Spirocyclinidae (Munier-Chalmas, 1887) Maync, 1950

SCHLAGINTWEIT, FELIX & RASHIDI, KOOROSH, 2020, Broeckinella Hensoni N. Sp., A New Larger Benthic Foraminifera From The Upper Maastrichtian Of Iran And A Revision Of The Genus Broeckinella Henson, 1948, Acta Palaeontologica Romaniae 16 (2), pp. 57-67 : 60-63

Family Spirocyclinidae (Munier-Chalmas, 1887) Maync, 1950

Remarks: In the definition of the families Cyclamminidae and Spirocyclinidae, Albrich et al. (2015, p. 255) do not follow the classification of Kaminski (2014). According to these authors “the genera with polygonal subepidermal patterns should be ascribed to the Family Spirocyclinidae instead of the Cyclamminidae ”. In this definition, the genus Broeckinella possessing a polygonal subepidermal pattern should therefore be included in the Spirocyclinidae .

Subfamily Pseudochoffatellinae Loeblich & Tappan, 1985

Genus Broeckinella Henson, 1948 emended

Remarks: The generic diagnosis of Loeblich and Tappan (1987, p. 104) only referred to the megalospheric form. It needs to be emended with respect to data obtained from a microspheric specimen described here. The diagnosis of Loeblich and Tappan (op. cit.) is emended as follows (added changes in bold letters)…….“chambers rapidly increasing in breadth to become arcuate but not completely cyclical, so that the test is successively flabelliform, complanate, and finally reniform in the macrospheric stage. Microspheric stage with a few annular chambers, so that the test is ovoid to discoidal ”.

Broeckinella arabica Henson, 1948

Figs. 4b–d , 5–6 .

*1948 Broeckinella arabica n. gen., n. sp. – Henson, p. 93, pl. 7, fig. 6, text-fig. 13a–c.

1978 Broeckinella arabica Henson – Cherchi and Schroeder, p. 514, fig. 1 A–C.

2004 Dicyclina schlumbergeri – Khosrow Tehrani and Afghah, pl. 2, fig. 4.

2008 Dicyclina schlumbergeri – Khosrow Tehrani et al., pl. 1, fig. 6.

2016 Broeckinella arabica Henson – Schlagintweit and Rashidi, p. 57, fig. 9a–e.

Emended description: Test finely agglutinated, compressed, with numerous chambers rapidly increasing in width so that the megalospheric test becomes flabelliform. A tiny proloculus (diameter ~ 0.07-0.1 mm) is followed by about 8-10 planispiral chambers that increase rather rapidly in width ( Fig. 6e ). The chamber margins are subdivided by exoskeletal elements, both vertical and horizontal resulting in a meshwork (or pattern) of tiny polygonal cells displayed in shallow tangential sections (= zone 1 in Henson 1948; see Fig. 4a ) ( Figs. 4b , 6 a-d). Toward the chamber interior a zone follows where only main partitions are present, aligned between successive chambers (= zone 2 in Henson 1948; see Fig. 4a ) ( Figs. 4c , 6b, d ). The central part is undivided ( Figs. 4b , 6c, e ). The multiple foramina are arranged in the median plane, not related to the main partitions (that can therefore not be termed septula). The microspheric test is ovoid to discoidal due to final annular chambers ( Fig. 5b–c ). A proloculus is not observable. The planispiral part, contrasting the A-form, consists of numerous (~ 26) chambers. The internal structure is identical to the A-form.

Remarks: The material of B. arabica from the Tarbur Formation does not include centered sections. Data on the test dimensions therefore only comprise incomplete sections attaining a maximum size of 2.4 mm for megalospheric and up to 4.6 mm for microspheric forms ( Tab. 2). B. arabica is intermediate in size between the distinctly smaller B. neumannae and the larger B. hensoni n. sp. ( Tab. 3). The description of Henson (1948) was based on a single specimen, a megalospheric form (see Cherchi and Schroeder, 1978). The specimen from the Tarbur Formation illustrated in Fig. 5b is the first record of a microspheric specimen. The differences between the two generations are summarized in Table 2.

B. arabica was figured as Dicyclina schlumbergeri from the Maastrichtian of the Tarbur Formation by Khosrow Tehrani and Afghah (2004) and the Maastrichtian of the Amiran Formation (SW Iran, Zagros Zone) where the authors distinguished a Loftusia-Dicyclina assemblage zone. Dicyclina schlumbergeri is rather common in the Tarbur Formation (see Schlagintweit and Rashidi, 2018).

Broeckinella hensoni Schlagintweit and Rashidi nov. sp. Figs. 5a , 7-8 .

Holotype: Equatorial section of an assumed macrospheric specimen showing flabelliform test and illustrated in Fig. 7f , thin-section 2NG N. The diameter of the holotype specimen is ~ 3.65 mm.

Etymology: The species name is dedicated to Francis Roger Spencer Henson (1901-1967) in honour for his fundamental works on larger imperforate foraminifera from the Middle East area. For further information on F.R.S. Henson and his merits see Hughes (2013).

Type-locality: Naghan section ( Figs. 2–3 ).

Type-level: Late Maastrichtian of the Tarbur Formation.

