Cyclamminidae Marie, 1941

Schlagintweit, Felix & Rashidi, Koorosh, 2017, Persiacyclammina Maastrichtiana N. Gen., N. Sp., A New Larger Benthic Foraminifer From The Maastrichtian Of Iran, Acta Palaeontologica Romaniae 13 (1), pp. 15-23 : 16-20

Family Cyclamminidae Marie, 1941

?Subfamily Choffatellinae Maync, 1958

Remarks: Persiacyclammina n. gen. fully fits the diagnosis of the superfamily Loftusioidea (= Loftusiacea in Loeblich and Tappan, 1987, p. 97). The Loftusiidae possess an agglutinated wall, with imperforate epidermis and inner alveolar layer, but elongate coiling axis and inner chamber pillars, two characteristics lacking in Persiacyclammina n. gen. Therefore, it seems more appropriate to include Persiacyclammina n. gen. into the Family Cyclamminidae Marie. The subfamiliar attribution however remains unclear; Persiacyclammina n. gen. is tentatively assigned to the subfamily Choffatellinae Maync (see diagnosis in Loeblich and Tappan, 1987, p. 101). It is worth mentioning that the relevance of structural features, and wall structure, for the diagnosis of the families (and subfamilies) of the Loftusioidea is still debated. This leads to different generic composition of families and subfamilies (see Loeblich and Tappan, 1987; Athersuch et al., 1992; Kaminski, 2014; Albrich et al., 2015).

Genus Persiacyclammina n. gen., n. sp.

Type species: Persiacyclammina maastrichtiana n.sp.

Origin of the name: Combination of Persia and Cyclammina Brady, 1879 .

Horizon and locality: Late Maastrichtian limestones of the Tarbur Formation of the Naghan section ( Fig. 1 ).

Diagnosis: Test free, subcylindrical to elongate, early stage (sub)planispirally coiled and involute with a few whorls of broad and low chambers. Periphery broadly rounded. Adult stage uncoiling and rectilinear with at least up to four chambers, nearly constant in width and rounded to slightly elliptical in transverse section. Wall microgranular with only a few agglutinated grains, with thin imperforate outer layer (epidermis), middle layer of simple, fine alveoles, and increasingly coarser inner (subepidermal) meshwork of beams and rafters. Pseudotriangular shaped radially arranged vertical partitions (subepidermal septula) are related to the latter, and project somewhat into the chamber lumen. They are stretching downward to the chamber floor, but are only barely attached to the chamber roof. At the margin of the perforat- ed central area, they alternate with intercameral foramina. In the early growth stage, foramina are single, basal to areal, rapidly becoming cribrate.

Comparisons: Loftusia Brady co-occurring with Persiacyclammina n. gen. in the Tarbur Formation, has large, fusiform, ovoid or globular test, planispirally enrolled with increasing elongate coiling axis. Besides exoskeleton, Loftusia also possesses an endoskeleton ( Loeblich and Tappan, 1987, p. 110). The Paleocene to Holocene Cyclammina Brady does not uncoil, and displays a prominent and thick subepidermal meshwork; the thickness exceeds that of the chamber lumen ( Loeblich and Tappan, 1987, p. 105). Several genera of the Lituolidae de Blainville display test morphologies (elongate, early stage coiled, later uncoiling) similar to Persiacyclammina n. gen., Ammobaculites Cushman for instance, but these have a simple agglutinated wall, lacking both exo- and endoskeleton. Pseudocyclammina Yokoyama (Late Juras- sic-Late Cretaceous) possesses a strongly agglutinated wall with coarse subepidermal network and lacks the lay- er of fine and simple alveoles of Persiacyclammina n. gen. Also septula are lacking in the former, instead a few irregular pillars may be present, and the chamber shape as well as the foraminal pattern are different ( Loeblich and Tappan, 1987, p. 102). The Late Jurassic Rectocyclammina Hottinger possesses an agglutinated wall, with imperforate outer layer and subepidermal choffatelloid network ( Loeblich and Tappan, 1987, p. 103).

Lacking septula, also the terminal, circular aperture in the central part is of Rectocyclammina different from Persiacyclammina n. gen. Zagrosella that has recently been described from the same locality as Persiacyclammina n. gen. (see Schlagintweit and Rashidi, 2017) differs from the latter above all by its lacking of a reticulate subepidermal network and septula, the foraminal pattern (cribrate, but just a few rather large openings), thick septa, and the presence of few irregular pillars.

