Deltapliomera, E.B & Adrain & Karim, 2018

E. B, Neo, Adrain, Jonathan M. & Karim, Talia S., 2018, The pliomerid trilobite Ibexaspis and related new genera, with species from the Early Ordovician (Floian; Tulean, Blackhillsian) of the Great Basin, western USA, Zootaxa 4525 (1), pp. 1-152 : 23

Deltapliomera n. gen.

Type species. Deltapliomera humphriesi n. sp., from the Fillmore Formation (Blackhillsian; Carolinites nevadensis Zone ), southern Confusion Range, Ibex area, Millard County, western Utah, USA.

Other species. Deltapliomera inglei n. sp., Fillmore Formation (Tulean; Heckethornia bowiei Zone ), western Utah; D. heimbergi n. sp., Fillmore Formation (Tulean; Panisaspis sevierensis Zone), western Utah; D. eppersoni n. sp., Fillmore Formation (Blackhillsian; Bathyurina plicolabeona Zone ), western Utah; Deltapliomera n. sp. A, Fillmore Formation (Tulean; Panisaspis sevierensis Zone), western Utah.

Etymology. The town of Delta, Utah, and the genus name Pliomera . Gender is feminine.

Diagnosis. Sagittal glabellar height in anterior view 29.9–35.0% width across posterior projections (excluding genal spines); anterior course of axial furrows strongly anteriorly divergent; size of librigenal field reduced, trapezoidal in shape; posterior branch of facial suture along lateral border very short; tuberculate sculpture on first pygidial axial ring usually effaced at least medially; distal tips of pygidial pleural spines usually expanded and club-shaped.

Discussion. Deltapliomera was recovered as sister to Millardaspis in the phylogenetic analysis, and the taxa share a reduction in later ontogeny of clusters of tubercles on the glabellar lateral lobes that are prominent early; librigenal fields with a swollen rim adjacent to the lateral border furrow; and very broad librigenal lateral border furrows.

Species of Deltapliomera occur at several horizons with more or less equally common species of Ibexaspis . There is little question of correct association of sclerites, however, as species belonging to either genus also occur at some horizons in the absence of any member of the other genus. Ibexaspis rupauli and I. leuppi do not occur with any other member of the overall clade, nor does D. inglei . Reference to the morphology of these species removes any potential confusion when species do co-occur.