Iranaspidion elephas, Fortey & Heward, 2015

Fortey, Richard A. & Heward, Alan P., 2015, A new, morphologically diverse Permian trilobite fauna from Oman, Acta Palaeontologica Polonica 60 (1), pp. 201-216 : 207-214

Iranaspidion elephas sp. nov.

Fig. 3.

Etymology: From Latin elephas , elephant; referring to prominent cheek tubercles, and the form of the hypostome.

Type material: Holotype: complete enrolled exoskeleton, NHMUKPI It 29087. Paratypes: enrolled exoskeletons, NHMUKPI It 29076, 29086, 29092, 29091 (prepared to show hypostome); unfigured, NHMUKPI It 29021, 29110–29120 (almost complete with hypostome); cephalon, NHMUKPI It 29090; pygidia, NHMUKPI It 29085, 29094, unfigured, NHMUKPI It 29122–29136, 29145; cephalic doublure, NHMUKPI It 29088; pygidial doublure, NHMUKPI It 29089.

Type horizon: Kungurian–Roadian (Permian).

Type locality:Allochthonous Qarari limestone Wadi Khawr al Jaramah, Oman.

Diagnosis.— Iranaspidion with undivided basal glabellar lobes; genal ridges end posteriorly in prominent bosses; sculpture of sparse subdued tubercles; pygidium with first rib inflated.

Description.—Cephalon 0.6–0.7 times as long (sag.) as wide, with short, stout triangular genal spines. Glabella widest across frontal lobe, this being about 0.6–0.7 times glabellar length, including occipital ring. Although the frontal glabellar profile is rounded across the midline, the anterolateral corner is slightly angulate where the axial furrows end, so that the overall shape of the composite anterior glabellar lobe is somewhat wedge-shaped. L1 deeply defined by posterior glabellar furrow, subdivided into central and lateral lobes, the latter also well defined by axial furrows running more or less exsag. and inner furrows which are shallower posteriorly. The lateral lobes are twice as long (exsag.) as wide and taper at the front into an acutely triangular termination. Composite anterior glabellar lobe is 80–87% as long as its maximum width shortly in front of eyes, its anterior profile almost semicircular. Posterior end marked by a pair of gentle swellings separated by a sulcus, which extends forwards on a level with the anterior ends of the palpebral lobes. Two pairs of narrow, lateral glabellar furrows weakly defined and inward-forward directed; S2 short; S3 somewhat longer and outer end at front edge of eye. Narrow lateral glabellar lobes not inflated. Axial furrows deep and narrow, and continuing as preglabellar furrow only slightly narrower over mid-line. Occipital ring widening medially and with large, but diffuse median tubercle. Anterior cranidial border narrows medially to less than half its maximum width seen in dorsal view, where it tends to be somewhat acuminate, with steeply downturned margin. Palpebral lobes elevated to level of top of glabella and sloping inwards, half length (exsag.) of preoccipital glabella (sag.). Sutures of usual ditomopygid form, with anterior sections tracking axial furrows and extending this line almost to margin, posterior divergent sections cutting off spine-like postocular fixed cheek comprised of the inner part of the posterior border. Surface sculpture of subdued tubercles usually most evident anterior to S1.

Free cheek with short, stout, pointed genal spine about the same length as the eye. The well-defined, convex bor- der maintains constant width until it passes into the spine, downturned sharply along cephalic margin. Posterior border furrow deeper than lateral border furrow, which it meets at not quite ninety degrees; short section of convex posterior border slopes down to genal angle. Subsemicircular eye lobe has high visual surface underlain by a narrow, inflated eye

→ Fig. 2. Ditomopygine trilobite Hentigia ornata sp. nov. from Kungurian–Roadian (Permian) of Wadi Khawr al Jaramah, Oman. A. Enrolled complete specimen, NHMUKPI It 29077; cephalon in dorsal (A 1), lateral (A 2), and anterior (A 3) views; incomplete pygidium and half thorax in dorsal view, showing prominent anterior knob (A 4). B. Cephalic shield plus 4 thoracic segments, NHMUKPI It 29078; in dorsal (B 1), anterior (B 2), and lateral (B 3) views. C. Enrolled complete specimen, NHMUKPI It 29083; cephalon in dorsal (C 1) and lateral (C 2) views, pygidium and half thorax in dorsal (C 3) and anterior (C 4) views. D. Enrolled complete specimen, NHMUKPI It 29081; cephalon in dorsal (D 1) and anterior (D 2) views. E. Holotype, enrolled complete specimen, NHMUKPI It 29079; cephalon in dorsal (E 1) and anterior (E 3) views, pygidium and half thorax in dorsal view (E 2), thorax in lateral (E 4) and dorsal (E 5) views. F. Enrolled complete specimen, NHMUKPI It 29082; cephalon in dorsal view (F 1), thorax and ventral view of cephalic doublure from beneath, showing rostral plate (F 2). G. Cephalic shield plus 1 thoracic segment, NHMUKPI It 29080; in dorsal (G 1), anterior (G 2), and lateral (G 3) views. H. Enrolled complete specimen, NHMUKPI It 29084; cephalon in dorsal view. Scale bars 2.5 mm.

