Pseudoolenoides ludificatus ( Hintze, 1953 )

Adrain, Jonathan M. & Karim, Talia S., 2012, 3467, Zootaxa 3467, pp. 1-97 : 13-18

Pseudoolenoides ludificatus ( Hintze, 1953)

Plates 1–7

1953 Goniotelus ? ludificatus Hintze , p. 161, pl. 27, figs 12–19.

1996 Pseudoolenoides ludificatus (Hintze) ; Fortey and Droser, p. 88.

Material. Holotype, cranidium, AMNH-FI 26498 , and paratypes AMNH-FI 26499–26505 , and assigned specimens SUI 129972–130020 , 130111–130115 , from Section K-South 1.5 T m, Kanosh Formation (Dapingian; Pseudoolenoides dilectus Zone ), southern Confusion Range , Ibex area Millard County, western Utah, USA.

Diagnosis. Hypostome with large subtriangular spines at shoulder and posterolateral corner; anterior lobe of middle body set off from anterior wing by distinct inflated ridge; pygidium strongly dorsally vaulted; posteromedian pygidial spine very short in large specimens.

Description. Cranidial measurements were made on the most complete specimens of Pl. 1–2. In cases where only the right or left side of the specimen was preserved, the distance to the sagittal line from this side was doubled. Cranidium weakly vaulted; sculpture of closely spaced raised lines covers glabella, fixigena, and LO; sculpture of prominent tubercles also present on glabella, LO, and anterior and posterior areas; sculpture of fine raised lines present on anterior border; width across midlength of palpebral lobes 117.7% (115.1–121.5%) sagittal length, width across posterior projections 157.0% (Pl. 2, fig. 2) sagittal length; anterior border about half as long (sag.) as LO (sag.), abaxially tapered, anterior margin strongly peaked medially, posterior margin less peaked medially and bowed around anterior margin of glabella, in anterior view dorsal margin nearly transverse, slightly ventrally bowed medially, ventral margin broadly "U" shaped, in lateral view border forms a ventrally sloping shelf; sculpture of fine raised lines arranged in anastomosing pattern present on posterior part of anterior border and arranged subparallel to margin present on anterior part; anterior border furrow is short, dorsally concave, moderately shallow almost along entire course, developed into short deeper slit on either side of anterior glabellar margin (Pl. 1, fig. 2); anterior sections of facial sutures laterally convex opposite anterior border, very slightly laterally concave opposite rear of anterior border furrow, and strongly laterally bowed opposite frontal areas, width across maximum point of divergence (β) 84.8% (81.1–86.6%) cranidial sagittal length; frontal areas weakly dorsally inflated, strongly sloped downward from interocular fixigena; palpebral lobes large, distance across Ύ 73.9% (71.7–74.9%) cranidial sagittal length, distance across Ɛ 81.4 % (80.0–84.3%) cranidial sagittal length; lobe strongly but unevenly laterally bowed, anterior curve shallower than posterior curve, so lobe slung posteriorly; lobe with prominent, inflated border around margin with sculpture of fine raised lines arranged in anastomosing pattern that continues from fixigena; palpebral furrow well defined, running inside inflated rim, furrow subdivided into distinct anterolateral and posterior sections that overlap posterolaterally (Pl. 1, figs 2, 3), anterolateral section deepest opposite lateral margin of lobe, shallow, but distinct opposite anterior margin of lobe, posterior section much shallower; interocular fixigena held at oblique angle above horizontal plane, with almost no dorsal inflation, sloping toward glabella (Pl. 1, fig. 8); preocular field subtriangular, with inflation similar to that of interocular fixigena, sloped down anteriorly from horizontal plane toward anterior border furrow, with sculpture of fine anastomosing lines, scattering of prominent tubercles present on anterolateral corner of preocular field; very weak eye ridge present, developed