Eisenackitina venusta Tsejelnjuk, 1982

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 : 18

Eisenackitina venusta Tsejelnjuk, 1982 ( Fig. 4Q, R and

Fig. 5A, B )

1982 Eisenackitina venusta sp. nov., Tsejelnju, p. 40, pl.3, fig. 3.

1997 Eisenackitina venusta Tsejelnju, Geng et al. , p. 54, pl. 2, figs. 1–5. p. 55, pl. 3, fig. 7

2023 Eisenackitina venusta Tsejelnju, Rong et al. , p. 58, figs. 8 (3–5).

Material: Systematic study was performed based on 11 photomicrographs.

Description: Most of our specimens are fully flattened. Te vesicle (longer than wider, 67–87 μm long, and 60–83 μm wide) is conical or sub-conical, with relatively straight flanks. Te chamber is slightly constricted near the aperture so that there is a weak shrink between the membranous collar and the chamber. Te serrated collar expands and everts distally, with a length of about 5 μm. Te basal margin is blunt or broadly rounded. Te basal region of some specimens is inflexed. While some specimens have an outward base, it could be observed that the basal mucron is a small concentric pit. Te vesicle surface is covered by closely spaced and irregular miniature verrucate ornaments, and the interval of size is 1 μm. Near the collar and the basal center, the ornaments are significantly diminished.

Measurements: Measured data based on 11 specimens.

Comparison and remarks: In the Yangtze Platform, the E. venusta was firstly found by Geng et al. (1997). According to Geng et al. (1997) and Wang et al. (2020), E. venusta (97 μm long and 92 μm wide) has a flared and everted collar at the aperture, a truncated conical mucron at the basal center, and is covered by dense granular ornaments on the vesicle surface. Te specimens in this study and reported by Geng et al. (1997) and Wang et al. (2020) are consistent. Even though the ornamentation may not be correct for the genus, due to previous authors considering the same features for the species, the same characteristics are considered herein.

E. venusta and E. rimosa have consistent vesicle morphology, analogous ornaments, and similar basal mucron. Te long-everted collar of E. venusta is the most important feature to differentiate it from E. rimosa ( Wang et al., 2020) .

Locality and stratigraphic horizon: According to Tsejelnjuk (1982), E. venusta was found in the upper Telychian Furmanov Formation of Podolian. Research in recent years has shown that it is an important Telychian species in the Yangtze Platform. It was reported from the Xiaoxiyu and Huixingshao formations of western Hunan Province ( Geng et al., 1997; Rong et al., 2023; Wang et al., 2020) and Jukeng Formation of South Jiangsu Province ( Rong et al., 2023). Twelve specimens were found in the lower Shenxuanyi Member of the Majia section in this study .

Eisenackitina zhangjiajieensis Geng et al., 1997

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)

Fig. 5 Llandovery chitinozoans from the Shenxuanyi Member.Scale bars represent 50 μm (except the scale bar of specimens B, F, J, R, S and T represent 10 μm). A, B Eisenackitina venusta Tsegelnjuk,1982 (A N83-6. B close-up of N47-7 showing the ornaments). C-F Eisenackitina zhangjiajieensis Geng et al., 1997 (C N87-2. C N90-12. E N97-7. F close-up of N97-7 showing the ornaments). G Conochitina (?) sp. 1 (G Ch3-1). H Belonechitina sp. 1 (H N3-5). I Belonechitina sp. 2 (I N103-1). J–M Sphaerochitina palestinaense Grahn et al., 2005 (J close-up of N62-14 showing the ornaments. K N9-15. L N70-6. M N62-14). N–T Angochitina bipedata Geng et al, 1997 (N N55-15. O N55-7. P N39-11. Q N19-4. R close-up of N19-4 showing the ornaments. S close-up of N55-7 showing the ornaments.T close-up of N94-6 showing the ornaments)