socle about one-quarter the height of the eye itself. The most notable feature of the cheek is the genal field, which mostly consists of an inflated ridge running parallel to the border, the posterior end of which is inflated into a prominent knob in the genal corner, which can be almost spine-like. Sculpture on the dorsal part of free cheek negligible, but several strong raised lines or ridges follow the cephalic margin and become finer on vertical part of border.

Ventral cephalic surface shows doublure which is recurved beneath lateral parts of free cheek, carrying fine lines, anteriorly flattening out as concave connective sutures are approached. Rostral suture bowed forwards. Rostral plate suboval, about two thirds as long as wide, with weakly indicated lateral knobs; it carries a transverse, arcuate furrow across its posterior part, around which the fine ridges elsewhere on the venter do not continue.An enrolled specimen was prepared to reveal the hypostome. The middle body is extremely convex tr.) and carries pits along the sagittal line, which are flanked on either side by a few, very prominent terrace ridges two of which conjoin across the midline near the posterior end. Round maculae are positioned low down on the middle body at hypostomal mid-length. Anterior wings are vertical and flattened anteriorly, posteriorly triangular, and still steeply upwardly directed. Viewed from the posterior hypostome’s appearance resembles an elephant’s head with ears extended. Lateral borders are narrow adjacent to the maculae, widening somewhat backwards and merging with flattened posterior border, which has a slightly raised rim, and a tripartite posterior margin. Border furrow narrow and deep except at end of middle body, where it is marked only by a change in slope.

Thorax of nine segments, with well-developed double annuli and broad facets to accommodate tight enrolment. In the enrolled state some specimens show all the pleural tips and a small part of the anterolateral part of the pygidial border, accommodated beneath the cephalic rim (Fig. 3C). Thorax has very little sculpture.

Pygidium with maximum width anteriorly, similar to dorsal axial length, and outline deeply parabolic. Axis of max. transverse width anteriorly like that of adjacent pleural lobe. Pleural field with ten (or faint eleven) ribs and a small triangular terminal area. Of these, the first is inflated and runs out beyond border adjacent to facet.Axis has 22 or 23 axial rings of which the last ten are very narrow (sag.) and may be difficult to discern if the preservation is imperfect. The terminal piece is bisected. Axial profile is box shaped: with flattened tops to the axial rings, where pairs of low tubercles are developed at either side. The sloping flanks of the axis have a broad, depressed area of presumed muscle insertion running the whole length of the axis next to the axial furrow. Border slopes gently downwards, no more than 10% axial length, and very slightly wider posteromedially. Doublure of similar width reflexed horizontally posteriorly, but progressively tucked up towards the dorsal surface anterolaterally; with terrace ridges. Dorsal surface of ribs with weak turberculate sculpture.

Discussion. —In spite of the prepared specimen being enrolled the hypostome was detached, indicating that the sutures were still functional, even though with its long anterior wings it is clear that the hypostome must have been buttressed firmly against the doublure in life. This hypostome is generally similar to that assigned to Hentigia by Haas et al. (1980), though the maculae are smaller and nearer the marginal furrow. The indications of strong musculature along the flanks of the pygidial axis suggest firmly anchored longitudinal muscles that may have facilitated very rapid enrollment. The cuticle of this species seems to be thick, so in encapsulated state it would have been well protected.

Iranaspidion elephas differs from the type species in its undivided basal glabellar lobes and weaker tuberculate sculpture; in particular, the distinctive genal ridges terminating posteriorly in bosses provide a good specific character for the new species. Kobayashi and Hamada (1978) assigned a well-preserved pygidium to I. sagittalis that has rather coarse tubercles on the pleural ribs which have not been seen on any Omani specimen. Kobayashi and Hamada (1984) described Pseudophillipsia (Nodiphillipsia) hanaokensis from a cranidium and pygidium originating from the late Permian Akasaka Limestone, Japan, which could well be related to the Oman trilobite under consideration although the illustrations are too poor to judge specific distinctions.

