Vol. 90 No. 6 pp.1955–1975 ACTA GEOLOGICA SINICA (English Edition) Dec. 2016 Systematic Revision of Trilobites from the Middle Ordovician (Darriwilian) Klimoli Formation of the Zhuozishan Area, Inner Mongolia, China LEE Seung-Bae1, LEE Dong-Chan2,*, WOO Jusun3 and ZHANG Xingliang4 1 Geology Division, Korea Institute of Geoscience and Mineral Resources, Daejeon, 305-350, Republic of Korea 2 Department of Earth Science Education, Chungbuk National University, Cheongju, 361-763, Republic of Korea 3 Division of Polar Earth-System Sciences, Korea Polar Research Institute, Incheon, 406-840, Republic of Korea 4 Early Life Institute and State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an 710069, China Abstract: New morphologic information permits systematic revision of trilobites from the Middle Ordovician Klimoli Formation of the Zhuozishan area, Ordos Basin, Inner Mongolia. The new assemblage is composed of 10 species of the Raphiophoridae, Nileidae, Asaphidae, and Telephinidae. An asaphid, aff. Mioptychopyge lashachungensis (previously Paraptychopyge lashachungensis) displays an intermediate morphology between the Chinese nobiliasaphine genera Mioptychopyge and Zhenganites. The pygidial doublure is regarded as the most significant character to differentiate Symphysurus klimoliensis (previously Nileus klimoliensis) of the Nileidae from such closely allied taxa as Poronileus. A nileid, cf. Peraspis kujandensis displays typical nileid morphology, unlike the type species, Peraspis lineolata, which might turn out to be an asaphid. Ampyx gongwusuensis sp. nov. of the Raphiophoridae is the first record of the genus in the Zhuozishan area and reveals morphologic details that might be employed to resolve Ampyx taxonomy in China. Morphologic differences between A. gongwusuensis and Abulbaspis ordosensis might represent a case of sexual dimorphism. Key words: Invertebrate paleontology, Trilobita, systematics, Klimoli Formation, Darriwilian, Zhuozishan, Inner Mongolia 1 Introduction The Zhuozishan area of Inner Mongolia is located in the northwestern part of the Ordos Basin, which experienced cratonic basin stage during the early Paleozoic (Yang et al., 2015). There exposed are early Middle Ordovician (Dapingian) to Late Ordovician (late Katian) sedimentary strata, which yield abundant trilobites, graptolites, and cephalopods (Chen et al., 1984; Zhou et al., 1989). Lu (in Lu et al., 1976) reported three trilobite species in the area: Bulbaspis ordosensis, Nileus klimoliensis, and Paraptychopyge lashachungensis. This work presents a systematic revision of the three species and reports cooccurring species based on a new collection comprising about 130 specimens, many of which are well preserved * Corresponding author. E-mail: dclee@chungbuk.ac.kr and articulated. The specimens were collected from an about 1-m thick interval at the base of the section of the Klimoli Formation exposed along a foothill of Zhuozishan located between Laoshidan and Gongwusu counties (Fig. 1). One specimen assigned to Abulaspis ordosensis (Lu in Lu et al., 1976) was collected from a horizon 24 m above the interval. The lithology of the sampling interval consists of alternating layers of dark gray, medium-bedded, peloidal lime mudstone and thin-bedded black shale. 2 Stratigraphy of Sampling Interval Lu (in Lu et al., 1976) noted that Bulbaspis ordosensis and Nileus klimoliensis occur in the upper part of the Lower Ordovician Klimoli Formation and © 2016 Geological Society of China 1956 Vol. 90 No. 6 ACTA GEOLOGICA SINICA (English Edition) http://www.geojournals.cn/dzxben/ch/index.aspx http://mc.manuscriptcentral.com/ags Dec. 2016 Fig. 1. Locality map of the section near Gongwusu county, Zhuozishan area near the border between Inner Mongolia and Ningxia, China where the trilobite specimens were collected. (a), Map of China showing the location of Fig. 1b map indicated by the black rectangle. (b), Map of sampled locality, Gongsuwu section; locality indicated by a star, at GPS coordinate 39° 21’59”N, 106° 52’ 47”E; ‘G6’ is Jingzanggaosu expressway and ‘S314’ is Wushigaosu provincial road. (c), Field photograph (facing south) of the sampled locality indicated by a white arrow. (d), Field photograph of the sampled interval indicated by a white bar. Paraptychopyge lashachungensis occurs in ‘Lower Ordovician strata’. In establishing a biostratigraphic framework of the western Ordos region, Chen et al. (1984, fig. 1) presented a stratigraphic column based on a continuous Ordovician outcrop exposed at the eastern side of Dongshan near Laoshidan County, which consists of the Sandaokan, Zhuozishan, Klimoli, and Wulalike formations in ascending order; the sampling locality (Fig. 1) of this study is considered to be a part of this outcrop. Chen et al. (1984) recorded the occurrence of as many as 16 trilobite genera from the uppermost 3-m thick interval of the Zhuozishan Formation (‘interval 8’). The assemblage was known to contain Ovalocephalus, Sinoharpes (reassigned to Dubhglasina; see Zhou and Zhen, 2008), Pseudosphaerexochus, and Pseudocalymene, which have not been found in our collection, with the occurrence of Nileus the only taxon comparable to the present trilobite assemblage. Chen et al. (1984) also recognized a total of seven intervals from the Klimoli Formation and grouped them into three units; the upper unit (‘interval 7’) is characterized by occurrences of diverse graptolites and no trilobites; the middle unit (‘interval(s) 3 to 6’) by those of diverse trilobites as well as graptolites; the lower unit (‘interval(s) 1 and 2’) by those of less diverse graptolites and trilobites. The occurrence of Nileus klimoliensis and Paraptychopyge lashachungensis was recorded throughout the intervals of the middle unit; Bulbaspis sp. is listed only in interval 4 of the middle unit. The occurrence of the first two species in the present collection suggests that the sampling interval belongs to the Klimoli Formation. N. klimoliensis is here transferred to Symphysurus and P. lashachungensis to aff. Mioptychopyge (see below). However, such morphologically distinct trilobites as Hammatocnemis (referred to Ovalocephalus; see Zhou and Zhen, 2008), Remopleurides, and Shumardia from the middle unit have not been found and only a single poorly preserved graptolite specimen has been found in the present collection. Thus, it cannot be determined to which interval of Chen et al. (1984) the present sampling interval is exactly correlated. Based on the graptolite occurrence, the Klimoli Formation was considered to be of Llanvirn age by Chen et al. (1984, table 2; see also Zhou et al., 1989) and later was correlated to early–middle Darriwilian age by Chen et al. (2010, fig. 11). Recently Wang et al. (2013) carried out an integrated biostratigraphic study on the formation based on conodonts and graptolites; their sampling locality is about 14 km north of the locality of the present study. They referred the limestone-dominated lower unit yielding abundant conodonts to the Histiodella kristinae Biozone of middle Darriwilian age (Wang et al., 2013, fig. 16). 3 Composition of Assemblage Of about 130 specimens, 47.0% is assigned to the Nileidae, 45.5% to the Raphiophoridae, 6.7% to the Asaphidae and 0.8% to the Telephinidae. Taking into consideration that articulated specimens should contribute more to the composition, the raphiophorids account for 53.7% of the assemblage, the nileids 41.0%, and asaphids 4.8% (Table 1). The following four species account for 82% of the fauna; Ampyx gongwusuensis sp. nov. (37%), Symphysurus klimoliensis (Lu in Lu et al., 1976) (36%), aff. Mioptychopyge lashachungensis (8% ), and cf. Peraspis kujandensis (2% ). The composition may be referable to the Nileid biofacies as defined by Zhou et al. (1989) from the Zhuozishan area. The present assemblage Dec. 2016 ACTA GEOLOGICA SINICA (English Edition) http://www.geojournals.cn/dzxben/ch/index.aspx Table 1 Trilobite faunal composition of the collection. Raw number of articulated specimens is converted by multiplying two in considering their contribution of cranidium and pygidium. Isolated free cheeks, hypostomes and thoracic segments are excluded from the calculation. Number in parenthesis is based on the raw number Articulated Cephalothorax Thoracopygidium Cephalon Cranidium Pygidium Subtotal Proportion Asaphidae 0 Nileidae 28 (14) Raphiophoridae Telephinidae 80 (40) 0 0 3 14 0 0 0 2 7 9 4.8 % (6.7 %) 20 1 15 10 77(63) 41.0 % (47.0 %) 1 0 5 1 101(61) 53.7 % (45.5 %) 0 0 1 0 1 0.5 % (0.8 %) contains less nileids (50% in Zhou et al., 1989) and much more raphiophorids (20% in Zhou et al., 1989). 4 Systematic Paleontology Terminology follows Whittington and Kelly (1997); terminology of thoracic axial morphology of the Nileidae follows Whittington (2000). Open nomenclature follows Bengtson (1988). All the specimens are housed in the Otog Comprehensive Geological Museum, Otog Banner, Inner Mongolia, China (OCGM-Inv). Proportional values of measurement are all in average, unless otherwise noted. Abbreviations: sag. = sagittal, exsag. = exsagittal, tr. = transverse 4.1 Taxon 1 Family Asaphidae Burmeister, 1843 Subfamily Nobiliasaphinae Balashova, 1971 http://mc.manuscriptcentral.com/ags Vol. 90 No. 6 1957 Genus Mioptychopyge Zhou et al., 1998 Type species.—Ptychopyge trinodosa Zhang, 1981, from the Dawangou Formation, lower Llanvirn Series, Kanlin, Kalpin, north-west Tarim, Xinjiang; by original designation. aff. Mioptychopyge lashachungensis (Lu in Lu et al., 1976) Figs. 2a, 3a–3m Synonymy: 1976 Paraptychopyge lashachungensis Lu in Lu et al., p. 65, pl. 11, figs. 1–3 Figured specimens: Two cranidia (OCGM-Inv. 1413, 1327), three pygidia (OCGM-Inv. 1417, 1513, 1438), free cheek (OCGM-Inv. 1440) and hypostome (OCGM-Inv. 1525). Description: The cranidium is wider than long; the sagittal length is 72% of width along the posterior cranidial margin. The frontal area is 47% of cranidial width and 135% of glabellar width. Anterior branches of the facial suture is divided into three distinct sections to define a six-sided frontal area, the anterior end of middle section being located at the level of the anterior 10% of the exsagittal cranidial length and the posterior end at the level of the anterior 38%. The anterior sections strongly converge forward and meet at an acute angle, forming a pointed anterior cranidial margin; the middle sections moderately converge forward and are longest; posterior sections diverge forward. The inflection from posterior to middle sections is more angular than from middle to anterior sections. The posterior branches of the facial suture are moderately sinuous and the distal end is strongly curved backward. The preglabellar furrow is shallow and disappears sagittally. The frontal area is relatively long (20% of cranidial length). The anterior Fig. 2. Reconstruction of representative trilobite species from the Klimoli Formation; scale bars = 5 mm. (a), aff. Mioptychopyge lashachungensis (Lu in Lu et al., 1976). (b), Symphysurus klimoliensis (Lu in Lu et al., 1976). (c), cf. Peraspis kujandensis (Chugaeva, 1958). (d), Ampyx gongwusuensis sp. nov. 1958 Vol. 90 No. 6 ACTA GEOLOGICA SINICA (English Edition) http://www.geojournals.cn/dzxben/ch/index.aspx http://mc.manuscriptcentral.com/ags Dec. 2016 Fig. 3. Photographs of specimens assigned to aff. Mioptychopyge: (a)–(m), aff. Mioptychopyge lashachungensis (Lu in Lu et al., 1976); (n), aff. Mioptychopyge sp. indet.; scale bars = 5 mm. (a–d), Cranidium, OCGM-Inv. 1413, (a) dorsal view, (b) anterior view, (c) posterior view, (d) lateral view. (e–f), Pygidium, OCGM-Inv. 1417, (e) dorsal view, (f) lateral view. (g–h), Pygidium, OCGM-Inv. 1513, (g) posterior view, (h) dorsal view. (i), Hypostome, OCGM-Inv. 1525, ventral view. (j), Pygidium, OCGM-Inv. 1438, dorsal view. (k), Cranidium, OCGM-Inv. 1327, dorsal view (note weakly developed baccula on the right side of palpebral area of fixigenae). (l–m), Free cheek, OCGM-Inv. 1440, (l) dorsal view (no the inner margin of doublure and fine terrace lines), (m) lateral view. (n), Pygidium, OCGMInv. 