late devonian - GeoScienceWorld

J. Paleont., 76(2), 2002, pp. 229–238 Copyright q 2002, The Paleontological Society 0022-3360/02/0076-229$03.00

NEW CHONOSTROPHIID BRACHIOPODS FROM THE FAMENNIAN (LATE DEVONIAN) OF THE SANTANGHU BASIN, XINJIANG, NORTHWEST CHINA ZHONG-QIANG CHEN1

AND

NEIL W. ARCHBOLD

School of Ecology and Environment, Deakin University, Rusden Campus, 662 Blackburn Road, Clayton, Vic 3168, Australia 1 Present address: Institute of Geology and Paleontology, Tohoku University, Aoba, Aramaki, Sendai 980-8578, Japan

ABSTRACT—Two new genera of the Chonostrophiidae are proposed herein to accommodate the resupinate shells from the Famennian sediments of the Late Devonian in the Santanghu Basin of the Balikun area, Xinjiang Province, northwestern China. Santanghuia santanghuensis new genus and species is distinguishable from other chonostrophiids by the possession of a pair of long dorsal anderidia and absence of a dorsal median septum. Balikunochonetes liaoi new genus and species is distinct because of the presence of a pair of anderidia with secondary anderidia, and a dorsal median septum. Santanghuia new genus is considered to be phylogenetically related to Chonostrophia of late Early to Middle Devonian age, while Balikunochonetes has possibly given rise to Chonostrophiella of Early Devonian age and is a likely ancestor of Tulcumbella of Early Carboniferous age.

INTRODUCTION

CHONOSTROPHIIDS are distinctive among the chonetid brachiopods because of their resupinate shells. When proposing the family, Muir-Wood (1962) only included Chonostrophia Hall and Clarke, 1892. Subsequently six additional genera have been assigned to the Chonostrophiidae (Campbell and Engel, 1963; Boucot and Amsden, 1964; Boucot and Harper, 1968; Boucot, 1975; Isaacson, 1977; Racheboeuf and Lesperance, 1995). Afanasjeva (1988) concluded that the Chonostrophiidae included seven genera, notably Chonostrophia Hall and Clarke, 1892; Chonostrophiella Boucot and Amsden, 1964; Tulcumbella Campbell and Engel, 1963; Notiochonetes Muir-Wood, 1962; Allanetes Boucot and Johnson, 1967; Australostrophia Caster, 1939; and Gamonetes Isaacson, 1977 (5Pleurochonetes Isaacson, 1977; see Racheboeuf, 1992, p. 44). However, more recently, Racheboeuf (1992, 1998) has reduced the number of genera to only three: Chonostrophia, Chonostrophiella, and Tulcumbella. Hence, although the relationships of these genera are not clear, the family is reduced in size. The northwestern Chinese specimens described herein also have resupinate shells and share many external and internal features with Chonostrophiella and Chonostrophia, and hence belong to the Chonostrophiidae. Our new material is distinguishable from previously proposed genera, and is described as Santanghuia n. gen. and Balikunochonetes n. gen. The addition of two new genera to the Chonostrophiidae adds to the knowledge of the phylogeny of the family. Only seven species of five genera of the Chonetidina have been reported from the Famennian deposits of the Upper Devonian (Afanasjeva, 1988; Racheboeuf, 1995a, 1995b, 1998). The genera are Longispina Cooper, 1942, of the Devonochonetinae; Retichonetes Muir-Wood, 1962, of the Retichonetinae: Cedulia Racheboeuf, 1979, of the Tornquistiinae; Herrerella Racheboeuf, 1995b, of the Anopliidae Muir-Wood, 1962; and Plicochonetes Paeckelmann, 1930, of the Rugosochonetinae. In the summer of 1995, one of the authors (Z. Q. C.) investigated the Late Paleozoic rocks of the Santanghu Basin (China) with a research team of Nanjing Institute of Palaeontology and Geology, Chinese Academy of Sciences, for the purposes of petroleum exploration. The new material was collected from the Santanghu village section, central Santanghu Basin, Balikun County, Xinjiang Province, northwestern China (Fig. 1). The figured specimens are housed in the Museum of Victoria, Melbourne (NMV), Australia.

