Protopliomerella, Adrain, 2011

Adrain, Jonathan M., 2011, Revision of the Lower Ordovician (lower Floian; Tulean) pliomerid trilobite Protopliomerella, with new species from the Great Basin, western USA 3144, Zootaxa 3144, pp. 1-113 : 27

Protopliomerella n. sp. A

( Plate 41, Plate 42, figs 1–13)

Material. Assigned specimens SUI 126346–126359, from Section YH 129.5 m, Yellow Hill Limestone (lower Floian; Tulean; Heckethornia hyndeae Zone ), Yellow Hill, near Pioche, Lincoln County, eastern Nevada.

Discussion. Specimens of Protopliomerella n. sp. A differ from those of P. okeeffeae in possessing more coarsely granulose cranidial sculpture, and more tuberculate dorsal thoracic and pygidial sculpture. Cranidia have a less anteriorly tapered glabella with a more faintly impressed S3, the interocular fixigenae are longer, and pygidia are slightly narrower and more elongate, with a narrower and more elongate terminal piece and longer, more strongly posteriorly directed pleurae. The librigena (Pl. 42, fig. 4) is not well preserved, but it shows coarser lateral border sculpture, and a possibly wider posterior section of the librigenal field. The species are otherwise very similar, but the sculptural difference between specimens of similar sizes is striking. Protopliomerella okeeffeae is known from a single cranidium ( Adrain et al., 2009, fig. 14L) at Section YH 128.9 m, at which Protopliomerella n. sp. A does not occur.