Genus Simulopaladin nov.

Type species: Simulopaladin tridentifer sp. nov.; see below.

Species included: The type species and Paladin (Paladin) simulator Haas, Hahn, and Hahn, 1980 .

Etymology: Combination of Latin simulo, resembling and Paladin .

Diagnosis.—Ditomopygine trilobites having low overall convexity, relatively weakly forward-expanding composite anterior glabellar lobe and relatively wide and flat cephalic border; occipital ring with pair of prominent lateral tubercles in addition to occipital tubercle; inflated ridge on free cheek running parallel to border; pygidium with 8–9 pleural ribs and approximately twice as many axial rings that break up into paired tubercles posteriorly. Dorsal surface sculpture lacking.

Fig. 3. Ditomopygine trilobite Iranaspidion elephas sp. nov. from Kungurian–Roadian (Permian) of Wadi Khawr al Jaramah, Oman. A. Holotype, enrolled → complete specimen, NHMUKPI It 29087; cephalon in dorsal (A 1), anterior (A 2), and lateral (A 4) views; pygidium and half thorax in dorsal view (A 3). B. Enrolled complete specimen, NHMUKPI It 29086; cephalon in dorsal (B 1) and anterior (B 2) views; pygidium and half thorax in dorsal view (B 3). C. Enrolled complete specimen, NHMUKPI It 29076; cephalon in dorsal (C 1) and lateral (C 3) views; pygidium and half thorax in dorsal view (C 2). D. NHMUKPI It 29094; pygidium in anterior (D 1) and dorsal (D 2) views. E. NHMUKPI It 29085; pygidium in posterior (E 1) and dorsal (E 2) views. F. NHMUKPI It 29090; incomplete cephalon in dorsal view. G. NHMUKPI It 29093; cranidium in dorsal view. H. Enrolled specimen, NHMUKPI It 29092; cephalon in dorsal view H 1) and lateral (H 2, showing posterior tubercle on subocular ridge) views. I. NHMUKPI It 29088; cephalic doublure in ventral view, showing rostral plate.

. Enrolled specimen, NHMUKPI It 29091; in lateral (J 1) and ventral (J 2, showing hypostome) views. K. NHMUKPI It 29089; pygidial doublure in ventral view. Scale bars 2.5 mm.

Discussion.— Brezinski (2003, 2008) has summarised research on the genus Paladin Weller, 1936 . He notes that Paladin is a typical genus on the North American palaeoplate during the Carboniferous, where it evolved into a number of endemic species invariably found “in deep water deposits” ( Brezinski 2008: 513). A clade identified from western Russia and Ukraine is not considered closely related and only just extends into the early Permian. However, a number of Tethyan later Permian species have been assigned to Paladin , and these, as in the case of the species described below, are associated with diverse faunas occupying what was probably a shallow limestone platform. Moreover, they have a deep 1S furrow crossing the glabella cutting off a median basal glabellar lobe, which is a typical ditomopygine construction. It is probable that the similarities between these species and Paladin sensu stricto species are a matter of convergence, mostly a question of having a long (sag.) anterior glabellar lobe and flattened cephalic borders. The construction of the occipital ring in the species described below carrying a pair of prominent lateral tubercles is likely to be a good, derived character, although excellent preservation is necessary to see them. These tubercles are homologous with weaker ones on the thoracic axial rings, and paired tubercles on the pygidial axis. A species undoubtedly closely related to S. tridentifer was described from Afghanistan by Haas et al. (1980) as Paladin (Paladin) simulator but the reconstruction (1980: 117) fails to show either the occipital tubercles or the genal ridge. The preservation of the holotype is incomplete in the occipital region, so the former omission is understandable; however, the genal ridge seems very prominent and obvious.

The erection of another genus within the already finely divided Ditomopyginae is justified in this case because the several features that originally suggested that Permian species should be assigned to Paladin by previous authors serve also to separate these forms from other members of the subfamily. Paladin itself may not have survived the Carboniferous ( Brezinski 2003). However, P. (Paladin) trigonopyge Osmólska, 1968 from the Asselian (fide Haas et al. 1980: 119) of Spitsbergen does not belong within the new genus as it lacks the typical ditomopygine glabellar structure.

Geographic and stratigraphic range.— Afghanistan, Oman; Artinskian–Roadian (Permian).

