Panisaspis sp. 2

Neo, Usa & Adrain, Jonathan M., 2011, 2969, Zootaxa 2969, pp. 1-68 : 23

Panisaspis sp. 2

Fig. 36.4, 36.7, 36.10

Material. Assigned specimen SUI 125837 , from Section H 127.1 m, Fillmore Formation (Tulean; Heckethornia bowiei Zone ), southern Confusion Range , Ibex area, Millard County, western Utah, USA .

Discussion. A pygidium from Section H 127.1 m represents a distinct new species of Panisaspis , but does not provide enough material to allow formal naming. It differs from the pygidia of the co-occurring species Panisaspis deltaensis (cf. Figs. 19.2 and 36.4) in its denser and coarser granulose sculpture; longer, narrower axis; wider terminal piece; more conical spines; and much narrower and shorter third spine pair. It is most similar to the pygidium of Panisaspis n. sp. A, but its sculpture is denser and coarser; the terminal piece is longer and narrower, with a shallower impression; and both the third and fourth spine pairs are shorter. Compared to the pygidia of the younger species P. sevierensis and P. millardensis , that of Panisaspis sp. 2 possesses denser granulose sculpture which is coarser overall than that of P. sevierensis , and coarser than that of P. millardensis except near the tips of the third and fourth spine pairs; a slightly wider axis; a terminal piece with less distinct and more anteriorly located impressions and a less exposed posterior border; less widely splayed spines; and a relatively shorter fourth spine pair. However, the pygidium of the younger species P. rancherensis , which closely resembles that of the oldest species, P. loganensis , is narrower overall; possesses much coarser and sparser granulose sculpture; has a shorter and narrower terminal piece; and lacks the elongate third spine pair. Pygidia of the older species P. topscityensis and P. quattuor are not very similar. That of P. topscityensis possesses finer sculpture except for larger axial granules; strongly tapered, more elongate spines overall, with the fourth pair relatively much longer; and lacks terminal piece impressions. Panisaspis quattuor pygidia differ in being dorsally nearly effaced; possessing less splayed, narrower, more tapered spines; lacking the length differentiation between the third and fourth spine pairs; and possessing a narrower, strongly tapered terminal piece with a less exposed terminus.

Although the single cranidium representing Panisaspis sp. 1 co-occurs at this horizon, its coarser, sparser sculpture suggests that it is unlikely that they represent a single species. The other members of Panisaspis possess pygidia with similar sculpture as the cranidia, e.g., Panisaspis quattuor ; or slightly coarser sculpture, e.g., P. rancherensis .