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STRATIGRAPHY AND AGE

The Famennian rocks exposed at the Santanghu section consist of yellow calcareous sandstones interbedded with argillaceous and

tuffaceous limestones in the lower part of the section, and black shales in the upper part of the section. These sediments were previously referred to as the Lower Carboniferous ‘‘Hebukehe Formation’’ (Wu, 1991, p. 170). However, based on restudying the lithology and biostratigraphy of the Hebukehe river section, Hoboksar Mongolian Autonomous County, northern Xinjiang, type section of the Hebukehe Formation, Xu et al. (1990) considered that the ‘‘Hebukehe Formation’’ (Zhao, 1986) is lithologically and biostratigraphically same to the earlier established Hongguleleng Formation (Hou et al., 1979) of the same area. As a result, the ‘‘Hebukehe Formation’’ has been treated as a junior synonym of the Hongguleleng Formation and abandoned by Xu et al. (1990). Recently, Liu et al. (1997) and Liao et al. (1998) assigned the marine and terrestrial sediments of the Santanghu Basin to the Hongguleleng Formation and Laoyemiao Formation (Compiling Group of Regional Stratigraphic Chart of Xinjiang Uygur Autonomous Region, 1981), respectively. These two formations are heteropic because of the common appearance of the same microfloral assemblage (see below). Accordingly, the marine succession of the Santanghu section yielding the specimens described herein belongs to the Hongguleleng Formation (Liao et al., 1998). The new material was found in calcareous sandstones (bed 3, in Fig. 2) in association with bivalve and miospore fossils. The overlying and underlying beds yield abundant brachiopods, marked by the occurrence of species identified by the senior author as Pripyatispirifer sulcifer (Hall and Clarke), Cyrtospirifer

FIGURE 1—Map showing the fossil locality. 1, Road; 2, highway; 3, freeway; 4, boundary of country; 5, city; 6, county or town; 7, outcrop section; 8, desert.

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FIGURE 2—Columnar section showing the fossil horizon. Numbers 2–6 of the left side of the lithologic column represent beds. Stratigraphic subdivision follows Liao et al. (1998). 1, argillaceous and tuffaceous limestone; 2, calcareous sandstone; 3, shale; 4, andesite.

FIGURE 3—The ventral and dorsal interiors of Santanghuia santanghuensis n. gen. and sp. 1, Ventral interior (based on specimens NMV P149189, NMV P149204); sp: spine; t: tooth; dp: denticular plate; mym: myophragm, 35; 2, dorsal interior (based on specimens NMV P149164, NMV P149168, NMV P149183); cp: cardinal process; my: myophore; a: anderidium, 35.

junggarensis Zhang, Cyrtospirifer zadonicus Lyashenko, Hunanospirifer cf. wangi Tien, ‘‘Tenticospirifer’’ taerbahataiensis Zhang, ‘‘Uchtospirifer’’ sp., Schuchertella sp. and Mesoplica sp. (Fig. 2). All these forms can be found in the brachiopod fauna of the Hongguleleng Formation in the adjacent Junggar Basin (Zhang et al., 1983; Xu et al., 1990). In particular, two endemic species ‘‘Tenticospirifer’’ taerbahataiensis Zhang [it could not belong to the true Tenticspirifer Tien, 1938 on the basis of Ma and

Day’s (2000) revision of the genus] and Cyrtospirifer junggarensis Zhang of the Hongguleleng Formation in its type locality (Zhang et al., 1983; Xu et al., 1990) are also present in the Santanghu collections, indicating both faunas are coeval. Furthermore, Pripyatispirifer sulcifer has also been reported from the Famennian of South China (Liu et al., 1982). Cyrtospirifer zadonicus was described by Lyashenko (1959) from the Famennian →

