Dolerobasilicus? sp., 1934

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 : 327

Dolerobasilicus? sp.

Fig. 8.8

1915 Megalaspis sp. ; Reed 1915, p. 36, pl. 7, fig. 3.

Material. Incomplete pygidium from the Lower Naungkangyi Beds (probable Darriwilian) at Nawa, Fig. 8.8 ( Reed, 1915, pl. 7, fig. 3), GSI 11535.

Discussion. Although this species is known only from one incomplete pygidium, enough is preserved to show that it has an unusually deeply curved, elongate profile, relatively narrow axis and prominent ribs. Reed (1915) compared this specimen with the pygidium of Megalaspis (now Megistaspis ) a diverse genus that is confined to the Baltic palaeoplate in the Ordovician. A more plausible comparison is with Dolerobasilicus , described from Korea. Revision of Dolerobasilicus yokusensis Kobayashi 1934 by Lee & Choi (1988) includes several pygidia (e.g. Lee & Choi, 1988, pl. 1, fig. 9) with similar elongate form and about ten ribs. While the evidence is incomplete, it is sufficient to suggest the presence of this genus in Myanmar.

Figures

FIGURE 8. (1–6) Birmanites yunnanensis (Reed) from the Shihtien Formation (Darriwilian), Pupiao, Baoshan Prefecture, western Yunnan, China. 1. Librigena (original of Reed 1917, pl. 7, fig. 3), GSI 11892. 2. Pygidium (original of Reed 1917, pl. 7, fig. 6), GSI 11895. 3. Pygidium (original of Reed 1917, pl. 7, fig. 8), GSI 11897. 4. Librigena (original of Reed 1917, pl. 7, fig. 5), GSI 11894. 5. Articulated specimen (original of Reed 1917, pl. 6, fig. 12), GSI 11887. 6. Cephalon (original of Reed 1917, pl. 6, fig. 14), GSI 11889. (7, 10) Remopleuriidae gen. et sp. indet. (Reed) from the Shihtien Formation (Darriwilian), Pupiao, Baoshan Prefecture, western Yunnan, China. 7. Cranidium, (original of Reed 1917, pl. 6, fig. 9), GSI 11884. 10. Librigena (original of Reed 1917, pl. 6, fig. 10), GSI 11885. (8) Dolerobasilicus? sp. (Reed), Pygidium (original of Reed 1915, pl. 7, fig. 3), GSI 11535, Lower Naungkangyi Beds, Nawa, northern Shan State, Myanmar. (9) Nileus sp., Hypostome (original of Reed 1917, pl. 8, fig. 5), GSI 11904, Shihtien Formation (Darriwilian), Pupiao, Baoshan Prefecture, western Yunnan, China. (11, 12) Niobe sp. (Reed). 11a, b. Pygidium (original of Reed 1915, pl. 5, fig. 14), GSI 11516, Hwe Mawng Beds (uppermost Katian), Nati, northern part of Shan State, Myanmar, original and retrodeformation. 12. Pygidium (original of Reed 1917, pl. 6, fig. 11), GSI 11886, Shihtien Formation (Darriwilian), Shidian, Baoshan Prefecture, western Yunnan, China. Scale bars = 5 mm for 1–6, 8, 9; = 2 mm for 7, 10–12)