Angochitina sp. 5

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 : 25

Angochitina sp. 5 ( Fig. 8F–M )

Material: Systematic study was performed based on 63 photomicrographs.

Description: Te ovoid chamber (shoulder is inconspicuous) with convex flanks, rounded margin and base. Te flexure between the chamber and neck is also rounded. Te neck is cylindrical, and occupies 1/3 of the total length. Some intraspecific variation specimens have significantly shorter necks (less than 1/3 of the total length). Te neck transitions into a slightly dilated membranous collar at the aperture, with a Dp/Dc ratio of 1.54–2.60. Te ornaments on the vesicle surface are discontinuous triangular membranes that shrink into distinct crests. Tese longitudinally arranged spines are not dense, the interval of size is 2–5 μm. Te ornaments near the aperture are significantly reduced.

Measurements: Measured data based on 24 specimens.

Comparison and remarks: Its ovoid chamber and cylindrical neck are similar to those of Angochitina cf. paucispinosa Miller et al., 1997 , Angochitina echinata Eisenack, 1931 , A. fentouensis , A. hansonica , A. rarispinosa , and A. longicollis , but its triangular membranous spines with marked crests are different from theirs. Although Mullins and Loydell (2001) also reported some discontinuous membranes at the base of the spines of A. longicollis , it is different from that of Angochitina sp. 6 by longer and denser spines. Besides, Angochitina sp. 1 reported in this study has denser ornaments and a narrower neck. Terefore, they are different taxa, and the current study tentatively assigns it to Angochitina sp. 5 .

Locality and stratigraphic horizon: Specimens were discovered from the Shenxuanyi Member.

Figures

Fig. 8 Llandovery chitinozoans from the Shenxuanyi Member. Scale bars represent 50 μm (except the scale bar of specimens A, B, I and M represent 10 μm). A, B Angochitina sp. 3 (A close-up of N8-14 showing the ornaments. B close-up of N11-1 showing the ornaments). C–E Angochitina sp. 4 (C N21-9. D N21-10. E N37-3). F–M Angochitina sp. 5 (F N19-3. G N31-2. H N19-13. I close-up of N19-13 showing the ornaments. J N7-19. K N4-17. L N4-6. M close-up of N7-19 showing the ornaments)