- Email: [email protected]
Brachiopods from the Permian–Triassic boundary beds at the Selong Xishan section, Xizang (Tibet), China
Journal of Asian Earth Sciences 17 (1999) 547±559
Brachiopods from the Permian±Triassic boundary beds at the Selong Xishan section, Xizang (Tibet), China Shuzhong Shen a,*, Jin Yugan b a
School of Ecology and Environment, Deakin University, Rusden Campus, 662 Blackburn Road, Clayton, Victoria, 3168, Australia b Nanjing Institute of Geology and Palaeontology, Academia Sinica, Nanjing, Jiangsu, 210008, People's Republic of China Accepted 22 January 1999
Abstract The brachiopods from the Waagenites Bed and the upper part of the Coral Bed above and below the Permian±Triassic sequence boundary at the Selong Xishan section of southern Xizang suggest a rich brachiopod fauna existing in Selong, and a rapid invasion of Tethyan brachiopods into the Himalayas at the very end of the Permian. A transgression beginning from the Waagenites Bed and a rapid ¯ooding at the beginning of the Triassic is re¯ected by changes in composition of the Permian brachiopod assemblages in Selong. However, the dominant forms in the Permian±Triassic sequence boundary beds, including Krotovia, Spiriferella and Neospirifer, extend from the underlying beds of the Selong Group without signi®cant evolutionary change. A brief discussion of each taxon and descriptions of two new species, Stenoscisma selongensis and Martinia attenuatelloides, are presented. # 1999 Elsevier Science Ltd. All rights reserved.
1. Introduction The Selong Xishan section is one of a number of candidates for the global boundary stratotype for the Permian±Triassic boundary. This boundary sequence is entirely composed of carbonates. The biostratigraphical boundary level is indicated by the ®rst appearance of both Otoceras and Hindeodus parvus which have been respectively proposed as the key indicators (Wang et al., 1989; Xia and Zhang, 1992; Wang et al., 1993; Orchard et al., 1994; Jin et al., 1996). Increasing data from systematic studies on the section also made it valuable in understanding better the end-Permian mass extinction in the eastern Himalayas. This section is situated near the second highest peak in the world, the Xixiabangma Mount (8012 m above sea level) in Nyalam County of southern Xizang, and lies on the western side of the main road from Lhasa, the * Corresponding author. Tel.: +61-3-9244-7428; fax: +61-3-92447480. E-mail address: [email protected] (S. Shen)
provincial capital of Xizang, to Kathmandu in Nepal (Fig. 1). 2. Stratigraphic succession Permian carbonate-dominated beds at the Selong Xishan section reach a thickness of 9 m. These beds were commonly assigned to the upper part of the Selong Group (Jin et al., 1996) or an independent lithostratigraphic unit, the Baka Formation (Rao and Zhang, 1985). The carbonates are characterized by a dominance of poorly sorted, angular biogenic debris. The topmost 1.08 m of the Selong Group is named the Coral Bed because it is distinguished by the occurrence of abundant tabulate and solitary rugose corals along with some bryozoans. It was assigned to Unit 3 of ``the Prechanghsingian Bed'' by Wang et al. (1989). This bed is composed of medium bedded grainstone and seams mainly formed in a high-energy shoal environment. The contact between the Selong Group and the overlying Kangshare Formation is marked by the Caliche Bed, a thin layer of pedogenic calcrete which
1367-9120/99/$ - see front matter # 1999 Elsevier Science Ltd. All rights reserved. PII: S 1 3 6 7 - 9 1 2 0 ( 9 9 ) 0 0 0 0 4 - 8
548
S. Shen, J. Yugan / Journal of Asian Earth Sciences 17 (1999) 547±559
Fig. 1. Map showing the location of the Selong Xishan Section and the brachiopod horizons for this study (data and locality map after Jin et al., 1996).
