Protopliomerella contracta ( Ross, 1951 )

Adrain, Jonathan M., 2011, Revision of the Lower Ordovician (lower Floian; Tulean) pliomerid trilobite Protopliomerella, with new species from the Great Basin, western USA 3144, Zootaxa 3144, pp. 1-113 : 7-13

Protopliomerella contracta ( Ross, 1951)

( Plates 1–8)

1951 Protopliomerops contracta Ross , p. 136, pl. 33, figs 16, 17, 22 (only; pl. 33, fig 15 = Protopliomerella seegeri ; pl. 33, figs 18, 19, 23–32 = P. kerouaci ).

1953 Protopliomerops contracta Ross ; Hintze, p. 31.

1953 Protopliomerops contracta Ross ; Hintze, p. 35–36.

non 1963 Protopliomerella contracta (Ross) ; Hu, p. 89, pl. 13, figs 21–23.

1973 Protopliomerella contracta (Ross) ; Demeter, p. 59.

= 1973 Protopliomerella pauca Demeter , p. 59, pl. 4, figs 3, 13, 14.

? 1973 Genus and species undetermined (not described); Demeter, pl. 5, fig. 10 (only; pl. 5, figs 5, 16, 17 = gen. and sp. indet.).

1987 Protopliomerella contracta (Ross) ; Edgecombe and Chatterton, p. 345.

2009 Protopliomerella contracta (Ross) ; Adrain et al., p. 563, fig. 13A, D.

2009a Protopliomerella contracta (Ross) ; McAdams and Adrain, p. 497, 499.

Material. Assigned specimens SUI 115229 , 125997–126018 from Section HC 6 221.5 m, Garden City Formation ( lower Floian ; Tulean; Protopliomerella contracta Zone ), Bear River Range, Franklin County, southeastern Idaho, USA ; SUI 115228 , 126019–126051 from Section G 210.2 m and 230.1 m, Fillmore Formation ( lower Floian ; Tulean; Protopliomerella contracta Zone ), southern Confusion Range , Ibex area, Millard County, western Utah, USA . The species also occurs at Section D 155.9 m, Fillmore Formation ( lower Floian ; Tulean; Protopliomerella contracta Zone ), southern House Range , Ibex area, Millard County, western Utah, USA .

Diagnosis. Median glabella and thoracic axial rings densely covered in fine tubercles; librigenae very long and narrow, with very strongly posterodorsally curved posterior projection; pygidial axis and pleurae strongly tuberculate.

