Niobe Angelin 1851

Niobe ? sp.

Figs 8.11, 12

1915 Asaphus cf. ornatus Pompeckj; Reed, p. 29–30, pl. 5, fig. 14.

Material. Pygidium from the Hwe Mawng Beds (uppermost Katian) at Nati, Fig. 8.11 (Reed, 1915 pl. 5, fig. 14), GSI 11516. Reed (1915, p. 30) also mentions an asaphid thorax from a much larger individual, unfigured, but we did not locate this specimen.

Discussion. A cast from the counterpart of the specimen figured by Reed (1915) shows some lateral extensive deformation, and a simple retrodeformation of this specimen is shown in Fig. 8.11b, suggesting that the pygidium was originally slightly less than twice as wide as long. It is not otherwise badly preserved. Four progressively shorter and relatively well-defined pleural ribs fade under halfway across the pleural fields, and interpleural furrows are not developed. Four (faint fifth) axial rings on the axis, of which only the first two pass across the mid part of the axis, posterior 40% of the axis slightly convex and unfurrowed. The termination of the ribs usually marks the inner edge of the doublure in asaphids, which would indicate a straight line converging on the posterior part of the axis, around which it would be deeply embayed. The pygidial border is hardly developed. The structure of the pygidium is more like that of a niobinid than any other asaphid group. In the type species of the genus the pygidium has a well-developed border and lobe-like pleural rib terminations, but this is not true of all species that have been attributed to Niobe. No post-Tremadoc species are currently recognised in China (Zhou & Zhen, 2008). However, two specimens of thorax + pygidium figured by Lu et al. (1965, pl. 94, figs 15, 16) under the name Basiliella yunnanensis (Reed) are much more like the Niobe considered here in their short pygidial pleural furrows, and unlike the type material of yunnanensis considered above. Outside China, the closest match is probably with the pygidium of the holotype of Niobe occulta Fortey, 1975 from the late Floian of Spitsbergen (Fortey, 1975, pl. 6, fig.1) with slightly longer pleural furrows and more axial rings, but without cephalic sclerites it is not possible to make further comparison. In view of the stratigraphical difference from other niobines it is identified with question accordingly. A small pygidium from the Shihtien Formation at Pupiao, Yunnan, described by Reed (1917, pl. 6, fig. 11) as Asaphus aff. expansus is more similar to that of Niobe sp. than other asaphid pygidia (see Fig. 8.12) although with one less pleural furrow. It is recorded here as Niobe sp.