Tuleaspis, 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 : 35-36

Tuleaspis n. sp. A

Plate 42, figs 35–41

Material. Assigned specimen SUI 129753 from Section G 155.6 m, Fillmore Formation, southern Confusion Range, Ibex area, Millard County, western Utah, USA, and SUI 129754 from Section HC5 203.7–204.2T m, Garden City Formation, east side of Hillyard Canyon, Bear River Range, Franklin County, southeastern Idaho, USA. Both are from the Tulean (low Psalikilopsis cuspidicauda Zone ).

Discussion. One cranidium and one pygidium are assigned to Tuleaspis n. sp. A. Although the pygidium is from Section G in Utah and the cranidium is from Section HC 5 in Idaho, we feel justified that they represent a single species because each sclerite clearly represents an Ibexaspis group pliomerid, and the only known cooccurring pliomerids are well-known species of Panisaspis McAdams and Adrain, 2011b, and Protopliomerella Ross, 1951 (revised by McAdams and Adrain [2011c]). Additionally, both horizons are from the same biostratigraphic zone, and share many species in common. The pygidium overall is rather different to that of T. jeneki , but Tuleaspis n. sp. A is also a considerably older taxon, and the additional segment and terminal piece of T. jeneki likely represent a derived condition. The sculpture of the pygidium is coarser and more widely spaced than that of the cranidium, but this is also true of T. jeneki , and therefore does not indicate that the sclerites might represent different species.

The cranidium of Tuleaspis n. sp. A differs from those of T. jeneki (cf. Pl. 42, fig. 40, Pl. 44, fig. 3) in being much more strongly vaulted (sag., particularly tr.) and narrower relative to sagittal length; with sculpture of slightly larger tubercles, evenly distributed on the glabella rather than concentrated on the lateral lobes; a slightly longer, more inflated, and more strongly anteriorly bowed anterior border; slightly shorter, wider, and considerably more inflated glabella with a smaller L1 relative to the other lobes; longer SO; LO with a more prominent median tubercle and fewer tubercles at the lateral corners; wider axial furrows; shorter, slightly wider, more anterolaterally positioned palpebral lobes; posterior portion of the palpebro-ocular suture describing a much less acute angle opposite the posterior fixigenae; longer, narrower posterior fixigenae; and a posterior border with more tubercles on the posterior margin.

The pygidium of Tuleaspis n. sp. A is quite different from that of T. jeneki (cf. Pl. 42, fig. 41, Pl. 46, figs 24, 29) because it possesses four segments and lacks a terminal piece, compared to five segments and a large terminal piece; it is relatively shorter, wider, and less posteriorly tapered in outline, as well as slightly more vaulted (sag., particularly tr.); the axis is shorter and broader, with more strongly inflated and medially shortened axial rings, and longer articulating and inter-ring furrows; the axial furrows are wider and shallower; the pleural spines are narrower and more closely spaced; and the sculpture is generally smaller, more sparsely distributed tubercles, with effaced areas along the midlength of the first axial ring and on the pleural spines.

Tuleaspis n. sp. A is compared to Tuleaspis ? n. sp. B in the discussion of the latter species.