as continuation of palpebral border running to S3; posterior fixigena with inflation similar to that of frontal area, sloped down toward posterior border furrow; posterior section of facial suture nearly transverse, extended laterally beyond lateral extent of palpebral lobe; posterior border furrow long (exsag.) and deep medially, shallower adaxially, distal tip significantly shallower and nearly effaced at contact with posterior facial suture, sharp contact medially with posterior border and posterior fixigena; posterior border moderately dorsally inflated, moderately short (exsag.) proximally, longer distally, strongly directed downward from horizontal plane, distal tip nearly subquadrate; entire border covered with small prominent tubercles, of about the same size as those on adjacent posterior fixigena; posterior margin of posterior border directed slightly anteromedially to fulcrum, nearly transverse from fulcrum adaxially; glabella with maximum width opposite Ύ 50.2% (47.9–52.3%) sagittal length excluding LO; glabella bullet shaped in dorsal view, sagittal length (excluding LO) 70.8% (69.7– 73.4%) that of cranidium, moderately dorsally inflated with slight peak medially (Pl. 1, fig. 2), sitting below maximum height of fixigena in anterior view; lateral profile weakly curved, with portion anterior to palpebral lobes strongly downturned from horizontal plane; axial furrows nearly effaced and slightly laterally bowed around LO, width across posterior contact of furrows with posterior margin 51.5% (50.2–53.2%) cranidial sagittal length; axial furrows confluent with SO; axial furrows deepest adjacent to portion of glabella posterior to S1, much shallower anteriorly from S1, of nearly equal width from posterolateral corner of glabella anteriorly to S3 and running nearly parallel to sagittal axis, anterior to S3 furrows slightly narrower and directed strongly anteromedially, running without obvious distinction into anterior border furrow; fossula expressed dorsally as small round swelling situated adjacent to axial furrow opposite S3 (Pl. 1, figs 1, 6), expressed ventrally as small pit (Pl. 1, fig. 7); S1 visible in dorsal view (Pl. 1, figs 1, 2), expressed as smooth area lacking sculpture, straight, anterolaterally directed, in contact with axial furrows; S2 and S3 faintly visible on some specimens in dorsal view as short indentation along lateral margin of glabella; L1 defined partially by S1, with weak independent inflation; L2 not prominent, also with very weak independent inflation; uniformly strong tubercles on part of glabella posterior to S3 give way to progressively finer tubercles on anterior portion of glabella; LO long, sagittal length 15.5% (14.0–16.1%) that of cranidium, longer sagittally than exsagittally, posterior margin strongly posteriorly bowed, anterior margin nearly transverse, with sculpture of scattered prominent tubercles similar to those on glabella, sculpture of prominent anastomosing lines continues from glabella onto anterior portion of LO (Pl. 1, fig. 1); median node weakly expressed on larger specimens (Pl. 1, fig. 2) and more prominent on smaller specimens (Pl. 2, fig. 2), set just anterior to midpoint of LO; SO deep and broad (sag.; exsag.), anterior and posterior edges with sharp contact with rear of main glabella and anterior edge of LO respectively, nearly transverse to slightly anteriorly bowed medially, joining axial furrow in smooth curve so that it resembles confluent continuation of axial furrow, slightly deeper at this contact; doublure of broad, lenticular articulating surface underlying LO (Pl. 1, fig. 7, Pl. 2, fig. 10), with sculpture of fine, closely spaced raised lines set mainly transversely; rear margin of posterior border with ventral transverse groove to receive anterior edge of first thoracic segment; small triangle of doublure at distal tip of anterior border.