Remarks: The elongate vertical elements (partitions) that project somewhat into the chamber lumen represent a significant characteristic of Persiacyclammina n. gen. For instance, elongate beams are present in some representatives of the Choffatellinae , Amijiella Loeblich & Tappan and Bramkapmpella Redmond ( Loeblich and Tappan, 1987). In these taxa, the structural elements are attributed to the exoskeleton as not being connected to the intercameral foraminal pattern contrary to a septulum (see Hottinger, 2006). In Persiacyclammina n. gen., however, the disposition of the vertical partitions is related to the arrangement of the intercameral foramina towards the inner margin of the perforated (cribrate) central area, i.e. an alternating disposition of both (e.g., Fig. 3 ).

Appearing as an extension of the subepidermal alveolar layer (exoskeleton), these are here called “subepidermal septula”, thus implying their endoskeletal nature (see Hottinger, 2006, for definition and short discussion). Also the shape and the disposition of these elements in Persiacyclammina n. gen. are different.

Septula (= radial partitions in Henson, 1948, Douglass, 1960, or Schroeder, 1975) are straight or curving (zig-zag shaped) as for instance in the radial zone of the Orbitolinidae ( Hottinger, 2006, fig. 71). As in several soritoidean taxa, septula are stretching from the chamber base to the roofs throughout their length (e.g., Henson, 1950, De Castro, 1985, Consorti et al., 2016). In Persiacyclammina n. gen. instead, the somehow asymmetric subepidermal septula attain a pseudotriangular shape, obviously only attaching to the previous septum (= chamber floor) but not or only barely attaching to the newly formed septum (= chamber roof) ( Fig. 4 ).

Persiacyclammina maastrichtiana Schlagintweit & Rashidi , n.sp.

Figs. 2 pars, 3–8

Origin of the name: The species name refers to the Late Cretaceous Maastrichtian stage.

Holotype: Very slightly oblique equatorial section illustrated in Figure 5d , thin-section 2NG 81-1.

Paratypes: Specimens in figs. 6a–g, 7, 8a–b.

Description: Test free, subcylindrical to elongate, early stage (sub) planispirally coiled and involute with two to two and a half whorls of broad and low chambers increasing gradually in breadth as added. There are about seven to nine chambers in the first, and nine to twelve chambers in the second whorl. The proloculus is subspherical, and possibly contains an internal microcrystalline membrane (thickness: ~7 µm;?detached from the inner wall) ( Fig. 6B and detail). In the coiled part, the septa are convex, and distinctly curved in direction of enrollment. The test periphery is broadly rounded; with slight axial depressions on both sides (slightly biumbonate). The adult stage is uncoiling, uniserial and rectilinear with at least up to four chambers, nearly constant in both width and height; rounded to slightly elliptical in transverse section. The apertural face is moderately convex. Wall microgranular with only a few agglutinated grains, a thin imperforate outer layer (epidermis), middle layer of simple (= nonbranching), fine alveoles, and increasingly coarser subepidermal meshwork of beams and rafters towards the chamber interior ( Fig. 3 ); septa pierced, massive. In tangential sections, the subepidermal meshwork often displays a rounded pattern. Pseudotriangular shaped radially arranged vertical partitions (subepidermal septula) are related to the subepidermal network. They project somewhat into the chamber lumen, stretching downward to the chamber floor. Obviously, they only attach to the previous septum (= chamber floor) but not or only barely to the newly formed septum (= chamber roof). Transverse sections of the uncoiled part cuts about 24 to 30 septula corresponding to a diameter of 0.85–1.0 mm. The septula appear not aligned but irregularly alternating between subsequent chambers ( Fig. 7m ). At the margin of the perforated (cribrate) central area, they alternate with intercameral foramina (e.g., Fig. 8e–f, j ). In the early growth stage, foramina are single, basal to areal ( Fig. 6c, e ), later becoming cribrate. It appears as that the foramina in the uncoiled portion are disposed in circles forming a concentric pattern (see Fig. 8f ).

Dimensions (in mm):

axial diameter (thickness) = up to 1.4 (mostly ~0.9)

test length (height) = up to 2.5

inner diameter of proloculus: 0.18–0.34 (mostly ~0.25) thickness septum = 0.04–0.075

chamber height enrolled part (incl. septum) = 0.25–0.35 diameter foramina = 0.025–0.04

thickness epidermis = ~0.01

epidermis + alveolar layer = 0.06–0.1

thickness of septula = ~0.02

length of septula = up to 0.3

Figures

Fig. 1 Location of the Naghan section, the type locality of Persiacyclammina maastrichtiana n. gen., n. sp.

