis Pfernder, 1938 ; Vaziri-Moghaddam et al. 2013: 154, fig. 14E.

2016 Pararotalia ? sp.; Schlagintweit et al. 2016: 177, fig. 7G.

Etymology: From Latin sidera, star; due to the typical umbilical outline and from the heavy feathering.

Type material: Holotype: APNU-Tf12, complete specimen sectioned along the axial direction ( Fig. 4A ). Paratypes: APNU-Tf12, complete specimen sectioned along the subaxial direction ( Fig. 4G, K ); AP- NU-Tf11, oblique basal sections of complete specimen ( Fig. 5D, H ); APNU-Tf14, oblique centred section of a complete specimen ( Fig. 5F ); all from type locality.

Type locality: Rod Abad section, Fars, Iran .

Type horizon: Base of Tarbur Formation , Maastrichtian, Cretaceous .

Material. —About 150 oriented sections and 80 random sections.

Diagnosis. —Medium-size lamellar perforate shell of chambers arranged in a low trochospire. The dorsal side is low convex. Convexity of the ventral side may be sometimes exaggerated. Periphery unkeeled, slightly acute or somewhat rounded. A large massive umbilical plug occupies the central part of the ventral side. Piles present all around the umbilical plug. Ventral sutures heavy feathered. Folia small and slightly oblique. Presence of spiral, vertical (funnels) and intraseptal interlocular spaces.

Description. —A set of 10 to 14 piles bed circularly the umbilical plug, some of these piles are fused with the plug periphery forming a lobed outline. Chamber walls are thick, but the wall of the last chambers may appear thinner. The spiral canal bears between the piles and the umbilical plates. There may be funnels between the piles line and the umbilical plug, but it is sometimes difficult to distinguish the spiral canal from the funnels. The intraseptal interlocular space opens to the exterior and is partially subdivided by the branches of the feathering. The feathered space may be very wide, so much to reach the periphery the dorsal side. There are three whorls; the last one is sometimes incomplete. There are seven chambers in the first, 10–11 chambers in the second and 15–16 in the third whorl. Shell diameter of most complete specimens ranges 0.85–0.9 mm and its thickness may vary between 0.5 mm and 0.55 mm; the diameter on axial ratio is around 1.6. The plug diameter at the umbilicus of adult specimens is 0.23 mm, it extends longitudinally for more than 0.4 mm. Feather branches are up to 0.12 mm long and 0.05 mm thick. No microspheric specimens have been found, the diameter of the megalosphere is around 0.06 mm.

Remarks.—Specimens from Turkey described in İnan (1988) display slightly higher diameter and axial values than the Iranian specimens (max. diameter: 1.1 mm; max. axial thickness: 0.67). These measurements are here taken into consideration as intraspecific variability. The last chambers appear frequently well rounded and their wall is thin. This may be due to poor calcification during the last shell growth stage.

Overall, the dimensions of E. siderea sp. nov. are reduced with respect to the Paleocene representatives, E. lenticula and E. subsphaerica . Hottinger (2014) does not provide complete measurements of E. dienii , but E. siderea appears smaller. E. dienii displays also a more acute periphery, less pronounced feathering and smaller umbo than E. siderea . The Middle East E. harabekayisensis has a thicker chamber wall, less piles, larger plug and less marked feathers form.

than E. siderea . The piles surrounding the umbilical plug in E. siderea are well separated and clearly distinguishable in axial view, unlike most of the Paleocene allies, which piles frequently appear fused to the central plug or extremely reduced in dimension (see Hottinger 2014: pl. 6.8–11). A table comparing the measurements of all Elazigina species is presented in Table 1.

Stratigraphic and geographic range.— Elazigina siderea sp. nov. is here described from the Maastrichtian of Iran and recognized from equivalent shallow-water carbonates of Turkey and Oman ( Schlüter et al. 2008). Potentially, its presence can be extended along the whole Anatolian and Arabian sector. In this work, Elazigina siderea sp. nov. characterizes the Rod-Abad section and the upper part of the Mandegan section, beneath the first occurrence of Palaeoelphidium multiscissuratum (Smout, 1955) (see the column in Consorti et al. 2018: fig. 1C). Kathina sp. reported in Piryaei et al. (2010: fig. 12) at the lower part of Tarbur Formation is probably E. siderea sp. nov. and should be taken into consideration as a further record.

Figures

Fig. 4. Rotaliid foraminifer Elazigina siderea sp. nov. (A, holotype) from the Maastrichtian of Rod Abad section, Iran; axial (A, B, D, I, K), subaxial (E–H, J, L, N, O), oblique (C), and transversal-basal (M) sections. A–D, G, J–O. APNU-Tf12 (type-level). F, H, N. APNU-Tf11. E. APNU-Tf4. Abbreviations: f, feathers; pi, piles; pl, umbilical plug; sc, spiral canal.

Fig. 5. Rotaliid foraminifer Elazigina siderea sp. nov. from the Tarbur Formation of Rod Abad (A, C, D, F–J) and Mandegan (B, E, K) sections, Iran; transversal (A, C, E, J), transversal-basal (B, O), transversal-oblique (D, F–I, L), and tangential (K, M, N, P) sections. C, J, L, M. APNU-Tf12 (typelevel). D, G–I, P. APNU-Tf11. A, N. APNU-Tf10. F. APNU-Tf14.O. APNU-Tf4. B, E. APNU-Rt53. K. APNU-Rt55.Abbreviations: f, feathers; fo, folia; is, intraseptal canals; pi, piles; pl, umbilical plug; pr, proloculus; up, umbilical plate; sc, spiral canal.