Parurgonina valanginiana, SCHLAGINTWEIT & YAZDI-MOGHADAM & GRANIER & HOSSEINZADEH, 2024

SCHLAGINTWEIT, FELIX, YAZDI-MOGHADAM, MOHSEN, GRANIER, BRUNO & HOSSEINZADEH, ROHOLLAH, 2024, Parurgonina Valanginiana N. Sp. From The Valanginian Of Sw Iran (Zagros Zone): The First Cretaceous Record Of The Genus, Acta Palaeontologica Romaniae 20 (1), pp. 31-42 : 34-39

Parurgonina valanginiana sp. nov.

Figs. 4c , 5 - 6

1994 Pseudochrysalidina arabicus Henson – Shakib, pl. 7.3, fig. 10.

2011 Valdanchella – Jamalian et al., fig. 7n, fig. 12a - c. 2016 Falsurgonina pileola – Hosseini et al., fig. 7d - f. 2016 Falsurgonina pileola – Hosseini et al., fig. 7d - f. 2020 Pseudochrysalidina arabica – Esrafili-Dizaji et al., fig. 6A.

Origin of the name: Referring to the Valanginian stage.

Horizon and locality: Valanginian carbonates of the Fahliyan Formation from the Kuh-e Siah section ( Figs. 1- 2 ).

Holotype: Slightly oblique axial section shown in fig. 5e; sample RAP 10825.

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Description: Test high-conical with almost plane or convex base, starting with a comparably large embryonic chamber (protoconch) which is situated in a (sub)apical position ( Fig. 5 a-d). It is followed by a second, also comparatively large, hemispherical to lunular to hemispherical chamber laterally attached to the former ( Fig. 5 a-e) (= deuteroconch in Cuvillier et al., 1968, p. 150). Both chambers are connected by a single pore ( Fig. 5a ). These in turn are followed by a short trochospiral (‘helicospiral’) early stage with numerous chambers that apparently lack endoskeletal pillars.

Adult stage is rectilinear with up to 16 chambers and oblique stolon systems ( Fig. 6a, c ). The marginal chamber part is undivided (e.g. Figs. 5g, 5i ). The main central part is occupied by irregular distributed pillars showing a typical semi-lunular shape in transverse sections ( Fig. 5i, 5k and 5m above) [= section courbée en forme de crochet (curved section forming a hook) Schroeder in Schroeder et al., 1975, p. 324]. As can be discerned in axial sections, the pillars are not aligned between subsequent chambers; instead they are more or less alternately arranged (e.g., Fig. 5e , 6a, 6c ). They broaden (partly also fused) at the base (= pointed towards the cone base). The foramina are represented by multiple large pores irregularly piercing the septa and are linked to the lunular pillars in the central part ( Fig. 5 i-j, 5l). In axial sections, the foramina are arranged in oblique lines between subsequent chambers (= perforations obliques, Cuvillier et al., 1968) ( Fig. 6a, c , adult part). Obliquely arranged marginal foramina are present in the adult rectilinear test part ( Fig. 5e, n ). The wall is thick with pseudo-keriothecal texture ( Gusič, 1969; Schroeder in Schroeder et al., 1975), a feature barely discernible in the Iranian specimens.

Dimensions: See Table 1.

Tabel 1. Biometric data of Upper Jurassic P. caeliensis (Cuvillier et al.) and lowermost Cretaceous P. valanginiana sp. nov. compared. * Cuvillier et al. (1968) ** Pleş et al. (2015) *** Gušić (1969 for Lituonella dinarica ) **** measured from Schroeder et al. (1975, pl. 1, fig. 2).

Remarks: Parurgonina displays a discontinuous fossil record including Parurgonina primaeva Kamoun & Peybernès 1993 from the Middle Jurassic (upper Bajocian–lower Bathonian) to the Upper Jurassic P. caelinensis (uppermost Oxfordian–lowermost Tithonian, Bassoullet, 1997a; Pleş et al., 2015, 2019). In fact, the only difference between the Upper Jurassic specimens and those from the Iranian Fahliyan Formation that we could observe is the comparably large embryonic chamber(s) at the apex (Tab. 1). According to literature data, the diameter of the megalospheric embryo for P. primaeva is 0.200 mm and 0.110 -0.160 mm for Upper Jurassic specimens of P. caelinensis . The large-sized embryo of the Lower Cretaceous specimens reaches up to 0.22 mm in size.

