Eisenackitina rimosa, Li & Yan & Wang & Maletz & Liang & Yao & Wu & Chen & Cheng & Fang & Wang, 2025

Li, Yangui, Yan, Chunbo, Wang, Chuanshang, Maletz, Jörg, Liang, Yan, Yao, Huazhou, Wu, Haizhi, Chen, Weixiong, Cheng, Jingqing, Fang, Zichen & Wang, Xiaofeng, 2025, Chitinozoans from the Telychian (Llandovery, Silurian) Shenxuanyi Member, upper Ningqiang Formation of the northwestern Yangtze Platform, China, Swiss Journal of Palaeontology (20) 144 (1), pp. 1-33 : 17-18

Eisenackitina rimosa Umnova, 1976 ( Fig. 4N–P )

1976 Eisenackitina rimosa sp. nov., Umnova, p. 405, fig. 19.

1997 Eisenackitina rimosa Umnova, Geng et al. , p. 53, pl. 2, figs. 7–9. p. 54, pl. 3, figs. 5–6 & 9–10.

2021 Eisenackitina rimosa Umnova, Li et al. , p. 10, pl. III, figs. 16–17.

Material: Systematic study was performed based on eight photomicrographs.

Description: Te vesicle is sub-conical. All the specimens are flattened, with a body length of 66.9–88.13 μm, a L/ Dp ratio of 1.03–1.14, and a Dp/Dc ratio of 1.10–1.31. Te flanks are slightly convex, the chamber transitions directly into the aperture, no flexure, shoulder, or neck are observed. Tere is a very short, circular and serrated membranous collar at the end of the aperture. Te basal margin is blunt, or broadly rounded. Te basal region is always inflexed so that no more details of the basal scar are observed. Te vesicle is covered with dense verrucate ornaments. Te spacing between the ornaments is usually less than 1 μm, and usually becomes slightly sparse near the aperture.

Measurements: Measured data based on eight specimens.

Comparison and remarks: Geng et al. (1997) discussed the morphological features of E. rimosa in detail. Its conical vesicle (with a length of 119 μm, and a L/Dp ratio of 1.3) has a short membranous collar. Tere are no flexures, necks, and shoulders observed. Te vesicle surface is covered with granular ornaments. A circular and wide basal scar (10 μm in diameter) is located at the center of the base. Te morphological features of our specimens are consistent with the statement of Geng et al. (1997).

Eisenackitina zhangjiajieensis Geng et al., 1997 is an index species used to indicate the Telychian of the Yangtze region ( Wang et al., 2020). Its vesicle surface is covered with verrucate ornaments, consistent with E. rimosa . But it is different from E. rimosa in its vesicle is trapezoidal and with an aspect ratio of less than one.

Locality and stratigraphic horizon: Tis species was first described from the upper Ludlow of the Kustiskaya bore (southeastern Russia) by Umnova (1976). But in the Yangtze Platform, its stratigraphic range is longer. It was reported from the upmost Aeronian and lower Telychian Luoreping Formation of western Hubei Province ( Li et al., 2021; Wang et al., 2020) to the Ludlow Guandi Formation of Qujing region, Yunnan Province ( Cai et al., 2020; Geng et al., 1997). In the current study, it was found from the lower Shenxuanyi Member of the Majia section.

Figures

Fig. 4 Llandovery chitinozoans from the Shenxuanyi Member.Scale bars represent 50 μm (except the scale bar of specimens M and P represent 10 μm). A–C Bursachitina rectangularis (Zaslavskaya, 1983) (A N62-4. B N54-12. C N66-7). D–F Bursachitina sp. 1 (D N21-11 & 12. E N39-26. F N37-1). G–I Bursachitina (?) sp. 1 (G N91-4. H N56-5. I N39-3). J-M Eisenackitina causiata Verniers, 1999 (J N59-9. K N60-16. L N87-6. M close-up of N59-9 showing the ornaments). N-P Eisenackitina rimosa Umnova, 1976 (N N45-5. O N43-3. P close-up of N43-3 showing the ornaments).P-Q Eisenackitina venusta Tsegelnjuk, 1982 (P N47-7. Q N47-7)