FIGURE 4—Santanghuia santanghuensis n. gen. and sp. 1, Ventral valve (NMV 149205), showing the strong impressions of a pair of divergent denticular plates, forming an angle of about 30 degrees to the hinge margin, 34; 2, ventral valve (NMV P149204), paratype, illustrating hinge spines projecting posterolaterally in a low angle to hinge margin, impressions of a ventral myophragm and a pair of denticular plates, 34; 3, dorsal valve (NMV P149190) in interior view, showing a pair of prominent anderidia, 34; 4–5, specimen (NMV P149185) with two valves conjoined in dorsal and ventral views, holotype, 34; 6, ventral valve (NMV P149197), 32.5; 7, dorsal internal mold (NMV P149193), showing a pair of anderidia extending anteriorly to the anterior margin, 34; 8, dorsal valve (NMV P149164) in interior view, paratype, illustrating a pair of conspicuous anderidia, but without dorsal median septum, 34; 9, ventral valve (NMV P149189), 34; 10–11, two dorsal internal molds (NMV P149158, 149157), illustrating long anderidia, both 34; 12, incomplete dorsal valve (NMV P149192) in interior view, 33; 13, incomplete dorsal internal mold (NMV P149188), illustrating a short cardinal process, 34.5; 14, dorsal valve (NMV P149168) showing a pair of high anderidia and radial pustulae, 33.5; 15, incomplete dorsal internal mold (NMV P149178), illustrating a short cardinal process, impressions of socket ridges and long anderidia, 33.5; 16, dorsal internal mold (NMV P149183), paratype, showing impressions of socket ridges and long anderidia, 34.5.

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JOURNAL OF PALEONTOLOGY, V. 76, NO. 2, 2002 (Nalivkin, 1937), southern Mongolia (Durante et al., 1996), the Junggar Basin (Zhang et al., 1983); and South China (Tan, 1987). In addition, abundant miospores are also associated with the above brachiopods in the Santanghu section (Liu et al., 1997), and were referred to the Retusotriletes simplex-Apiculiretusispora hunanensis Assemblage, which is characteristic of the Famennian Laoyemiao Formation of the same basin (Liu et al., 1997; Liao et al., 1998). Moreover, the Hongguleleng Formation at its type locality has been well constrained as Famennian by studies on plants (Cai, 1986), corals (Liao and Cai, 1987; Xu et al., 1990), conodonts (Zhao and Wang, 1990; Xu et al., 1990; Xiao, 1997), brachiopods (Zhang et al., 1983; Xu et al., 1990), bryozoans (Xiao, 1997), echinoderms (Lane et al., 1997), and miospores (Xu et al., 1990). As a result of these correlations, the fauna of the Hongguleleng Formation in the Santanghu Basin is also referred to the Famennian. MEMBERS OF THE CHONOSTROPHIIDAE

FIGURE 5—The measurements of the valve length and width of Santanghuia santanghuensis n. gen. and sp. 1, L/W and T/W of 28 dorsal valves, L/W: ratio of valve width and valve length; T/W: ratio of valve width and thickness; 2, frequency distribution of valve length of 28 dorsal valves. The horizontal axis represents valve width (in mm), the vertical axis represents the specimen number; 3, L/W and T/W of 18 ventral valves, (L/W and T/W are used in Fig. 5.1); 4, frequency distribution of valve length of 18 ventral valves.

of the Russian Platform. Hunanospirifer cf. wangi Tien [previously named Tenticospirifer tenticulum (Verneuil) by Tien (1938), Zhang et al. (1983), Xu et al. (1990) and Chen (1995)] was found in association with the Yunnanella fauna in the Famennian of the Xikuangshan area, central Hunan, South China (Hou et al., 1996, p. 161). Comparable material of the species was also reported from the Famennian of the Tarim Basin, southern Xinjiang (Chen, 1995). Mesoplica has a stratigraphic range from the Late Devonian to earliest Carboniferous (Muir-Wood and Cooper, 1960), but is frequently present in the Famennian in northeastern Kazakstan