1307, dorsal view. cranidial border is flat and occupies 58% of the preglabellar area length. The border furrow is shallow, widening slightly distally, and gently curved forward. The preglabellar field is shorter (sag.) than the anterior cranidial border. The axial furrows are moderately deep and wide along the pre- and postocular areas of the fixigena and shallower along the palpebral areas of the fixigena; the furrows are strongly curved laterally to delimit glabellar inflation and moderately curved inward along the palpebral areas and parallel-sided along the postocular areas. The glabella is pyriform, moderately convex, and inflated laterally at mid-glabellar length; the exsagittal length of the inflated part is 15% of glabellar length; a shallow furrow is developed along the adaxial margin of the inflated part; the inflation tends to be more weakly developed in larger cranidia. The subcircular depression is faintly developed along the glabellar crest and located around mid-glabellar length; a weakly convex fusiform lobe is present immediately in front of the subcircular depression and along the glabellar crest; its anterior end is located at the level of the mid-frontal area length; two or three pairs of short furrows are impressed adaxially from the axial furrows and located opposite within the sagittal length of the fusiform lobe. The S1 is Dec. 2016 ACTA GEOLOGICA SINICA (English Edition) http://www.geojournals.cn/dzxben/ch/index.aspx obliquely directed posteriorly and merges with the axial furrows anteriorly at mid-way of the glabellar lateral inflation, and they merge together posteriorly and adaxially to define the posterior of the median node; the L1 is subtriangular in outline. The median node is weakly convex and located opposite the posterior end of the palpebral lobes, which are apparently large (length inferred to be 28% of cranidial length). The bacculae are elongate (exsag.) and weakly raised along the posterior two-thirds of the palpebral areas of the fixigena; baccular furrows are faintly impressed. The occipital ring is subrectangular and gently curved backward; the occipital furrow is indistinct and deepens as a distinct elongate slit at the distal end. The posterior area of the fixigena is transverse and narrow (exsag.); a large protuberance is present immediately adjacent to the occipital ring and in front of the posterior cranidial border furrow. The posterior cranidial border is narrow (exsag.) and strongly raised as a narrow rim proximally and it progressively widens distally; the border furrow with flat bottom slightly widens distally. The frontal glabellar lobe and posterior areas of the fixigenae are ornamented with fingerprint-like fine terrace lines. The librigenae have a broadly based, long genal spine. The librigenal field gently slopes down. The lateral border furrow is deep and wide, and becomes narrower and shallower posteriorly into the genal spine tip. The eye socle is narrow. The doublure is wide; its inner margin extends along half of the librigenal field width. The librigenal field and spine are ornamented with fingerprintlike terrace lines and the doublure has fine terrace lines parallel to the librigenal margin. The hypostome has a deeply notched posterior margin. The middle body is subhexagonal in outline and moderately convex. The lateral margin gently curves outward; the lateral border furrow is shallow and deepens posteriorly as a distinct subcircular apodemal pit; the lateral border widens posteriorly and is ornamented by terrace lines subparallel to the margin. The pygidium is subsemicircular in outline; the length is 68% of width across the posterolateral ends of the articulating facets. The axial furrows are moderately deep and straight; the axis gently tapers posteriorly with a maximum width of 20% of pygidial width and the length is 78% of pygidial length; up to 10 subrectangular axial rings are defined by shallow inter-ring furrows which disappear adaxially; axial furrows defining the terminal piece shallow out posteriorly and adaxially. The articulating facet is elongate (tr.), triangular in outline and steeply downslopes anteriorly; there is a fulcrum at halfway of the maximum pleural field width. The pleural field is flat in the proximal half and then gently http://mc.manuscriptcentral.com/ags Vol. 90 No. 6 1959 downslopes distally. Seven pairs of pleural furrows are recognized; they are moderately deep and wide, and become progressively shallower and narrower posteriorly; the anteromost pair distally reaches the abaxial 20% of half of the pygidial width; the interpleural furrows are shallower, narrower and shorter than the pleural furrows. The marginal border furrow is absent. The doublure is moderately wide and becomes slightly wider posteriorly; the inner margin reaches mid-width of the pleural field and is located well inside the distal ends of the pleural furrows; the posterior margin is deeply indented into the anterior one-third of the sagittal length. The pygidial surface is ornamented by relatively widely spaced, fingerprint-like, fine terrace lines; the doublure is ornamented with terrace lines which are subparallel to the pygidial margin and spaced progressively wider toward the margin. Discussion and remarks: One cranidium and two pygidia of Paraptychopyge lashachungensis were illustrated by Lu et al. (1976, pl. 11, figs. 1–3). The holotype cranidium differs from the present cranidia in being larger and having a shorter (sag.) frontal area and more weakly developed glabellar inflation at the midglabellar length. These differences are interpreted as intraspecific and/or ontogenetic variation (compare with Figs. 3a, k). The two paratype pygidia are indistinguishable from those of the present collection. Lu (in Lu et al., 1976) assigned this species to Paraptychopyge because the following two cranidial features were thought to be well accommodated within the generic diagnosis defined by Balashova (1964, p. 11): sagittal length of the frontal area is one-sixth of cranidial length and exsagittal length of the postocular area of the fixigenae is equal to or slightly greater than exsagittal length of the palpebral lobes. As the frontal area of the present cranidia is one-quarter to one-fifth of the cranidial length, the shorter frontal area of the holotype cranidium is interpreted as an ontogenetic feature. In the holotype cranidium, the size and shape of the palpebral lobes cannot be accurately determined due to poor preservation; it seems that a curved furrow on the left side was interpreted as an outline of the palpebral lobe by Lu (in Lu et al., 1976). With the course of the anterior and posterior branches of the facial suture, the palpebral lobes of the present cranidia, although incomplete, appear to be much longer than the postocular area of the fixigenae (Fig. 2a). The two features employed by Lu are thus not considered taxonomically valuable for the assignment of this species to Paraptychopyge. Of Paraptychopyge species from Baltoscandia, the Zhuozishan species is most similar to P. plautini in sharing a hexagonal frontal area and seven pairs of relatively long pygidial pleural furrows 1960 Vol. 90 No. 6 ACTA GEOLOGICA SINICA (English Edition) http://www.geojournals.cn/dzxben/ch/index.aspx (Balashova, 1964, pl. 3, figs. 5–9). However, P. plautini is readily distinguished by having a shorter frontal area apparently with no preglabellar field, smaller palpebral lobes, more weakly impressed and less obliquely directed S1, more distinctly developed bacculae, a longer (exsag.) postocular area of fixigenae defined by weakly sinuous posterior branches of the facial suture, a wider and longer pygidial axis, and convex distal ends of the pygidial pleural ribs. It is concluded that the Zhuozishan species is not a member of Paraptychopyge. The Zhuozishan species displays a combination of characters of Mioptychopyge Zhou, Dean, Yuan and Zhou, 1998, Ningkianites Lu, 1975, Opsimasaphus Kielan, 1959 and Zhenganites Yin in Yin and Lee, 1978. Turvey (2007) transferred these Chinese genera to the subfamily Nobiliasaphinae Balashova, 1971 after comprehensively reviewing many effaced asaphids from South China in comparison with those from Baltoscandia; he concluded that the Chinese nobiliasaphines share hypostomal and cranidial morphologies distinguishable from those of the Baltoscandian asaphids (see Turvey, 2007, text-fig. 7). The Zhuozishan cranidia have a pear-shaped glabella as do the nobiliasaphines. The glabella inflates at midglabellar length and the inflation reduces with growth (compare Fig. 3a, 3k, and Lu et al., 1976, pl. 11, fig. 1). An identical inflation is well developed in Dolerobasilicus, a Korean nobiliasapine genus (Lee and Choi, 1992, pl. 1, figs. 2–3) which also reduces ontogenetically. Bacculae are recognized in the Zhuozishan cranidia and some of the nobiliasaphine genera such as Zhenganites and Mioptychopyge (e.g., Zhou et al., 1998, pl. 2, fig. 6, pl. 3, fig. 4); in the former genus, the large protuberance on the fixigena behind the eyes is interpreted as a baccula; the Zhuozishan species have both elongated (exsag.) bacculae and a protuberance behind it (Fig. 3a). Ontogenetic information is required to assess identity of these cephalic structures and their taxonomic value, as claimed by Lee and Choi (1999). An axial fusiform lobe delineated by weakly impressed furrows is present along the glabellar crest of the Zhuozishan species (Figs. 2a, 3a). An identical lobe is found in Mioptychopyge trinodosa (e.g., Zhou et al., 1998, pl. 3, fig. 4), which is described as ‘an axially extended, spear-shaped ridge.’ The lobe or ridge is apparently absent in other Mioptychopyge species (e.g., M. suni, Turvey, 2007, pl. 3, fig. 8), whereas it is observed in other nobiliasaphines (e.g., Nobiliasaphus nobilis, Přibyl and Vaněk, 1965, pl. 2, fig. 7) and even in nonnobiliasasphines (e.g., Pseudobasiliella kuckersiana, Balashova, 1971, pl. 2, fig. 7). The lobe is of little taxonomic use for generic assignment of the Zhuozishan species. http://mc.manuscriptcentral.com/ags Dec. 2016 The most noticeable feature of the Zhuozishan cranidia is that the anterior branches of the facial suture are distinctly divided into three sections to form a hexagonal outline (Figs. 3a, 3k). A similar hexagonal outline is observed in the three Chinese nobiliasaphine genera, except for Opsimasaphus, which displays laterally convex anterior branches of the facial suture (e.g., O. pseudodawanicus, Turvey, 2007, fig. 13). The relative length and direction of the middle section display noticeable variations. The Zhuozishan species is most similar to Zhenganites xinjiangensis (e.g., Zhou et al., 1998, pl. pl. 2, fig. 6) in sharing forward-converging middle sections; Zhenganites guizhouensis, the type species, however, shows laterally convex anterior branches without noticeable inflections (Yin and Lee, 1978, pl. 174, figs. 3–5). The Zhuozishan species differs in having the middle sections longer than the anterior sections, posterior sections longer than middle sections, and less strongly forward-converging anterior sections. This character varies too much among species of each genus to be used to attribute the Zhuozishan species to a specific genus. The variations observed in Mioptychopyge are as follows: in M. trinodosa, the middle sections are parallel-sided, as long as the anterior sections, and longer than the posterior sections; in M. suni, the middle sections diverge forward and are shorter than the anterior sections but longer than the posterior sections; and in M. tatsaotzensis, the middle sections converge forward and are shorter than the anterior and posterior sections (compare Zhou et al., 1998, pl. 3, fig. 4; Turvey, 2007, pl. 3, fig. 8; Lu et al., 1976, pl. 10, fig. 3). Ningkianites insculpta, the type species, displays the distinct hexagonal outline but with slightly forward-diverging middle sections and longer anterior sections (e.g., Turvey, 2007, pl. 5, fig. 2). However, Ningkianites fenhsiangensis has a laterally convex outline as in Z. guizhouensis (Yi, 1957, pl. 2, figs. 2a–2b); it is questionable that the cranidium of N. fenhsiangensis truly belongs to Ningkianites because it has a very short (sag.) preglabellar area and a narrow (tr.) frontal area. In the Zhuozishan cranidia, the frontal area width is about half of the posterior cranidial margin width as in Zhenganites and Ningkianites, whereas it is much wider in Mioptychopyge and Opsimasaphus (character 1 in Table 2). The Zhuozishan cranidia are least consistent with Zhenganites in terms of preglabellar area length and palpebral lobe size (characters 2 and 3 in Table 2). The Zhuozishan cranidia are least consistent with those of Mioptychopyge in terms of cranidial length to width ratio (character 4 in Table 2). The median node of the Zhuozishan species is located at the level of the posterior ends of palpebral lobes as in Dec. 2016 ACTA GEOLOGICA SINICA (English Edition) http://www.geojournals.cn/dzxben/ch/index.aspx http://mc.manuscriptcentral.com/ags Vol. 90 No. 6 1961 Table 2 Quantitative data for comparison of the Chinese nobiliasaphine genera. Characters are described in the diagram below Character aff. Mioptychopyge lashachungensis Mioptychopyge Mioptychopyge trinodosa Mioptychopyge suni Mioptychopyge tatsaotzensis Zhenganites Zhenganites xinjiangensis Zhenganites guizhouensis Opsimasaphus pseudodawanicus Ningkianites insculpta 1 a/e 47% 71% 70% 71% 48% 48% 68% 51% Mioptychopyge (e.g., Zhou et al., 1998, pl. 3, fig. 4). It is located anterior to the posterior ends in Zhenganites (e.g., Z. guizhouensis, Yin and Lee, 1978, pl. 174, fig. 4; Z. xinjiangensis, Zhou et al., 1998, pl. 2, fig. 10), whereas it is posterior to the ends in Ningkianites and Opsimasaphus (e.g., N. insculpta, Lu 1975, pl. 7, fig. 4; O. pseudodawanicus, Turvey, 2007, pl. 3, fig. 13 and Lu, 1975, pl. 5, fig. 25). The posterior branches of the facial suture of the Zhuozishan species are moderately sinuous, whereas those in Zhenganites and Mioptychopyge are strongly sinuous (e.g., Zhou et al., 1998, pl. 2, fig. 6, pl. 3, fig. 4) and those of Opsimasaphus and Ningkianites are weakly sinuous (e.g., Turvey, 2007, pl. 3, fig. 13, pl. 5, fig. 2). The subrectangular occipital ring of the Zhuozishan species is reminiscent of M. tatsaotzensis (Lu et al., 1976, pl. 10, fig. 3) and O. pseudodawanicus (e.g., Turvey, 2007, pl. 4, fig. 3). The ring is subtrapezoidal in Zhenganites, Ningkianites and M. trinodosa (e.g., Zhou et al., 1998, pl. 2, fig. 6; Turvey, 2007, pl. 5, fig. 2; Zhou et al., 1998, pl. 3, fig. 4), whereas it is strongly convex posteriorly in M. suni (e.g., Turvey, 2007, pl. 3, fig. 8). The nobiliasaphine pygidia are generally wider than long and the Zhuozishan pygidia show an intermediate value in terms of the length to width ratio (character 5 in Table 2). The Zhuozishan pygidia are characterized by a narrowest axis as in those of M. tatsaotzensis (character 6 in Table 2). The doublure of the Zhuozishan pygidia is Cranidium 2 3 b/d c/d 22% 29% 24% 30% 27% 30% 23% 28% 23% 32% 15% 45% 13% 45% 17% 44% 25% 24% 21% 29% 91% 72% 72% 5 g/f 60% 67% 73% 63% 64% 52% 52% Pygidium 6 h/f 20% 27% 33% 26% 21% 25% 25% 70% 75% 55% 54% 26% 26% 4 d/e 72% 94% 97% 7 j/i 29% 41% 28% 46% 49% 49% 26% narrower (Fig. 3j), as in O. pseudodawanicus and M. trinodosa (character 7 in Table 2); unlike the other two species, the doublure in M. trinodosa becomes strongly wider posteriorly; Z. xinjiangensis has the widest doublure, accounting for approximately half of the pygidial width. The Zhuozishan pygidia are readily distinguished from those of Ningkianites and Zhenganites; Ningkianites is characterized by its distinctly impressed marginal border furrow (e.g., N. insculpta, Turvey, 2007, pl. 5, fig. 4) and Zhenganites by its convex distal ends of the pleural ribs (e.g., Z. xinjiangensis, Zhou et al., 1998, pl. 2, figs. 7, 12). The subsemicircular pygidial outline is reminiscent of O. pseudodawanicus (e.g., Lu, 1975, pl. 6, figs. 7–8) and M. tatsaotzensis; the length and depth of the pleural furrows are also similar in these species; M. tatsaotzensis and the Zhuozishan species further share a longer postaxial region. Turvey (2007) claimed that hypostomal characters are the most informative in classifying effaced asaphids and employed them to differentiate the Chinese nobiliasaphines from the Baltoscandinian asaphids (textfig. 7). An incomplete hypostome in ventral view (Fig. 3i) displays a subhexagonal middle body, a deep and circular apodemal pit at the posterior end of the lateral border furrows and a deeply, widely-notched posterior margin. Of the Chinese nobiliasaphine genera under comparison, the hypostome is recorded for M. suni (Li et al., 1975, pl. 18, 1962 Vol. 90 No. 6 ACTA GEOLOGICA SINICA (English Edition) http://www.geojournals.cn/dzxben/ch/index.aspx fig. 4), O. pseudodawanicus (Turvey, 2007, pl. 4, fig. 9) and Z. xinjiangensis (Zhou et al., 1998, pl. 2, fig. 8). That of M. suni in ventral view is readily differentiated by its wider and rounded middle body, narrower lateral border and pair of large maculae delimited by a middle furrow anteriorly and a posterolateral border furrow posteriorly; both furrows are of approximately equal depth. The partially preserved hypostome of O. pseudodawanicus seen in dorsal view is distinguished by a diamond-shaped middle body; in other words, the anterior half of the middle body strongly narrows forward. The hypostome of Z. xinjiangensis in ventral view shares the subhexagonal middle body but has a slightly wider lateral border. In Z. xinjiangensis, a pair of smaller maculae are located immediately adaxial to the deep posterior end of the lateral border furrows and surrounded by shallow middle and posterior border furrows. This clearly contrasts with the condition in M. suni where middle and postero-lateral border furrows of equal depth delimit the large maculae. It is thought that the Zhuozishan hypostome, although maculae are poorly preserved, has a similar configuration to that of Z. xinjiangensis. It is certain that the Zhuozishan species is more closely related to Mioptychopyge and Zhenganites than Ningkianites and Opsimasaphus. Although the species appears to bear more resemblance to Mioptychopyge, lack of accurate information on hypostomes and palpebral lobes prevents us from ascribing it with confidence to the genus. Since the hexagonal outline of the anterior branches of facial suture, in combination with other characters such as subsemicircular pygidium, are considered to be unique among the nobiliasaphine genera, it is possible that the species might belong to a new genus. 4.2 Taxon 2 aff. Mioptychopyge sp. indet. Fig. 3n Figured specimens: Pygidium (OCGM-Inv. 1307). Remarks: A single incomplete pygidium differs from the pygidia of aff. Mioptychopyge lashachungensis (see above) in having a sagittally longer outline, up to 10 pairs of wider pleural and interpleural furrows, up to 13 axial rings, and a relatively straight anterior margin without curving posteriorly at the fulcrum. 4.3 Taxon 3 Family Nileidae Angelin, 1854 Genus Symphysurus Goldfuss, 1843 Type species: Asaphus palpebrosus Dalman, 1827, from Husbyfjöl in Västergötland, Sweden; subsequently designated by Barrande (1852). Symphysurus klimoliensis (Lu in Lu et al., 1976) http://mc.manuscriptcentral.com/ags Dec. 2016 Figs. 2b, 4a–4t Synonymy: 1976 Nileus klimoliensis Lu in Lu et al., p. 66, pl. 12. fig. 3. Holotype: Exoskeleton lacking free cheeks (23927, Lu in Lu et al., 1976, pl. 12, fig. 3) housed in Nanjing Institute of Geology and Palaeontology. Type horizon and locality: Middle Ordovician Klimoli Formation, Lashizhong, Zhuozishan area, Inner Mongolia, China. Figured specimens: Three exoskeletons (OCGM-Inv. 1475, 1401, 1301), thoraco-pygidium (OCGM-Inv. 1397), three cranidia (OCGM-Inv. 1473, 1515, 1412), two pygidia (OCGM-Inv. 1432, 1306), hypostome (OCGMInv. 1441), and thoracic segments (OCGM-Inv. 1484). Diagnosis: Species with moderately convex exoskeleton; cephalic axial furrows shallow and narrow; thorax of eight segments with elongated (tr.) goggleshaped lobe defined by shallow furrow in axial rings. Pygidium subsemicircular without marginal border furrow; doublure narrow (about one-third of pygidial width). Dorsal surface covered with fingerprint-like, fine terrace lines. Description: The exoskeleton is elliptical in outline and 60% wider than long. The cephalon is semi-circular in outline and about one-third of exoskeletal length. The cranidium is subtrapezoidal in outline with a rounded anterior margin; the sagittal length is 90% of width along the posterior cranidial margin. There are no furrows in the frontal area on the external surface; the narrow flat anterior border is recognized in internal mold and delimited by a shallow furrow that disappears sagittally. The anterior branches of the facial suture diverge forward and then strongly turn adaxially along the cranidial margin; posterior branches are straight and run obliquely at about 40° from the exsagittal line. The axial furrows are shallow and not impressed in the frontal area and are impressed away from the facial suture posterior to the frontral area; they are slightly curved adaxially around the level of the posterior ends of the palpebral lobes and then diverge slightly posteriorly. The glabella rapidly downslopes forward into the frontal area and is otherwise moderately convex; the glabellar crest is weakly carinated. Five pairs of large muscle impression areas are weakly impressed; the anteriormost pair is smallest and closest to each other; a small median node (visible only on the internal mold) is located between the anterior and posterior ends of the palpebral lobes (at the level of the posterior 31% of cranidial length). The occipital ring is elongate (tr.) spindle-shaped and defined by a weakly impressed occipital furrow. The palpebral lobe is semicircular in outline and 38% of cranidial length; the mid-palpebral point is located at the level of the anterior Dec. 2016 ACTA GEOLOGICA SINICA (English Edition) http://www.geojournals.cn/dzxben/ch/index.aspx http://mc.manuscriptcentral.com/ags Vol. 90 No. 6 Fig. 4. Photographs of specimens of Symphysurus klimoliensis (Lu in Lu et al., 1976); scale bars = 5 mm. (a–c), Exoskeleton with displaced free cheeks, OCGM-Inv. 1475, (a) dorsal view, (b) lateral view, (c) magnified ventral view of hypostome (note the alternation of wider and narrower terrace lines). (d–f), Cranidium, OCGM-Inv. 1473, (d) dorsal view, (e) lateral view (note the flat anterior border defined by shallow furrow), (f) anterior view. (g), Exoskeleton lacking free cheeks, OCGM-Inv. 1401, dorsal view. (h–j), Pygidium, OCGM-Inv. 1432, (h) dorsal view (note the inner margin of doulbure), (i) posterior view, (j) anterior view. (k), Hypostome, OCGM-Inv. 1441, ventral view. (l), Cranidium, dorsal view, OCGM-Inv. 1515. (m–n), Cranidium, OCGM-Inv. 1412, (m) dorsal view, (n) magnified view of frontal area showing terrace lines. (o–p), Pygidium (latex cast), OCGM-Inv. 1306, (o) posterior view, (p) dorsal view. (q–r), Incomplete exoskeleton, OCGM-Inv. 1301, (q) dorsal view, (r) lateral view. (s), Magnified view of pygidium of thoraco-pygidium, OCGM-Inv. 1397, dorsal view (note the presence of fingerprint-like terrace lines and the absence on axial region). (t), Thoracic segments, OCGM-Inv. 1484, ventral view (note the presence of “ventral ridge” and “oval area” of Whittington (2000)). 