As remarked by Cuvillier et al. (1968), Parurgonina may be confused with the gross homeomorphic Paravalvulina (ex. Dukhania ) arabica ( Henson, 1948) described from the ‘Infravalanginian’ limestones and shales containing Pseudocyclammina lituus of subsurface Qatar (Dhukan wells), later erroneously assigned to the Hauterivian by Banner et al. (1991) and Whittaker et al. (1998) (see next chapter for biostratigraphic remarks on genuine Pseudocyclammina lituus ). As indicated by Banner et al. (1991), P. arabica has a quadriserial (juvenile) to triserial growth (adult), lacks a pseudo-keriothecal wall, the pillars are not triangular in axial sections ( Banner et al., 1991, figs. 98, 102-104; Schroeder et al., 1975, pl. 2, fig. 1) and do not display the typical semi-lunular shape in transverse sections (e.g., fig. 4i, k). Moreover, the multiple foramina in the adult part of the central zone of P. arabica appear predominantly perpendicular to the septa ( Banner et al., 1991, figs. 99, 102-104), while crosswise oblique in P. valanginiana . Another difference is that P. valanginiana does not show a marginal thickening of the chamber. Therefore, the chamber height remains more or less constant from the marginal to central test area as remarked by Gušić (1969, p. 69).

Like Barkerina dobrogiaca ( Neagu 2000) or Valdanchella miliani ( Schroeder 1968) in the middle and western parts of Neotethys, P. valanginiana might represent a Valanginian marker taxon endemic to the Arabian Plate.

Figures

Fig 4. a-b. Parurgonina caelinensis (Cuvillier et al.), (modified from Velić, 2007, pl. 10, figs. 10-11) from the Upper Jurassic of Croatia and Parurgonina valanginiana sp. nov. (c.) from the Lower Cretaceous of Iran. Red dotted lines mark the septa of the rectilinear chambers.

Fig 5. Parurgonina valanginiana sp. nov. from the Valanginian Fahliyan Formation of SW Iran (a–h, j–k, m–n) and the Upper Jurassic of Algeria (i, l; from Schroeder et al., 1975, pl. 2, figs. 3-4). a–d. (Sub)axial sections of juvenile specimens showing embryo and ‘praevalvulind’ early stage sensu Septfontaine (2020); samples RAP 10825 (a–c), RAP 10869 (d). e. Slightly oblique axial section dissection the apical embryo; holotype specimen, sample RAP 10825. f. Subaxial section showing well developed thickened pillars in the central test part; sample RAP 10825 (= Fig. 12a in Jamalian et al., 2011 illustrated as Valdanchella). g. Tangential section showing the undivided marginal chamber area in the part following the ‘praevalvulinid’ stage; sample RAP 10825. h. Tangential oblique section; sample RAP 10825. i. Slightly oblique transverse section showing lunular pillars (from Schroeder et al., 1975, pl. 2, fig. 4, copyright by Swiss Geological Society). j. Oblique section; sample RAP 10825. k. Oblique section showing lunular pillars; sample RAP 10825. l. Slightly oblique transverse section (from Schroeder et al., 1975, pl. 2, fig. 3). m. Oblique transverse section; sample RAP 18025. n. Subaxial section; sample RAP 18025

Fig. 6. Parurgonina valanginiana sp. nov. from the Valanginian Fahliyan Formation of SW Iran. a-c, f subaxial sections; samples RAP 10825 (a), sample RAP 10869 (b-c, f) (b, c = Figs. 12c and 12b in Jamalian et al., 2011 illustrated as Valdanchella). d-e, g, j transverse sections, partly slightly oblique; samples RAP 10869 (d-e), RAP 10827 (g, j). h-i, k Oblique sections; samples RAP 10869 (h), RAP 10825 (i, k). Abbreviation: pi = pillar.

Fig. 1.A. Simplified geological map of Iran (modified after Schlagintweit and Yazdi-Moghadam, 2021) showing the main tectonic subdivisions. B. Road map and position of the studied section. C. Tectono-stratigraphic units of the Zagros belt (modified after Yazdi-Moghadam and Schlagintweit, 2021) with position of the Kuh-e Siah section. Abbreviations: BF Balarud Fault, CEIM Central East Iran Microplate, HZF High Zagros Fault, KZF Kazerun Fault, MFF Mountain Front Fault, MZRF Main Zagros Revers Fault, MZT Main Zagros Thrust, SSZ Sanandaj-Sirjan Zone, UDMA Uromia Dokhtar Magmatic Arc, ZFTB Zagros Fold Thrust Belt.

Fig. 2. Lithological log of the Kuh-e Siah section with distribution of larger benthic foraminifera and calcareous green algae.