Description: Test finely, agglutinating, large (up to almost 8 mm), flattened with an early evolute planispiral stage followed by a flabelli- to reniform adult growth stage ( Fig. 7f ). Axial sections display almost constant chamber width ( Fig. 7a ). Further details on the early stage are limited by the available sections. The adult part consists of up to 50 chambers. There are five to seven chambers in the last mm of the test. Wall finely agglutinated. Exoskeleton consisting of one short horizontal and two orders (short, and longer) of subepidermal vertical (or radial) partitions (beams and rafters) together forming a subepidermal network ( Fig. 8e ). Due to the shortness of the secondary partitions this network of polygonal cells is only visible in shallow tangential sections. Longer vertical partitions (beams) are aligned between successive chambers, and reach slightly deeper into the chamber lumen. The central part of the chamber lumen is undivid- ed (e.g., Fig. 8e in the lower part; see Henson, 1948: fig.13c). Multiple foramina (one row) arranged in the median plane. Microspheric specimens not reported.

Dimensions: See table 3.

Comparisons: Amongst the three Late Cretaceous species of the genus, Broeckinella hensoni is distinctly larger then B. arabica Henson (double the size!) and B. neumannae Gendrot (five times larger!) (see table 3). With respect to the time-equivalent B. arabica , the distinctively lower number of chambers per last mm test length (8 to 14 in B. arabica against 5 to 7 in B. hensoni ), due to a greater chamber height, is notable.

Figures

Fig. 4 Internal structure of Broeckinella arabica Henson. a Drawing of a slightly oblique equatorial section (slightly modified from Henson, 1947, fig. 13c; see also Cherchi and Schroeder 1978, fig. 1C). 1 = subepidermal layer (network; exoskeleton), 2 = zone with transverse partitions only, 3 = undivided chamber interior (lacking endoskeleton); septa with foramina. b Tangential equatorial section of Broeckinella arabica showing the three zones of Henson (1948). Thin-section Rt 85, Mandegan section. c Tangential equatorial section showing main partitions aligned between successive chambers (detail from Fig. 6d). Thin-section NG 42-1, Naghan section.

Fig. 5 Broeckinella hensoni n. sp. (a) and Broeckinella arabica Henson (b–d) from the upper Maastrichtian of the Tarbur Formation, Naghan section. a Foraminiferal wackestone with Broeckinella hensoni n. sp., thin-section 2NG 197. b Foraminiferal wackestone with Broeckinella arabica Henson, 2NG 128-1. c–d Details from b, showing a microspheric specimen. Scale bars in c and d = 1 mm.

Fig. 6 Broeckinella arabica Henson, upper Maastrichtian Tarbur Formation of the Mandegan (a, d) and Naghan sections (b– c, e–f), Zagros Zone, SW Iran. a, c–d Oblique equatorial sections, partly fragmentary, in some parts crossing the subepidermal network (e.g., a and left side of d). Note the undivided central part of the chambers in c. b Tangential section in the plane with only main partitions aligned between subsequent chambers (= zone 2 in Henson 1948; see Fig. 6a). e–f Oblique sections. Note initial planispiral part in the megalospheric specimen in e passing the proloculus (arrow). Note also the chambers undivided in the central part in e. Thin-sections: Rt 104 (a), NG 42-1 (b), NG 21 (c), Rt 85 (d), 2NG 49 (e), 2NG 112 (f). Scale bars 0.5 mm.

Fig. 7 Broeckinella hensoni n. sp., upper Maastrichtian Tarbur Formation of the Naghan section, Zagros Zone, SW Iran. a, c Subaxial sections. Specimen shown in A displays more than 40 chambers in the uncoiled adult part. d Detail from c showing initial coiled part. e Oblique equatorial section. f Slightly oblique equatorial section showing flabelliform test morphology (test diameter: ~6.6 mm). Thin-sections: 2NG 153 (a), 2NGN (b, f), 2NG 38 (c–d), NG 197-1 (e). Scale bars 1.0 mm.

Fig. 8 Broeckinella hensoni n. sp., upper Maastrichtian Tarbur Formation of the Naghan (a, d–e) and Mandegan (b–c, f) sections, Zagros Zone, SW Iran. a Oblique equatorial section. Note porcelaneous test of Cuvillerinella sp. below. b Detail showing fine subepidermal network (sn, below), followed by zone with radial partitions (rp) only and finally the undivided central chamber part with foramina (f) piercing the septa (s). c Oblique section cutting the initial planispiral part. d–e Oblique equatorial sections showing zones of different internal structure (see Text-Figure 3). f Detail from c showing initial planispirally coiled part with numerous chambers. Note also the fine subepidermal network and main partitions (right side). Thin-sections: 2NG 166 (a), Rt 67-1 (b), RT 72 (c, f), 2NG 118 (d), 2NG 172 (e). Scale bars 1.0 mm for a, c–e, 0.2 mm for b and f.

Fig. 2 Location of the Naghan and Mandegan sections in the Zagros Zone, SW Iran.

Fig. 3 Naghan section, along the road from Naghan to Izeh with the type-level of Broeckinella hensoni n. sp. marked by an asterisk (left side).