Simulopaladin tridentifer sp. nov.

Fig. 4A–F .

Etymology: From Latin tridentifer , carrying three teeth; with reference to the occipital structure.

Type material: Holotype: nearly complete enrolled exoskeleton NHMUKPI It 29096. Paratypes: enrolled exoskeleton, NHMUKPI It 29101; cephalon, NHMUKPI It 29100, also with cuticle; cephalic shield, NHMUKPI It 29095; cranidium, NHMUKPI It 29097, 29099 see below).

Type horizon: Kungurian–Roadian (Permian).

Type locality: Allochthonous Qarari limestone, Wadi Khawr al Jaramah, Oman.

Description.—Cephalon slightly wider than long, of lower convexity (sag.) than other ditomopygines from Oman; glabella slopes gently down along its length. Glabella expands forwards, but less markedly than many ditomopygines, such that the axial furrows adjacent to the posterior parts of the frontal lobe embrace an acute angle of less than 45°. Pyriform frontal glabellar lobe 1.4–1.7 times longer than posterior part of glabella with only very faint indications of lateral glabellar furrows on most specimens. However, one specimen ( Fig. 4F ) shows the furrows adjacent to the axial furrows better expressed: S2 and S3 very short, narrow and inwardly directed; pair of elongate oval swellings on the posterolateral end of the composite frontal lobe probably represent L2. Posterior furrow S1 deep and short. Basal glabellar lobe divided into central and lateral lobes by deep furrows running nearly exsag, slightly fainter towards rear; median lobe subrectangular; lateral lobes twice as long as wide, attenuated forwards. Occipital ring of similar width (sag.) to posterior lobe, widening medially as defined by more-or-less tripartite occipital furrow, which has a transverse median portion. Notable are the three tubercles on the occipital ring: the occipital tubercle flanked by two other boss-like tubercles towards the outer edge of ring. The latter correspond with a change in slope on the thoracic axis. Facial sutures diverge at about 20° in front of eyes, and behind eyes run for a short distance almost exsagitally before curving outwards sharply to cut off spine-like postocular cheeks, which are spine-like and curved backwards distally. Semicircular palpebral lobes lacking distinct rims, close to one-third glabellar length (exsag.), somewhat elevated. Cranidial border is flat in front of glabella, in dorsal view less than width (sag.) of occipital ring; anteriorly deflected sharply vertically, where fitting below pygidial margin during enrolment. Surface sculpture lacking.

Free cheek divided into inner, convex raised rib-like ridge and outer flattened border separated by a wide, but not unusually deep border furrow. The ridge approximately follows the lower profile of the eye, and is slightly inflated at its posterior end. Since there is a broad depression beneath the eye, the genal ridge makes a prominent and upstanding feature. The enrolled specimen on Fig. 4C shows that genal spines were probably present but the genal angle is vertically broken. Short section of posterior border furrow meets lateral border furrow at close to a right angle. Dorsally flat and wide border very sharply downturned at its margin to form a vertical “wall” about as deep as the border is wide. Anterior edge of this wall slopes towards midline along suture. Eye is underlain by a narrow convex eye socle one-third height of eye anteriorly. Eye is not high compared with that of Hentigia with visual surface three times or more as long as high in lateral view. Extent of doublure shown by exfoliated specimen ( Fig. 4F ), flat under border, and curving upward almost to reach furrow at base of genal ridge.

Nine thoracic segments of similar form along length of thorax, with facets developing at about half way across pleurae that have similar transverse width to axis. Anterior band of thoracic pleura feebly developed adaxially to fulcrum. During enrolment the narrow preannulae are visible, and the tips of the anterior five segments are telescoped beneath the genal border, the posterior four with tips just tucked into anterolateral cephalic doublure. The axial rings show weak indications of lateral tubercles like those on the occipital ring.

Pygidium 1.25 times wider than long, with gently convex border widest postaxially, where it occupies about 15% of pygidial length. Pleural fields show eight, possibly nine ribs, the first extending on to the border, but the posterior part of the pleural field is almost smooth-triangular, and more segments may be present in this area. 16–19 axial rings decrease in size progressively along the whole length of the axis. Only the first 2–4 rings are defined by ring furrows which cross the midline; posterior rings are defined by prominent paired nodes separated by a depressed median smooth area, which decrease in size regularly posteriorly to the sloping axial tip. Flanks of the axis marked by a low, but inflated area for muscle insertion, which can show evidence of segmentation comparable with that on the thoracic axis.

