Heliolitidae Lindström, 1876

Cui, Yu-Nong & Wang, Guang-Xu, 2023, Early Katian, Late Ordovician, heliolitine corals from southern Kuruktag in northeastern Tarim Basin of China, Acta Palaeontologica Polonica 68 (2), pp. 273-295 : 291-293

Family Heliolitidae Lindström, 1876 Genus Apekinella Ospanova, 2012a

Type species: Apekinella zeravshanica Ospanova, 2012a, Upper Ordovician , Shakhriomon-2 section, Shakhriomon district, west of Zeravshan Ridge, Tajikistan .

Remarks.—The diagnostic features of Apekinella were discussed by Ospanova (2012a). The genus was originally assigned to Stelliporellidae Bondarenko, 1971 . However, this family is characterized by long septal plates forming a polygonal structure at the axis, a feature being absent in Apekinella . Therefore, Apekinella is placed herein in Heliolitidae Lindström, 1876 .

Stelliporella Wentzel, 1895 , and Derivatolites Bondarenko, 1971 , have similarly longer septal plates, both of which can be distinguished from Apekinella by the presence of axial structure. Derivatolites further differs in having more widely spaced corallites and the development of an axial structure formed by connection of opposite septa.

Apekinella zeravshanica Ospanova, 2012a

Fig. 15 .

2012a Apekinella zeravshanica sp nov.; Ospanova 2012a: 45, pl. 5: 1a, 1b.

Material.—Two sectioned specimens, NIGP 201016 and NIGP 201017, both from the Yuanbaoshan Formation (lower Katian) of southern Kuruktag, Tarim Basin, China.

Emended diagnosis.—Species of Apekinella with TaDs 1.00– 1.80 mm. Septa long, strongly curved, almost extending to the axis. Tabulae complete, horizontal or slightly concave. Corallites commonly separated by 1–5 rows of discontinuous tubules.

Description.—One complete corallum is measured, of low domical form, 27.58 mm wide and 10.88 mm high. Corallites rounded or sub-rounded, with TaDs varying from 1.36 to 1.70 mm (average 1.51 mm). Corallite walls complete, slightly wavy, 0.04–0.08 mm thick (average 0.07 mm). Septa laminate, 12 in number, with a maximum width of 0.15–0.42 mm (average 0.33 mm). Septa long, strongly curved, almost extending to the axis. Tabulae complete, mostly horizontal or slightly convex, Ta5 15–16. Corallites contiguous or separated by narrow coenenchyme. Coenenchyme consisting of polygonal tubules formed by discontinuous vertical elements, with up to 15 tubules surrounding each corallite. Corallites separated by 1–5 rows of tubules, with centers 1.13–1.86 mm apart (average 1.67 mm). Tubules commonly complete, convex, concave or oblique. Diaphragms 0.22–0.32 mm in diameter, 19–20 per 5 mm.

Remarks.—These specimens differ from the type material of Apekinella zeravshanica Ospanova, 2012a, from the Upper Ordovician Archalyk Member of the Shakhriomon area, western Zeravshan Ridge, Tajikistan, only in having lager crorallites, the latter being about 1.0– 1.2 mm in diameter. For this reason, we assign these specimens to Apekinella zeravshanica and revise the range of corallite size as 1.00– 1.80 mm in the diagnosis of this species.

Stratigraphic and geographic range.—The Yuanbaoshan Formation (lower Katian) of southern Kuruktag, northeastern Tarim, China; the Archalyk Member (upper Katian) of the Shakhriomon area, western Zeravshan Ridge, Tajikistan.

Figures

Fig. 15. Heliolitine tabulate coral Apekinella zeravshanica Ospanova, 2012a, from the Yuanbaoshan Formation (lower Katian) of southern Kuruktag, Tarim Basin, Northwest China. A. NIGP 201016.A1, A2, transverse sections.A3, A4, longitudinal sections. B. NIGP 201017. B1, B2, transverse sections. B3, longitudinal section.