varies laterally in thickness (Fig. 2). A rapid negative excursion of d13C value in this bed and signi®cant lowering d13C value in the basal levels of the Kangshare Formation has been detected (Wang et al., 1997). This
unusual negative excursion of d13C value indicates that the Caliche Bed is coincident with the Permian± Triassic sequence boundary. The Kangshare Formation is 7.0 m thick and is
S. Shen, J. Yugan / Journal of Asian Earth Sciences 17 (1999) 547±559
549
Fig. 2. A, Permian±Triassic strata at the Selong Xishan section; B, C, close-up views of the Permian±Triassic boundary beds with laterally-varietied Caliche Bed. 1, the Coral Bed; 2, the Caliche Bed. 3; the Waagenites Bed; 4, the Otoceras Bed.
divided into three beds (Jin et al., 1996). The Waagenites Bed at the base contains coarse bioclastics, which are strikingly similar in composition to those of the Coral Bed of the Selong Group. The Waagenites Bed, however, contains greater amounts of ostracod and gastropod shells within the bioclastics in additional more micritic lime in the matrix. This bed represents lag carbonate deposits formed in shallow, medium-energy shoal and in inter-shoal depressions. The Otoceras Bed consists of stylo-compacted corroded packstone. The boundary between this bed and the Waagenites Bed is indistinct on a polished surface as well as in thin sections. Instead, there is a thin tran-
sitional bed with mixed dolomitized bioclastic wackstone, packstone and lime mudstone. No apparent depositional gap can be documented based on petrographic evidence. The Ophiceras Bed is separated from the underlying Otoceras Bed by a distinct erosional surface. This bed consists of shell debris packstone, of which most shell fragments are of ammonoids, bivalves and gastropod coquina. Crinoid debris is sparse. This bed represents a sequence ranging from proximal to distal tempestite formed above wave base. These upward-®ning cycles are likely formed in the response to a gradual reduction in the impact of seaward currents.
550
S. Shen, J. Yugan / Journal of Asian Earth Sciences 17 (1999) 547±559
In summary, the Permian±Triassic deposits at the Selong Xishan section represent a rapid transgression at the very end of the Permian. This Permian transgression probably started from the Waagenites Bed. The latest Permian transgression rapidly ¯ooded in the Triassic Otoceras Zone and reached a maximum in the Ophiceras Zone. There is no traceable depositional gap between the Waagenites Bed and the Otoceras Bed. 3. Brachiopod composition, preservation and age problems Brachiopod faunas of this region have been frequently reported [Ting (Ding in present spelling), 1962; Chang and Ching (Zhang and Jin in present spelling), 1976; Jin, 1985; Wang et al., 1989]. Chang and Ching (1976) grouped the brachiopods from the Selong Group into three assemblages, namely the Taeniothaerus, the Callimarginatia and the Chonetella nasuta Assemblage in ascending order. Among them, the Taeniothaerus and the Chonetella nasuta Assemblages were found in Selong. Recently, Shi and Shen (1997) recognized an assemblage which is similar to those of the Lamnimargus himalayensis Zone in the Himalayan region from the middle part of the Selong Group. Estimated ages for the Chonetella nasuta Assemblage range from Guadalupian to Wuchiapingian (Jin, 1985) or from late Guadalupian (Midian) to Wuchiapingian (Shi and Shen, 1997). It seems hardly possible to narrow down the age estimation because most of the stratigraphic ranges of brachiopod taxa are fairly long. Wang et al. (1989) and Wang et al. (1993) divided the topmost part of the Selong Group into two parts, ``the Prechanghsingian Bed'' and ``the Changhsingian Bed'' or Unit 4 (6±17 cm in thickness). Brachiopods such as Waagenites cf. barusiensis (Davidson), Paracrurithyris pigmaea (Liao), Phricodothyris sp., Martinia sp. and Araxathyris sp. from ``the Changhsingian Bed'' were reported and were named as the Waagenites barusiensis±Paracrurithyris pigmaea Assemblage. Among them, Paracrurithyris pigmaea is a guide to the brachiopod faunas usually occurring in the topmost part of the Changhsingian beds in South China (Liao, 1980). However, it has long been debated whether the brachiopod shells from the Waagenites Bed of the Permian±Triassic boundary beds in Selong are reworked or simply agitated by contemporaneous wave action (Zhang, 1974, p. 77; Yin and Guo, 1979, p. 41; Wang et al., 1989, p. 221, etc.). Evidently, Permian brachiopods from Selong pose two long-standing major problems as do those from other areas of the Himalayas: (1) How to identify the diagnostic features of the Lopingian fauna? (2) Are the brachiopods from the Waagenites Bed reworked?
