Illaenus caecoides Reed, 1917

Fortey, Richard A., Wernette, Shelly J. & Hughes, Nigel C., 2022, Revision of F. R. C. Reed’s Ordovician trilobite types from Myanmar (Burma) and western Yunnan Province, China, Zootaxa 5162 (4), pp. 301-356 : 346

Illaenus caecoides Reed, 1917

Fig. 15.5

1917 Illaenus caecoides sp. nov.; Reed, p. 45–6, pl. 7, figs 9–10.

Material. Lectotype (selected herein): dorsal exoskeleton, Fig. 15.5 ( Reed, 1917, pl. 7, fig. 9), GSI 11898. Additional type material: pygidium ( Reed, 1917, pl. 7, fig. 10), GSI 11899. Both specimens from the Shihtien Formation (Darriwilian) at Banpo Village in Shidian County, western Yunnan.

Remarks. We were unable to make a satisfactory cast of the lectotype, and Reed’s original illustration is reproduced here. Although the dorsal exoskeleton is complete it is much abraded. Reed (1917, p. 46) inferred that this was a blind species of “ Illaenus ” but we regard it as more probable that the abrasion of the dorsal surface has removed evidence of the facial sutures and the visual surfaces from a more typical illaenid. If this is so there are very few possible specific characters, and the species will not be recognisable until more collections are made from the type locality.

Figures

FIGURE 15. (1–4) Metopolichas? sp. 1 (Reed) from the Li-Lu and Kunlein formations (Katian), northern Shan State. 1. Hypostome (original of Reed 1915, pl. 7, fig. 15), GSI 11546, Mân-ngai. 2. Hypostome (original of Reed 1915, pl. 7, fig. 16), GSI 11547, Lilu. 3. Partial cranidium (original of Reed 1915, pl. 7, fig. 14), GSI 11545, Tâ-Pangtawng. 4a, b. Immature cephalon (original of Reed 1915, pl. 7, fig. 17), GSI 11548, Makmongshai, original and retrodeformation. (5) Illaenus caecoides Reed, Complete specimen (refigured from Reed 1917, pl. 7, fig. 9), GSI 11898, Shihtien Formation (Darriwilian), Banpo Village, Shidian County, Baoshan Prefecture, western Yunnan, China. (6–8) Phorocephala mansuyi, Cranidium (refigured and original from Reed 1917, pl. 8, fig. 7), GSI 11848, dorsal and lateral views, Shihtien Formation (Darriwilian), Pu-piao, Baoshan Prefecture, western Yunnan, China. (9) Metopolichas sp. 2 (Reed), Cephalon (original of Reed 1917, pl. 8, fig. 9), GSI 11910, Shihtien Formation (Darriwilian); Pupiao, Baoshan Prefecture, western Yunnan, China. (10) Stygina? sp. (Reed), Cranidium (original of Reed 1915, pl. 7, fig. 13), GSI 11544, Hwe Mawng Beds (uppermost Katian), Mong-Ha, northern part of Shan State, Myanmar. Scale bars = 2 mm for 1, 10; = 1 mm for 2, 4, 6–9; = 5 mm for 3, 5.