Discussion.—A trilobite from the Artinskian of Afghanistan described by Haas et al. (1980), as Paladin (Paladin) simulator is identical in most respects with the Omani species, and is assuredly congeneric. As noted previously, the occipital ring on this Afghan material is not well-preserved, so the presence or absence thereon of the occipital tubercles typical of Simulopaladin tridentifer must remain in doubt. What is not in doubt is that the cephalic border was of similar width to that of S. tridentifer and that the genal ridge is present. The pygidial axis is wider on P. (P.) simulator and the axial rings hardly distinguishable, but given the poor state of the unique articulated specimen on which this species is based it is possible that preservational differences might account for these apparent distinctions from S. tridentifer . It is also possible that the Omani and Afghan species will prove synonymous, but this is not provable. Since it is most unlikely that new material from the type locality of P. (P.) simulator can be collected (at least in the short term) we consider it best to be cautious about naming for the moment, and the new species name is proposed with that in mind. Several other species can be suggested to belong to Simulopaladin . Paladin opisthops Kobayashi and Hamada, 1979 (pl. 2: 5), from Thailand, seems to show a similar occipital structure, but the specimen is crushed. The pygidium is shorter, with wider border, than that of S. tridentifer . Pseudophillipsia pyriformis Qian, 1977 , from the Dalongian (late Permian) of Guizhou Province, China, is based on a fragmentary cephalon, but does show the pyriform composite anterior glabellar lobe and wide border of Simulopaladin .

Genus Acanthophillipsia Yuan, Zhao, and Mao, 1992

Type species: Acanthophillipsia guiyangensis Yuan, Zhao, and Mao, 1992 ; Maoku Formation, Wordian (Permian) Guizhou Province, China.

Geographical and stratigraphical range.—South China, Oman; Wordian (Permian).

Acanthophillipsia felicitae sp. nov.

Fig. 5F, G.

Etymology: In honour of Felicity Heward, who collected several of the best trilobites.

Holotype: Enrolled exoskeleton NHMUKPI It 29107.

Type horizon: Kungurian–Roadian (Permian).

Type locality: Allochthonous Qarari limestone Wadi Khawr al Jaramah, Oman.

Other material.—One crushed enrolled exoskeleton, NHMUKPI It 29102; cranidium, NHMUKPI It 29146; from the type locality.

Description.—The material of this species is limited, but well-preserved and complete, although the larger example is crushed. Ditomopygine glabellar structure, with a prominent S1 cutting off a basal glabellar lobe, and inflated lateral basal lobes, which are wedge shaped, wider forwards, and much longer (exsag.) than the occipital ring (sag.). All the glabella, including the occipital ring, is covered with coarse tubercles. Anterior glabellar lobe is as long as wide and expands forwards with broadly rounded front to anterior border, which is narrow and almost tucked beneath frontal lobe. The glabellar tubercles are prominent and round, about eight across the glabellar width at its widest. They serve to obscure the glabellar furrows. Occipital ring widest medially and also carrying somewhat more subdued tubercles. The material to hand does not show the facial sutures clearly. Length of eyes (exsag.) about 40% cephalic length (sag.) subtended by prominent crescentic palpebral lobe which also carries tubercles. Very prominent and convex eye socle two-thirds as high as eye, beneath which is a deep and wide furrow. Between this furrow and the marginal border furrow the genal field is a notably inflated ridge carrying a single line of coarse tubercles more or less parallel with socle. The narrow (dorsal view) anterior border itself does not carry tubercles. Posterior border widens laterally where curved backwards. Genal spines lacking, but genal angle rounded. Much of the genal border is nearly vertical, but divided lengthways by a prominent furrow that extends around perimeter of cephalon (Fig. 5F). On this part there are no tubercles. It is possible that the groove served a coaptative function to receive the margin of the pygidium, but neither specimen is sufficiently undisturbed to prove this.

Nine thoracic segments with distal parts of pleurae steeply downturned. Tubercles are present on thoracic axial rings, but are much finer than those on the cephalon. Pygidium of usual ditomopygine form. Pygidium on the holotype is slightly displaced beneath the thorax, possibly concealing one ring anteriorly. Although twisted, the larger pygidium shows 9 pairs of deeply defined and convex ribs, and up to 21 axial rings, of diminishing size posteriorly. A probable equivalent number of muscle impressions along the flanks of the pygidial axis become hard to distinguish posteriorly. Surface tuberculation on pygidium of relatively fine scale on ribs and on the first four or five axial rings, particularly. Pygidial border narrow and convex, and entirely without tubercles.