Description. Cranidium narrow anteriorly and very wide posteriorly, relatively short, with sagittal length 49.2% (45.9–54.0%) width across genal angles, moderately vaulted axially and strongly vaulted pleurally; anterior border narrow, short, of even length axially and abaxially, very slightly anteriorly bowed, with dense sculpture of very small tubercles and transverse line of perforate tubercles at mid-length on some specimens (e.g., Pl. 1, figs 7, 9), slightly effaced anteriorly, and with shallow median arched rostral suture in ventral rim of border occupying about 1/3 total width (anterior view), anterior face of border slightly tapered at lateral corners; anterior border doublure expressed mainly as anterior face, only a rim ventrally; anterior border furrow short, incised, deepest in apodemal pits at meeting with axial furrows, with short (oblique) steeply posteromedially angled lateral branches along lateral limits of border, and very gently anteriorly bowed along broad median section; glabella moderately inflated (sag., tr.), lower anteriorly, long, narrow, widest posteriorly across L1 and gently tapered anteriorly, with width 91.4% (82.7–97.3%) length, and with three well defined, nearly equally sized posterior lateral lobes; L1 slightly narrower and more triangular, L2 and L3 slightly longer and wider, sub-square, lateral lobes nearly effaced except for rim of tiny tubercles around edges; L4 ill-defined, short, very narrow, triangular, LF ill-defined, as S4 reaches to anterior border with only a sliver of glabella exposed anterolaterally on each side; median lobe long, roughly evenly rectangular, slightly greater than 1/3 maximum glabellar width, densely covered in tiny tubercles and granules, some of which are perforate; glabellar sulci short, deep, slightly longer and deeper at abaxial ends and at posteriorly directed adaxial end of S1, generally anterolaterally angled at about 45º above horizontal (S1) or 30º above horizontal (S2 and S3); S4 branches anteromedially from exsagittal end of S3, very short, moderately deep, shallower anteromedially, with course about 45º above horizontal, about half as wide (tr.) as S3, better visible on large specimens (e.g., Pl. 4, fig. 1), partially obscured by anterior border and furrow in smaller specimens; SO very short medially for about half total width, slightly longer laterally, starting even with inner tip of S1, very deep, confluent with axial furrows and posterior border furrow, rimmed by tiny tubercles on anterior edge far abaxially and posterior edge of glabella; LO short, wide, slightly rounded and convex posteriorly, very slightly tapered laterally, gently inflated, very slightly posterodorsally raised (lateral view), granulose, with prominent median node located close to posterior margin, and flanked by tiny tubercles along margin, and more tiny tubercles along lateral margins; LO doublure short, lens-shaped, slightly longer medially than laterally, with sculpture of very fine transverse ridges; axial furrows moderately narrow, slightly wider along LF and slightly constricted along posterior half of L1, very deep, laterally bowed from base of glabella to mid-L2, then anteriorly convergent, lined with tiny tubercles on glabella and margin of fixigenae; palpebro-ocular ridges located across from LF, abutting anterior border, ridges comma-shaped, short, wide anteriorly, with strongly convex anterolateral margin, sharply tapered posterolaterally along short post-ocular ridge, steeply raised, with adaxial slope of about 50º above horizontal, with dense granulose sculpture; palpebro-ocular furrows very narrow, deep, incised along main part of palpebro-ocular ridge and suddenly shallower along post-ocular ridge, very shallowly sigmoid in course; interocular fixigena very short, narrow, nearly equilaterally triangular; posterior fixigena subrectangular, very long and very broad, slightly broader posteriorly, strongly downturned after fulcrum located roughly even with lateral edge of palpebro-ocular ridge, with dense sculpture of granules, small pits, and tiny tubercles (some perforate), except effaced along glabellar and posterior border margins, but with rim of tiny tubercles just inside those furrows; posterior border furrow short, especially near LO, deep, incised, transverse in course along most of border, but sharply anteriorly curved at genal angle; posterior border short adaxially, expanded ventrolaterally to maximum at genal angle, then suddenly tapered to a point, effaced but for anterior margin granules, tiny tubercles on posterior edge beginning at about half width, and small nubby genal spine; doublure short, turned posterodorsally until about half width, to form short articulating tongue set off by very short, moderately deep anterior furrow, then expanded toward genal angle, then cut by facial suture at genal angle.

Rostral plate unknown.

Hypostome long, narrow, with maximum width across spines midway between shoulders and posterolateral corners, and with width across shoulders 67.6% (62.8–71.9%) sagittal length; anterior border extremely short medially, expanded laterally into small, nearly equilaterally triangular wings with large, deep wing process pits located just anterolateral of center; anterior border furrow very short, moderately deep medially, shallowed laterally toward meeting with lateral border furrow; middle body long, ovoid, gently posteriorly tapered, with elliptical strongly ventrally inflated anterior lobe of about 3/4 total length, with sculpture of small tubercles overlying granules on about anterior third, posterior lobe roughly crescentic, moderately long medially, tapered laterally to a point at about half length of hypostome, moderately ventrally inflated, effaced; middle body furrow long, very shallow, strongly posteriorly bowed; lateral border furrows narrow, deep, incised, slightly shallower at junction with lateral branches of middle body furrow; lateral border moderately downturned, very narrow at long, shallow lateral notch, then expanded to shoulders and further expanded to widest point at posterolateral corners and merged with posterior border, granulose, with small nubby spines at shoulders, longer conical spines midway between shoulders and posterolateral corners, and longer, more robust conical spines at corners; posterior border furrow moderately deep, short; posterior border fairly narrow, long, downturned like lateral border, with wide, triangular median taper tipped with moderately long spine, granulose; lateral and posterior border doublure faces outward at lateral notch, then folds in medially, wide, and equally long along posterior border, slightly upturned along edges (lateral view), effaced.

