Liexiaspis Liu, 1982

Wei, Xin & Zhou, Zhiqiang, 2023, Floian, Early Ordovician, trilobites from the Olongbluk Terrane, northwest China, Acta Palaeontologica Polonica 68 (4), pp. 683-693 : 691

Genus Liexiaspis Liu, 1982

Type species: Liexiaspis zhengjiaensis Liu, 1982 ; upper Tremadocian , Lower Ordovician , Madaoyu Formation; Liexi, western Hunan Province, China .

Species included: Type species and Liexiaspis sp. of Fang et al. (2022).

Liexiaspis sp.

Fig. 7 .

Material.— Two pygidia ( NIGP 203177–203178 ) from the middle part of the Duoquanshan Formation ( upper Floian , Lower Ordovician), Shihuigou section, northwestern Qinghai Province, China .

Description.—Pygidium is subhexagonal in outline, roughly as wide as long. Axis tapers rapidly rearwards, occupying about 64% and 45% of the pygidial length and the maximum width respectively; composed of four rings with articulating half-ring and terminal piece, which are well defined by axial ring furrows forwardly arched. Pleural region has four pairs of ribs separated by deep interpleural furrows, and becoming slightly narrower (tr.) and more posteriorly directed rearwards. Terminal piece is triangular, laterally enclosed by the fourth pair of ribs.

Remarks.—The present specimens agree well with the pygidium of the type species Liexiaspis zhengjiaensis Liu (1982: 339 , pl. 238: 13) from the Madaoyu Formation (upper Tremadocian, Lower Ordovician) of western Hunan Province especially in the shape of the pygidial axis, and the number of the pleural ribs and axial rings. Herein, we prefer to regard our specimens as species indeterminate because of the lack of associated cranidia from the same horizon. Another species, Liexiaspis sp. , figured by Fang et al. (2022: fig. S1-h) from the Madaoyu Formation (middle Floian, Lower Ordovician) of western Hunan Province differs clearly from the present form in having five axial rings and five pairs of pleural ribs.

Figures

Fig. 7. Pliomerid trilobite Liexiaspis sp., from the middle part of the Duoquanshan Formation (upper Floian, Lower Ordovician) of Shihuigou, Delingha, northern Qinghai Province, China. A. NIGP 203177, pygidium. B. NIGP 203178, pygidium. Scale bars 2 mm.