Librigenal measurements were made on the specimens of Pl. 4, figs 7, 11, 13, 15. Main body of librigena (excluding anterior projection and genal spine) with maximum width behind eye 51.7% (48.5–53.4%) exsagittal length; anterior section of facial suture with length 55.3% (43.8–64.6%) exsagittal length of main body and posterior section of facial suture with length 42.1% (34.7–52.7%) exsagittal length of main body; anterior section nearly transverse opposite field, slightly curved across lateral border; posterior section "L"-shaped, curved very slightly across posterior border; visual surface rarely preserved intact, but long, relatively tall, and bulbous, bounded by shallow circumocular furrow (Pl. 4, fig. 9); field with prominent background sculpture of fine raised lines arranged in anastomosing pattern; distinct broad, raised band just below visual surface, set off from main part of field by sculpture running perpendicular to that of sculpture on main part of field, change in slope, and narrow band of prominent tubercles present on main part of field; lateral border furrow moderately broad and deep, slightly shallower anteriorly, does not meet posterior border furrow due to disruption by prominent ridge running from genal angle onto field; posterior border furrow slightly deeper than lateral border furrow, but otherwise similar; lateral border broad, with lateral margin gently and nearly evenly arcuate, curve strongest at midlength, border flattened and moderately inflated forming a ridge along lateral margin (Pl. 4, fig. 6), slightly wider posteriorly than anteriorly, with sculpture of fine raised lines running subparallel to margin, oriented more linearly anteriorly and abaxially, pattern more irregular along abaxial margin and posteriorly, lines more closely spaced and oriented subparallel to margin on lateral and ventrolateral aspects of border; posterior border with sculpture of raised lines oriented in anastomosing pattern on anterior part, sculpture much finer on posterior part; sculpture from lateral and posterior borders continuous across lateral and posterior border furrows up to genal field (Pl. 4, fig. 11); genal spine apparently long (Pl. 4, fig. 4), but not completely preserved on any recovered specimens, curved, inflation similar to that of lateral border, with sculpture of fine raised lines running down length of spine on all aspects, arranged in a "V"-shaped pattern, sculpture appears to be more subdued posteriorly; area in front of base of genal spine (confluence of lateral and posterior borders) swollen, developed into prominent ridge that cuts across posterior portion of genal field, sculpture of fine raised lines continues from genal field over ridge; anterior projection with subparallel raised lines continuous from lateral border; doublure differentiated into ventrally curved sector and flat, slightly upturned adaxial sector anteriorly beneath anterior part of lateral border and anterior projection, upturned portion flatter beneath posterior border; doublure beneath posterior border with faint fine raised lines set subparallel to posterior margin on posterior portion, sculpture more effaced anteriorly, doublure widens toward base of genal spine where sculpture joins that on doublure beneath lateral margin and continues onto ventral surface of genal spine in "V"-shaped pattern; inner margin of doublure describes smooth continuous arc, with curve strongest posteriorly at intersection of lateral and posterior borders and opposite posterior border; small Panderian notch (Pl. 4, figs 14, 20) developed along doublure beneath posterior border just adjacent to base of genal spine.

Rostral plate relatively narrow, very long, hourglass shaped in outline (Pl. 5, fig. 1); anterior part (Pl. 5, figs 4, 27) significantly longer (sag. and exsag.) than doublural portion, trapezoidal outline in anterior view; doublural portion short (sag. and exsag.), slightly shorter abaxially, distal tips reach beyond distal extent of anterior section, subsemilunate shaped in ventral view (Pl. 5, fig. 8) with posterior margin describing broad, gently curved arc; connective sutures set at strongly oblique angle, chevron shaped (Pl. 5, fig. 1), articulate with anterior projection of librigena; in lateral view describe strongly curved arc (Pl. 5, figs 17, 24); sculpture of fine, raised lines covers external surface of rostral plate, transversely oriented on majority of rostral plate to slightly upwardly arched medially on anterior portion, interior surface largely smooth with very faint expression of external sculpture (Pl. 5, fig. 22).

