Protoconites minor Chen, Xiao, and Yuan, 1994

Guo, Junfeng, Chen, Yanlong, Song, Zuchen, Zhang, Zhifei, Qiang, Yaqin, Betts, Marissa J., Zheng, Yajuan & Yao, Xiaoyong, 2020, Geometric morphometric analysis of Protoconites minor from the Cambrian (Terreneuvian) Yanjiahe Formation in Three Gorges, South China, Palaeontologia Electronica (a 46) 23 (3), pp. 1-21 : 13-15

Protoconites minor Chen, Xiao, and Yuan, 1994

Figure 2.1 –18; Figure 10.1 -27

1994 Protoconites minor Chen, Xiao, and Yuan , p.

397, pl. IV, figures 10–11

1996 Protoconites minor ; Ding et al., pl. 33, figure 9 2002 Protoconites minor ; Chen et al., pl. 4, figure 6 2002 Protoconites minor ; Xiao et al., p.368, figures 7.9–7.11, 7.14–7.15

2002 Protoconites minor ; Yuan et al., p.65, figure 77 2004 Protoconites cf. minor ; Zhao et al., figure 2(e) 2005 Protoconites ; Wang et al., figure 4.2

2008 Protoconites minor ; Guo et al., figure 5.(a)-(c) 2009 Protoconites sp. ; Guo et al., figure 3.(a)–(e) 2011 Protoconites mino r; Wang et al., figure 4.J–K 2017 Protoconites sp. ; Guo et al., figures 1.1–1.2, 3.2 2018a Cambrorhytium cf. C. majo r; Chang et al.,figure 3.M

Types. Holotype (HBM-496) and paratype (HBM-506) were designated by Chen et al. (1994) and reposited in the Nanjing Institute of Geology and Palaeontology, Academia Sinica.

Material. More than 1048 specimens from the Terreneuvian Yanjiahe Fm., in Three Gorges (mainly derived from the Dingjiaping, Gunziao, Yangjiachong, and Muyang sections). All specimens are reposited in Chang’an University.

Description. Smooth conical compressions about 5–50 mm long, with a pointed apex that expands to a squared-off termination (with the aperture). Tubes 0.2–0.4 mm in diameter at apex and up to 1–7 mm at aperture. Angle of divergence 13–25 degrees. Straight or bent at the posterior part. No preserved holdfast or tentacle-like structures; no annulations or transverse markings. During the early ontogenetic stage, they are relatively wide at the aperture. Growth is primarily by aggradation on the margin of anterior aperture. Smallest specimens show no lateral bending, however, with the increasing of size, specimens are often preserved with lateral bending.

Discussion. Protoconites bears some similarities with Cambrorhytium , a tubular form that is found in Stages 3–Wuliuan in Canada (Stephen Fm.), Utah (Marjum Fm.), South China (Shuijingtuo Fm. and Shipai Fm.) and Siberia (Sinsk Fm.) (Conway Morris and Robison, 1988; Ponomarenko, 2005; Zhang and Hua, 2005; Chang et al., 2018a). However, Cambrorhytium is much larger (30–50 mm long) than Protoconites . Cambrorhytium major is also characterized by faint tentacle-like structures and transverse annulations. In their original diagnosis, Chen et al. (1994) noted annulations on Protoconites minor , but careful re-examination by Xiao et al. (2002) revealed no such features. Archotuba conoidalis (Hou et al., 1999) from the lower Cambrian Chengjiang Biota also shares a broadly similar overall shape with Protoconites , but like Cambrorhytium is much larger and bears transverse annulations not seen in Protoconites . Lantianella and Piyuania , similar tubular genera from the Ediacaran Lantian Biota in South China (Yuan et al., 2011, 2016; Wan et al., 2016), also have tentacle-like structures, transverse annulations and internal structures which distinguish them from P. minor . Protoconites also bears similarities to Sphenothallus from Cambrian Stages 3–Wuliuan in South China (Shuijingtuo Fm., Niutitang Fm., Shipai Fm., and Kaili Fm.) (Zhu et al., 2000; Peng et al., 2005; Muscente and Xiao, 2015; Chang et al., 2018a). However, Protoconites can be easily distinguished from Sphenothallus by lacking a pair of robust, longitudinal thickenings and transverse ribs. While P. minor lacks tentacle-like structures, transverse annulations and internal structures seen in Cambrorhytium , Archotuba conoidalis , Lantianella , and Piyuania , broad morphological similarities may implicate a close phylogenetic relationship between these taxa.

Occurrence. The holotype and Ediacaran specimens are derived from the upper Doushantuo Fm. black shales at Miaohe , Yinchang city, Hubei Province (Chen et al., 1994; Ding et al., 1996; Chen et al., 2002; Xiao et al., 2002; Yuan et al., 2002) and Taoying, Jiangkou county , Guizhou Province (Zhao et al., 2004; Wang et al., 2005, 2011) . The material described herein is derived from the middle Yanjiahe Fm. silty shale (Bed 3, Terreneuvian, Fortunian), Yichang area , Hubei Province .

Figures

FIGURE 2. Protoconites minor from the Cambrian (Terreneuvian) Yanjiahe Formation in Yichang, Hubei, China. 1. No. Y-24B (2); 2. No. Y-41A (5)-1; 3. No. Y-765A (3); 4. No. Y-127B (1); 5. No. Y-28 (2); 6. No. CH-179A (3); 7. No. Y-273A (1); 8. No. Y-41A (14); 9. No. Y-445 (2); 10. No. Y-494 (2)-2; 11. No. Y-40A (11); 12. No. Y-1234 (3); 13. No. Y-844A (2); 14. No. Y-785 (2); 15. No. Y-40B (9)-1; 16. No. Y-880 (6); 17. No. Y-596 (2)-1; 18. No. Y-531 (3)-2. “CH” means the locality of the fossils from Dingjiaping section, “Y” means the locality of the fossils from Yangjiachong section.

FIGURE 10. Protoconites minor from the Cambrian (Terreneuvian) Yanjiahe Formation showing morphological variance during the ontogeny. Size of these specimens increases from right to left and from top to bottom. 1. No. Y-596 (2)- 2; 2. No. Y-735A (20)-2; 3. No. Y-800A (19)-2; 4. No. Y-469B (5); 5. No. Y-581 (2); 6. No. Y-134 (10); 7. No. Y-523; 8. No. Y-1236 (2); 9. No. Y-29; 10. No. Y-617A (4)-3; 11. No. Y-558A (17); 12. No. Y-141A (19)-1; 13. No. Y-558A (33); 14. No. Y-617A (2); 15. No. Y-546A (2); 16. No. Y-732A (20); 17. No. Y-142A (8)-1; 18. No. Y-816A (4); 19. No. Y-1230A (45); 20. No. Y-425A (2); 21. No. Y-561A (5); 22. No. Y-567 (2); 23. No. Y-732A (32)-1; 24. No. Y-173A (4); 25. No. Y- 1227A (10); 26. No. Y-51A (2); 27. No. Y-24B (2). “Y” means the locality of the fossils from Yangjiachong section.