Librigena long, narrow, crescentic, with width of field at midpoint of eye 14.0% (12.0–14.9%) length of lateral border furrow; anterior branch of facial suture very short along eye and field, meets lateral border at about 95º angle, segment along border about twice longer, anteroventrally directed at low angle; posterior branch of facial suture very long, with gently convex segment just after eye to about half length of field, then gradual slope down to lateral border, with junction of about 30º; eye small, ovoid, moderately inflated, highly elevated on tall, granulose socle (ventrolateral views), socle nearly contacts lateral border at anterolateral margin; librigenal field wedge- shaped, very narrow, especially posteriorly and at anterolateral corner of eye, strongly posteriorly tapered, densely covered in very small tubercles overlying granules, with scattered small pits concentrated along dorsal edge and under eye; lateral border furrow narrow, deep, incised, with very slightly posteriorly curved course; lateral border wide, equal to widest part of field, of roughly equal width until strongly tapered from end of librigenal field to pointed posterior tip, moderately ventrolaterally bowed, with curvature stronger posteriorly, with wide, rectangular, anteroventrally rotated anterior projection, and tapered posterior projection exposing slice of doublure in external view, and with dense sculpture of tiny tubercles with scattered granules; doublure wide, effaced, tapered to point at posterior end, truncated anteriorly even with beginning of anterior projection.

Thorax of at least 12 segments, but total number unknown; segments highly arched pleurally and axially, short and relatively broad, with relatively narrow axis 39.3% (31.4–55.6%) width across posterior pleural band; articulating half ring fairly long medially (about equal to axial ring), tapered laterally, semilunate, slightly inset posteriorly toward axial ring, laterally truncated in some specimens (Pl. 7, figs 9, 34), smooth; articulating furrow moderately long, deep, shallower medially and very deep laterally in apodemal pits just inside axial furrows, transverse to moderately posteriorly bowed in course; axial ring moderately long, wide, slightly anteriorly tapered but subrectangular, moderately inflated, posterodorsally raised (lateral view), with dense granulose sculpture overlain posteromedially by moderately (Pl. 2, figs 1, 3, 11) to very densely (Pl. 7, figs 4, 9, 19) concentrated tiny tubercles sometimes spilling over posteriorly (posterior view), with slightly larger tubercles marking each corner of ring, and with small tubercle protruding from posterior margin at posterolateral corners; doublure lens shaped, long medially, strongly tapered laterally, reaches most of way to posterior edge of articulating furrow, with sculpture of very fine transverse ridges; axial furrows narrow, expanded laterally at triangular junction with pleural furrow, very deep along posterior half of axial ring, shallower anteriorly, strongly anteriorly convergent, lined by tiny tubercles on edges of pleurae and axial ring of most segments; inner pleurae fairly narrow (wider on more anterior segments e.g., Pl. 2, figs 3, 11), roughly transverse, with dorsal surface gently ventrolaterally sloped due to lateral change in inflation of posterior band; fulcral angle moderate to steep, about 45–70º below horizontal (steeper on posterior segments); outer pleurae wide, from slightly more than half to about 80% of total pleural width (including spines); anterior pleural band wide, reaches to even with base of pleural spine, very short adaxially, slightly expanded abaxially, with extremely short articulating ridge on anterior edge of inner pleurae (best visible on Pl. 2, figs 3, 11) set off posteriorly by incised furrow, and with small anteriorly directed hook structure at ventrolateral tips (lateral view), finely granulose, rimmed posteriorly by slightly larger granules projecting into pleural furrow; pleural furrow very short and very deep for majority of course, abruptly shallowed at ventrolateral extremity (lateral view), course mainly transverse, with gentle anterior curvature far abaxially (lateral view); posterior pleural band moderately long, about three times longer than anterior band, ventrolaterally expanded, broad, moderately inflated, more so near axis (anterior or posterior view), with inflation decreasing ventrolaterally and band flattening toward plural spine, with granulose sculpture overlain by tiny tubercles concentrated laterally and on posterior face (posterior view), also with coarse granules lining anterior margin; pleural spine long, wide, slightly anterolaterally rotated and flattened (lateral view), with single tip on some more anteriorly located specimens (Pl. 2, figs 16, 17) and with variably well developed notch separating spine into smaller anterior point and larger posterior point on more posterior segments, e.g., Pl. 2, fig. 2, Pl. 7, figs 2, 3, 18; doublure long and broad, covers spine from even with tip of anterior pleural band downward, with rounded notch along posterior pleural band, and with posterior margin twisted dorsoposteriorly to form short articulating shelf on posterior margin of posterior pleural band (ventral, posterior views).

