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 : 28

Protopliomerella n. sp. B

( Plate 42, figs 14–25)

1973 Genus and species undetermined (not described); Demeter, pl. 6, figs 10, 12 (only; pl. 6, figs 1–9, 11 = gen. and sp. indet.).

Material. Assigned specimens SUI 126360–126364, from Section D 94.4 T m, Fillmore Formation (lower Floian; Tulean; low Psalikilopsis cuspidicauda Zone ), southern House Range, Tule Valley, Millard County, western Utah, USA.

Discussion. Protopliomerella n. sp. B is known from only a few sclerites (two librigenae and three pygidia), but the unique pygidial morphology of seven segments demonstrates that it is a new species. The pygidium is somewhat similar to that of P. bowlesi , but in addition to possessing another segment, it is longer and wider overall; the axis is relatively wider anteriorly and narrower posteriorly; the pleurae are more laterally directed, not as tightly backturned, and less strongly vaulted; the inter-ring furrows are shorter; and the sculpture is slightly less effaced, with small tubercles or granules particularly noticeable running along the adaxial side of the pleurae just outside the interpleural furrows. Librigenae differ in that those of P. bowlesi are more strongly curved; much wider, particularly across the anterior part of the field; and possess a relatively narrower lateral border, with a shorter posterior projection and longer anterior projection.

The librigena of the younger species P. kerouaci more closely resembles that of Protopliomerella n. sp. B, but its librigenal field is somewhat wider anteriorly and narrower posteriorly, and it has a slightly narrower lateral bor- der with a much longer and strongly posterodorsally directed posterior projection. The pygidia are not closely similar, as that of P. kerouaci has only five segments, and a large, complexly impressed terminal piece. The pygidium of the younger species P. seegeri somewhat more closely resembles that of Protopliomerella n. sp. B (in that it also resembles that of P. bowlesi ), but again, it possesses only six segments, with strongly backturned and highly vaulted pleurae, and its axis is fairly densely covered in small tubercles.

Demeter (1973, pl. 6, figs 10, 12) figured two seven-segmented pygidia likely assignable to Protopliomerella n. sp. B from Section G at about 150.1 m. We have collected horizons G 148.2, 151T and 151.5T, but have not recovered any material assignable to this species.