Mongoliolites obliterans ( Bondarenko, 1958 )

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 : 282-284

publication ID	https://doi.org/ 10.4202/app.01023.2022
persistent identifier	https://treatment.plazi.org/id/03F35C14-FF84-FFAE-885B-FC5683AF44D9
treatment provided by	Felipe
scientific name	Mongoliolites obliterans ( Bondarenko, 1958 )
status

Treatment

Mongoliolites obliterans ( Bondarenko, 1958)

Fig. 8 View Fig .

1958 Plasmoporella obliterans sp. nov.; Bondarenko 1958: 214, 215, pl. 5: 5–7; pl. 6: 4, 5.

Material.—Three sectioned specimens, NIGP 201000– 201002 from the Yuanbaoshan Formation (lower Katian) of southern Kuruktag, Tarim Basin, China.

Emended diagnosis.— Mongoliolites species with TaDs 0.75–1.01 mm. Corallite walls formed by the fusion of peripheral parts of septa. Septa wedge-shaped, short. Tabulae mostly complete, sparsely spaced.

Description.—Only one single complete corallum measured, of low domical form, 33.79 mm wide and 22.72 mm high. Corallites rounded with clear outlines, TaDs 0.75–1.01 mm average 0.92 mm). Corallite walls consisting of thickened trabeculae. Septa triangular to lachrymiform in shape, 12 in number, 0.13–0.19 mm long (average 0.15 mm), with maximum widths ranging from 0.10 to 0.19 mm, extending onefifth of the TaD. Corallite walls weakly to moderately developed. Tabulae mostly complete and sparse, generally convex, some strongly concave or curved, Ta5 12–16. Corallites commonly separated by narrow coenenchyme, with centers 1.04–1.66 mm apart (average 1.33 mm). Dissepiments flat or slightly convex, generally 0.21–0.44 mm wide (average 0.35 mm). The number of dissepiments in 5 mm 20–22.

Remarks.—Our material is clearly conspecific with the holotype of Plasmoporella obliterans Bondarenko, 1958 , from the Upper Ordovician Dulankara Formation of the Chu-Ili Terrane in southern Kazakhstan, except that the former has slightly smaller (0.75–1.01 mm) corallite size. We therefore extend the range of corallite size in the revised diagnosis of this species. This species was originally assigned by Bondarenko (1958) to Plasmoporella on the basis of the development of 12 trabeculae, but later given by her ( Bondarenko 1992) an uncertain taxonomic position. In this paper, we attribute this species to Mongoliolites based on the presence of corallite wall.

A comparison of Mongoliolites obliterans with similar species is shown in Table 2 and discussed below. Mongoliolites paradoxides Bondarenko and Minzhin, 1977 , from central Mongolia differs from M. obliterans in having larger corallites (1.0– 1.5 mm in diameter), more complete tabulae, and less developed septa. Mongoliolites sp. described below is separated by larger corallite size (1.51–1.67 mm in diameter) and shorter septa.

Stratigraphic and geographic range.—The Yuanbaoshan Formation (lower Katian) of southern Kuruktag, northeastern Tarim, China; the Dulankara Formation (lower Katian) of the Chu-Ili Terrane, southern Kazakhstan.

Mongoliolites sp.

Fig. 9 View Fig .

Material.—One sectioned specimen, NIGP 201003, from the Yuanbaoshan Formation (lower Katian) of southern Kuruktag, Tarim Basin, China.

Description.—One single complete corallum measured, of low domical form, 21.16 mm wide and 7.83 mm high. Corallites rounded or sub-rounded, TaDs 1.51–1.67 mm (average 1.56 mm). Corallite walls thick, straight to weakly wavy. Septa short, 0.11–0.15 mm in length, arranged in 12 rows in later growth stages. Tabulae complete, flat, slightly sagging or convex, with some incomplete, Ta5 8–10. Corallites mostly in contact, or separated by dissepiments, with centers 1.75–2.13 mm apart (average 1.88 mm). Coenenchyme less developed. Dissepiments generally flat or slightly convex, average 14–16 per 5 mm.

Remarks.—The present material has better developed coenenchyme compared with other described Mongoliolites species, and probably represents a new species. However, it is left in open nomenclature due to limited material.

A comparison of Mongoliolites sp. with similar species is shown in Table 2 and discussed below. Mongoliolites paradoxides Bondarenko and Minzhin, 1977 , from the Upper Ordovician of central Mongolia is generally similar to Mongoliolites sp. discussed herein, but differs in having smaller corallite size (1.0– 1.5 mm in diameter) and less developed coenenchyme. Mongoliolites? giganteus recorded by White and Yang (2004) from the Stile End Formation (upper Katian) of the Stockdale Farm, Longsleddale, Lake District, England differs in larger corallite size (3.0– 3.8 mm in diameter), sparser tabulae (2–6 per 5 mm) and less developed coenenchyme. Wang et al. (2021) described M. contiguus ( Hall 1975) from the “Trelawney Beds” of the New England Region in northeastern New South Wales, which differs in possessing much less developed coenenchyme and more septa.