Possessing reversed convexity of valves, Chonostrophia, Chonostrophiella, and Tulcumbella are the typical representatives of the Chonostrophiidae (Afanasjeva, 1988; Racheboeuf, 1992, 1998; Racheboeuf and Herrera, 1994). Of the other genera which Afanasjeva (1988) included in the Chonostrophiidae, Isaacson (1977, p. 165) considered that Allanetes, Notiochonetes, and Pleurochonetes were derived from one stock, while Australostrophia, Chonostrophia, and Chonostrophiella were derived from another stock. Racheboeuf (1992, p. 42) proposed the subfamily Notiochonetinae to include Allanetes, Notiochonetes, and Pleurochonetes. The familial assignment of Australostrophia is debated. Boucot (1975, p. 634) considered Australostrophia to be a chonostrophid shell, with morphological features very close to those of both Chonostrophia and Chonostrophiella of the Appohimchi Realm rather than to Notiochonetes of the Malvinokaffric Realm. Isaacson (1977, p. 167) stated that the close similarity of Australostrophia to Chonostrophiella, (as illustrated by Boucot, 1973, pl. 11, figs. 17–25), allows for the former’s inclusion into the Family Chonostrophiidae, although generic distinct between the two is subtle. In comparison, Racheboeuf (1992) considered that Australostrophia is not a chonostrophiid, but more probably allied to the strophochonetids, and provisionally placed it in ‘‘incerta familia’’. Later, Racheboeuf and Herrera (1994, p. 555) regarded Australostrophia as a resupinate strophochonetid, and assigned it to the Strophochonetidae. However, the ventral valve of Australostrophia mesembria (Clarke, 1913), type species of the genus, is weakly convex, while the dorsal is very gently concave (Boucot, 1975, p. 635). Hence, the valves of Australostrophia are not really resupinate. Following Racheboeuf (1992, 1998), we therefore herein tentatively exclude Australostrophia from the Chonostrophiidae. As a result, in considering these two new genera described herein, the Chonostrophiidae includes Chonostrophia, Chonostrophiella, Tulcumbella, Santanghuia, and Balikunochonetes. PHYLOGENY OF THE NEW GENERA

The occurrence of chonostrophiid shells in the Famennian is a significant feature for the phyletic trends of the Chonostrophiidae. Chonostrophia and Chonostrophiella were extinct before the Givetian (Boucot and Harper, 1968; Boucot, 1975), while Tulcumbella abruptly occurs in the Tournaisian of the Early Carboniferous. The presence of Santanghuia and Balikunochonetes in the Famennian probably fills the missing gap in the evolution of the family. The development of the dorsal median septum is as criterion to distinguish the evolutionary trends of the Chonostrophiidae. Through the loss of a dorsal median septum and by extending and strengthening the dorsal anderidia, we can infer that Santanghuia is phylogenetically related to Chonostrophia of late Early to Middle Devonian age, even if it did not give rise to the latter

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genus. Balikunochonetes could be derived from Chonostrophiella or Australostrophia (both Early Devonian) and is possibly the ancestor of Tulcumbella (Early Carboniferous). The evolutionary sequence is that median septum is always present in the dorsal valve, but the dorsal anderidia varied from short and simple to long, complex, and absent. SYSTEMATIC PALEONTOLOGY