Table 1 Brachiopods recorded from the upper part of the Coral Bed and the Waagenites Bed of the Selong Xishan section Species Waagenites sp. Krotovia arcuata Waterhouse Stenoscisma timorense Hayasaka and Gan Stenoscisma selongensis n. sp. Martinia attenuatelloides n. sp. Martinia spp. Bullarina cf. rostrata Jin and Sun Cleiothyridina deroyssii (L'Eveille) Spiriferella rajah (Salter) S. nepalensis Legrand-Blain Neospirifer sp. Spiriferellina sp. Girtyella? sp.
Coral Bed Waagenites Bed
The brachiopods reported in this paper were collected by the senior author in April, 1994, from the upper part of the Coral Bed and the Waagenites Bed of Jin et al. (1996), which correspond to the upper part of Unit 3 and Unit 4 of Wang et al. (1989) of the Selong Group (Fig. 1). Further visits were made in 1996 and 1998. Despite careful search for brachiopods from the boundary beds, particularly those from the Otoceras Bed, no brachiopods from the Otoceras Bed were found. In total, 13 species of 10 genera were recognized (Table 1). 3.1. Coral bed The brachiopods from the basal levels of the carbonate-dominated part of the Selong Xishan section were re-studied (Shi and Shen, 1997) recently. They were correlated with the Lamnimargus himalayensis Zone in the Himalayas, including Chonetella nasuta (Waagen), Cleiothyridina sp., Gruntina grunti (Shi and Shen), Taeniothaerus? sp., Neospirifer kubeiensis Ting, Spiriferella rajah (Salter) and spiriferinacean. The specimens are abundant but mostly disarticulated and fragmentary. Among the others, Cleiothyridina sp., N. kubeiensis and S. rajah are dominant and extend upward into the Coral Bed. The Coral Bed is composed of medium bedded grainstone with up to 80% skeletal debris, of which over 65% are subrounded, separated segments of crinoid stems and less than 15% abraded fragments of brachiopods, bivalves and bryozoans. They are well sorted and closely compacted. The matrix is mostly micritic, but occasionally calcite spar or oxidized dolomite are found. Abundant terrigenous clastics such as quartz silts and feldspar appear in the topmost 10 cm. Brachiopod fossils from the upper part of the Coral Bed are of relatively low diversity and include seven species of ®ve genera. These brachiopods are also dis-
S. Shen, J. Yugan / Journal of Asian Earth Sciences 17 (1999) 547±559
551
Fig. 3. 1, Stenoscisma timorense Hayasaka and Gan; posterior view, 2, 129358, Coral Bed; 2±8, Stenoscisma selongensis n. sp.; 2±5, ventral, dorsal, side and anterior views of a complete specimen, 2, 129359; 6±8, ventral, posterior and dorsal views, beak of ventral valve cut and etched to show the spondylium supported by a septum, holotype, 2, 129360; 9±12, Girtyella? sp.; side, anterior, ventral and dorsal views of a complete specimen with etched beak showing two dental plates in ventral valve and a median septum in dorsal valve, 2, 129361; 13±16, Bullarina cf. rostrata Jin and Sun; anterior, side, ventral and dorsal views of a complete specimen with etched beak, 2, 129362; 17±20, Spiriferella rajah (Salter); anterior, ventral, side and dorsal views of a small complete specimen, 1.5, 129363. (All specimens are from the Waagenites Bed unless otherwise stated.)
