Phorocephala mansuyi ( 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 : 348

Phorocephala mansuyi ( Reed, 1917)

Figs 15.6-8

1917 Bathyurus mansuyi sp. nov.; Reed, p. 50–51, pl. 8, fig. 8.

1975 Phorocephala mansuyi (Reed) ; Lu, p. 189, 396.

1984 Phorocephala mansuyi (Reed) ; Zhou, Yin & Tripp, p. 24.

Material. Holotype: cranidium from Shihtien Formation (Darriwilian) at Pupiao, Baoshan Prefecture, Figs 15.6–8 ( Reed, 1917, pl. 8, fig. 8), GSI 11848.

Discussion. The single example of this species is too fragile to cast successfully and we are obliged to re-use Reed’s original (1917) illustration, with the cast showing preglabellar features. Phorocephala species vary with regard to the size of the eyes, though they are always prominent. In P. mansuyi the palpebral lobes are of relatively moderate size and posteriorly positioned, and in this regard this species is different from several other large-eyed Chinese species, such as P. quadrata Zhou & Dean, 1986 ; these last authors also reviewed other species that might be assigned to Phorocephala .

Phorocephala mansuyi was the first of these species to be named and therefore is potentially a senior name for a few other species with moderately-sized palpebral lobes. These include particularly the type species, P. typa Lu, 1965 , and P. shizipuensis Yin in Yin & Li (1978) from Guizhou Province (see Zhou et al., 1984). The former (see Lu, 1975, pl. 34, fig. 13) has a slightly wider cranidium than P. mansuyi and its preglabellar field is the same width (sag.) as the cranidial border, whereas on P. mansuyi the border is certainly narrower than the preglabellar field. One cranidium of P. shizipuensis illustrated by Zhou et al. (1984, fig. 5v) has similar general proportions to the type, and only known specimen of P. mansuyi , and on this specimen the border also seems to be convex rather than “upturned” ( Zhou et al., 1984, p. 24) as claimed from P. shizipuensis . However, the cranidial border does seem to be wider than on P. mansuyi on several specimens used to illustrate P. shizipuensis by Zhou et al. (1984). Since both P. mansuyi and P. typa are known from only one cranidium apiece there is no way of assessing variation in these species, and the eventual status of P. mansuyi will depend on new collections.

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.