Vietnamia sp. A

Lee, Dong-Chan, 2013, Late Ordovician trilobites from the Xiazhen Formation in Zhuzhai, Jiangxi Province, China, Acta Palaeontologica Polonica 58 (4), pp. 855-882 : 872-873

Vietnamia sp. A

Fig. 8Q.

Material.—One incomplete cephalon (repository number NIGP−152031).

Remarks.—This species differs from co−occurring Vietnamia yushanensis sp. nov. in having a strongly dorsally arched anterior cephalic margin, posterior cranidial border furrow that is smoothly curved forwards distally, moderately convex sagittal area between L 1, more weakly developed intermediate lobe, and truncated anterior glabellar margin. The dorsal flexure of the anterior cephalic margin of this species is the strongest of the Vietnamia species described herein.

Turvey (2005: pl. 4: 2) illustrated a rostral plate of Vietnamia douvillei ( Mansuy, 1908) . The impression of the rostral plate of Vietnamia yushanensis sp. nov. (Fig. 8 Q 1, Q 2) accords with the morphology of V. douvillei ; a fissure in the middle of left half (Fig. 8 Q 2) represents a connective suture. The upside down anvil−shaped rostral plate of Vietnamia differs from Neseuretus (see Whittington 1966: pl. 5: 5, 6, 8, 10; Hammann 1983: pl. 4: 39b) in being laterally bounded by less divergent connective sutures, and from Calymenesun and Reedocalymene (see Peng et al. 2000: text−fig. 1 A – E, pl. 3: 1–3) in having a doublure sector that is much wider (tr.) than the border sector.

http://dx.doi.org/10.4202/app.2010.0036