Hypostomal measurements were made on specimens of Pl. 3, figs 1, 6, 12, 16. Hypostome with maximum width (excluding anterior wings) across middle middle body 100.2% (97.0–106.1%) sagittal length; ventral surface covered with sculpture of raised lines, arranged in anastomosing pattern on middle body, aligned subparallel with margins on borders and anterior wings; middle body with maximum width 78.0% (71.8–84.0%) maximum length of middle body; sculpture on middle body with lines broken up into closely spaced, short segments; anterior margin turned up at nearly 90° angle to form anterior-facing wall, with sculpture of subparallel raised lines oriented subparallel to margin becoming progressively effaced toward margin; anterior area grades into middle body across sharp break and distinct change in sculpture, lines oriented subparallel to margin change to being oriented in anastomosing pattern at change in slope; anterior wing best preserved on a single specimens (Pl. 3, figs 1, 5), extended dorsolaterally, lacking sculpture of raised lines on anterior portion, set off from anterior lobe of middle body by distinct inflated ridge; lateral border directed obliquely from anterior wing forming shoulder, strongly bowed inward from shoulder to posterior margin; lateral border furrow initiated opposite posterior margin of anterior wing; lateral and posterior border forming rim-like ridge enclosing middle body, weakly inflated, strongly ventrally flexed, with sculpture of very closely spaced raised lines oriented subparallel to hypostomal margin; lateral and posterior border furrows shallow, expressed largely as a change in slope between middle body and border, forming deep pit opposite inward bow of lateral border; distinction between lateral and posterior border clearly defined as posterolateral corner of posterior border is developed into a short posteriorly directed spine; posterior margin of posterior border broadly bowed anteriorly, with weak posteriorly directed peak developed medially; middle furrow set at about two-thirds distance posteriorly on middle body, expressed as pair of very slightly anterolaterally directed, deep, hook-shaped furrows, with distal tip forming hook, separated from lateral border furrow by strip of inflated middle body; macula small but prominent, lacking sculpture of fine raised lines; middle body with moderate ventral inflation, pinched slightly at middle furrow; doublure moderately broad behind anterior wings and posterior projection at posterolateral corner of posterior border; doublure behind posterior border narrows posteromedially; entire doublure with sculpture of several fine raised lines similar to that on anterior wing, sculpture less prominent along internal margin of doublure.

Thorax incompletely known; width of axis slightly greater than that of articulating half ring; general construction of segments consists of a tuberculate, highly dorsally inflated axial ring, generally with larger, linearly arranged tubercles with smaller tubercles scattered between,

a long, deep ring furrow, a large lenticular and smooth articulating half ring, very shallow axial furrows, a prominent pleural furrow that is long (exsag.) and shallow adaxially and deep and short at distal tip, an anterior pleural band composed of short (exsag.) inflated strip, with sculpture of small scattered tubercles present at and adjacent to fulcrum, anterior margin forming narrow ridge that sets off short anterolateral tongue with a short spike (Pl. 4, fig. 1) which articulates with a narrow ventral notch beneath the lateral edge of the pleurae of the next segment anteriorly (or the posterior border of the cranidium) (Pl. 5, fig. 26), a posterior pleural band slightly longer (exsag.) than anterior band, posterior margin slightly sinuous, with sculpture of prominent tubercles generally linearly arranged subparallel to posterior margin of pleurae, sculpture of anastomosing lines present beneath tubercles on both anterior and posterior pleural bands, continues across pleural furrow with exception of deepest distal tip, across articulating tongue and spike, and across pleural spine; large pleural spine derived from both anterior and posterior pleural bands, directed posteriorly to posterolaterally depending on position of segment in thorax, lateral margin slightly abaxially bowed opposite posterior margin of pleurae,very small projection is set at the anterior margin of the axial furrow; ventrally, the doublure forms a lenticular articulating surface beneath the axial ring with sculpture of fine, very subdued, closely spaced raised lines (Pl. 5, fig. 5), sculpture is nearly effaced abaxially; doublure also present beneath pleural spine, with additional thin strip continuing along posterior margin of pleural region to fulcrum, with sculpture of fine, widely spaced raised lines; fulcrum is set close to the axis, and the portion of the pleura distal to the fulcrum is turned down from about 40° to about 45° from horizontal.