Terminology is that of Williams and Brunton (1997) and Racheboeuf (1998). Supra-ordinal classification follows Williams et al. (1996); the classification of the Chonetidina follows Racheboeuf (1998). Phylum BRACHIOPODA Dumeril, 1806 Subphylum RHYNCHONELLIFORMEA Williams, Carlson, Brunton, Holmer, and Popov, 1996 Class STROPHOMENATA Williams, Carlson, Brunton, Holmer, and Popov, 1996 Order PRODUCTIDA Sarycheva and Sokolskaya, 1959 Suborder CHONETIDINA Muir-Wood, 1955 Superfamily CHONETOIDEA Bronn, 1862 Family CHONOSTROPHIIDAE Muir-Wood, 1962 Genus SANTANGHUIA new genus Type species.Santanghuia santanghuensis new genus and species. Diagnosis.Medium-sized chonostrophiids with semicircular outline; interarea catacline; pseudodeltidium short, arched; shell exteriors finely costellate; row of hollow spines along hinge margin, projecting posterolaterally in less than 45 degrees. Ventral interior teeth stout, supported by laterally extending denticular plates; myophragm thick, high, long, extending anteriorly to midlength of shell (Fig. 3.1). Cardinal process strong, short, pentalobed, myophore consisting of a broad median lobe and two narrow lateral lobes at each side; dorsal median septum absent; socket ridges indistinct; anderidia thick, broad, long, extending anteriorly up to anterior margin with angles varying from 10 degrees up to 20 degrees (Fig. 3.2). Etymology.From the Santanghu village, the only village in the Santanghu Basin of northeastern Xinjiang Province, northwestern China and southwestern Mongolia. Discussion.Santanghuia has resupinate shells, a semicircular outline, a catacline ventral interarea and the delicate ornament of Chonostrophiella, however, the internal dorsal anderidium arrangement of Santanghuia is highly distinctive. The absence of a dorsal median septum also differentiates Santanghuia from Chonostrophiella, the latter having a low median septum which always extends anterior to the muscle fields. The development of alternating parvicostellate ornamentation of Chonostrophia is significantly different from the fine costellae of Santanghuia. The pair of short dorsal anderidia of Chonostrophia is distinctive from the longer ones in the dorsal valve of Santanghuia which almost extend to the anterior margin. Tulcumbella Campbell and Engel, 1963 (also see McKellar, 1969, p. 16–17, pl. 3, figs. 20–37) is distinct from Santanghuia in having a much shorter ventral myophragm and a rounded, long dorsal median septum, and lacking long dorsal anderidia. Sometimes the coarse radial costae are also in relief on the dorsal internal mold of Dawsonelloides Boucot and Harper, 1968; these radial ornaments however clearly differ from the dorsal anderidia of Santanghuia. SANTANGHUIA

new species Figures 3, 4, 5 Diagnosis.Small to medium in size; hingeline straight, slightly narrower than maximum width at midvalve; cardinal extremities slightly obtuse; costellae fine, dense, low, rounded, frequently SANTANGHUENSIS

FIGURE 6—The interiors of Balikunochonetes liaoi n. gen. and sp. 1, Ventral valve (based on specimen NMV P149173, 149210, 149215); sp: spine; t: tooth; dp: denticular plate; mym: myophragm, 35. 2, dorsal interior (based on specimens NMV P149187, 149213, 149214); cp: cardinal process; my: myophore; sr: socket ridge; ms: median septum; aa: adventitious anderidium; a: anderidium, 35.5.

bifurcate, concentric rugae absent; approximately six hollow spines symmetrically arranged along hinge margin on each side of ventral umbo. Shell inner surfaces strongly pustulose. Description.Ventral valve concave, occasionally almost flat; umbo slightly flattened posteriorly, concave anteriorly; anterior and lateral margins usually abruptly bent ventrally, forming a shallow but distinctive concentric concave separating margins from flanks and umbonal region; interarea flat, about one millimeter high but long; delthyrial angle varying from 90 to 100

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CHEN AND ARCHBOLD—DEVONIAN BRACHIOPODS FROM CHINA TABLE 1—Measurements of all studied specimens of Balikunochonetes liaoi n. gen. and sp. (in millimeters). Specimen number

Shell length

Ventral width

149186 149187 149189 149195 149197 149200 149202 149280 149209 149210 149211 149212 149213 149214 149215

10.15 9.10 9.50 10.00* 8.05 7.85 5.07 6.52 8.01 7.05 11.78 9.56 8.05 7.85 7.85

8.00

Dorsal width

14.00 15.50 18.05 11.80 12.40 8.00 11.06 12.08 11.50 19.50 13.90 11.57 11.02 11.98

Thickness 0.50* 3.50* 1.00* 2.00* 0.50* 0.50* 0.50* 1.50* 1.50* 1.00* 3.51 1.50* 2.50 2.50* ?

The * value is estimated.

