Angochitina sp. 1

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 : 24

Angochitina sp. 1 ( Fig. 7F, G )

Material: One flattened specimen.

Description: Its outline is slender, with a total length and a L/Dp ratio of 171 μm and 2.58, respectively. Te chamber is cono-ovoid, with convex flanks and a round margin and base. Te chamber shrinks evenly into the neck, and the neck is conical and gradually contracts distally. Te flexure between the chamber and the neck is weak. Tere is a long membranous collar (15 μm long) at the end of the aperture. Te neck length (including the collar) is approximately half of the total length. Te ornaments on the vesicle surface are discontinuous membranes, distributed longitudinally and reduced at the neck and base.

Measurements: Measured data based on one specimen.

Comparison and remarks: Chitinozoans covered by membranous ornaments are unusual in the Llandovery. Although the membranous ornaments of Hercochitina ( Jansonius, 1964) are also arranged longitudinally ( Paris et al., 1999) and exhibit good continuity ( Soufiane & Achab, 2000), its conical chamber (without neck) differs from the cono-ovoid chamber (with tubular neck) of Angochitina sp. 1 . Te ornaments of Ramochitina (Sommer and van Boekel, 1964) are distinct crests (vertical rows of spines or membranes) ( Paris et al., 1999). In contrast, the membranous ornaments of Angochitina sp. 1 lack distinct crests, indicating they are different species. Te vesicle form of Angochitina sp. 1 is similar to A. longicollis , both of them have ovoid chamber and longer neck. But A. longicollis is mainly covered by simple and hollow spines ( Laufeld, 1974; Nestor, 1994). Although in the report of Mullins and Loydell (2001), figure 7 of plate 2 shows the membrane at the base of the spinous ornaments of A. longicollis , they are different species as Angochitina sp. 1 does not have distinct crests.

Te specimen we recognize appears to be a transition element of Angochitina ( Eisenack, 1931) and Ramochitina (Sommer and van Boekel, 1964) . Due to its vesicle form resemble that of A. longicollis , this study tentatively assigns it to Angochitina sp. 1 .

Locality and stratigraphic horizon: It was recognized in the uppermost of the Shenxuanyi Member.

Figures

Fig. 7 Llandovery chitinozoans from the Shenxuanyi Member.Scale bars represent 50 μm (except the scale bar of specimens D, E, G, K and M represent 10 μm). A–E Angochitina synaphacantha (Geng et al., 1997) (A N39-27. B N42-8. C N23-7. D, E close-up of N39-27 showing the ornaments). F-G Angochitina sp. 1 (F N4-21. G close-up of N4-21 showing the ornaments). H–M Angochitina sp. 2 (H N5-7. I N2-12. J N7-11. K close-up of N5-7 showing the ornaments. L N3-19. M close-up of N3-19 showing the ornaments). N–S Angochitina sp. 3 (N N3-14. O N10-3. P N8-14. Q N64-7. R N58-67. S N11-1)