552
S. Shen, J. Yugan / Journal of Asian Earth Sciences 17 (1999) 547±559
articulated and fragmentary. They are characterized by abundant thick-shelled ventral valves of Spiriferella and Neospirifer, which are abraded and similar to those from the underlying beds. Most shells were broken by strong wave action, leaving few articulated shells for re-deposition in the Waagenites Bed. The age of the Coral Bed was considered to be either Guadalupian±Wuchiapingian (Chang and Ching, 1976; Jin, 1985) based on the brachiopods or Chihsian (Wang et al., 1993; Xia and Zhang, 1992). Conodonts indicate ages no later than Wuchiapingian (Wang and Wang, 1995). This suggests that most of the Changhsingian is missing here. Following the age estimation of Waterhouse (1978), Shi and Shen (1997) suggested a Midian±Wuchiapingian age for the Lamnimargus himalayensis Zone of the Himalayas. Since there is no signi®cant dierence between the brachiopods from the Coral Bed and those of the overlying Waagenites Bed, their age is probably either late Wuchiapingian or early Changhsingian.
3.2. Waagenites bed Preservation of brachiopod and bryozoan fossils in the Waagenites Bed is appreciably better than that in the Coral Bed. Although a majority of the brachiopod shells in this bed are not well preserved, many more shells from the Waagenites Bed are articulated, complete in outline (Fig. 3) and exhibit very ®ne surface ornaments. Bioclastics are ®ner in size and form around 35%, and sometimes less than 10%, of the rock. Bioclastics are usually well sorted, ranging from 0.5 mm to 2.0 mm in diameter. Packstone with poorly sorted bioclastics is also observed where the diameter of bioclastics may be up to 20 mm with slightly abraded unbroken crinoid stems. No quartz grains and other intra-clastics, coated grains and other reworked deposits have been found (Jin et al., 1996, pl. V.1, Fig. 3). The better preservation indicates that the brachiopods of the Waagenites Bed were unlikely to have been reworked from the underlying beds. Brachiopods from the Waagenites Bed tend to be smaller in size and contain more stalked forms. Largesized and thick-shelled forms such as Neospirifer kubeiensis Ting and Taeniothaerus etc., which are common in the underlying beds, do not extend upward into the Waagenites Bed. On the other hand, such smaller forms as Martinia, Waagenites and some terebratulids have not been found from the underlying beds. The species of the genus Stenoscisma are speci®cally dierent between the Waagenites Bed and the underlying Beds. The beds below the Caliche Bed are dominated by large-sized S. gigantea (Diener), whereas Stenoscisma selongensis n. sp. from the Waagenites
Bed is characterized by its small size. This size dierence is shown even for the same species. For example, Spiriferella rajah (Salter) from the Coral Bed is generally about 60 mm in width and only represented by abraded ventral valves, but specimens from the Waagenites Bed are more complete and less than 26 mm in width. All these dierences prove the brachiopods of the Waagenites Bed are not reworked from the underlying beds. However, these species belong to the same suite of the brachiopods from the Selong Group and thus cannot provide a precise age. Echinauris and Krotovia arcuata Waterhouse were ®rst reported in the Pija Shale±Siltstone Member of the Senja Formation in north-west Nepal, and assigned a Baisalian or late Djhul®an (Wuchiapingian) age by Waterhouse (1978). Cleiothyridina deroyssii (L'Eveille) is widespread in the Carboniferous and Permian in the Boreal and Gondwanan Realms. Stenoscisma timorense Hayasaka and Gan was recorded from the beds ranging from the early Guadalupian to the Changhsingian in Timor (Broili, 1916), Kashmir (Diener, 1899), Zhongba and Nyalam of Xizang (Chang and Ching, 1976) and probably the Salt Range, Pakistan (Grant, 1965). Bullarina rostrata Jin and Sun was recorded from the Goqoi Limestone of the Changhsingian and the Lasila Limestone of the Late Guadalupian (Jin and Sun, 1981). Spiriferella rajah (Salter) is one of the most common species in our collection and has a relatively long stratigraphic range. It has been reported in the lower Senja Formation of possibly Changhsingian age in Nepal (Waterhouse, 1966, 1978), Lamnimargus himalayensis Zone of probable Late Permian age (Muir-Wood and Oakley, 1941), and the Kuling Shale (Diener, 1903). Spiriferella nepalensis Legrand-Blain (=S. qubuensis Chang) is also a common element in the upper part of the Selong Group (Chang and Ching, 1976). It was recorded from the Upper Permian of Qubu, Xizang (Ting, 1962) and the Marginalosia kalikotei Zone of supposed Changhsingian age in Northwest Nepal (Waterhouse, 1966, 1978). The elements of a small brachiopod association, the Waagenites barusiensis±Paracrurithyris pigmaea Assemblage, is presumed to be from Unit 4 (Wang et al., 1989) which corresponds with the Waagenites Bed (Jin et al., 1996). This assemblage, however, has not been con®rmed by our repeated collection. In addition to Waagenites cf. barusiensis (Davidson), Paracrurithyris pigmaea Liao, Phricodothyris sp., Martinia sp. and Araxathyris sp., it also contains Hustedia (Z.Q. Chen, personal communication) and some terebratulids. All brachiopods of this association are rather small in size and mostly stalked. A close study of this collection shows that Paracrurithyris pigmaea is represented only by an incomplete ventral valve (Wang et al., 1989, pl. 1, Fig. 2). The character-
S. Shen, J. Yugan / Journal of Asian Earth Sciences 17 (1999) 547±559
istic outline and hinge line do indicate an ambocoeliid anity, but diculty arises in identifying its generic state.
