Pseudoolenoides dilectus Hintze 1953
Creators: name: Adrain, Jonathan M.
name: Karim, Talia S.
Publisher: name: Zenodo
Year: 2012
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Trilobita
Proetida
Bathyuridae
Pseudoolenoides
Pseudoolenoides dilectus

description: Pseudoolenoides cf. dilectus Hintze, 1953   
Plate 16, figs 24–35  
 Material. Assigned specimens SUI 130026–130028 from Section K-South 1.5 T m, Kanosh Formation (Dapingian; Pseudoolenoides dilectus Zone), southern Confusion Range, Ibex area Millard County, western Utah, USA.   
 Description. Pygidial measurements were made on the three figured specimens. For measurement of the distance across the pygidium of Pl. 16, fig. 34, the distance to the sagittal line from the left side was doubled. Pygidium strongly vaulted, with maximum width across anterior margin of third segment 224.9% (212.8–239.9%) sagittal length (excluding articulating half ring and post-axial spine); axis of four segments and terminal piece, maximum axial width across first ring 46.1% (45.3–46.6%) maximum pygidial width; width across fourth segment 63.1% (61.5–65.3%) width across first segment; length of axis excluding articulating half ring just shorter than sagittal length of pygidium; articulating half ring nearly as long (sag.) as first axial segment, sagittal length 15.0% (14.4–15.6%) pygidial length, anterior margin subsemicircular, ring sits just below first segment in sagittal profile of axis, gently dorsally convex in sagittal profile, sculpture of very fine and faint granules arranged in anastomosing pattern, pattern stronger along posterior margin and merges smoothly onto lateral portion of first axial segment; articulating furrow short (sag. and exsag.), very deep, slit-like, and transverse medially, with distal ends shallow, almost effaced, and directed anterolaterally; first ring furrow short (sag. and exsag.), nearly transverse with a slight posterior bow medially, deepest medially, progressively shallower abaxially, terminating in a deep pit at intersection with axial furrow; second and third ring furrows similarly transverse with median posterior bow becoming more prominent, about same length (sag. and exsag.) as first, distal tips of third ring furrow almost completely effaced; first axial ring of equal length sagittally and exsagittally, subtrapezoidal in outline, wider across anterior margin than posterior margin, sculpture composed of a band of prominent medium to small sized tubercles arranged along anterior margin, a prominent medium sized median tubercle separate from the anterior band, and a row of smaller tubercles located medially along the posterior margin, background sculpture of fine raised anastomosing lines also present, in lateral view distal portion of ring covered only with sculpture of anastomosing lines and granules arranged in similar pattern; second and third rings progressively smaller and with essentially the same morphology, except that anterior and posterior margins are more similar in width, bands of tubercles are more closely spaced across entire ring, and distal portion of third ring is almost completely smooth in lateral view (Pl. 16, fig. 32); fourth segment poorly expressed, fused with terminal piece, can be identified in dorsal view by median tubercle, also expressed in lateral view by smooth area on distal portion of segment (Pl. 16, fig. 32); axis terminated by broad, posteriorly rounded terminal piece, sculpture of prominent medium and small widely spaced tubercles form band along posterior margin of terminal piece, tubercles less dense medially, background sculpture of fine, raised anastomosing lines present between tubercles; axis distinctly terminated in dorsal view, in lateral view posterior margin of axis forms gentle scarp compared to post-axial region that is nearly horizontal (Pl. 16, fig. 30); post-axial region strongly downturned from horizontal plane, very short in dorsal view and slightly longer in lateral view, in posterior view sculpture of raised lines crosses region horizontally; facet developed into strongly ventrally downturned and posterolaterally directed wing-like flange, with short spike-like point along anterior margin (Pl. 16, fig. 34), adaxial portion covered with sculpture of fine granules arranged in anastomosing pattern, abaxially sculpture of granules changes to prominent raised lines also arranged in anastomosing pattern; first segment longest (exsag.), anterior margin nearly transverse to fulcrum, which is set very close to axis, anterior margin directed posterolaterally distal to fulcrum, strongly laterally bowed forming rounded corner; first pleural band set off from margin by very faint and shallow posterolaterally directed accessory furrow, inflated, distal tip extended into short posteriorly directed spine, spine formed primarily from posterior pleural band, sculpture of raised anastomosing lines present on entire band including pleural furrow and spine; pleural furrow longest (exsag.) medially, anterior margin forming distinct break with anterior pleural band, posterior margin gradually merging into posterior pleural band, distal tip forming deep slit-like pit oriented almost parallel to sagittal axis, terminated at border; second pleural furrow with generally same morphology as first, but slightly shorter, directed more strongly posteriorly, and with distal tip not terminating in deep slit-like pit; first interpleural furrow expressed as small, deep pit at distal end of pleurae, subsequent interpleural furrows not expressed; morphology of second pleural segment generally similar to first segment, but progressively narrower, directed more posterolaterally, and distal tip terminating at border and not forming short spine; third and fourth segments with no associated expression of pleural bands, pleural region adjacent to third ring and fourth ring fused to terminal piece with segments not expressed; border flattened, with no dorsal inflation, external margin forming narrow rolled rim (Pl. 16, fig. 31), sculpture of prominent raised lines continues without disruption from pleurae, border slightly concave anterior to pleural spine, also slightly concave between pleural spine and posterior median spine, in posterior view border strongly peaked medially at posterior median spine (Pl. 16, figs 31, 33, 35); border set off from pleurae in lateral and posterior view by change in slope, in dorsal view distinction is less apparent; posterior median spine short, thorn-like, widest (tr.) at intersection with posterior margin of pygidium, narrows posteriorly to form a distinct point, in lateral view spine is slightly upturned from horizontal plane, sculpture of densely spaced anastomosing lines covers spine, lines are slightly coarser and less densely spaced on lateral margins of spine, in dorsal view lines form a "V" along sagittal axis of spine; in ventral view relatively broad doublure visible (Pl. 16, figs 25, 26), widest opposite first and second pleural segments, tapers posteriorly, sculpture of raised lines oriented roughly parallel to inner margin of doublure.   
 Discussion. Three pygidia from Section K-South 1.5T m clearly represent a species closely related to P. dilectus, which was collected from the same horizon, but which we did not encounter in our sampling. The pygidia just as clearly are not conspecific with P. dilectus. While they possess a single pair of pleural spines, in common with P. dilectus, which implies a single unreleased thoracic segment, they show only two axial rings behind the first, and a very short, wide terminal piece showing no evidence of segmentation. They are smaller than Hintze's pygidia of P. dilectus, but not markedly so, and are definitely holaspid. There is no possibility that ontogenetic change could transform one to the other. Pygidia of P. dilectus (e.g., Pl. 11, figs 6, 8, 9) have four well expressed rings behind the first, and have a much longer terminal piece behind these five rings. The posterior axis is fully circumscribed posteriorly and exhibits a strong break in slope to the post-axial area. That of the pygidia of Pseudoolenoides cf. dilectus is gently merged posteriorly with the post-axial area, with only a gentle break in slope. Overall, they are also much wider relative to their length than those of P. dilectus. They certainly represent a distinct unnamed species of Pseudoolenoides and for that reason are given extended written description above.
description: Published as part of Adrain, Jonathan M. & Karim, Talia S., 2012, 3467, pp. 1-97 in Zootaxa 3467 on pages 23-24