degrees; pseudodeltidium very short and gently arched. Dorsal valve slightly moderately convex, most convex at umbonal region; ears small, flattened; interarea very low and anacline; umbo evenly convex, moderately sloping, gradual to lateral and anterior margins. Fine costellae with rather narrower interspaces, bifurcate up to four times, originating at beak, about eight costellae per 5 mm at anterior margin; cardinal spines hollow, coarse, about 1 mm in diameter, projecting posterolaterally in an angle varying from 20 degrees to 45 degrees; concentric growth lines fine, dense, becoming more pronounced anteriorly. Teeth stout, oblique, divergent, supported by strong denticular plates, about 2 to 4 mm long, extending laterally in an angle of approximately 30 degrees with hingeline; myophragm originating anterior to pseudodeltidium. Cardinal process short, myophore deeply grooved, forming five lobes directed posteriorly; sockets deep, board, and triangleshaped, with pronounced socket ridges, subparallel to hinge in juveniles, and divergent in maturity by an angle varying between 10 and 20 degrees; median septum absent; anderidia straight, broad, thick, high, originating anterior to chilidium, extending anteriorly almost to anterior margin; adductor scars dendritic. Inner surface ornamented by rows of radial papillae. Etymology.Named for the Santanghu village. Types.Holotype, a complete specimen (NMV P149185) with conjoined but opened valves. Paratypes, a ventral valve (NMV P149204), a dorsal internal mold (NMV P149183) and a dorsal interior (NMV P149164). Other material examined.One complete conjoined shell, 24 isolated dorsal valves (or internal molds), and 15 isolated ventral valves (Appendix 1). Figured material, NMV P149157–NMV

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P149158, NMV P149164, NMV P149168, NMV P149178, NMV P149183, NMV P149185, NMV P149188, NMV P149189, NMV P149190, NMV P149192, NMV P149193, NMV P149197, NMV P149204–NMV P149205. Measurements.Twenty-eight dorsal valves range in width from 6 to 19 mm, length from 3 to 13 mm and thickness from 1 to 4 mm in thickness (Fig. 5.1). Eighteen dorsal valves have a width varying between 8 and 16 mm, a length from 5 to 11 mm and a thickness ranges from 0.5 to 1 mm (Fig. 5.3). The detailed measurements of each studied specimen are given in Appendix 1. The majority of dorsal valves range in width from 12 to 13 mm (approximately 28.57 percent, see Fig. 5.2). The majority of ventral valves are those (about 27.78 percent) having valve width of 10 to 11 mm (Fig. 5.4). The holotype (NMV P149185) is 7.75 mm long, 12.40 mm wide and about 4.20 mm thick. Occurrence.Famennian; Santanghu Formation, the Santanghu Basin, Balikun County, Xinjiang Province, northwestern China. Discussion.The long dorsal anderidial arrangement is not known for any other chonostrophiid. Like the new species, some specimens of Sanjuanetes chaparensis (Suarez in Brockmann et al., 1972) figured by Racheboeuf and Herrera (1994, fig. 3a, 3c, 3d) also possess a flat ventral valve, very fine costellae, a strong ventral myophragm, and lacks a dorsal median septum, but they have a flat dorsal valve and much shorter dorsal anderidia. Genus BALIKUNOCHONETES new genus Type species.Balikunochonetes liaoi new genus and species. Diagnosis.Medium-sized chonostrophiid, semicircular outline; anterior region of ventral valve rugose; row of spines along hinge margin, projecting posterolaterally in angles varying between 75 to 90 degrees with hinge margin. Ventral myophragm broad, high, long, extending anteriorly over half shell length of shell (Fig. 6.1); dorsal interior median septum thin, extending anteriorly up to midvalve; anderidia broad, thick, extending anteriorly almost to anterior margin with angles varying from 15 degrees up to 35 degrees, a pair of posteriorly extending, subparallel, weakly developed adventitious anderidia present adjacent to each anderidium (Fig. 6.2). Other features similar to Santanghuia n. gen. Etymology.Named for the Balikun County, Xinjiang Province, northwestern China, which is the fossil locality. Discussion.Balikunochonetes n. gen. is comparable with Santanghuia in the fine costellae, resupinate shells, distinct pentalobed cardinal process and dorsal anderidia, and ventral internal structures, but clearly differs from Santanghuia in possessing distinctive rugae on the ventral valve, a conspicuous dorsal median septum, and two pairs of short adventitious anderidia in the dorsal interior. Apart from a chonostrophiid profile, the new genus is also comparable with Chonostrophiella in its fine costellae, the cardinal