1963 1964 Vol. 90 No. 6 ACTA GEOLOGICA SINICA (English Edition) http://www.geojournals.cn/dzxben/ch/index.aspx 60% of cranidial length; the anterior end is located more adaxially than the posterior end. The cranidial surface is ornamented with fingerprint-like, fine terrace lines; those in the frontal area are more widely spaced and subparallel to the anterior margin but are much less distinct in the internal mold. The librigenal fields slope down steeply; border burrows are not impressed. The postero-lateral corner is rounded. The eyes are large. The cephalic doublure is moderately wide, and ornamented with fine terrace lines parallel to the cephalic margin. The hypostome is subquadrate in outline. The anterior wing is small and triangular. The anterior margin is almost straight, the lateral margin is strongly convex laterally and the posterior margin is gently tripartite. The middle body is rounded; the anterior lobe is twice as long (sag.) as the posterior lobe; the lateral border furrow deepens and widens posteriorly with the deepest pit at the posterior end. The ventral surface is covered with alternating thicker and thinner fingerprint-like, round-crested terrace ridges; the dorsal surface is covered with less strongly raised terrace ridges. The thorax has eight segments and is one-third of carapace length. The axial furrows are shallow and parallel-sided; the axial region is moderately convex and 43% of thoracic width; the axial rings are elongate (tr.) trapezoidal; an elongate (tr.) goggle-shaped lobe is present in each ring, which is posteriorly and laterally delineated by a shallow furrow (the lobe corresponds to the ‘oval area’ and the furrow to the ‘ventral ridge’ of Whittington (2000)); anterior and posterior ventral ridges are present in each axial ring; the anteromost is much more prominent; anterior and posterior ridges are overlapped and expressed as a shallow furrow on the external surface. The pleurae are horizontal and then slope down from the fulcral line; the distal ends of the pleurae are gently curved posteriorly. Pleural furrows are shallow and wide, diagonal, and disappear halfway down pleural width; the anterior pleural band is strongly raised as an elongate triangular ridge and the posterior pleural band is moderately convex. The fulcrum of the first pleura is located very close to the axial furrows; fulcral lines gently diverge posteriorly from the first to fourth pleurae and are parallel-sided from the fourth to eighth pleurae; the width (tr.) of the articulating facet changes accordingly; fulcral processes are small. The thoracic surface is ornamented with weakly raised, fingerprint-like, fine terrace lines subparallel to the transverse lines. The doublure is almost half the pleural width and ornamented with more widely spaced terrace lines subparallel to the lateral margin--. The pygidium is subsemicircular in outline with a gently convex anterior margin with a length 57% of width. http://mc.manuscriptcentral.com/ags Dec. 2016 The axial furrows are shallow and slightly curved adaxially to delineate a funnel-shaped axis; seven axial rings and a terminal piece are recognized; inter-ring furrows are faintly impressed; up to six pairs of rounded, weakly impressed muscle impression areas are recognized. The pleural field gently slopes down; the pleural and interpleural furrows are faintly impressed, except for the anteriormost pair; up to three pleural ribs are recognized; the fulcrum is the same as in thoracic pleurae. The doublure is moderately wide (about one-third of pygidial width and length) and becomes slightly wider posteriorly; it is moderately indented into the anterior quarter of its sagittal length. Fine, fingerprint-like terrace lines are present on the external surface of the pleural region, but absent on the axial region; the doublure is ornamented with more widely spaced terrace lines parallel to the pygidial margin. Remarks: Lu in Lu et al. (1976) erected Nileus klimoliensis based on a single exoskeleton lacking free cheeks (pl. 12, fig. 3). Several articulated, well-preserved exoskeletons in the present collection provide morphologic details for systematic revision of this Zhuozishan nileid. From Nileus armadillo (Dalman, 1827) the type species (e.g., Schrank, 1972, pl. 6, figs. 1–3, 5–6; Nielsen, 1995, figs. 147–151), the Zhuozishan species differs in having a longer (sag.) frontal area, a longer (exsag.) posterior area of the fixigenae, and much smaller palpebral lobes. The axial furrows of the Zhuozishan species are distinctly impressed away from the facial suture, whereas in N. armadillo the furrows are only recognized along the palpebral areas of the fixigenae and meet the anterior and posterior ends of the palpebral lobes. A subsemicircular pygidium of the Zhuozishan species lacks the marginal border furrow, whereas in N. armadillo, the pygidium is fusiform in outline with a more strongly convex anterior margin and a distinct border furrow. The Zhuozishan species has a narrower doublure with an inner margin subparallel to the pygidial margin, whereas in N. armadillo, the doublure is much wider and the inner margin is convex adaxially. In reviewing the concept of the family Nileidae, Whittington (2003) diagnosed Nileus Dalman, 1827, the genotype, as having a glabellar organ expressed as a median node in the internal mold, ventral ridges in the thoracic axial region as muscle insertion areas, oval depressed areas between the ridges on the visceral surface (see also Whittington, 2000), and nonfulcrate thoracic pleurae; the absence of such features corresponding to the ridges and oval areas on the external surface is also considered as diagnostic in Nileus. A similarily positioned median node is found in the internal molds of the Zhuozishan crandia (e.g., Figs. 4d, 4m, 4q). The thoracic Dec. 2016 ACTA GEOLOGICA SINICA (English Edition) http://www.geojournals.cn/dzxben/ch/index.aspx axial features are also observed on the visceral surface (Fig. 4t), which are, however, observed as a goggle-shaped lobe, which corresponds to the oval areas that are fused into a single lobe, defined by a shallow furrow, which corresponds to the ventral ridge, on the external surface as well as the internal mold (Figs. 4a–4b, 4q, 4t); the lobes and furrows are more distinct in the internal molds. The thoracic pleurae of the Zhuozishan species are definitely fulcrate because the horizontal inner pleural portion is present adaxial to the fulcral line (Figs. 4a, 4q). Most cranidial features in the diagnosis of Nileus as defined by Fortey (1975, p. 40) are found in the Zhuozishan cranidia; unlike Nileus, however, the cranidial length in the Zhuozishan species is always longer than the transverse width between the palpebral lobes (length 89% of transverse width). In reviewing Elongatanileus Ji, 1986 in comparison with Nileus, Poronileus and Peraspis, Fortey (1997) noted that Nileus has the maximum cranidial width at the palpebral lobes; it is noted that the Zhuozishan cranidia are widest between palpebral lobes (113% of cranidial length). The pygidial doublure allows us to differentiate the Zhuozishan species clearly from Nileus (see Fortey, 1975, fig. 4). Because it has a relatively narrow doublure with an inner margin almost parallel to the pygidial margin, as in Symphysurus Goldfuss, 1843 (compare Figs. 4a, 4h with Fortey, 1975, fig. 4E), the Zhuozisan species is assignable to that genus. Also the nature of the pygidial doublure distinguishes the Zhuozishan species from two welldefined Darriwilian (late Arenig to Llanvirn) Nileus species from China, N. walcotti Endo, 1932 from South China and N. sericeus Turvey, 2007 from Xinjiang; N. walcotti has a fusiform pygidium with a wide doublure (e.g., Turvey, 2007, pl. 10, figs. 3, 6) and N. sericeus has a subsemicircular but sagittally shorter pygidium with a wide doublure (e.g., Zhou et al., 1998, pl. 5, figs. 8, 11). Given that the thoracic pleural details from the articulated specimen and/or pygidial doublure are not known, some Nileus species are quite comparable with the Zhuozishan species. For example, the Zhuozishan species is comparable with N. glazialis costatus (e.g., Fortey, 1975, pl. 10, figs. 1, 5) in the cranidial and pygidial morphologies and with N. orbiculatoides svalbardensis (e.g., Fortey, 1975, pl. 11, fig. 3) in hypostomal morphology. In cranidial and pygidial aspects, the Zhuozishan nileid is also comparable to Poronileus Fortey, 1975 and Symphysurus but it is more similar to the latter. Poronileus was diagnosed cranidially by Fortey (1975, p. 51) as being longer than wide, of low convexity, pitted and having axial furrows connecting anterior and posterior ends of the palpebral lobes. From Poronileus, the Zhuozishan species http://mc.manuscriptcentral.com/ags Vol. 90 No. 6 1965 differs in having axial furrows incised away from the posterior end of the palpebral lobes and the surface covered only with fingerprint-like, fine terrace lines (compare Poronileus fistulosus, the type species, e.g., Fortey, 1975, pl. 13, fig. 1, pl. 41, fig. 3). However, some Poronileus species display a cranidial morphology that is found to deviate from the diagnosis but be rather similar to the Zhuozishan crandia (e.g., P. jugatus, Fortey, 1975, pl. 17, fig. 1). The pygidial morphology also allows us to differentiate the Zhuozishan species more convincingly from Poronileus; the Zhuozishan pygidia have a wider than long outline (length 58% of width and 67% in Poronileus), much narrower doublure, and no marginal border furrow (see also Fortey, 1975, fig. 4). The diagnosis of Symphysurus (Fortey, 1986, p. 256) describes its cranidium as having well-defined axial furrows, parallel-sided or slightly forward-expanding glabella, and terrace