Pygidium of five segments and terminal piece, relatively long and narrow, with width measured across anterior pleural band 107.5% (99.7–117.0%) sagittal length excluding articulating half ring, strongly axially and pleurally vaulted; articulating half ring wide, moderately long, laterally tapered, effaced anteriorly, but with dense granules on posterior half and projecting into articulating furrow; articulating furrow moderately long, deep, deepest just inside axial furrow in apodemal pits; axis very wide anteriorly, strongly tapered posteriorly to point at tip of terminal piece, highly vaulted anteriorly, with convexity decreasing posteriorly toward moderately inflated terminal piece; axial rings subrectangular with rounded lateral margins, first ring moderately long, wide, subsequent rings shorter and narrower, with fifth ring about half width of first, and a little more than half length, each ring individually moderately inflated, with sculpture of dense granules overlain by tiny tubercles concentrated on anterior and posterior margins of rings, with small tubercles, small perforated tubercles, and pits concentrated medially and roughly in a transverse line on each ring; inter-ring furrows deep, long between anterior rings, posterior furrows short, furrows increasingly longer medially and laterally tapered to form lens shape on larger specimens (e.g., Pl. 8, fig. 1) terminal piece triangular, long, fairly wide anteriorly, strongly posteriorly tapered to a point, moderately inflated, with sculpture like that of axial rings except non-linear; axial furrows widely anteriorly divergent, fairly narrow, wider at intersections with inter-ring furrows, deep, lightly or not impressed over fifth pleurae, then merged with fifth interpleural furrow along terminal piece; pleurae individually moderately inflated, with narrow inner pleurae (decreases posteriorly) and very wide outer pleurae, very strongly backturned, with first pair nearly subparallel but slightly laterally bowed, and fourth and fifth pairs posteriorly convergent, and with large spines on posterior bands; interpleural furrows short, deep, incised, backturned like pleurae; anterior pleural band present only on first segment, very similar to that of thoracic segments, very strongly backturned, very short, wide, granulose, with small anteriorly facing hook articulating structure at ventrolateral tips; pleural furrow backturned like pleurae, short, deep; posterior pleural bands long and wide, with granulose sculpture topped by line of small tubercles just anterior to edge of interpleural furrow, and line of smaller tubercles on anterior edge of first 1–3 pleurae, also with tiny pits interspersed; pleural spines long, narrow, slightly laterally flattened, posteroventrally tapered, triangular (lateral view), with pointed and slightly dorsally recurved tips (lateral view), tips free and narrowly separated, spines granulose, with line of tiny tubercles on ventrolateral margin of first spine (lateral view), and with line of small pits near tips (posterior view); spine bases merged ventrally into short, granulose border with raised rim on anterolateral margin; doublure roughly triangular (anterior view), very long medially, steeply anterolaterally tapered, effaced.

Ontogeny. Cranidial ontogeny of P. contracta (cf. Pl. 4, fig. 1 and Pl. 5, fig. 16) involves broadening of the cranidium overall; narrowing of the anterior border and development of the median notch in the anteriorly expressed doublure; reduction in size of the palepebro-ocular ridges relative to overall cranidial dimensions; a slight decrease in the steepness of the fixigenae (anterior view); effacement of the strips of fixigena bordering the axial and posterior border furrows; overall decrease in coarseness of fixigenal granules and development of the pits; widening of the axial furrows; expansion of the posterior glabella and narrowing of the anterior; slight elongation of S1–S3; development of S4; lengthening of SO; reduction in coarseness of SO tubercles and size of median node; and reduction of the genal spines to nubs.

The hypostome becomes more elongate overall; the middle body lengthens, tapers posteriorly, and increases in inflation; the lateral border widens posteriorly; the posterior border lengthens; spines develop at the shoulders and the other three pairs of spines elongate slightly. Librigenal changes are subtle in these specimens because of their fairly close size, but it is possible to see that the platform supporting the eye grows taller (ventrolateral views); the librigenal field elongates slightly; the granules on the field decrease as deeper pits develop; and the lateral border widens slightly, especially toward the posterior tip.