4. A comparison with other similar faunas in the Peri± Gondwanan region The faunal succession of brachiopods from the Permian±Triassic boundary beds in the Salt Range of Pakistan (Grant, 1970) is closely comparable with that at Selong despite dierences in preservation. Those from both the White Sandstone in the upper part of the Chhidru Formation and the Dolomite Unit of the Kathwai Member, Mianwali Formation, are not only scarce, but also poorly preserved and patched in rare fossiliferous lenses. A close analysis shows that the brachiopods from the White Sandstone and other parts of the Chhidru Formation are ``much or all correlative with the Guadalupian'' (Grant, 1970). The faunal relation is comparable with that between the Coral Bed and rest of the Selong Xishan section. Brachiopods from the Kathwai Member, Mianwali Formation, include some elements of the underlying Chhidru Formation such as Linoproductus, Martinia and Spirigerella in additional to small brachiopods such as Crurithyris? extima Grant, Ombonia sp., Orthothetina sp., Lingula sp. and Spinomarginifera sp. Grant (1970, pp. 124, 148) precluded the possibility that these brachiopods were reworked from the underlying Chhidru Formation and considered that the fauna of the Dolomite Unit of the Kathwai Member is younger than that of the Chhidru Formation and contains latest Guadalupian, Wuchiapingian and Triassic elements. However, many more Tethyan forms invaded the Salt Range during the Lopingian. These include such characteristic brachiopods as Oldhamina, Enteletina, Spinomarginifera, Ombonia etc. The occurrence of the Tethyan foraminifer Colaniella (Nakazawa et al., 1975), and the Tethyan conodont Clarkina (Wardlaw and Pogue, 1995) prove that the Chhidru Formation ranges in age from latest Wuchiapingian to Changhsingian. This invasion probably re¯ected a rapid expansion of the tropical belt and an anti-tropical immigration of brachiopods into the Peri± Gondwanan region along the west coast of the Palaeotethys by the end of the Permian. It did not reach to the Selong area until the latest Changhsingian so that very few Tethyan forms appeared in the Waagenites Bed of the Selong Xishan section. In Kashmir, the brachiopod fauna from Unit E1 (2.6 m in thickness) of the Khunamuh Formation (Nakazawa et al., 1975, p. 38) is similar to that from the Waagenites Bed. This fauna comprises the brachiopods Linoproductus cf. lineatus (Waagen),
553
Lissochonetes morahensis (Waagen), Dielasma? sp., Waagenoconcha purdoni (Waagen), Athyris? sp., Schellwienella sp., Derbyia sp., Marginifera himalayensis Diener and Pustula sp.; bivalve Palaeoneilo sp., Etheripecten haydeni Nakazawa, E. cf. hiemalis (Salter), Cyrtorostrata a. lunwalensis (Reed), Nuculopsis sp., Claraia bioni Nakazawa as well as foraminifer Nodosinella longissima M-Maklay and Lunucammina sp. Some Claraia are preserved in an articulated state and considered to have been buried nearly in situ. Other fossils are more or less transported from elsewhere, such as shallower sea-bottom, before burial (Nakazawa et al., 1975, p. 38). The brachiopod elements such as Linoproductus, Lissochonetes, Waagenoconcha, and Marginifera himalayensis are long ranging and are not substantially dierent in composition from those in the underlying Division IV of the Zewan Formation. Judging from the evidence presented, the situation is somewhat analogous to that of the Selong Xishan section. All of the above-mentioned brachiopod faunas seem to share some general characteristics. For instance, they are all found within a horizon tens of centimeters to several meters in thickness near the Permian± Triassic sequence boundary. This horizon also contains brachiopods from the underlying beds coexisting with some small brachiopods. This situation seems to ®t the interpretation that the continental shelf in the Peri± Gondwanan region may have received very few sediments from greater Gondwanaland during the latest Permian. A ``starved'' deposit, which is very thin but represents a relatively long duration, may therefore be present. All fossils described in this paper are housed in the Nanjing Institute of Geology and Paleontology, Academia Sinica.