lines on the cranidial surface. The cranidial morphology of the Zhuozishan species is consistent with that diagnosis. From Symphysurus palpebrosus (Fortey, 1986, fig. 1), the Zhuozishan cranidia differ in having a less convex cranidium, much shallower axial furrows, much finer terrace lines, and a slightly more posteriorly located median node. The pygidium of Symphysurus is diagnosed as having a subsemicircular outline, a long and dorsal weakly defined axis, and a doublure subparallel to the margin, and lacking a distinct border (Fortey, 1986, p. 256). The Zhuozishan pygidia only differ from those of S. palpebrosus in having a funnel-shaped axis and terrace lines on the surface (e.g., Fig. 4h); S. palpebrosus is described as having terrace lines only on the cranidial surface and thoracic axial rings. Of described Symphysurus species, the Zhuozishan species is most similar to Symphusurus arcticus from Spitbergen (Fortey, 1975, pl. 21, figs. 1–16). It differs in having eight (seven in S. arcticus) thoracic segments, a longer (sag.) frontal area, and a narrower pygidial doublure. We thus conclude that the Zhuozishan species should be transferred into Symphysurus. Two Symphysurus species from Shaanxi, S. carinatus and S. subquadratus were recorded by Lu (1975, pl. 24, figs. 4–7, pl. 25, figs. 1–5). These two species are readily distinguished by having deep axial furrows and a fairly convex glabella and thoracic axial region, which are more comparable to those of S. palpebrosus (Fortey, 1986, fig. 1). Chang and Fan (1960) erected five new species of Symphysurus from Gansu and Qinghai based on inadequate material. Fortey (1986) suggested that all these might be transferred into Poronileus because of their smaller palpebral lobes and medially constricted glabella. The exsagittal length of the palpebral lobe accounts for 1966 Vol. 90 No. 6 ACTA GEOLOGICA SINICA (English Edition) http://www.geojournals.cn/dzxben/ch/index.aspx 42% of cranidial length in the Spitsbergen Poronileus species described by Fortey (1975), whereas it is about 40% in well-defined Symphysurus species such as S. palpebrosus (Fortey, 1986), S. angustatus (Ebbestad, 1999) and S. arcticus (Fortey, 1975); it is 39% in S. klimoliensis. The glabellar constriction occurs along the palpebral area of the fixigenae in the Chinese species (Chang and Fan, 1960, pl. 1, fig. 1, pl. 2, figs. 3–5, 7–11, 19, 21, text-figs. 5–10; Zhou et al., 1982, pl. 66, fig. 10) and the intensity of the constriction varies among them. The glabella is similarily constricted in S. arcticus (e.g., Fortey, 1975, pl. 21, fig. 1)- and S. klimoliensis (e.g., Fig. 4g). These two features are not so differentiated as to allow us to transfer these species erected by Chang and Fan (1960) into Poronileus. It is apparent that the associated pygidia (Chang and Fan, 1960, pl. 2, figs. 7–8, 19) are wider than long and have a fairly wide doublure, which is reminiscent of Nileus. Zhou in Zhou et al. (1982) erected S. longmendongensis from Shaanxi based on a single cranidium (pl. 66, fig. 12). The cranidium is most similar to S. klimoliensis (compare with Fig. 4d) among the above-mentioned Chinese species, but has its axial furrows connecting the anterior and posterior ends of the palpebral lobes. Zhou in Zhou et al. (1982) erected two Poronileus species from Ningxia, P. angustus (pl. 66, figs. 13–14) and P. miboshanensis (pl. 67, figs. 1–4). Although it is difficult to assess these species due to poor preservation, the cranidia of both species appear to be comparable to those of S. klimoliensis (compare Fig. 4l) and cf. Peraspis kujandensis (see below). An associated pygidium (pl. 66, fig. 14) is more similar to that of Poronileus (pl. 66, fig. 14) and the other (pl. 67, fig. 3) is not of Poronileus or Symphysurus type; the associated hypostome (pl. 67, fig. 4) is similar to that of Poronileus (e.g., Fortey, 1975, pl. 13, fig. 8). It seems that the Ningxia material represents a mixture of more taxa than described by Zhou et al. (1982). Accurate taxonomic assessment of all these Chinese species awaits detailed morphologic information based on more and better-preserved specimens that reveal the nature of the pygidial doublure in particular, which will eventually confirm whether or not Poronileus truly occurs in China. 4.4 Taxon 4 Nileid gen. et sp. indet. Fig. 5j–k Figured specimens: Incomplete cephalon (OCGM-Inv. 1540). Remarks: The incomplete cephalon is characterized by smaller palpebral lobes (26% of cranidial length), a longer (exsag.) postocular area of the fixigenae, with the mid- http://mc.manuscriptcentral.com/ags Dec. 2016 palpebral point at mid-glabellar length. Since other exoskeletal information, in particular the correctly associated pygidium (where is this specimen???) , is not available, the generic and specific attribution (NB. the species is the key taxon) cannot be determined. 4.5 Taxon 5 Genus Peraspis Whittington, 1965 Type species: Niobe lineolata Raymond, 1925 from Table Head Formation, Aguathuna, Port au Port peninsula, western Newfoundland, Canada; subsequently designated by Whittington (1965). Remarks: In erecting Peraspis, Whittington (1965) assigned it to the Nileidae because it lacks the median suture. Later, Whittington (2003) excluded it from the family by claiming instead its asaphid affinity because the type species, Peraspis lineolata Whittington, 1965 shows the asaphid condition in regard to the glabellar tubercle and thoracic axial features. The tubercle is located much more posteriorly, near the occipital furrow, and is observed on the external surface as well as the internal mold (Whittington, 1965, pl. 34, fig. 9). The thoracic axial rings are equipped with an articulating furrow and half ring (e.g., Whittington, 1965, pl. 34, figs. 1, 9) instead of having nileid thoracic axial features (Whittington, 2000 for detailed discussion on the latter). The glabellar turbercle in some species later assigned to Peraspis is of nileid-type in that it is more anteriorly located and observed only in the internal mold (e.g., Ross, 1970, pl. 15, fig. 4 for Peraspis erugata; Dean, 1973, pl. 4, fig. 5 for Peraspis yukonensis; Fortey, 1975, pl. 19, fig. 1, pl. 20, figs. 1, 3 for Peraspis erugata and Peraspis omega); the nature of the tubercle cannot be determined in Peraspis kolouros (Norford and Ross, 1978, fig. 6). The presence of a nileid or asaphid-type thoracic axial configuration cannot be confirmed for these species, as noted by Whittington (2003). These later-described Peraspis species share with the type species the presence of genal spines and more deeply impressed pygidial pleural furrows, which differentiates Peraspis from other nileids (Fortey and Chatterton, 1988). However, some features are observed in these species that are significantly different from P. lineolata, which lead us to question whether Peraspis is a natural group: the preglabellar area of these species has a very narrow preglabellar or anterior cranidial border furrow (e.g., P. erugata and P. kolouros) or apparently lacks the furrow (e.g., P. omega), whereas P. lineolata has a distinct furrow delimiting the glabellar front; the thorax is parallel-sided in these species, whereas it widens posteriorly in P. lineolata; and the posterior end of the pygidial axis in these species falls short of the marginal border furrow, whereas it reaches the furrow in Dec. 2016 ACTA GEOLOGICA SINICA (English Edition) http://www.geojournals.cn/dzxben/ch/index.aspx http://mc.manuscriptcentral.com/ags Vol. 90 No. 6 1967 Fig. 5. Photographs of specimens: (a–i), (l), cf. Peraspis kujandensis (Chugaeva, 1958); (j–k), Nileid gen. indet.; (m), Telephina sp. indet.; scale bars = 5 mm. (a–d), Exoskeleton lacking librigenae, OCGM-Inv. 1465, (a) dorsal view, (b) lateral view, (c) anterior view, (d) posterior view. (e), Cranidium, OCGM-Inv. 1314, dorsal view. (f–h), Cranidium, OCGM-Inv. 1478, (f) dorsal view, (g) lateral view, (h) anterior view. (i), Thoraco-pygidium OCGM-Inv. 1322, lateral view. (j–k), Incomplete cephalon, OCGM-Inv. 1540, (j) lateral view, (k) dorsal view. (l), Thoraco-pygidium, OCGM-Inv. 1370, dorsal view (note the inner margin of doublure). (m), Cranidium, OCGM-Inv. 1404, dorsal view. P. lineolata. These features of P. lineolata are more asaphid-like. Hypostomal morphology may enable us to resolve this problem. Nevertheless, Whittington (2003, p. 642) questioned the association of nileid-type hypostomes with P. lineolata (Whittington, 1965, pl. 35, figs. 6, 8). The association of the nileid-type hypostome is confirmed in P. yukonensis (Dean, 1973, pl. 4, figs. 1, 3), P. erugata (Fortey, 1975, pl. 19, figs. 4, 8), P. omega (Fortey, 1975, pl. 20, fig. 6) and P. kolouros (Norford and Ross, 1978, pl. 2, fig. 9); the hypostomal association in P. erugata from Nevada, USA has also been questioned (see Dean, 1973, p. 21 and Fortey, 1975, p. 48). The systematic assessment of Peraspis awaits the discovery of correctly associated hypostome for the type species. In addition, morphologic features of P. lineolata that deviate from those of typical nileids and other included species need to be resolved in a phylogenetic context, which may lead to modification of the concept and familial position of Peraspis. Since cf. Peraspis kujandensis from the Zhuozishan area (see below) has a nileid glabellar tubercle and a thoracic axial configuration as seen in Symphysurus klimoliensis, it is retained in the Nileidae. cf. Peraspis kujandensis (Chugaeva, 1958) Figs. 2c, 5a–5i, 5l Synonymy: 1958 Symphysurus kujandensis Chugaeva, 1968 Vol. 90 No. 6 ACTA GEOLOGICA SINICA (English Edition) http://www.geojournals.cn/dzxben/ch/index.aspx 1958, p. 68, pl. 7, figs. 15, 17–19, non fig. 16 [? = Damiraspis margiana Ghobadi-Pour et al., 2009]. Figured specimens: Exoskeleton lacking free cheeks (OCGM-Inv. 1465), two cranidia (OCGM-Inv. 1314, 1478) and thoraco-pygidium (OCGM-Inv. 1322, 1370). Description: The subtrapezoical cranidium has a rounded anterior margin. The anterior branches of the facial suture are relatively strongly convex laterally; the posterior branches are straight and run obliquely at about 30° from the exsagittal line for most of its length then smoothly turn at an obtuse angle of about 135° in the distal one-quarter. There is no anterior cranidial border and preglabellar furrows are present. The axial furrows are parallel-sided and shallow, shallower along the anterior half of the postocular areas of the fixigenae and mostly impressed away from the facial suture; they are not impressed in most of the frontal area, but strongly divergent abaxially for a short distance immediately anterior to the palpebral lobes. The frontal area slopes down steeply. The glabella behind the frontal area is weakly convex and horizontal; the median node is small and located at the level of the posterior end of the palpebral lobes. Up to six pairs of small muscle insertion areas are recognized along the glabellar crest. The occipital ring is elongate (tr.) spindle-shaped and the occipital furrow is shallow and wide and disappears sagittally. The palpebral lobes are semi-circular in out-line and flat with a length (exsag.) of 26% of the cranidial length and the mid-palpebral point slightly posterior to the mid-cranidial length; the anterior end is located more adaxially than the posterior end. The postocular