The thorax is not sufficiently well known to discuss ontogenetic trends, as only segments from similar positions can be compared. Pygidial ontogenetic changes (cf. Pl. 8, figs 1, 17) include overall elongation of the pygidium relative to width; a slight decrease in the width of the axis compared to total width; relative decrease in size of the terminal piece, particularly in length; lengthening of inter-ring furrows; slight reduction in density of axial sculpture; and development of tubercles on the pleurae.

Discussion. Protopliomerella pauca Demeter, 1973 , was based on three specimens ( Demeter, 1973, pl. 4, figs. 3, 13, 14) from the Mesa Section in the southern House Range at Ibex. Two cranidia were collected from the same horizon, but the single pygidium was from a horizon 15.24 metres upsection. Demeter stated that the paratype cranidium was a juvenile specimen, but it is almost exactly the same length (1.67 mm) as the holotype and both are juveniles. These cranidia fall in size between the smallest and second-smallest P. contracta cranidia illustrated herein (Pl. 5, figs 14, 16). The pygidium is the largest specimen at 1.92 mm sagittal length, which is very close to one of the smallest pygidia in this study, that of Pl. 8, fig. 20 (1.95 mm). Hence, it is also a small juvenile. The morphology of Demeter's specimens matches that of comparably sized P. contracta specimens, and the species appear to be synonyms. This is borne out by their stratigraphic occurrence. Conversion of the Mesa Section footages to correlative metreages at Section G shows that the cranidia occur at the equivalent of approximately G 206.8 m, and the pygidium at about G 222.1 m. Our samples containing sclerites of Protopliomerella contracta occur at G 210.2 m and G 230.1 m. Hence, the species are apparently morphologically identical (to the extent the morphology of P. pauca is known) and are from the same stratigraphic interval. Demeter stated (1973, p. 60) that a distinguishing feature of P. pauca was the "lack of accessory anterior glabellar furrows", i.e., lack of S4. This is ontogenetic; due to the small size of the figured cranidia, S4 is not visible (cf. Pl. 5, figs 14, 16).

Protopliomerella contracta most closely resembles P. okeeffeae . The cranidia of P. contracta are distinguished by their shorter, less anteriorly convex anterior border; shorter SO, S1, and S2; narrower axial furrows; smaller, more anterolaterally located palpebro-ocular ridges; and longer posterior fixigenae. Hypostomes of P. contracta are more elongate; the anterior wings are narrower relative to width across the shoulders; the middle body is more elongate and less posteriorly tapered, with a larger patch of coarse granules anteriorly; the lateral border is wider; the posterior border is much longer; and the border spines are much longer and thicker. Librigenae of the two species differ in that those of P. contracta are longer; the anterior section of the librigenal field is longer, while the posterior section is wider; and the lateral border is narrower, somewhat less inflated, and more strongly laterally curved. Thoracic segments of the two species differ mainly in sculpture, as those of P. contracta possess densely tuberculate axial rings, while those of P. okeeffeae are more sparsely, but more complicatedly tuberculate (see description of latter species). Pygidia also differ prominently in sculpture; those of P. contracta are densely tuberculate, particularly on the axis and the posterior margin of the pleurae; they also have a wider axis; deeper, wider axial furrows; more elongate anterior inter-ring furrows; and more posteriorly directed, less ventrally curved pleural spines.

Although Protopliomerella contracta stratigraphically succeeds P. seegeri , the two taxa do not closely resemble each other. Protopliomerella seegeri is easily distinguished by its six-segmented, more posteriorly tapered pygidium; as well as its shorter, wider glabella; hypostome with a highly granulose anterior lobe of the middle body and border; and much more sparsely granulose and tuberculate cranidium, thoracic segments and pygidia.

Protopliomerella contracta and P. kerouaci share the unusual morphological feature of a transverse row of tiny pits on the anterior border, as do P. bowlesi and P. seegeri ; this may be a synapomorphy. Protopliomerella seegeri , P. contracta , and P. okeeffeae bear small protruding tubercles from the lateral corners of the thoracic axial rings, and this unusual feature may also prove to be synapomorphic.