Fig. 3 Wall-structure of Persiacyclammina maastrichtiana n. gen., n. sp. from the upper Maastrichtian of SW Iran Thin-section: NG 83-1.

Fig. 4 Schematic drawing of part of one chamber of Persiacyclammina maastrichtiana n. gen., n. sp. showing the interpretation and nomenclature of structural elements (without scale).

Fig. 2 Typical microfacies of samples with Persiacyclammina maastrichtiana n. gen., n. sp. (P), from the upper Maastrichtian Tarbur Formation of the Naghan section. a–b Wackestones/packstones with benthic foraminifera, among many porcelaneous and agglutinating taxa such as Dicyclina sp. (D), Zagrosella rigaudii Schlagintweit & Rashidi (Z), and remains of dasycladalean algae [(d) here: Pseudocymopolia anadyomenea (Elliott) (Ps) and others in A]. c–d Wackestones/packstones with debris of rudists, larger benthic foraminifera [Dicyclina sp. (D), Loftusia sp. (L), Omphalocyclus macroporus Lamarck (O)]. Thin-sections: 2NG 81-3 (a), 2NG 85-4 (b), 2NG 138 (c), 2NG 159 (d).

Fig. 5 Persiacyclammina maastrichtiana n. gen., n. sp., upper Maastrichtian Tarbur Formation of the Naghan section, Zagros Zone, SW Iran. a, centered axial section. c–h, variously cut oblique sections. b, i, tangential sections. Abbreviation: r.n. = reticulate network. Thin-sections: NG 65 (a), NG 81 (b, h), NG 83-3 (c), NG 88 (d), 2NG 81 (e, g), NG 120 (f).

Fig. 6 Persiacyclammina maastrichtiana n. gen., n. sp., upper Maastrichtian Tarbur Formation of the Naghan section, Zagros Zone, SW Iran. a–c, Almost centered equatorial sections. Arrow: Detail from b, showing remnants of an organic membrane inside the proloculus. d (holotype specimen), g, i, k, Oblique equatorial sections. e–f, h, j, l, Oblique sections. m, Oblique section of specimen with four uncoiled chambers (last chamber is broken). Note differing coiling axis of enrolled and uncoiled parts. Arrows in c and g = single, basal to areal foramina of the early growth stage. Abbreviations: p = proloculus, s = septum, s.s. = subepidermal septulum. Thin-sections: NG 71 (a), 2NG 159 (b), 2NG 83 (c), 2NG 81-1 (d–e, h), NG 107 (f), NG 144-2 (g), NG 52-2 (i), NG 113 (j), NG 116 (k), 2NG 81 (m).

Fig. 7 Persiacyclammina maastrichtiana n. gen., n. sp., upper Maastrichtian Tarbur Formation of the Naghan section, Zagros Zone, SW Iran. a, Oblique equatorial section. b–c, m, q, Oblique sections. d, j, Oblique axial sections. e–f, l, o, Subaxial sections. g–i, k, Axial sections. n, p, Longitudinal sections. Abbreviations: r.n. = reticulate network, s.s. = subepidermal septulum. Thin-sections: 2NG 81-4 (a, f), 2NG 81-1 (b), NG 84 (c), 2NG 85-2 (d), 2NG 81 (e), 2NG 81-2 (g, q), 2NG 71 (h, m), 2NG 64 (I), 2NG 76 (k), 2NG 86 (l), 2NG 97 (n), NG 121 (o), 2NG 138 (p).

Fig. 8 Persiacyclammina maastrichtiana n. gen., n. sp., upper Maastrichtian Tarbur Formation of the Naghan section, Zagros Zone, SW Iran. a, f–h, l, Oblique sections. b–d, Oblique sections through the uncoiled part. i–j, Transverse sections, slightly oblique of the uncoiled part. k, subtransverse section. m–n, Details of oblique sections showing structural elements. Abbreviations: a.l. = alveolar layer, f = foramen, r = rafter, s = septum, s.s. = subepidermal septulum, r.n. = reticulate network. Thin-sections: 2NG 81-2 (a), 2NG 55 (b), 2NG 114 (c), 2NG 1 (d), NG 74 (e), 2NG 81-4 (f, h), 2NG 81-1 (g), 2NG 71 (i), NG 83-3 (j), NG 81 (k), 2NG 18-2 (l), 2NG 85-4 (m), 2NG 81-3 (n).