5. Systematics and descriptions Family Rugosochonetidae Muir-Wood, 1962 Genus Waagenites Paeckelmann, 1930 Waagenites sp. Fig. 4Ð5, 6 Remarks. The two ventral valves display smooth ears, costellate surface, shallow sulcus and short median septum that characterize the genus Waagenites. They are closer to the Waagenites specimens of South China rather than those of the Salt Range in their less convex pro®le and more costellate. These valves closely resemble W. sureshanensis Ching in costellation and outline, but the latter has two elevated parallel ridges in the vascular marking areas. They are also similar to
554
S. Shen, J. Yugan / Journal of Asian Earth Sciences 17 (1999) 547±559
Fig. 4. 1±3, Krotovia arcuata Waterhouse; 1±2, anterior and side views of a complete ventral valve, 2, 129342, Coral Bed; 3, anterior view of another ventral valve showing the inconspicuous elongated spine bases, 2, 129343, Waagenites Bed; 4, Spiriferella nepalensis Legrand-Blain; ventral valve, 2, 129344, Waagenites Bed; 5±6, Waagenites sp.; 5, ventral valve, 3, 129345; 6, ventral valve, 2, 129346, Waagenites Bed; 7±8, Neospirifer sp.; ventral and anterior views of an incomplete ventral valve, 1, 129347, Coral Bed; 9±10, Cleiothyridina deroyssii (L'Eveille); 9, ventral view, 1, 129348, Waagenites Bed; 10, dorsal view, 1, 129349, Waagenites Bed; 11±12, Spiriferellina sp.; ventral view, 2, 129350; ventral view, 2, 129351, Coral Bed; 13±15, Martinia spp.; 13, ventral valve, 2, 129352; 14, ventral valve, 1, 129353; 15, ventral valve, 1, 129354, Waagenites Bed; 16±20; Martinia attenuatelloides n. sp.; 16, ventral view of a ventral valve, 2, 129355, Waagenites Bed; 17±19, dorsal, ventral and side views, holotype, 2, 129356, Waagenites Bed; 20, ventral view, 2, 129357, Waagenites Bed; 21±24, Stenoscisma timorensis Hayasaka and Gan; ventral, dorsal, side, and anterior views, 2, 129358, Coral Bed.