area of the fixigenae is triangular. Librigena and hypostome are unknown. The thorax has eight segments, with a sagittal length about one-third of exoskeletal length. The axial furrows are shallow and obliquely directed posteriorly in each segment, defining elongate (tr.) trapezoidal axial rings. The axial region is weakly convex and gently tapers posteriorly, with a maximum width of 28% of thoracic width at the first segment; a goggle-shaped lobe and furrow are present in each axial rings, as in Symphysurus klimoliensis. The pleurae are horizontal and then they slope gently down distally from the fulcral line; the pleural furrows are diagonal and shallow. The anterior pleural band is strongly raised as an elongate triangular ridge and the posterior pleural band is moderately convex; the ridges downslope anteriorly to form articulating facets. The fulcrum of the first pleura is located halfway along the posterior cranidial margin; fulcral lines gently diverge posteriorly from the first to the fourth pleurae and are parallel-sided from the fourth to the eighth pleurae. Pleurae proximal to the fulcral line are ornamented with http://mc.manuscriptcentral.com/ags Dec. 2016 fine, transverse terrace lines. The doublure is nearly half of the pleural width and ornamented with more widely spaced terrace lines subparallel to the lateral margin. The pygidium is semicircular with a relatively straight anterior margin, length 46% of width. The axial furrows are shallow and slightly curved adaxially to define a funnel-shaped axis, which is narrow, 24% of pygidial width. Five axial rings and a terminal piece are recognized; the inter-ring furrows are faintly impressed. The pleural field is weakly convex; only the anteromost pleural furrow is impressed. The marginal border is narrow, of uniform width and ornamented with weakly developed fine terrace lines; the border furrow is shallow. The doublure, indicated by paradoublural line in some specimens (e.g., Fig. 5a) is narrow with the lateral extremity of the inner margin located at the distal 21% of half of the pygidial width and it slightly widens posteriorly; sagittally it is indented into the posterior twothirds of the doublure length. Remarks: Chugaeva (1958) erected Symphysurus kujandensis from Kazakhstan based on partially articulated specimens (pl. 7, figs. 15–19). Its cranidium is indistinguishable from the Zhuozishan cranidia, except for slightly larger palpebral lobes and a wider outline; these are considered to be due to preservation and/or ontogeny. The thoraco-pygidia are also indistinguishable from the Zhuozishan specimens. The second associated cranidium (fig. 16) is not a nileid, but an asaphid (compare with Damiraspis margiana Ghobadi-Pour et al. 2009, figs. 10D–E). From the co-occurring Symphysurus klimoliensis (Lu in Lu et al., 1976), it is readily distinguished by its smaller palpebral lobes (exsagittal length is 26% of cranidial length and 39% in S. klimoliensis), a narrower thoracic and pygidial axial regions (pygidial axis width is 24% of pygidial width and 33% in S. klimoliensis), a semicircular and shorter (sag.) pygidium (length is 46% of width and 58% in S. klimoliensis) with a relatively straight anterior margin, and a longer (tr.) inner horizontal thoracic pleural portion. From Poronileus, it clearly differs in having smaller palpebral lobes, a semicircular, sagittally much shorter pygidium (length is 67% in Poronielus) with a narrower marginal border, and narrower doublure. Of Peraspis species, the Zhuozishan species is most similar to P. erugata from Spitsbergen (Fortey, 1975, pl. 19, figs. 1–9, 11). However, it has a longer (exsag.) posterior area of the fixigenae, smaller palpebral lobes, a shallower and narrower pygidial marginal border, a narrower pygidial axis, which is 24% of pygidial width (30% in P. erugata), a narrower pygidial doublure with the inner margin at distal 21% of pygidial width (30% in P. erugata) and eight thoracic segments (seven in P. Dec. 2016 ACTA GEOLOGICA SINICA (English Edition) http://www.geojournals.cn/dzxben/ch/index.aspx erugata). The cranidia of two Poronileus species, P. angustus and P. miboshanensis from Ningxia erected by Zhou (Zhou et al., 1982, pl. 66, fig. 13, pl. 67, fig. 2), are as similar to those of this species as in S. klimoliensis. A correctly associated pygidium is needed to provide information for taxonomic assessment (see above). Peraspis is one of a few nileid genera that has genal spines and a lateral librigenal border. Fortey and Chatterton (1988) interpreted their presence as a probable secondary attainment from primitive nileids, which lack them. The lack of a genal spines and border in the Zhuozishan species (e.g., Chugaeva, 1958, pl. 7, fig. 15) leads us to provisionally assign it to Peraspis. 4.6 Taxon 6 Family Raphiophoridae Angelin, 1854 Subfamily Raphiophorinae Angelin, 1854 Genus Ampyx-- Dalman, 1827 Type species: Ampyx nasutus Dalman, 1827 from Asaphus expansus Biozone or A. raniceps Biozone of the Asaphus Limestone, upper Arenig Series, Västanå, Östergötland, Sweden; by monotypy. Ampyx gongwusuensis sp. nov. Figs. 2d, 6a–6j, 6n–6o Derivation of name: After “Gongwusu,” a county near the sampling locality. Holotype: Exoskeleton lacking free cheeks (OCGMInv. 1464, Figs. 6e–6f). Type horizon and locality: Middle Ordovician Klimoli Formation, exposed at a foothill located between Laoshidan and Gongwusu counties, south of Wuhai, Zhuozishan area, Inner Mongolia, China. Figured specimens: Six exoskeletons lacking free cheeks (OCGM-Inv. 1366, 1464, 1429, 1461, 1463, 1346), exoskeleton with displaced free cheeks and hypostome (OCGM-Inv. 1311) and cephalo-thorax (OCGM-Inv. 1460). Diagnosis: Species with pear-shaped glabella; front end situated at level of anterior cranidial border furrow in dorsal view. Subtriangular pygidium with narrow axis and distinct rim along pleural field margin. Exoskeletal surface smooth except for pygidial marginal border ornamented with fine terrace lines. Description: The exoskeleton (excluding frontal glabellar spine and librigenae) is elliptical and of low convexity. The cranidium is subtriangular; the facial suture is straight and runs obliquely posteriorly and turns more posteriorly at the level of the anterior one-quarter of cranidial length; the posterolateral corner is rounded. The anterior cranidial border -is narrow, short (tr.) and slightly http://mc.manuscriptcentral.com/ags Vol. 90 No. 6 1969 arched dorsally; the anterior cranidial border and the preglabellar furrow cross each other sagittally, forming an ‘X’ in anterior view. The axial furrows are moderately deep but shallower in the posterior half. A pair of slit-like anterior pits are located midway between the glabellar front end and the level of the maximum glabellar width. The glabella is pear-shaped and of high convexity, with a maximum width of 26% of cranidial width; the S1 is pitlike and located at the level of the minimum glabellar width; the L1 is subcircular. Two pairs of muscle insertion areas are present in the posterior half of the glabella; they are subcircular and slightly depressed, located on the glabellar side but away from the axial furrows and within the posterior half of the glabella; the posterior one is immediately anterior to L1 and smaller than the anterior one. Two additional pairs of small muscle insertion areas are recognized in some specimens, located within the anterior half of the glabella and posterior to the level of maximum glabellar width; these anterior smaller pairs are closer to the axial furrows. The glabellar frontal spine is slender, circular in cross section and projecting horizontally, with an observed maximum length of 35% of cranidial length. The glabellar front beneath the spine is short and vertical in lateral view. The occipital ring has a straight anterior margin and a convex posterior margin, divided into a pair of elongate (tr.) anterior lobe and a rimlike posterior lobe; the occipital furrow is shallow and deepens abaxially to delineate posterior end of the L1. The fixigenae are moderately convex and gently slope down distally; a pair of weakly developed ridges run across the fixigenae from the axial furrows at the level of the midglabellar length to the deep distal pit of the posterior cranidial border furrow; the ridges are weakly convex anterolaterally and become indistinct near the axial furrows. The bacculae are small, rounded, weakly developed and located immediately abaxial to the L1. The posterior cranidial border is rim-like; it runs horizontally and then slopes steeply down distally from the distal quarter of cranidial width and continues into the rim-like posterior lobe of the occipital ring. The posterior cranidial border furrows widen and deepen distally with a very distinct rounded pit at the distal end. The cranidial surface is smooth. The librigenal lateral border is wider than the anterior cranidial border and it narrows posteriorly; the librigenal spine is straight and long. The hypostome bears maculae and has a relatively wide posterior border. The thorax has six segments; the length is 29% of exoskeletal length and a width of 91% of the cranidial posterior margin width. The lateral margin is strongly convex outward with maximum curvature at the boundary between the second and third (from the anterior) segments; 1970 Vol. 90 No. 6 ACTA GEOLOGICA SINICA (English Edition) http://www.geojournals.cn/dzxben/ch/index.aspx the anterolateral end of the first segment is located at the point where the posterior cranidial border abruptly begins to slope down distally. The axis is parallel-sided and 21% of maximum thoracic width; the articulating furrow is shallow and deepens distally. The pleurae are straight (tr.) and flat; the anteromost pleural furrow is weakly sinuous and of relatively uniform width; the posterior pleural furrows widen distally; a narrow ridge is present along the lateral end of each pleura; the distal end is bent steeply downward. The surface is smooth. The pygidium is subtriangular with the length 45% of width and 30% of exoskeletal length; the lateral margin is slightly convex outward. The axis uniformly tapers posteriorly and is narrow (21% of pygidial width); the posterior end reaches the rim along the plerual field margin. Up to 18 axial rings are recognized; a pair of circular muscle impression areas are present at the distal end of each axial ring (visible only in internal mold); interring furrows are faintly impressed. The pleural field is flat and gently slopes down posteriorly; a narrow but distinct rim, raised above the pleural field, is developed along the margin. The pleural furrows are straight and shallow; the anteromost one is most distinct and slightly curved posteriorly; a narrow straight ridge is present behind each pleural furrow; the interpleural furrows are imperceptible. The marginal border slopes steeply down and is of uniform width; the posterior margin arches moderately upward in posterior view. The pygidial surface is smooth, except for the marginal border, which is ornamented with fine terrace lines subparallel to the pygidial margin. Remarks: This new species differs from the type species, Ampyx nasutus Dalman, 1827 (Whittington, 1950, pl. 74, figs. 3–9) in having a narrower axial region, shallower muscle impressions on the glabella, an