Neseuretinus birmanicus ( Reed, 1906 )

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 : 338

Neseuretinus birmanicus ( Reed, 1906)

Figs 12.9,11–15

Synonymy. See Turvey, 2005, p. 560; also Ghobadi Pour & Popov 2009

Material. Lectotype (selected Turvey, 2002, p. 560): cranidium from probable Lower Naungkangyi Beds (probable Darriwilian) at Kunkaw, Fig. 12.9 ( Reed, 1906, pl. 5, fig. 27), GSI 8341. Additional material: pygidium from Lower Naungkangyi Beds (probable Darriwilian) at Loikok, Figs 12.14 , 15 ( Reed, 1915, pl. 8, fig. 5), GSI 11553; 2 cranidia from Upper Naungkangyi Beds (Katian) at Lilu (Reed, pl. 8, figs 1,4), GSI 11549, 11552 respectively; cranidium from Hwe Mawng Beds at Pa-hki ( Reed,1915, pl. 8, figs 2), GSI 11550; pygidia from the Lower and Upper Naungkangyi Beds (Katian) at Lilu and Loi Kok (Reed, pl. 8, figs 3,5), GSI 11551, 11553 respectively. Material from new collections: crandidium, pygidium with partial thoracic segment, and pygidium from Pupiao Formation (Katian) at Pupiao, Figs 12.11–13 , CMC 91532–91534 respectively.

Discussion. Turvey (2005) gave a full description of this species, and it is not necessary to reillustrate all Reed’s material in this work. The lectotype is refigured here for the record. Well-preserved articulated specimens from Iran attributed to N. birmanicus have been described by Ghobadi Pour & Popov (2009), who included several other species in their synonymy. As presently conceived, N. birmanicus has a long stratigraphic range. The type material is likely to come from the Lower Naungkangyi Beds and is probably Darriwilian in age, as is material from Loikok. This is the same age as the good specimens from Iran figured by Ghobadi Pour and Popov (2009). However, the other specimens in Reed (1915) refigured by Turvey (2005) are from the Upper Naungkangyi Beds and Katian in age. It does seem unlikely that a single species would have such an extensive stratigraphical range. Ghobadi Pour (written communication 2021) has pointed out that the Katian pygidia have eight pleural ribs, whereas Darriwilian examples from Iran and Myanmar have six ribs. If this is consistent, it does suggest that there are two taxa involved under the name birmanicus . Neseuretinus specimens from Uzbekistan figured by Kolobova (in Sokolov & Yolkin, 1978, pl. 27, figs. 1-5) under the name Calymenesun tingi were reassigned to Neseuretinus turcicus by Hammann & Leone (1997) and have six pygidial pleural ribs. There is also another poorly nown species from Afghanistan described by Wolfart (1970) ( Neseuretinus malestanus ) that may be an available name for the Katian species, with relevant Reed specimens illustrated by Turvey (2005). For present purposes we separate the Katian species from the Darriwilian type material as Neseuretinus aff. birmanicus pending a comparative treatment of all these taxa.

Also figured are some additional specimens of Neseuretinus aff. brimanicus collected from the Pupiao Formation at the Pupiao section in Baoshan Prefecture, W. Yunnan by NCH in 1999. These specimens provide a connection between Katian strata in northern Shan State and western Yunnan. However, a cranidium from the Shihtien Formation attributed to N. birmanicus in Zhang et al. (2014, fig. 5.41E) differs from the type of N. birmanicus in having a more rectangular glabella and more anteriorly positioned palpebral lobes. The palaeogeographical distribution of Neseuretinus was also discussed by Turvey (2002) who noted its wide distribution across Ordovician Gondwana and inferred its probable phylogeny. GSI 11550 figured by Turvey (2005, pl. 2, fig. 9) is reported as being from the Hwe Mawng Beds, and appears identical to specimens from the Upper Naungkangyi Beds.

Figures

FIGURE 12. (1–6,8,10) Reedocalymene unicornis (Reed) from the Shihtien Formation (Darriwilian), Pupiao, Baoshan Prefecture, western Yunnan, China. 1–3. Cranidium (original and refigured of Reed 1917, pl. 8, fig. 10a,b), GSI 11913. 4. Pygidium (refigured from Reed 1917, pl. 8, fig. 13), GSI 11911?. 5. Partial cranidium (original of Reed 1917, pl. 8, fig. 12); GSI 11912?. 6. Partial cranidium (refigured from Reed 1917, pl. 8, fig. 11), GSI 11912?. 8. Partial cranidium (refigured from Reed 1917, pl. 8, fig. 12), GSI 11912?. 10. Partial cranidium (original of Reed 1917, pl. 8, fig. 11), GSI 11912?. (7) Reedocalymene? sp. (Reed), Thorax and pygidium (original of Reed 1917, pl. 8, fig. 14), GSI 11914, Shihtien Formation (Darriwilian); Pupiao, Baoshan Prefecture, western Yunnan, China. (9,11–15) Neseuretinus aff. birmanicus (Reed) from the Li-Lu and Pupiao formations (Katian). 9. Cranidium (lectotype, original of Reed 1906, pl. 5, fig. 27), GSI 8341, Kunkaw, northern Shan State, Myanmar. 11. Cranidium; CMC IP 91532, Pupiao, Baoshan Prefecture, western Yunnan, China. 12. Pygidium and partial thorax, CMC IP 91533, Pupiao, Baoshan Prefecture, western Yunnan, China. 13. Pygidium, CMC IP 91534, Pupiao, Baoshan Prefecture, western Yunnan, China. 14, 15. Pygidium (original of Reed 1915, pl. 8, fig. 5), GSI 11553, Loikok, northern part of Shan State, Myanmar, dorsal and right lateral views. Scale bars = 2 mm for 1–6, 8–10, 12–15; = 5 mm for 7, 11.

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.