S. Shen, J. Yugan / Journal of Asian Earth Sciences 17 (1999) 547±559
the species Waagenites barusiensis (Davidson) in size, conspicuous ears, shallow sulcus and subtrapezoid outline, but the amount of costellae are more than twenty ®ve. W. barusiensis (Davidson) usually has thirteen simple costellae on the ventral valve. Family Overtoniidae Muir-Wood and Cooper, 1960 Genus Krotovia Fredericks, 1928 Krotovia arcuata Waterhouse, 1978 Fig. 3Ð1±3 1978 Krotovia arcuata Waterhouse, pp. 52±54, pl. 6, ®gs. 2±10. 1983a Krotovia arcuata Waterhouse, pp. 122±123, pl. 2, ®gs. 9±18. Remarks. This species are represented by 15 specimens, including two complete specimens with conjoined shells. They are essentially identical in external characters, except for the slightly transverse outline, with those described by Waterhouse (1978). The external ornamentation is particularly characteristic and consists of elongated elevations and pustules with spines about 1 mm in diameter. Spines arise from the pustules and are mostly arranged in quincunx, but irregularly developed on trail. Pustules are elongated and form inconspicuous costellae numbering about 4 in 5 mm. Nevertheless, the internal features of our specimens are completely unknown. Family Stenoscismatidae Oehlert, 1887 Genus Stenoscisma Conrad, 1839 Stenoscisma timorense Hayasaka and Gan, 1940 Fig. 4Ð21±24, Fig. 3Ð1 1940 Camarophoria timorensis Hayasaka and Gan, p. 129, pl. 9, ®gs. 1±7. 1965 Camarophoria purdoni Davidson; Grant, p. 149, pl. 20, ®gs. 1±4. 1976 Stenoscisma timorensis Hayasaka and Gan; Chang and Ching, p. 193, pl. 11, ®gs. 20±27, text®g. 7. 1989 Stenoscisma timorense (Hayasaka and Gan); Archbold and Bird, p. 110, ®g. 5A±Z, AA±BB. Remarks. This species shows a wide range of variations in shell shape and costation. Its costae commonly originate from midvalve or only develop on the anterior part of the shell and range from 1 to 6 in number on the sulcus (Hayasaka and Gan, 1940, p. 19). The present specimen, which is complete with articulate valves, agrees in outline and costation with the type-specimens from the Permian of Timor. This species has been considered as the synonym of Stenoscisma purdoni (Davidson) (Ustritsky, 1963, p. 22). However, the shell size of S. purdoni is usually
555
smaller, and the costae are much stronger and begin nearly from the beak. Stenoscisma selongensis n. sp. Fig. 3Ð2±8 1996 Stenoscisma a. globulina (Phillips); Jin et al., pl. V. 2, ®gs. 1±8. Holotype. A conjoined shell (129360) from the Waagenites Bed. Other material. A complete conjoined shell (129359) from the Waagenites Bed. Etymology. Referring to Selong, the type locality of this species. Diagnosis. Stenoscisma with pentagonal outline, variable costation, distinct convexity and anterior tongue. Description. Small to medium in size for genus, pentagonal in outline, biconvex in pro®le; maximum width nearly at midvalve; lateral sides nearly parallel; anterior margin truncated. Ventral valve ¯atly convex in anterior and lateral pro®le; beak obtuse, suberect; interarea inconspicuous; sulcus wide, beginning near midvalve, deepening abruptly; bottom generally ¯at, extended into long truncated tongue dorsally; ¯anks gently convex; surface costate except for smooth umbonal region, 1±3 in sulcus, if 3, with the middle one much stronger than the outer 2, each ¯ank with 1±2 weak costae. Dorsal valve strongly convex in anterior pro®le, but ¯atly convex in lateral pro®le, ¯anks sharply inclined, fold highly elevated with a deep groove along midline; costae 2±4 on fold, but fairly uneven in size, the middle 2 much higher than the outer 2, each ¯ank with 1±2 weak costae. Ventral interior with a spondylium supported by a median septum; dorsal interior with a median septum. Other characters unknown. Measurements (in mm). Registration no.
Length
Width
Thickness
129359 129360 (holotype)
10.5 15.7
9.5 14.5
7.5 11.5
Comparison. This species was tentatively referred to Stenoscisma a. globulina (Phillips) by Jin et al. (1996). Although only two complete specimens are available, the authors consider that there are sucient evidence, such as the distinct convexity, outline, anterior tongue and peculiarly arranged costae, to dierentiate it from existing species of Stenoscisma. The new species diers from S. globulina (Phillips) in its pentagonal outline, relatively large size and costation.
