Dalmanitina? dagon ( Reed, 1915 ), 1905

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 : 342-343

Dalmanitina? dagon ( Reed, 1915)

Figs 13.10 , 11

1915 Phacops (Pterygometopus) dagon ; Reed, pl. 9, figs 1–6, non fig. 3.

Material. Lectotype (selected herein): cephalic shield, original of Reed (1915) pl. 9, fig 1, GSI 11568. Pygidium, original of Reed (1915) pl. 9, fig. 5, GSI 11571. Upper Naungkangi Beds, Mangai. All specimens from Upper Naungkangyi Beds (Katian) at Man Ngai, northern Shan State.

Discussion. As considered above, Reed (1915) described a variety of what he termed Phacops (Pterygometopus) dagon as var. wynnei , which is regarded herein as a different taxon. The material of the nominate species is limited, and we have not been able to cast some of the original specimens, as they are fragile. The robust largest cranidium is selected as lectotype. A smaller cephalon illustrated by Reed (1915, pl. 9 fig. 2; Fig. 13.10 ) shows a well-defined anterior border, which was likely also present on the lectotype, though obviously broken medially in that specimen. Such a border is atypical of Dalmanitina , and may possibly suggest such genera as Mucronaspis , but without knowledge of the rest of the exoskeleton we prefer a provisional allocation to the older established genus. This border is extremely narrow on wynnei . The glabella of dagon is comparatively transverse anteriorly, and the bifurcation of the S1 is not so marked. Another small? cephalon illustrated by Reed (1915, pl. 9, fig. 3) is more like wynnei and is excluded from dagon here. The generic assignment of D.? dagon is equivocal, and the eyes are longer (exag.) than is typical for the dalmanitines according to Holloway (1981), a subfamily hard to delimit ( Hammann & Leone, 2007). The species is placed provisionally in Dalmanitina pending a more comprehensive revision of Late Ordovician species.

Figures

FIGURE 11. Encrinurella insangensis (Reed) from the Li-Lu and Kunlein Formations (Katian), northern Shan State, Myanmar. 1a, b. Cranidium (original of Reed 1915, pl. 8, fig. 16), GSI 11562, Hweyawt, original and retrodeforamtion. 2. Cranidium (original of Reed 1915, pl. 8, fig. 15), GSI 11561, Mân-ngai. 3. Cranidium (original of Reed 1915, pl. 8, fig. 18), GSI 11564, Makmongshai. 4. Cranidium (original of Reed 1906, pl. 5, fig. 24), GSI 8338, Kun-lein. 5. Pygidium (original of Reed 1915, pl. 8, fig. 19), GSI 11565, Mân-ngai. 6. Pygidium (original of Reed 1915, pl. 8, fig. 20), GSI 11566, Mân-ngai. 7. Pygidium (original of Reed 1906, pl. 5, fig. 20), GSI 8336, Insang. 8. Thorax (original of Reed 1906, pl. 5, fig. 25), GSI 8339, Ledet. 9. Cranidium and pygidium (lectotype, original of Reed 1906, pl. 5, figs 21&22), GSI 8335, Hweyawt. 10. Cranidium and pygidium (original of Reed 1906, pl. 5, figs 19 and 23), GSI 8334, Hweyawt. Scale bars = 2 mm.

FIGURE 13. (1) Hadromeros? submitis (Reed), Cranidium (original of Reed 1915, pl. 8, fig. 13), GSI 11560, Li-Lu Formation (Katian); Lilu, northern Shan State, Myanmar. (2) Placoparina? dravidicus (Reed), Pygidium (original of Reed 1915, pl. 8, fig. 12), GSI 11559, Lower Naungkangyi Beds; Mâ Shio, northern Shan State, Myanmar. (3) Sphaerocoryphe sp. (Reed), Cranidium (original of Reed 1906, pl. 5, fig. 26), GSI 8340, Naungkangyi Beds, Insang, northern part of Shan State, Myanmar. (4–9) Yanhaoia wynnei (Reed) from the Li-Lu Formation (Katian) and Hwe Mawng Beds (uppermost Katian), northern Shan State, Myanmar. 4. Cranidium (original of Reed 1915, pl. 9, fig. 3), GSI 11569, Mân-ngai. 5. Partial cranidium (original of Reed 1915, pl. 9 fig. 7), GSI 11573, Hwe Mawng. 6. Partial cranidium (original of Reed 1915, pl. 9, fig. 11), GSI 11577, Mong Ha. 7. Pygidium (original of Reed 1915, pl. 9, fig. 12), GSI 11578, Hpakhi. 8. Cranidium and thorax (cast from lectotype, original of Reed 1915, pl. 9, fig. 10), GSI 11576, Hwe Mawng. 9. Pygidium (original of Reed 1915, pl. 9, fig. 5), GSI 11571, Nawng Yu. (10–11) Dalmanitina? dagon (Reed) from the Li-Lu Formation (Katian) and Hwe Mawng Beds (uppermost Katian), northern Shan State, Myanmar. 10. Cranidium (refigured from Reed 1915, pl. 9, fig. 2), GSI 11568-11572, Mân-ngai. 11. Cephalon (original of Reed 1915, pl. 9, fig. 1), GSI 11568, Mân-ngai. (12) Illaenus sp. (Reed), Partial cranidium (refigured from Reed 1917, pl. 8, fig. 3), GSI 11906, Shihtien Formation (Darriwilian), Pupiao, Baoshan Prefecture, western Yunnan, China. Scale bar = 2 mm for 1, 3, 4, 6–9; = 5 mm for 2, 5, 10–12.