← FIGURE 7—Balikunochonetes liaoi n. gen. and sp. 1, Dorsal internal mold (NMV P149211), showing impressions of a broad median septum and a pair of anderidia, 34; 2, dorsal valve (NMV P149214) in interior view, illustrating impression of a short cardinal process, a pair of socket plates, a broad and thick median septum, a pair of long anderidia and two secondary adventitious anderidia originating at each anderidium, 34; 3, ventral internal mold (NMV P149215), showing a strong myophragm, a pair of divergent denticular plates and hinge spines projecting posterolaterally in a high angle, 34; 4–6, three ventral valves (NMV P149210, 149209, 149212), illustrating coarse hinge spines projecting posterolaterally in a high angle to hinge margin, concentric rugae becoming more pronounced anteriorly, and impression of a ventral myophragm, all 34; 7, incomplete dorsal internal mold (NMV P149187), showing the impressions of a short, strong cardinal process, a pair of thick socket ridges, a broad, high median septum and posterior parts of anderidia, 34.5; 8, incomplete ventral valve (NMV P149173) in interior view, illustrating the arched pseudodeltidium, traces of denticular plates and a thick, high ventral median septum, 34; 9, dorsal valve (NMV P149213) in interior view, showing a long, thick, high median septum, a pair of short socket plates, a pair of long, high anderidia and two broad, short secondary adventitious anderidia originating at each anderidium, 34; 10, dorsal external mold (NMV P149195), illustrating the impressions of a short, strong cardinal process and myophore consisting of five deeply grooved, posteriorly directed lobes, 35.

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spines extending posterolaterally in a high angle to the hinge margin, the presence of a dorsal median septum, and a long ventral myophragm. Balikunochonetes is distinct from Chonostrophiella in possessing a pair of much longer anderidia and two pairs of short adventitious anderidia in the dorsal interior, whereas a pair of rather short anderidia is visible in Chonostrophiella. Although Tulcumbella also has a dorsal median septum, like Balikunochonetes, the presence of a rather short ventral myophragm and absence of dorsal anderidia differentiate Tulcumbella from the new genus. Australostrophia Caster, 1939 (also see Racheboeuf and Herrera, 1994, fig. 5a–f) can be differentiated from the present new genus by its flatter dorsal valve, broader socket ridges, a thicker, broader but shorter dorsal median septum, and much shorter dorsal anderidia. The presence of parvicostellae and pair of much shorter dorsal anderidia and absence of a dorsal median septum clearly differentiate Chonostrophia from the new genus. BALIKUNOCHONETES LIAOI new species Figures 6, 7 Diagnosis.Hingeline straight, narrower than greatest width at midvalve; cardinal extremities obtuse; costellae fine, low, rounded; about four concentric rugae present anterior to midlength of ventral valve; six spines symmetrically arranged along hinge margin on each side of umbo, extending posterolaterally in angles varying from 75 degrees to 90 degrees; ventral interior myophragm broad, thick, high, originating anterior to pseudodeltidium. Description.Ventral valve gently concave; interarea flat, up to one millimeter high and about 10 to 15 mm long; delthyrial angle less than 90 degrees; pseudodeltidium short, arched; anterior and lateral margins slightly bent ventrally. Dorsal umbo convex, with moderately steep slopes to lateral margins; dorsal interarea very low and anacline; chilidium convex. Fine costellae frequently bifurcate, originating at beak, about nine per 5 mm near anterior margin; spines hollow, coarse, about 1.0 to 1.5 mm in diameter, four spines close to umbo on each side projecting posterolaterally in angles varying 75 degrees to 85 degrees; two spines distal to umbo on each side almost perpendicular to hinge margin; ventral valve rugose anterior to midlength of shell; concentric growth lines fine, dense, about twenty five to thirty in 10 mm near anterior margin. Teeth stout, divergent, forming approximately 35 degrees to the hingeline. Cardinal process short, pentalobed, myophore consisting of a stronger median lobe and two thinner lobes at each side; sockets deep and board, bounded by high, thick socket ridges divergent, forming an angle varying between 10 and 20 degrees with hingeline; dorsal median septum thick, high; anderidia originating anterior to chilidium; pair of adventitious anderidia about 10 mm long, originating at about three-fifths of length of each anderidium to cardinal process, extending posterolaterally, forming angles between 60 degrees and 70 degrees with anderidia, probably served, coupling with anderidia, as seat of attachment of adductor muscles; adductor scars elongate, ridge-shaped. Inner surface ornamented by rows of radial papillae. Etymology.Named for Professor Liao Zhuoting of the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, who organized the exploration of the Santanghu Basin. Types.Holotype, a dorsal valve (NMV P149213) with the internal structures. Paratypes, a ventral valve (NMV P149173) and a ventral internal mold (NMV P149215). Other material examined.Four isolated dorsal valves (or internal molds), and eight isolated ventral valves (or internal