abaxially convex facial suture, which is relatively straight in A. nasutus, a much less strongly curved anteriormost pygidial pleural furrow, and a much more distinct rim along the pygidial pleural field margin. Of the several Ampyx species from China, the Zhuozishan species is most comparable to Ampyx abnormalis Yi, 1957 (Peng et al., 2001, pl. 3, figs. 18–24, pl. 4, figs. 1–5; Lu, 1975, pl. 39, figs. 5–11, pl. 40, figs. 1– 7; Zhou et al., 1984, figs. 6a–b). However, it has a narrower axial region, a glabellar front end (excluding frontal spine) situated at the anterior cranidial margin furrow, whereas in A. abnormalis, the front end lies anterior to anterior cranidial margin, a sagittally longer pygidium with a much more distinct rim along the relatively straight pleural field margin, and a much longer genal spine. Ampyx hastatus and Ampyx triangularis from Ningxia (Zhou et al., 1982, pl. 69, figs. 7–8) have a much wider glabella, which protrudes anteriorly far beyond the http://mc.manuscriptcentral.com/ags Dec. 2016 cranidial margin; the features of these two species are considered more consistent with those of Rhombampyx (compare with Rhombampyx yii, Turvey, 2007, pl. 12, figs. 2–3, 7). Ampyx puntolineatus from Jilin (Zhou and Fortey, 1986, pl. 12, figs. 7, 8, 10, 12, 18) is distinguished by its strongly forward-tapering glabella and row of pits along the pygidial pleural and interpleural furrows. Ampyx chinensis from Sichuan (e.g., Lu et al., 1965, pl. 126, fig. 4) and Ampyx reedi from Yunnan (e.g., Lu et al., 1965, pl. 127, fig. 21) are based on too inadequate and poorly preserved material for comparison. A pygidium of Ampyx nanjiangensis from Xinjiang (Zhang, 1981, pl. 73, fig. 10) has a distinct rim along the pleural field margin as does A. gongwusuensis, but it is sagittally shorter and has a wider axis. Two pygidia that are associated with Mendolaspis paradoidyx from Xinjiang (Zhang, 1981, pl. 74, figs. 9– 10) have a narrow axis and a distinct rim, but the pygidia are sagittally shorter than the Zhuozishan pygidia. Turvey (2007) noted that even relatively well-known A. abnormalis and R. yii each might represent more than one taxon because their recorded stratigraphic occurrences are long and they are based on rather effaced and poorly preserved material. Well-preserved material of A. gongwusuensis reveals following morphologic details (Fig. 2d) that are not observed in other Chinese Ampyx species, including A. abnormalis, but are common even in some other raphiophorine genera. The preglabellar furrow sagittally crosses the anterior cranidial border furrow to form an ‘X’ in anterior view (e.g., Fig. 6g; Ampyx spongiosus, Fortey, 1975, pl. 22, fig. 1; Rhombampyx tragula, Fortey, 1975, pl. 28, fig. 3; Ampyxoides semicostatus, Whittington, 1965, pl. 13, fig. 4; Cnemidopyge costatus, Nielsen, 1995, fig. 253F). The glabellar front in lateral view is short and vertical beneath the frontal spine (e.g., Fig. 6j; R. tragula, Fortey, 1975, pl. 28, fig. 9). The distinct pit is present at the distal extremity of the posterior cranidial border furrow (e.g., Fig. 6e; Ampyx delicatulus, Fortey, 1975, pl. 25, fig. 4; Rhombampyx yii, Turvey, 2007, pl. 12, fig. 2). A pair of faintly raised ridges runs across the fixigenal field (e.g., Figs. 6a, 6f, 6h; A. spongiosus, Fortey, 1975, Nielsen, 1995, 1995, fig. 257H). The occipital ring is divided into a pair of elliptical anterior lobes and a rim-like posterior lobe, which continues into the rim-like posterior cranidial border (e.g., Fig. 6g; Lonchodomas clavulus, Whittington, 1959, pl. 32, fig. 4; L. tenuis, Nielsen, 1995, fig. 257H); the rim-like fusion of occipital ring and border is considered diagnostic to Raphioampyx (Turvey, 2007). A narrow, straight ridge is developed immediately behind each pygidial pleural furrow (e.g., Fig. 6a; A. spongiosus, Fortey, 1975, pl. 23, fig. 1; A. semicostatus, Whittington, 1965, pl. 12, fig. 10). Dec. 2016 ACTA GEOLOGICA SINICA (English Edition) http://www.geojournals.cn/dzxben/ch/index.aspx Of these taxa outside China, A. gongwusuensis is cranidially most similar to Ampyx porcus from Spitsbergen (e.g., Fortey, 1975, pl. 24, fig. 1) and Lonchodomas tenuis (e.g., Nielsen, 1995, fig. 257A) and pygidially to Lonchodomas normalis (e.g., Whittington, 1965, pl. 10, fig. 7). However, A. porcus has distinct rows of pits along the pygidial pleural and interpleural furrows and Lonchodomas is differentiated by having a frontal glabellar spine with a subquadrate cross-sectional outline and five thoracic segments. This complexity of similarities needs to be resolved to soundly differentiate the raphiophorine genera. 4.7 Taxon 7 Ampyx cf. abnormalis Yi, 1957 Fig. 6k–m Figured specimens: Thoraco-pygidium with cephalic outline (OCGM-Inv. 1418) and cranidium (OCGM-Inv. 1524). Remarks: The thoraco-pygidium differs from that of Ampyx gongwusuensis in having a sagittally shorter pygidium with a wider axis and a more posteriorly located maximum thoracic width, which is positioned in the third segment but is at the posterior end of the second segment in A. gongwusuensis (compare with Fig. 6d). The associated cranidium also differs in having a more rounded cranidial outline, a wider frontal spine base, and the glabellar front protruding beyond the anterior cranidial margin. In regard to cranidial and pygidial outlines, this species is comparable to Ampyx abnormalis (compare with Lu, 1975, pl. 40, figs. 1, 4 and Zhou et al., 1984, figs. 6a– 6b) but it has a much narrower thoracic and pygidial axial region, much shorter thoracic pleurae, and less strongly impressed anteromost pair of pygidial pleural furrows. There is no cranidium in A. abnormalis shown in other studies that clearly shows the glabellar frontal spine like that of the present cranidium. The Zhouzishan taxon is provisionally associated with A. abnormalis. 4.8 Taxon 8 Ampyx sp. indet. Fig. 7e–f Figured specimens: Cranidium (OCGM-Inv. 1431). Remarks: This species represented by a single cranidium differs from Ampyx gongwusuensis in having an anterior cranidial margin that is longer (tr.) and curved backwards sagittally. It is comparable to cranidia in Mendolaspis paradoidyx from Xinjiang (Zhang, 1981, pl. 74, figs. 7–8) but it has a much shorter (tr.) anterior border. Lu (1975) figured several smaller cranidia of Ampyx abnormis (pl. 39, figs. 5–9), which are similar to the present cranidium. These cranidia lack the glabellar http://mc.manuscriptcentral.com/ags Vol. 90 No. 6 1971 frontal spine and have an anteriorly convex anterior cranidial margin; however, it cannot be determined whether or not the present cranidium lacks the spine. 4.9 Taxon 9 Genus Abulbaspis-- Zhou and Zhou, 2006 Type species: Bulbaspis ordosensis Lu in Lu et al., 1976 from the Middle Ordovician Klimoli Formation, Zhuozishan area, Inner Mongolia, China; by original designation. Abulbaspis ordosensis (Lu in Lu et al., 1976) Fig. 7a–d. Holotype: Exoskeleton (23936, Lu in Lu et al., 1976, pl. 13, fig. 6) housed in Nanjing Institute of Geology and Palaeontology. Type horizon and locality: Middle Ordovician Klimoli Formation, Wulalike canyon, southern end of Gangdeer Mountains, south of Wuhai, Inner Mongolia, China. Figured specimens: Exoskeleton lacking free cheeks (OCGM-Inv. 1541). Remarks: The present specimen only differs from the holotype of Abulbaspis ordosensis (Lu et al., 1976, pl. 13, fig. 6) in having a larger frontal glabellar bulb with a shorter connective neck. The difference is considered as intraspecific since many Abubaspis and Bulaspis species display a similar variation (e.g., Abulbaspis ovulum Chugaeva, 1958, pl. 2, figs. 6–8; Bulbaspis mirabilis Chugaeva, 1958, pl. 3, figs. 1–2). This species is nearly indistinguishable from Ampyx gongwusuensis. It differs in having a spherical frontal glabellar bulb with a short connective neck (a spine in the latter), a glabellar front protruding slightly further beyond the anterior cranidial margin, a wide triangular depression adaxial to a pair of ridges in the anterior fixigenal field, and an entire posterior pygidial margin (a dorsally-arched margin in the latter). If the frontal glabellar bulb and connective neck are not preserved, it is likely that these differences would be interpreted as intraspecific within A. gongwusuensis. It is possible that the differences including the spherical bulb might be related to sexual dimorphism. Fortey and Hughes (1998) interpreted a bulb in the preglabellar field as a brooding pouch. Although it is a direct extension of the glabella, the spherical bulb in A. ordosensis might represent another type of brooding device. Since the specimen of A. ordosensis occurs in a bed 24 m higher than the horizon where A. gongwusuensis occurs, to confirm this possible interpretation of sexual dimorphism awaits further collection. 1972 Vol. 90 No. 6 ACTA GEOLOGICA SINICA (English Edition) http://www.geojournals.cn/dzxben/ch/index.aspx http://mc.manuscriptcentral.com/ags Dec. 2016 Fig. 6. Photographs of specimens of the Raphiophoridae: (a–j), (n–o), Ampyx gongwusuensis sp. nov.; (k–m), Ampyx cf. abnormalis Yi, 1957; scale bars = 5 mm. (a–c), Exoskeleton lacking free cheeks, OCGM-Inv. 1366, (a) dorsal view, (b) anterior view, (c) posterior view. (d), Cephalo-thorax, OCGM-Inv. 1460, dorsal view. (e–f), Exoskeleton lacking free cheeks, OCGM-Inv. 1464, holotype, (e) dorsal view, (f) magnified lateral view of cranidium (note four circular muscle impression areas alongside glabella). (g), exoskeleton lacking free cheeks (latex cast), OCGM-Inv. 1429, oblique anterior view. (h–i), Exoskeleton with displaced free cheeks and incomplete hypostome, OCGM-Inv. 1311, (h) dorsal view, (i) lateral view (note the free cheek and lateral border of posterior two thoracic segments). (j), Exoskeleton lacking free cheeks, OCGM-Inv. 1461, magnified lateral view of cranidium. (k), Incomplete exoskeleton, OCGM-Inv. 1418, dorsal view. (l–m), Cranidium, OCGM-Inv. 1524, (l) dorsal view, (m) lateral view. (n), Exoskeleton lacking free cheeks (external mold), OCGM-Inv. 1463, magnified view of glabellar frontal spine. (o), Exoskeleton lacking free cheeks, OCGM-Inv. 1346, magnified view of muscle impression areas on pygidial axial rings. Dec. 2016 ACTA GEOLOGICA SINICA (English Edition) http://www.geojournals.cn/dzxben/ch/index.aspx http://mc.manuscriptcentral.com/ags Vol. 90 No. 6 1973 Fig. 7. Photographs of specimens of the Raphiophoridae: (a–d), Abulbaspis ordosensis (Lu in Lu et al., 1976); (e–f), Ampyx? sp. indet.; scale bars = 5 mm. (a–d), Exoskeleton lacking free cheeks, OCGM-Inv. 1541, (a) dorsal view, (b) lateral view, (c) anterior view, (d) posterior view. (e–f), Cranidium, OCGM-Inv. 1431, (e) dorsal view, (f) oblique anterior view. 4.10 Taxon 10 Family Telephinidae Marek, 1952 Genus Telephina Marek, 1952 Telephina sp. indet. Fig. 5m Figured specimens: Incomplete cranidium (OCGMInv. 1404). Remarks: A single poorly preserved cranidium shows morphology of Telephina including a short (sag.) glabella with rounded anterior margin, a large occipital ring with a deep occipital furrow, tubercles on glabella, and reticulate pits on the fixigena (compare with Telephina bicuspis (Angelin, 1854) from Norway, Nikolaisen, 1963, pl. 1, figs. 1–10). The poor preservation prevents us from further assessing the species. 