Panisaspis rancherensis, Neo & Adrain, 2011

Neo, Usa & Adrain, Jonathan M., 2011, 2969, Zootaxa 2969, pp. 1-68 : 13-15

Panisaspis rancherensis n. sp.

Figs. 20–21

2009 Pliomeridae gen. nov. sp. nov. B; Adrain et al., p. 570.

Material. Holotype, cranidium, SUI 125714 , from Section H 172.5 T m and assigned specimens SUI 125715– 125730 from Section H 172.5 m, 172.5 T m, and 173.2 m, Fillmore Formation (Tulean; Psalikilus pikum Zone ), southern Confusion Range , Ibex area, Millard County, western Utah, USA.

Etymology. From The Rancher, a cafe and motel in Delta, Utah.

Diagnosis. L1 very small compared to other glabellar lobes; librigena narrow; pygidium narrow, with spines narrowly separated; dense sculpture of coarse granules all over pygidium.

Description. Cranidium short, narrow across glabella and very wide across posterior border (ratio not given due to breakage), highly vaulted across fixigenae (tr.), with gently vaulted (sag., tr.) glabella, and with dense sculpture of small granules and sparser small tubercles on all dorsal surfaces, with palpebro-ocular ridges, LO, and posterior border slightly effaced; anterior border moderately long, inflated, with arch-shaped cross section, broad, with gently curved anterior margin and short lateral limbs along anterior edge of palpebro-ocular ridges; anterior border furrow very short, slightly longer medially, deep, incised, gently anteriorly arched, with narrow roughly transverse lateral branches in front of palpebro-ocular ridges; palpebro-ocular ridges arc- to sigmoidally shaped, extend from S3 to approximately even with mid-L2, dorsolaterally extended; palpebro-ocular furrow very short, deep, but shallower adaxially, incised, gently sigmoidal; interocular fixigenae moderately narrow, triangular, posterior and lateral fixigenae moderately wide, short, rectangular, steeply ventrolaterally sloped; posterior border furrow short, deep, incised, sub-transverse until broadly rounded genal angle, then nearly perpendicular to slightly anteriorly convergent; posterior border slightly shorter than anterior border on average, shortest adaxially, flared to maximum length at genal angle, then strongly tapered anteriorly; axial furrows narrow, very deep, deepest in apodemal pits slightly anterolateral from S3, very gently laterally bowed, convergent with all other cranidial furrows; glabella long, moderately narrow, with maximum width across L2 or L3 (in larger specimens, e.g., Fig. 20.1, 20.19) 95.2% (92.9%– 96.5%) sagittal length, moderately vaulted, with distinct lateral lobes; L1 small, sub-ovoid, L2 slightly smaller than L3, both sub-rectangular, LF very large, wide, nearly semi-circular; lateral glabellar furrows short, deep, incised, reach not quite 1/3 across glabella, S2 and S3 similar, about 30º above horizontal, S1 slightly steeper and lengthened at inner end; SO moderately short, deep, shallower medially and very deep in lateral apodemal pits, convergent with axial and posterior border furrows; LO slightly longer than anterior border, slightly narrower than maximum glabellar width, sub-rectangular, with small but distinct median tubercle.

Rostral plate unknown.

Hypostome long, moderately wide, sub-ovoid, with width across shoulders 93.1% (88.8, 97.4%) sagittal length; hypostomal suture broadly anteriorly arched, slightly steeper along wings; anterior border vanishingly short medially, flared laterally into small subrectangular wings with large, deep wing process pits; anterior border furrow strongly anteriorly bowed, extremely short medially, slightly longer laterally, convergent with lateral branches middle body furrow and likewise lateral border furrow; middle body long, narrow, sub-ovoid, strongly ventrally convex at anterior, but deflated to nearly flat posteriorly, with large, egg-shaped anterior lobe and short, U- or V-shaped posterior lobe with lateral segments interrupting lateral border furrow, lobes densely granulose with pits on anterior lobe, except median middle body effaced on larger specimen; middle body furrow short, shallow, strongly Ushaped medially, with incised anterolateral branches (equivalent to anterior branches of lateral border furrow); lateral border furrow along posterior lobe of middle body moderately wide and deep, strongly posteriorly convergent; lateral border wide, gently downturned, densely granulose, with rounded margin; posterior border furrow short, shallow, indistinct; posterior border long, also with rounded margin; lateral notch short and deep, with tall, smooth doublure; posterior wing small, short, triangular.

Librigena narrow and wide, subtriangular, with short, very steep anterior branch of facial suture along field, then long and nearly horizontal along anterior projection of lateral border; posterior branch of suture long and sloped about 45º along field, then short along border; librigenal field roughly 30–60–90º triangular, with dense granulose sculpture overlaid by dense tubercles and scattered small pits concentrated posteriorly (seen as raised impressions ventrally); lateral border furrow narrow, long, deep, slightly convex toward border; lateral border wide, tapered posteriorly, strongly inflated, with long, subrectangular anterior projection, densely tuberculate with sculpture slightly coarser than that of field; border doublure wide, reaches about halfway to furrow, smooth, slightly projected above posterior tip, and abruptly terminated just anterior from anterior branch of facial suture.