Ross (1951) reported Protopliomerella contracta from a 135 foot range (525–660 feet above base of the Garden City Formation) at his Locality 6 (= HC6). He also assigned specimens from his Locality 5 (= HC5) to the species, but noted that while the species occurred within the same interval, only approximate biostratigraphic zonation was possible because he had collected the samples prior to accurately measuring the section. The holotype cranidium ( Ross, 1951, pl. 33, figs 17, 22) is from Locality 5. Further complicating matters, Ross's stratigraphic measurements and occurrence data contradict each other. His description of HC5 (1951, p. 15) notes the zone G(2), which was based on the appearance of P. contracta , from a 422 foot interval, and specifically lists P. contracta within a 215 foot span of this interval. This directly conflicts with the range of 135 feet given under the species description (p. 137). Adding the lithological thicknesses reported by Ross also gives the topmost appearance of P. contracta as 919 feet above the base of the formation at HC5; again, this directly contradicts the upper limit of 660 feet above base given in the species description.

Our measured sections HC5 and HC6 are at the same localities as Ross's localities 5 and 6 and sample the same faunas (see Adrain et al., 2009, p. 547–548). We have collected two species of Protopliomerella from three horizons in a 19.5 m interval at the top of HC6, and a third species from a horizon at HC5 that correlates with HC6 between the topmost horizon and the lower two horizons. Only the uppermost horizon, at HC6 221.5 m, yields Protopliomerella contracta . Ross's reported 41.1 m range therefore undoubtedly conflates multiple species of Protopliomerella . These factors also make it almost certain that his figured specimens represent more than one species, which is borne out by their morphology. Ross did not give the specific collecting horizon for any of his figured specimens, assigning them only to subdivisions c–e of his zone G(2) (and this information is uncertain at HC5), so it is impossible to determine their provenance accurately.

Hintze (1953, tables 6, 7) listed occurrences of Protopliomerella contracta , as well as Protopliomerella aff. P. contracta , and several different numbered species of Protopliomerella (all as Protopliomerops ) in his tables of species by horizon. He did not figure any specimens assigned to P. contracta , only those assigned to Protopliomerella sp. 6 (= P. bowlesi herein), and Protopliomerella aff. P. contracta (= a mixture of P. bowlesi and P. okeeffeae herein). The metreage of several cited horizons indicates the presence of true P. contracta , and those are cited in the synonymy. Occurrences of other species referred to as P. contracta or unnamed species of Protopliomerella are dealt with in the other synonymies and discussions.

Hu (1963) figured a somewhat damaged cranidium and a severely eroded pygidium from the Padre Formation of the El Paso Group, from the southern Franklin Mountains, western Texas, as Protopliomerella contracta . The specimens are too damaged and illustrated at too small a size for confident identification at the species level, but the morphology of the cranidium is consistent with Protopliomerella . Hu noted that the glabella appears subquadrate, rather than anteriorly tapered. This could be due to the compaction of the specimen, or it may be a genuine feature distinguishing this specimen from named species of Protopliomerella , including P. contracta .

Demeter (1973) reported P. contracta from 21 horizons encompassing a range of 389 feet, but figured only four specimens from only three horizons ( Demeter, 1973, pl. 4, figs. 2, 6, 11, 12). Of these four figured specimens, none represent P. contracta . They are assigned in synonymies of the appropriate species below. Demeter figured sclerites of P. contracta from Mesa Section (pl. 4, figs 3, 13, 14) which he misidentified as P. pauca (see discussion above), and an unidentified juvenile cranidium (pl. 5, fig. 10) which is likely also P. contracta .

Lee and Chatterton (1997a) described protaspid and meraspid specimens which they assigned to P. contracta from their horizons R6-94 and R6-114, reported as 94 and 114 metres above the base of the Garden City formation at Ross's (1951) Locality 6. Only specimens from R6-94 were figured. These metreages are difficult to interpret. Section HC6 was also measured at Ross's Locality 6 and also began at the St. Charles–Garden City contact, which is distinctive. The section was measured using a Brunton compass coupled to a 1.5 m jacob staff, and while standard amounts of measurement error can be expected, our measurements are easily reconciled with those of Ross (1949, 1951) and we have considerable confidence in their accuracy. The Stairsian–Tulean boundary lies in the interval HC6 135–142 m ( Adrain et al., 2009). Hence, "R6-94" of Lee and Chatterton would be well down within the Stairsian, far below the appearance of any species of the exclusively Tulean Protopliomerella . Further, Lee and Chatterton (1997b) reported the distinctive Stairsian telephinid Goniophrys Ross, 1951 , from R 6-119 m, which is above the horizons cited as bearing Protopliomerella . Despite this, the larger specimens ( Lee and Chatterton, 1997a, fig. 7.11, 7.12) definitely seem to represent a species of Protopliomerella , though they are too juvenile to assign at species level with any confidence.

