Dictyopselloides, Loeblich & Tappan, 1985

Dictyopselloides View in CoL ? tarimensis sp. nov.

Fig. 6 View Fig a-p

? 1984 Dictyopsella sp. – Bilotte, pl. 11, fig. 9.

? 1978 Dictyopsella kiliani Schlumberger – Luperto Sinni & Ricchetti, pl. 46, figs. 12, 15-16.

2018 Dictyopselloides cuvillieri (Gendrot) – Moro et al., fig. 4b, d, h, i-k (figured as Dictyopsella kiliani Schlumberger ).

Derivatio nominis: Referring to the Tarim Basin in southwestern China.

Type-level: Campanian? of the Yigeziya Formation.

Type-locality: Wuyitake section located ~7 kilometers southwest of Wuyitake Town in Aketao County, southwestern Tarim Basin ( Fig. 2 View Fig ). Coordinates: E75°28′50.46″, N38°58′55.89″ GoogleMaps .

Holotype: Axial-oblique section illustrated in Fig. 6c View Fig , sample YGZY-2.

Diagnosis: A low- to medium-conical large-sized dictyopsellid with a concave umbilical side, a closely coiled initial spire and one to three vertical partitions per chambers; a single rafter may be present within a few chambers.

Description: Test free, low to medium-conical or patelliform. Due to increasing chamber convexity at the base, the adult part exhibits an open umbilical region with a concave central depression (e.g., Fig. 6p View Fig ). The chambers are trochospirally coiled (7-8, max. 10 whorls) throughout with a more closely coiled initial spire ( Figs. 6c, f View Fig ). The chambers become successively broader during ontogeny whereas the height is only slightly (if ever) increasing. Marginally, the chambers are bending slightly upwards thereby overlapping partly with the previous chamber. The chambers are subdivided by one to three vertical (= beams) and sporadically (and not in all chambers) a single horizontal (= rafter) partition. The chamber width is decreasing towards the axis ( Figs. 6 View Fig f-g). Therefore, deep tangential sections show a closer set arrangement of vertical partitions ( Fig. 6n View Fig upper part) and a wider spacing in shallow tangential sections ( Fig. 6n View Fig lower part). In oblique sections, the visible distinction between rafters and beams might be difficult and ambiguous in some cases. Wall probably finely agglutinated.

Comparisons: Due to the lack of isolated specimens and centered thin-sections and missing informations in the original description (number of whorls, chamber height etc.), the comparison to the type-species D. cuvillieri (Gendrot) is primarily due to dimensional data. Gendrot (1968, p. 682) indicated diameters of 1.10 mm to 1.30 mm for the megalospheric (A-form) and 1.0 mm for microspheric (B-form) specimens. For the test height comparable dimensions were indicated for both forms with 0.13 mm to 0.15 mm meaning a rather flat overall morphology. As for differences between the two forms, Gendrot (1968) remarked that in the A-form the embryonic chamber is discernible (as protruding) at the apex. Another difference that can be deduced from the images of the isolated specimens provided by Gendrot (1968) is a higher number of chambers in the final whorl in the B-forms (~12-13, pl. 5, fig. 9 therein) compared to the A-forms (~7, pl. 5, fig. 7 therein; Fig. 6r View Fig ). D.? tarimensis sp. nov. is distinctly larger with test diameter up to 3.35 mm ( Fig. 6p View Fig ) and a height exceeding the one of the type-species distinctly. Although no dimensional data were included in the original description, the chamber height of the Chinese taxon is much larger (~ 0.20 mm in adult chambers) and might exceed even the total test height of D. cuvillieri . Although not indicated by Gendrot (1968), the number of whorls is different, with up to 10 in D.? tarimensis against 5 to 6? in D. cuvillieri (see Fig. 6s View Fig ).

Associated microfauna: Taxa described in the present contribution.