Chrysalidinidae Neagu, 1968

Schlagintweit, Felix & Rashidi, Koorosh, 2016, Some New And Poorly Known Benthic Foraminifera From Late Maatrichtian Shallow-Water Carbonates Of The Zagros Zone, Sw Iran, Acta Palaeontologica Romaniae 12 (1), pp. 53-70 : 54-57

Family Chrysalidinidae Neagu, 1968

Remarks: Loeblich and Tappan (1987, p. 185) defined the Chrysalidinidae as possessing a wall “finely agglutinated, canaliculate”. A different view was expressed by Banner et al. (1991) regarding the occurrence of protocanaliculate or canaliculated wall types as a facultative species/genus criterion, of no suprageneric importance in the Chrysalidinidae . Canaliculi (or canaliculated) refer to narrow, regular parallel arranged pores open to the exterior ( Banner et al., 1991, fig. 1b). Canaliculi were also named parapores by Hottinger (2006) that per definition “may be branching and anastomising”, ”may be laterally interconnected” and end “blindly beneath an outer solid pavement”. In the chrysalidinid genera Praechrysalidina , Chrysalidina or Dukhania , canaliculi are sometimes restricted to the last chambers only (see discussion in Banner et al., 1991). Banner et al. (1991) stressed that the development of canaliculi appeared in several line ages of benthic foraminifera and therefore concluded that the definition of suprageneric differences based on a sporadically appearing feature is useless. In the recent classification of agglutinated foraminifera of Kaminski (2014), the genus Accordiella with its non-canaliculate wall is included in the Chrysalidinidae .

Genus Accordiella Farinacci, 1962

Type-species: Accordiella conica Farinacci, 1962 Accordiella? tarburensis n. sp.

Figs. 5a pars, 6–7, 8 pars.

2016 agglutinated foraminifer chrysalinid – Afghah, fig. 6d pars.

Holotype: Axial section of the specimen illustrated in Figure 6a , thin-section Rt 87.

Origin of the name: The species name refers to the village of Tarbur.

Type locality: Mandegan section ( Fig. 2 ).

Type level: Late Maastrichtian of the Tarbur Formation.

Diagnosis: Medium conical possible representative of Accordiella with distinct convex apertural face and widely spaced, discrete pillars in the central part of the test.

Description: Test medium conical, low trochospiral, with 3 marginally overlapping chambers (per whorl) arranged in up to 10 whorls and distinctly convex cone base.

Details on the nepionic stage unknown. Spiral sutures clearly marked by test constrictions. Peripheral lumen of the chambers undivided (no exoskeletal elements). Chamber height decreasing towards the centre of the test. Adaxial area wide, distinctly convex, pierced by numerous cribrate foramina and with numerous, discrete endoskeletal pillars. Wall homogeneous very finely agglutinating, occasionally with thin dark outer layer (detectable in the best preserved specimens). Dimorphism has not been evidenced.

Dimensions (mm): (Data for Accordiella conica in brackets)

Test diameter (D): 0.8-1.4 mm (0.6-1.0 mm)

Test height (H): 0.7-1.4 mm (0.8-1.2 mm)

Ratio D/H: 0.8-1.2 (mostly ~1.1)

Apical angle: 60-90 degrees; mostly ~80 degrees (about 80 degrees)

Number of whorls: 5-10 (8-12)

Number of whorls per last 0.5 mm (measured along the cone mantel line = cml, see Hottinger & Drobne, 1980, fig. 3): 2 to 4

Thickness of pillars (central part): 0.025-0.04 mm.

Comparisons: The type-species Accordiella conica Farinacci, 1962 (upper Cretaceous of Italy) differs from A.? tarburensis by its broad axial region with an endoskeleton consisting of numerous, fine horizontal plates that are interconnected by vertical pillars or buttresses ( Farinacci, 1962; Torre, 1966; Loeblich and Tappan, 1987, p. 151) (see Fig. 8 ). In the original description, the central part of Accordiella was described as possessing a labyrinthic structure ( Farinacci, 1962, p. 7). Torre (1966, fig. 1) presented a schematic drawing of its central zone showing the presence of four horizontal plates per whorl. Stratigraphy of A. conica is middle Coniacian to lowermost middle Campanian ( Frijia et al., 2015). For the occurrences of the species in the Mediterranean area see the compilation in Radrizzani et al. (1987, tab.1). Compared to A.? tarburensis , the central part of A. conica is densely occupied by narrowly spaced irregular endoskeletal elements ( Fig. 8 ). According to Torre (1965), there are four chambers per whorl in A. conica contrasting Farinacci (1962) describing the species as triserially coiled throughout. In fact, four chambers are discernible in some specimens illustrated by Farinacci (1962, pl. 2, fig. 6, and?some specimens in pls. 4-5). So the more complicated central part of A. conica compared to A.? tarburensis might by an effect of more chambers per whorl in the former. Generally, the shape of the pillars of both taxa is different. In A. conica these are irregularly thickening, undulating, and merging whereas in A.? tarburensis they are straight, cylindrical, with a slight widening at the base and top. With thickness of ~ 0.017 mm to ~ 0.035 mm (own observations), the pillars of A. conica are more slender compared to A.? tarburensis . Due to the lack of horizontal plates in the central zone the generic position of the species A.? tarburensis is uncertain. An Accordiella - type larger benthic foraminifer has been recently described as Pseudoaccordiella ayaki Gallardo-Garcia & Serra-Kiel (in Serra-Kiel et al., 2016) from the Late Eocene (Priabonian) of Oman and Yemen (see Fig. 8 ).

Pseudoaccordiella is characterized by a pseudokeriothekal wall texture, a triserial nepionic, and a biserial neanic stage. The structure of the central part of Pseudoaccordiella and Accordiella is directly comparable. The tests of Pseudoaccordiella are larger than A. conica and A.? tarburensis (height up to 2.7 mm, measured from Serra-Kiel et al., 2016, fig. 30.4).

Figures

Fig. 5 Microfacies of some charactersistic samples. a Packstone with benthic foraminifera Gyroconulina columellifera Schroeder & Darmoian (G), Omphalocyclus macroporus (Lamarck) (O), Laffiteina sp. (L), Minouxia/Tetraminouxia (M), Accordiella? tarburensis n. sp. (Z), Sirtina (S). Thin-section Rt 105. b Wackestone with Loftusia sp. (L), and Broeckina cf. dufrenoyi (d’Archiac) (B), thin-section Rt 113.

Fig. 6 Accordiella? tarburensis n. sp., Late Maastrichtian Tarbur Formation of Mandegan section, Zagros Zone, SW Iran. a–d, f, h–m Axial and subaxial sections. e, g Oblique sections. Thin-sections: Rt 87 (a, g), Rt 67-3 (b), Rt 61-1 (c), SNSB-BSPG 2016 III-4 (d), Rt 89-3 (e), Rt 113-2 (f), Rt 67 (h), Rt 70 (i), Rt 105 (j), Ng 189 (k), Rt 82 (l), Rt 73 (m).

Fig. 2 Location map of the studied area.

Fig. 8 Stratigraphic distribution and general comparison of Accordiella conica Farinacci, Accordiella? tarburensis n. sp., and Pseudoaccordiella ayaki Gallardo-Garcia & Serra-Kiel, (from Serra-Kiel et al., 2016, fig. 30.3 and 30.7).