This is not the only problematic aspect of Lee and Chatterton's (1997a) paper. They illustrated material ( Lee and Chatterton, 1997a, fig. 6) which they assigned to Rossaspis pliomeris Demeter, 1973 . This species is from near the very base of the Stairsian, and was described from the Fillmore Formation in the Ibex area. It has not been reported from the Garden City Formation and we have not encountered it there in our sampling. The basis for the identification was not discussed. Most of the illustrated specimens are larvae or early meraspides and their species affinity cannot be established without evidence from cooccurring mature specimens. The largest cranidium ( Lee and Chatterton, 1997a, fig. 6.10), termed a holaspid by Lee and Chatterton but almost certainly a meraspid, does not closely resemble those of R. pliomeris (either based on Demeter's [1973, pl. 2, figs. 1–4] illustrated material or our own work in progress).

Further, Lee and Chatterton (1997a) illustrated a single protaspid specimen which they assigned to Kawina sexapugia Ross, 1951 . The specimen was said to be from their horizon R6-119. The age of this horizon was given as Zone G(2) ( Lee and Chatterton, 1997a, fig. 2, 1997b, fig. 1.2), yet as noted above material assigned to the Stairsian (Zone F) species Goniophrys prima was also said to be from this horizon (in fact, it represents fault-repeated Stairsian rocks; see below). In any case, Kawina sexapugia is from much younger, upper Blackhillsian ("Zone J"), strata. Lee and Chatterton did not explain the basis for the species assignment, which represents an extreme range extension. Larvae definitely associated with holaspides of Kawina sexapugia have never been described, and larvae in isolation cannot be associated with confidence with any species known only from larger material at different horizons.

Measurements given by Lee and Chatterton (1997a) would place all of the horizons within the Stairsian by comparison to our measurements of the same section, yet the Protopliomerella and Licnocephala Ross, 1951 , specimens illustrated certainly represent Tulean species. At the same time, a Stairsian species, G. prima , was illustrated and said to be from a stratigraphically higher horizon than the Tulean taxon Licnocephala . Section HC6 is terminated by an obvious fault which lies in a mostly covered interval at HC6 229.5–234.0 m in our measurements. Above this lie fault-repeated upper Stairsian strata with conspicuously different strike and dip than those of the main section. Lee and Chatterton appear not to have noticed this fault and to have assumed the Stairsian faultrepeated faunas above the fault stratigraphically succeeded the younger faunas below. Hence, they invoked a major range extension for G. prima . Goniophrys prima , however, occurs above the fault in association with a typical assemblage of other upper Stairsian species and no Tulean species. The mid-Tulean interval beneath the fault from which Protopliomerella and Licnocephala have been sampled at HC6 is 202–221.5 m in our measurements. This is almost double the measurement given by Lee and Chatterton (114 m), despite the sections ostensibly having been started from the same datum.

Adrain et al. (2009) have discussed the implications of the true occurrence of P. contracta for the Protopliomerella contracta Zone sensu Ross et al. (1997) in the Great Basin. Ross (1951), Hintze (1953), and Demeter (1973), among other workers, misidentified other species of Protopliomerella as P. contracta , which vastly and inaccurately increased its range. That these misidentifications occurred when working with material from the type locality, and from the closely correlated Fillmore Formation, indicates that assignment of non-Great Basin material and faunas to P. contracta or the P. contracta Zone is likely problematic. Faunal correlation in particular should be critically reexamined, because it is now clear that the presence of a species of Protopliomerella in a fauna does not necessarily indicate the presence of, or correlation with, the P. contracta Zone , as has previously been widely assumed.