Discussion.—In spite of the small number of specimens available, this species is known from a well-preserved holotype and a larger, crushed example, and is sufficiently distinctive to name formally. Indeed, it is strikingly like a Silurian encrinurid at first glance. It is immediately set apart from all others in Oman by its very coarse cephalic tuberculation. In this feature it is like the genus Acanthophillipsia , described from S. China (Guizhou Province) from four species of Wordian age ( Yuan et al. 1992). In particular, the type species,

Fig. 5. Trilobites from Kungurian–Roadian (Permian) of Wadi Khawr al Jaramah, Oman (except C, see below). A–E. Proetid trilobite Triproetus bonbon → sp. nov. A. Holotype, enrolled complete specimen, NHMUKPI It 29103; cephalon in dorsal (A 1), lateral (A 2), and anterior (A 3) views; pygidium and half thorax in dorsal view (A 4). B. Enrolled specimen, NHMUKPI It 29104; cephalon in dorsal (B 1) and lateral (B 2) views; damaged pygidium and half thorax in dorsal view (B 3). C. NHMUKPI It 29106, cheek from Jebel Qarari, Oman. D. Enrolled complete specimen, NHMUKPI It 29105; cephalon in dorsal C 1), lateral (C 2), and anterior (C 3) views; pygidium and half thorax in dorsal view (C 4). E. NHMUKPI It 29141; pygidium in dorsal view. F, G. Ditomopygine trilobite Acanthophillipsia felicitae sp. nov. F. Enrolled complete specimen, NHMUKPI It 29102; pygidium and half thorax in dorsal view (F 1); cephalon in dorsal (F 2), lateral (F 3), and anterior (F 4) views. G. Holotype, enrolled complete specimen, NHMUKPI It 29107; pygidium and half thorax in lateral (G 1), dorsal (G 3), and anterior (G 4) views; cephalon in dorsal view (G 2). H–I. Ditomopygine sp. indet. H. NHMUKPI It 29108; pygidium in dorsal view. I. NHMUKPI It 29109; pygidium in dorsal view. Scale bars 2.5 mm.

Acanthophillipsia guiyangensis , compares with the new species in its particularly coarse, rounded cephalic tubercles. However, neither this species, nor the other three species, have such well-developed lateral basal glabellar lobes as the species from Oman. Acanthophillipsia guiyangensis also has additional lines of tubercles on the genal field and tubercles present on the pygidial border. A remarkable groove running along the cephalic border in A. felicitae can be matched on the cheek of A. abrota Yuan, Zhou, and Mao, 1992 (pl. 2: 9). This structure seems unmatched on any other ditomopygine, and may prove of generic importance.The Oman record is the first time Acanthophillipsia has been recorded outside China.

Ditomopygine sp. indet.

Fig. 5H, I.

Material.—Two pygidia, one with four thoracic segments attached, NHMUKPI It 29108, 29109; from Kungurian– Roadian (Permian) allochthonous Qarari limestones of Wadi Khawr al Jaramah, Oman.

Discussion.—A further ditomopygine is present from pygidia in the collection, but without associated cephalic parts its generic assignment cannot be determined. It is distinguished by two features: each pygidial rib has an acute crest running along its length, and the muscle pads flanking the axis, and related to the axial rings, are particularly strongly developed, with furrows between them as strong as those separating the axial rings. These pygidia fall outside the range of variation of other species from the same fauna, but we are compelled to leave its taxonomy uncertain.

Figures

Fig. 4. Ditomopygine trilobite Simulopaladin tridentifer sp. nov. from Kungurian–Roadian (Permian) of Wadi Khawr al Jaramah, Oman. A. Holotype, enrolled complete specimen, NHMUKPI It 29096; cephalon in dorsal view (A1); pygidium and half thorax in dorsal (A2), lateral (A3), and anterior (A4) views. B. NHMUKPI It 29097; cranidium in dorsal (B1), anterior (B2), and lateral (B3) views.C. NHMUKPI It 29100; incomplete cephalon in dorsal (C1), anterior (C2), and lateral (C3) views. D. Enrolled specimen, NHMUKPI It 29101; cephalon in dorsal (D1) and lateral (D2) views; pygidium and half thorax in dorsal view (D3). E. NHMUKPI It 29099; cranidium and 4 thoracic segments in dorsal view. F. NHMUKPI It 29095; cephalon with cuticle showing occipital tubercles in dorsal (F1) and lateral (F2) views. Scale bars 2.5 mm.