Panisaspis loganensis, Neo & Adrain, 2011

Neo, Usa & Adrain, Jonathan M., 2011, 2969, Zootaxa 2969, pp. 1-68 : 21-22

Panisaspis loganensis n. sp.

Figs. 33–34

2009 Pliomeridae gen. nov. sp. nov. 1; Adrain et al., p. 559, fig. 9B, F.

Material. Holotype, pygidium, SUI 125827 , and assigned specimens SUI 115144 , 115145 , 125816–125826 , 185828 , from Section HC 5 185.6 m, Garden City Formation (Tulean; Hintzea celsaora Zone ), Bear River Range , Franklin County, southeastern Idaho, USA.

Etymology. From the town of Logan, Utah.

Diagnosis. Anterior border short and broadly arched; glabella strongly anteriorly tapered; linear (across rings and onto inner pleurae; outer pleurae effaced) sculpture of coarse granules on thoracic segments and pygidium.

Description. Description of P. loganensis is given as an extended comparison with P. quattuor due to the close morphological similarity of these species. Ratios are given for comparison with other members of the genus.

Cranidia of P. loganensis are imperfectly known, but the anterior border is wider, particularly along the anterolateral limbs, gently medially pointed, and the sculpture is of dense granules. The glabella is slightly narrower, with width across L1 94.4% (93.5, 95.2%) length, slightly shorter lateral furrows, smaller LF, and has densely granulose sculpture with less densely distributed small tubercles. LO is slightly shorter, narrower, and laterally tapered and rounded, with sculpture of small tubercles, and a more prominent median tubercle. The fixigenae have smaller pits, as well as dense granules, particularly along the edges near the axial and posterior border furrows, which are effaced in P. quattuor .

The hypostome is not known.

The librigenae of P. loganensis are smaller than all of those of P. quattuor except that of Fig. 26.24. They differ only slightly, mainly in sculpture, in the coarser lateral border granulation, granulose librigenal field, and longer anterior branch of the border of P. loganensis . The librigenal field may also be wider ( Fig. 33.18), but it seems to vary within the species (cf. Fig. 33.19). The width of the librigenal field is 46.5% (41.6–51.8%) its length.

The known segments of P. loganensis are somewhat smaller than those of P. quattuor . They differ most notably in possessing a tuberculate axial ring and posterior pleurae.

Pygidia of P. loganensis are tuberculate on the axis, inner pleurae, and lateral margins of the spines, and lack the dense ventral granules that those of P. quattuor possess. The axis is slightly wider, the spines are somewhat shorter relative to the axis, and the third spine is not well differentiated when compared to P. quattuor . The sagittal length from the articulating furrow to the tip of the terminal piece is 66.9% (62.8, 70.9%) the width across the fulcra.

Ontogeny. The cranidial anterior border broadens, particularly the lateral sections across the palepebro-ocular ridges, and develops a slight median point; the glabella tapers anteriorly; LF narrows; the axial furrows broaden; and sculpture becomes slightly finer. Librigenae elongate slightly; the field widens and its pits enlarge; and the lateral border furrow deepens. The thorax is not sufficiently well known to discuss segments ontogeny. Pygidial changes are not well represented in the available specimens. However, the pygidium overall elongates, the terminal piece becomes narrower and longer, and the tubercles on the pleurae near the axis disappear.

Discussion. Cranidia of P. loganensis differ from those of P. topscityensis most notably in having a much shorter, wider, and medially pointed anterior border; narrower, anteriorly tapered glabella with a smaller LF and larger L1; wider axial furrows; a shorter LO; a shorter posterior border; and coarser sculpture all over. The hypostome is not known for comparison. Librigenae of P. loganensis are wider altogether, with a shorter, wider field; shorter lateral border furrow; and shorter, narrower, less curved lateral border with a much shorter posterior projection. The larger librigenae also have coarser granulose sculpture on the field and border, but librigenae of Figs. 22.13 and 33.20 are closer in size, and that of P. topscityensis has much coarser lateral border sculpture; sculptural comparison may be affected by ontogeny. Thoracic segments are not known for P. topscityensis . Pygidia of these species are dissimilar. That of P. loganensis is plesiomorphic, with short, closely spaced, posteriorly directed spines and coarse sculpture; that of P. topscityensis has splayed spines, differentiated third and fourth spines, and is mostly effaced with a finely granulose axis.