Pygidial measurements were made on the specimens of Pl. 6, figs 1, 4, 5, 11. Pygidium with maximum width across posterior margin of second segment 185.6% (183.0–188.6%) sagittal length (excluding articulating half ring and post-axial spine); axis of four segments and long terminal piece, maximum axial width across first ring 36.6% (36.3–37.1%) maximum pygidial width; width across fourth segment 73.8% (69.7–78.7%) width across first segment; length of axis excluding articulating half ring equal to sagittal length of pygidium; articulating half ring short (sag.), sagittal length 9.8% (9.4–10.3%) pygidial length, anterior margin subsemicircular, ring sits below first segment in general sagittal profile of axis, gently dorsally convex in sagittal profile, sculpture of very fine and faint granules arranged in anastomosing pattern; first ring furrow moderately long (sag. and exsag.), transverse, shallowest medially, progressively deeper abaxially and ending in deep slit at intersection with axial furrow; subsequent ring furrows similarly transverse to very slightly posteriorly bowed, progressively shorter and shallower than first ring furrow; first axial ring slightly shorter sagittally than exsagittally, with sculpture of medium and small densely spaced tubercles, tubercles less dense medially, tubercles absent on distal portion of axial ring (Pl. 6, figs 6, 8) and replaced with sculpture of fine, raised anastomosing lines; posterior rings progressively smaller and with essentially the same morphology, except that tubercles are densely spaced across entire ring in dorsal view; axis terminated by broad posteriorly rounded terminal piece, sculpture of medium and small densely spaced tubercles covers terminal piece, tubercles become smaller and less densely spaced posteriorly, sculpture of fine, raised anastomosing lines covers posterior and posterolateral portions of terminal piece; axis distinctly terminated in dorsal view, in lateral view posterior margin of axis forms distinct almost vertical scarp; articulating facet on first segment developed into short spine-like point with a medial ridge directed anterolaterally, covered with sculpture of fine raised lines, densely spaced on adaxial portion, more widely spaced abaxially; first segment with maximum exsagittal pleural length 27.1% (22.5–30.4%) sagittal axial length, anterior margin slightly anteriorly bowed to fulcrum, which is set near axis, margin directed posterolaterally distal to fulcrum; anterior margin of first pleural band set off from margin by prominent posterolaterally directed accessory furrow, well inflated, with sculpture of scattered medium and small tubercles arranged in irregular transverse rows covering majority of pleural band, sculpture of fine raised lines present on proximal and distal tips of pleural band; pleural furrow longest (exsag.) medially, proximal and distal tips pinch out, with distal tip less dramatically pinched, terminated at border; subsequent pleural furrows with generally same morphology as first but becoming slightly shorter overall; first interpleural furrow expressed as moderately deep, elongated pit at distal end of pleurae, subsequent interpleural furrows very weakly or not expressed; morphology of pleurae of second and third segments generally similar to those of segment one, but progressively narrower and directed more posterolaterally; fourth and fifth segments with no associated expression of inflated pleural bands, pleural region adjacent to fourth ring and fifth ring fused to terminal piece is broadly triangularly shaped and depressed (Pl. 6, fig. 12); pleural bands and furrows terminated by weakly inflated, flattened border, with sculpture of prominent raised lines, oriented roughly parallel to transverse axis, moderately densely spaced; border runs from posterior margin of anterior pleural band of first segment to posterior spine; border slightly bowed outward opposite first and second pleural bands, bowed very slightly inward opposite terminal piece; border set off from pleurae by very shallow furrow and change in slope and inflation between pleurae and border; posterior median spine short (Pl. 6, fig. 1), anteriorly broad (tr.) at intersection with posterior margin of pygidium, but drastically narrows posteriorly to form a distinct narrow point, subcircular in cross section (Pl. 6, figs 3, 10), in lateral view spine is slightly upturned from horizontal plane, sculpture of fine, densely spaced anastomosing lines covers spine, lines are slightly more coarse and less densely spaced on lateral margins of spine; in ventral view relatively broad doublure visible (Pl. 6, fig. 22), widest opposite first and second pleural segments, tapers posteriorly, prominent sculpture of raised lines oriented roughly parallel to inner margin of doublure, sculpture continues posteriorly meeting in a "V" medially and continuing onto ventral surface of median spine.