Thorax unknown.

Pygidium of four segments, each with long spine, and triangular terminal piece, triangular in shape (excluding spines), with sagittal length from articulating furrow to tip of terminal piece 71.6% (67.6–76.3%) width measured across anterior pleural band of first segment, strongly vaulted axially and pleurally, with dense sculpture of small tubercles dorsally, and smaller granules ventrally (also visible along edges of pleural spines); articulating half ring wide but slightly narrower than first ring, short, slightly laterally tapered; articulating furrow nearly twice length of ring medially, tapered laterally, deep, deepest in lateral apodemal pits; axis wide anteriorly and strongly tapered posteriorly, strongly convex anteriorly and nearly flat across terminal piece; axial rings independently inflated, short, wide, with rounded margins, fourth ring slightly greater than half width of first ring; inter-ring furrows short (shorter posteriorly), wide, deep; terminal piece large, nearly equilaterally triangular, with pair of indentations in anterior margin and with posterior tip very nearly enclosed; axial furrows narrow deep, incised along first two or three segments (varies with size of pygidium), then shallow over third and/or fourth, with very narrow, wellimpressed furrow along sides of terminal piece; first segment only with both anterior and posterior pleural bands; inner pleurae very narrow, with steep fulcral angle; outer pleurae slightly wider, merged ventrolaterally into short wall ( Figs. 21.19, 21.21); anterior band very short, slightly flared ventrolaterally, strongly backturned; posterior pleural band (applies to all segments) long, merged into long, thick, conical spine with blunt tip; pleurae and therefore spines increasingly swept backward such that fourth spines are subparallel or gently convergent, spines of lengths such that the tips form points on an even arc; doublure fairly tall ( Fig. 21.24), with strong posteromedian peak and rapid anterolateral taper, smooth.

Ontogeny. Cranidia of P. rancherensis are too similar in size to preserve ontogenetic information. The number of hypostomal and librigenal specimens, and the lack of thoracic material prohibits their discussion. The pygidium broadens; the spines become slightly more separated from each other; the terminal piece enlarges and develops a pair of indentations; and the sculpture increases in density, but decreases slightly in coarseness.

Discussion. Panisaspis rancherensis possesses an interesting mix of plesiomorphic and derived features that necessitate comparison with all other species of Panisaspis . Compared to P. millardensis , P. sevierensis , and P.deltaensis , P. rancherensis cranidia are overall narrower; have much coarser sculpture; the glabella is relatively shorter and has a very small L1, even compared to the reduced L1 of the derived taxa; and the occipital tubercle is not as prominent. The librigenae are much narrower, with a longer, more wedge-shaped field, and lack the deep pits on the field, the sharp anterior curve of the lateral border, and the long posterior projection common to the aforementioned taxa. The hypostome of P. rancherensis is of the derived, ovoid, smooth-bordered style shared by P. millardensis and P. sevierensis ; P. deltaensis retains the plesiomorphic sub-rectangular hypostome with border spines. That of P. rancherensis is very similar to P. sevierensis , but is slightly narrower and more finely granulose. Pygidia of P. rancherensis are plesiomorphic. They lack the splayed spines, elongate third spine pair, and exposed terminal piece shared by the three derived taxa, and also possess much coarser tuberculate sculpture. Some of these differences, such as the plesiomorphic librigenae and pygidium, may be attributable to paedomorphosis, but more investigation of ontogenetic series would be required to examine this idea.

The group of plesiomorphic species ( P. loganensis , P. quattuor , and P. topscityensis ) resemble P. rancherensis in possessing librigenae with narrower, more elongate fields, a smoothly arcuate lateral border; and a short posterior projection of the border. The cranidium of P. topscityensis resembles that of P. rancherensis in its long, densely granulose anterior border; slightly larger (of the three plesiomorphic taxa) frontal lobe; and anteriorly rounded glabella. The cranidia of P. quattuor and P. loganensis have short, medially pointed anterior borders; a strongly tapered glabella; and wide interocular fixigenae. The rounded, sub-ovoid hypostome of Panisaspis rancherensis is unique; the other three taxa under consideration possess the plesiomorphic morphology of a spinose, sub-rectangular border. The pygidium of P. loganensis resembles that of P. rancherensis in its short, narrow shape with short, subparallel spines; small terminal piece; and sparse, coarse sculpture. However, as discussed above, these similarities may be due to paedomorphosis. It differs in having sparser sculpture, slightly shorter spines compared to the sagittal length, and a relatively narrower axis. The pygidia of P. quattuor and P. topscityensis are both wider and more elongate than that of P. rancherensis , with relatively narrower axes, longer spines, and much finer sculpture. That of P. quattuor is nearly dorsally effaced, and possesses a slight differentiation in the lengths of the third and fourth pairs of spines. That of P. topscityensis has widely splayed spines, and the third pair is very long compared to the fourth pair.

The pygidium of Fig. 21.28 has slightly different morphology and may be assignable to Panisaspis sp. 3 Compared to the similarly sized pygidium of Fig. 21.15, its pleural spines are much more splayed; the sculpture is coarser; and the terminal piece is smaller.