5 Conclusion A trilobite assemblage collected from the Middle Ordovician Klimoli Formation of the Zhuozishan area, Ordos Basin, Inner Mongolia was systematically described. The assemblage is primarily composed of the raphiophorids and nileids. New morphological data revealed by the systematic revision need to be incorporated to evaluate systematics of important Chinese raphiophorid taxa such as Ampyx and Abulbaspis, and nileid taxa such as Symphysurus and Poronileus. Acknowledgements The authors are grateful to Beatriz G. Waisfeld for giving constructive comments on an earlier version of the manuscript. We also thank for anonymous reviewers for reviewing the manuscript and Susan Turner for improving English of the taxonomic description sections. This work is financially supported by a grant from the Basic Research Project (GP2016-013) of KIGAM to S.-B. Lee and the Korea Research Foundation (Grant No. KRFR1A4007-2010-0011026) to D.-C. Lee. Manuscript received May 24, 2015 accepted Oct. 3, 2016 edited by Fei Hongcai and Susan Turner References Angelin, N.P., 1854. Paleontologia Scandinavica, Crustacea Formationis Transitionis. Lund: Lipsiae, 1–92. Balashova, E.A., 1964. Morphology, phylogeny and stratigraphic occurrence of the Early Ordovician subfamily Ptychopyginae in the Baltic region. Voprosy Paleontologii, 4: 3–56. (in Russian). Balashova, E.A., 1971. Trilobites of the new subfamily Pseudobasilicinae. Voprosii Paleontologii, 6: 52–60. (in Russian). Barrande, J., 1852. Système Silurien du centre de la Bohème. 1 ère partie, Prague and Paris: privately published, 1–935. Bengtson, P., 1988. Open nomenclature. Palaeontology, 31: 223–227. Burmeister, H., 1843. Die Organisation der Trilobiten aus ihren lebenden Verwandten entwickelt; nebst einer systematischen Uebersicht aller zeither beschriebenen Arten. Berlin: Reimer, 147 p. Chang, W., and Fan, J., 1960. Ordovician and Silurian trilobites of the Qilian Mountains . In: Geological Gazetter of the Qilian Mountains (4). Beijing: Science Press, 83–148 (in Chinese). Chen, J., Zhou, Z., Lin, Y., Yang, X., Zou, X., Wang, Z., Luo, K., Yao, B., and Shen, H., 1984. Ordovician biostratigraphy of western Ordos. Memoir of Nanjing Institute of Geology and Palaeontology, Academia Sinica, 20: 1–32 (in Chinese with 1974 Vol. 90 No. 6 ACTA GEOLOGICA SINICA (English Edition) http://www.geojournals.cn/dzxben/ch/index.aspx English summary). Chen, X., Zhou, Z.-Y., and Fan, J.-X., 2010. Ordovician paleogeography and tectonics of the major paleoplates of China. Geological Society of America Special Papers, 466: 85–104. Chugaeva, M.N., 1958. Trilobity Ordovika Chu-Iliyskikh Gor. Trudy Geologicheskogo Instituta, Akademiya Nauk SSSR, 9: 5–138 (in Russian). Dalman. J.W., 1827. Om Palaeaderna eller de så kallade Trilobiterna. Kongliga Svenska Vetenskaps-Akademiens Handlingar, 1826 (2): 113–162, 226–294. Dean, W.T., 1973. Ordovician trilobites from the Keele Range, northwestern Yukon Territory. Bulletin of the Geological Survey of Canada, 223: 1–28. Ebbestad, J.O.R., 1999. Trilobites of the Tremadoc Bjørkåsholmen Formation in the Oslo Region, Norway. Fossils and Strata, 47: 1–118. Fortey, R.A., 1975. The Ordovician trilobites of Spitsbergen II. Asaphidae, Nileidae, Raphiphoridae and Telephinidae of the Valhallfonna Formation. Norsk Polarinstitutt Skrifter, 162: 1– 207. Fortey, R.A. 1986. The type species of the Ordovician trilobite Symphysurus: systematic, functional morphology and terrace ridges. Paläontologische Zeitschrift, 60: 255–275. Fortey, R.A. 1997. Late Ordovician trilobites from southern Thailand. Palaeontology, 40: 397–449. Fortey, R.A., and Chatterton, B.D.E., 1988. Classification of the trilobite suborder Asaphina. Palaeontology, 31: 165–222. Fortey, R.A., and Hughes, N.C., 1998. Brood pouches in trilobites. Journal of Paleontology, 72: 638–649. Ghobadi-Pour, M., Popov, L.E., and Vinogradova, E.V., 2009. Middle Ordovician (late Darriwilian) trilobites from the northern Betpak-Dala Desert, central Kazakhstan. Memoirs of the Association of Australasian Palaeontologists, 37: 327– 349. Goldfuss, A. 1843. Systematische Übersicht der Trilobiten und Beschrebung einiger neuer Arten derselben. Neues Jahrbuch für Mineralogie, Geognosie, Geologie und PetrefaktenKunde, 1843: 537–567. Ji, Z., 1986. Upper Ordovician (Middle Caradoc-Early Ashgill) trilobites from the Pagoda Formation in South China. Professional Papers of Stratigraphy and Palaeontology, 15: 1–39. Kielan, Z., 1959. Upper Ordovician trilobites from Poland and some related forms from Bohemia and Scandinavia. Palaeontologia Polonica, 11: 1–198. Lee, D.-C., and Choi, D.K., 1992. Reappraisal of the Middle Ordovician trilobites from the Jigunsan Formation, Korea. Journal of the Geological Society of Korea, 28: 167–183. Lee, D.-C., and Choi, D.K., 1999. Ontogenetic changes of bacculae in Korean asaphid trilobites and their taxonomic implications. Journal of Paleontology, 73: 1210–1213. Li, Y., Song, L., Zhou, Z., and Yang, J., 1975. Stratigraphical gazetteer of Lower Palaeozoic, western Dabashan. Beijing: Geological Publishing House, 372 (in Chinese). Lu, Y. 1975. Ordovician trilobite faunas of central and southwestern China. Palaeontologia Sinica, New Series B, 10: 1–484. (in Chinese) Lu, Y., Chang, W., Chu, C., Chien, Y., and Hsiang, L., 1965. Trilobites of China. Beijing: Science Press, 767 (in Chinese). Lu, Y., Zhu, Z., Qian, Y., Zhou, Z., Chen, J., Liu, G., Yu, W., http://mc.manuscriptcentral.com/ags Dec. 2016 Chen, X., and Xu, H., 1976. Ordovician biostratigraphy and palaeozoogeography of China. Memoirs of the Nanjing Institute of Geology and Palaeontology, Academia Sinica, 7: 1–83 (in Chinese). Marek, L., 1952. Contribution to the stratigraphy and fauna of the uppermost part of the Králův Dvůr Shales (Ashgillian). Sborník Ústředního Ústavu Geologického, Svazek, 19: 429– 455. Nielsen, A.T., 1995. Trilobite systematics, biostratigraphy and palaeoecology of the Lower Ordovician Komstad Limestone and Huk Formations, southern Scandinavia. Fossils and Strata, 38: 1–374. Nikolaisen, F. 1963. The Middle Ordovician of the Oslo Region, Norway, 14. The trilobite family Telephinidae. Norsk Geologisk Tidsskrift, 43: 345–399. Norford, B.S., and Ross, R.J. Jr., 1978. New species of brachiopods and trilobites from the Middle Ordovician (Whiterock) of southeastern British Columbia. Geological Survey of Canada Bulletin, 267: 1–11. Peng, S.-C, Lin, T.-R., and Li. Y., 2001. Restudy on the trilobites (agnostoids and other polymerids) from the Miaopo Formation (Upper Ordovician) in eastern Yantze Gorge Area, western Hubei. Acta Palaeontologica Sinica, 40: 1–15 (in Chinese with English abstract). Přibyl, A., and Vaněk, J., 1965. Neue trilobiten des böhmischen Ordoviziums. Věstník Ústředního ústavu geologického, 40: 277–282. Raymond, P.E., 1925. Some trilobites of the lower Middle Ordovician of eastern North America. Bulletin of the Museum of Comparative Zoology at Harvard College, 67: 1–180. Ross, R.J. Jr., 1970. Ordovician brachiopods, trilobites, and stratigraphy in eastern and central Nevada. U.S. Geological Survey Professional Paper, 639: 1–103. Schrank, E., 1972. Nileus-Arten (Trilobita) aus Geschieben des Tremadoc bis tieferen Caradoc. Berichte der Deutschen Gesellschaft für Geologische Wissenschaften A, 17: 351–375. Turvey, S.T., 2007. Asaphoid trilobites from the Arenig-Llanvrin of the South China Plate. Palaeontology, 50: 347–399. Wang, Z.-H., Bergström, S.M., Zhen, Y.Y., Chen, X, and Zhang, Y.-D., 2013. On the integration of Ordovician conodont and graptolite biostratigraphy: New examples from Gansu and Inner Mongolia in China. Alcheringa, 37: 510–528. Whittington, H.B., 1950. Sixteen Ordovician genotype trilobites. Journal of Paleontology, 24: 531–565. Whittington, H.B., 1959. Silicified Middle Ordovician trilobites: Remopleurdiae, Trinucleidae, Raphiophoridae, Encymioniidae. Bulletin of the Museum of Comparative Zoology at Harvard College, 121: 371–496. Whittington, H.B., 1965. Trilobites of the Ordovician Table Head Formation, western Newfoundland. Bulletin of the Museum of Comparative Zoology at Harvard College, 132: 275–442. Whittington, H.B., 2000. Stygina, Eobronteus (Ordovician Styginidae, Trilobita): Morphology, classification, and affinities of Illaenidae. Journal of Paleontology, 74: 879–889. Whittington, H.B., 2003. The trilobite family Nileidae: Morphology and classification. Palaeontology, 46: 635–646. Whittington, H.B., and Kelly, S.R.A., 1997. Morphological terms applied to Trilobita. In: Kaesler, R.L. (ed.), Treatise on Invertebrate Paleontology, Pt. O. Arthropoda 1. Trilobita (revised). Volume 1. Lawrence: Geological Society of Dec. 2016 ACTA GEOLOGICA SINICA (English Edition) http://www.geojournals.cn/dzxben/ch/index.aspx America, Boulder and University of Kansas, O313–O329. Yang, M., Li, L., Zhou, J., Jia, H., Sun, X., Gong, T., and Ding, C., 2015. Structural evolution and hydrocarbon potential of the Upper Paleozoic northerm Ordos Basin, North China. Acta Geologica Sinica (English Edition), 89(6): 1636–1648. Yi, Y., 1957. The Caradocian fauna from Yangtze-Gorges. Acta Palaeontologica Sinica, 5: 527–560 (in Chinese with English summary). Yin, G., and Lee, S., 1978. Trilobita. In: Atlas of Palaeontology of southwest China, Guizhou (1). Beijing: Geological Publishing House, 843: 385–595 (in Chinese). Zhang, T., 1981. Trilobita. In: Palaeontological Atlas of Northwest China: Xinjiang Volume 1. Beijing: Geological Publishing House, 134–213, 305–318 (in Chinese). Zhou, Z., Li, J., and Qu, X., 1982. Trilobites. In: Palaeontological Atlas of Northwest China: Shaanxi-GansuNingxia Volume 1: Precambrian to Early Palaeozoic. Beijing: Geological Publishing House, 215–294 (in Chinese). Zhou, Z., and Fortey, R.A., 1986. Ordovician trilobites from North and Northeast China. Palaeontographica Abteilung A, 192: 157–210. Zhou, Z., Dean, W.T., Yuan, W., and Zhou, T., 1998. Ordovician trilobites from the Dawangou Formation, Kalpin, Xinjiang, north-west China. Palaeontology, 41: 693–735. Zhou, Z., Yin, G., and Tripp, R.P., 1984. Trilobites from the http://mc.manuscriptcentral.com/ags Vol. 90 No. 6 1975 Ordovician Shihtzupu Formation, Zunyi, Guizhou Province, China. Transactions of the Royal Society of Edinburgh: Earth Sciences, 75: 13–36. Zhou, Z., and Zhen, Y., 2008. Trilobite Record of China. Science Press, Beijing, 401 p. Zhou, Z.Y., and Zhou, Z.Q., 2006. Two new Ordovician trilobite genera from western marginal areas of the North China Platform. Acta Palaeontologica Sinica, 45: 112–113. Zhou, Z.Y., Zhou, Z.Q., and Zhang, J.L., 1989. Ordovician trilobite biofacies of North China Platform and its western marginal area. Acta Palaeontologica Sinica, 28: 296–313. About the first author Seung-Bae LEE, male; born in May 1977, Seoul, Republic of Korea; graduated from Seoul National University (Ph.D) in 2008; curator in natural history division at Gwacheon National Science Museum, Korea (2010–2014); currently senior researcher in Geological Research Center of Korea Institute of Geoscience and Mineral Resources, Daejeon, Korea; interested in Early Paleozoic trilobites and echinoderm paleontology, biostratigraphy, paleogeography, and evolution; currently serving as academic secretary of the Paleontological Society of Korea and professional advisor in paleontology of the Geological Society of Korea. Email: sblee@kigam.re.kr