Ontogeny. The glabella becomes much more rounded anteriorly (cf. Pl. 1, figs 2, 20); a very short preglabellar field is present medially (Pl. 1, fig. 20) on the smallest specimen, but the anterior margin of the glabella increasingly comes into contact with the anterior border furrow; S1 becomes less well impressed; palpebral lobes reduce in size compared to the rest of the cranidium, and the angle at which they are held relative to a horizontal plane increases from almost level with glabella in smallest specimens (Pl. 1, fig. 22); sculpture of tubercles and raised lines more prominent; median node of LO becomes less prominent.

Tubercles on pygidial axial rings arranged in two distinct rows on either side of axis on very small specimens (Pl. 7, fig. 20), become more coarse and dense and less clearly arranged in distinct rows, while scattering of background tubercles become more prominent, and there is overall fining of the axial tubercles in largest specimens; pleural bands with sculpture of single row of tubercles along anterior and posterior margins of segments changes to more densely spaced scattering of finer tubercles; pygidial border becomes broader; articulating flange becomes more prominent; posteromedian spine becomes significantly shorter, but retains upturn from horizontal plane.

Discussion. Pseudoolenoides ludificatus compares most closely with the other two plesiomorphic species, P. pogonipensis and P. aspinosus . Collectively, these species differ from the derived group in a large suite of characters (discussed above) and there is little point in attempting detailed comparisons between species drawn from either group. Pseudoolenoides ludificatus differs from P. aspinosus in the possession of an anterior border that is only faintly nasute, versus distinctly anteriorly pointed, a fixigenal boss anterior to the eye ridge, versus the faint oblique ridge (best seen on Pl. 8, fig. 1, right side) which characterizes Acidiphorus , less prominent eye ridge, medially slightly shorter SO, longer LO, faint fixigenal alae opposite L1, slightly smaller palpebral lobes, much smaller tubercles on the librigenal field, a narrower and less posteriorly lobate librigenal posterior border, a longer, narrower field, a better impressed lateral border furrow, a longer genal spine; a hypostome with quite radically different morphology (assuming that of P. aspinosus is correctly assigned; see below), with large subtriangular spines at the shoulder and posterolateral corners and more transverse, anteriorly convex middle furrows; a much more dorsally vaulted pygidium, with an anteriorly broader, more laterally lobate border, a shallower border furrow, and a shorter posteromedian spine.

Pseudoolenoides ludificatus differs from P. pogonipensis in having a relatively larger, more anteriorly pointed glabella, more distinct, oblique S1, narrower interocular fixigenae, a less prominent eye ridge; librigenae with a much less lobate posterior margin of the posterior border, with only a subtle versus very prominent accessory furrow; a hypostome that is broader relative to its length, with distinct spines on the posterolateral corners versus a broad posterior shelf; and a pygidium that is much more dorsally vaulted, narrower relative to its length, dominated by fine tuberculate versus fine raised line sculpture, with less inflated pleural bands, and with a very short versus apparently very long posteromedian spine.

Pseudoolenoides ludificatus occurs together at K-South 1.5T m with P. pogonipensis and Pseudoolenoides cf. dilectus (and apparently also with P. dilectus , though we did not encounter it in our sampling). There is little difficulty with sclerite associations, however, as P. ludificatus is very common, whereas P. pogonipensis is quite rare, and Pseudoolenoides cf. dilectus is very rare (only three specimens found).