molds). Figured material, NMV P149173, NMV P149187, NMV P149195, NMV P149209–NMV P149215. Measurements (in mm).See Table 1. Occurrence.Famennian; Santanghu Formation, the Santanghu Basin, Balikun County, Xinjiang Province, northwestern China. Discussion.Apart from the generic differences, the new species differs from Santanghuia santanghuensis n. gen. and sp. in having a relatively longer, thicker and broader ventral myophragm and a pair of relatively broader and thicker dorsal anderidia. ACKNOWLEDGMENTS

We thank Liao Zhuoting, Yao Zhaoqi, Shen Yanbin, Liu Lujun, and Shen Jianwei of Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, for their kind help of collecting specimens during field investigations in Santanghu Basin. This exploration was funded under the project of Professor Liao: ‘‘Fossil assemblage sequences and Palaeoecology of Carboniferous to Jurassic of the Santanghu Basin, northeastern Xinjiang, northwestern China.’’ Our thanks are also rendered to P. R. Racheboeuf of Universite´ Claude Bernard—Lyon and D. Brice of Laboratoire de Geologie, Lille Cedex, France for their critical reviews and advice. Technical editor J. Day of Illinois State University is also greatly acknowledged for his technical advice and providing the information of the latest revisions of two spiriferid species ‘‘Cyrtospirifer’’ sulcifer (Hall and Clarke) and ‘‘Tenticospirifer tenticulum (de Verneuil).’’ This research was carried out whilst the senior author was a recipient of both an Overseas Postgraduate Research Award tenurable at Deakin University and a Deakin University Postgraduate Research Award. REFERENCES

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APPENDIX 1—Measurements of all studied specimens of Santanghuia santanghuensis n. gen. and sp. (in millimeters). Specimen number

Shell length

149157 149158 149159 149160 149161 149162 149163 149164 149165 149166 149167 149168 149169 149170 149171 149172 149173 149174 149175 149176 149177 149178 149179 149180 149181 149182 149183 149184 149185 149188 149190 149191 149192 149193 149194 149196 149198 149199 149201 149203 149204 149205 149206 149281

8.00 8.75 7.60 7.75 7.00 6.75 7.25 5.05 7.03 11.02 9.05 5.70 10.05 8.03 6.03 8.03 7.30 6.67 7.75 4.50 6.85 3.50* 4.75 7.70 9.01 8.00* 7.25 5.50 7.75 9.80 8.50 8.25 11.50 13.00 7.25 6.75 7.25 7.90 5.03 7.85 8.50 9.00 6.50 7.50

The * value is estimated.

Ventral width

Dorsal width 13.40 14.50 12.05 12.25 12.50 11.00* 10.50 8.90

10.75 15.05 15.50 7.40 17.50 12.05 9.90 13.30 10.00* 12.67

10.05* 12.40

14.25 10.75 12.50 14.50 8.03 10.05 14.00 14.20 12.00 12.50

12.50 7.00 10.06 6.20 8.00 10.05 15.56 13.00 12.50 10.00* 12.40 16.80* 11.50 12.50 17.50* 19.00

Thickness 3.00* 2.60* 2.00* 2.50* 2.00* 2.50* 2.50* 2.00* 1.00* 1.00* 1.00* 1.50* 3.80* 3.00* 0.50* 2.00* 0.50* 0.50* 2.50* 2.00* 2.00* 1.00* 2.50* 2.00* 2.60* 2.00* 2.50* 4.20 3.80 3.90* 2.00* 2.50* 3.00* 4.00* 1.00* 0.50* 0.50* 0.50* 1.00* 1.00* 0.50* 0.50* 0.50* 0.50*