556
S. Shen, J. Yugan / Journal of Asian Earth Sciences 17 (1999) 547±559
Family Martiniidae Waagen, 1883 Genus Martinia McCoy, 1844 Martinia spp. Fig. 4Ð13±15 Remarks. A complete specimen with conjoined valves and nine ventral valves show the characters of the genus Martinia but possibly belong to more than one species. The subcircular outline, even biconvex pro®le and well-developed sulcus of some specimens recall the typical features of Martinia orbicularis Gemmellaro that occur widely in the Permian of the Tethyan Realm.
Remarks. The peculiar outline of the ventral valve, lateral and anterior pro®le, strongly incurved umbo and well-de®ned sulcus of this species shows a general resemblance with the genus Attenuatella, especially the species A. piyasini Waterhouse from Thailand (Waterhouse, 1983b, p. 134, pl. 4, Figs. 13±18). Lack of the crural plates inside the dorsal valve and very short hinge line exclude the possibility of belonging to this genus. On the other hand, these Attenuatella-type external features distinguish it from other species of Martinia.
Family Athyrididae McCoy, 1844 Genus Cleiothyridina Buckman, 1906 Cleiothyridina deroyssii (L'Eveille, 1835) Fig. 4Ð9, 10
Martinia attenuatelloides n. sp. Fig. 4Ð16±20 Holotype. A complete conjoined shell (129356) from the Waagenites Bed. Other material. Four ventral valves. Among them two are registered (129355, 129357). Etymology. Attenuatella, a generic name of brachiopods; -oides (Greek), similar. Diagnosis. Small Martinia with Attenuatella-type outline and pro®le, but very short and curved hinge line. Description. Small in size, elongately triangular in outline, unevenly biconvex in pro®le; maximum width near anterior commissure; hinge-line fairly short; cardinal extremities inconspicuous. Surface smooth, no regular ornament visible. Ventral valve of adults strongly convex in lateral pro®le and younger individuals usually less convex; lateral slopes sharply inclined outwards, but median region ¯attening in anterior pro®le; beak perhaps pointed but usually not preserved; sulcus shallow but distinct, originating from beak, slightly widening but not deepening anteriorly. Dorsal valve much less convex than ventral valve in pro®le, elongate with strongly merging umbo in outline; lateral slopes gently inclined. Ventral interior without dental plates; dorsal interior without crural plates. Other features unknown. Measurements (in mm). Registration no.
Length
Width
Thickness
129355 129356 (holotype) 129357
11.5 9.0 7.3
9.5 7.4 6.1
5.6 5.0 3.5
1835 Spirifer deroyssii L'EveilleÂ, p. 39, pl. 2, ®gs. 18±20. 1862 Athyris royssii (L'EveilleÂ); Davidson, p. 27, pl. 1, ®g. 6. 1883 Athyris royssii (L'EveilleÂ); Waagen, p. 475, pl. 39, ®g. 10; pl. 40, ®gs. 6±12. 1897a Athyris royssii (L'EveilleÂ); Diener, p. 59, pl. 10, ®gs. 1±3, 6. 1897b Athyris royssii (L'EveilleÂ); Diener, p. 47, pl. 5, ®g. 5. 1931 Athyris royssii (L'EveilleÂ); Grabau, pp. 120± 121, pl. 6, ®gs. 7a±d, 8a±c. 1934 Athyris (Cleiothyridina ) royssii (L'EveilleÂ); Grabau, pp. 110±111, pl. 7, ®gs. 9±10. 1964 Cleiothyridina royssii (L'EveilleÂ); Wang et al. p. 622, pl. 122, ®gs. 8±13. 1976 Cleiothyridina royssii (L'EveilleÂ); Chang and Ching, pp. 195±196, pl. 15, ®g. 8. Remarks. This well de®ned species is characterized by its subpentagonal outline, medium size, inconspicuous sulcus and fold on the anterior part. The present specimens usually have a medium size, subpentagonal outline, well-formed concentric lamellae and the medially placed muscle marks, which all recall the species of C. deroyssii. Family Elythidae Fredericks, 1919 Genus Bullarina Jin and Sun, 1981 Bullarina cf. rostrata Jin and Sun, 1981 Fig. 3Ð13±16
1897a Reticularia lineatus Diener, p. 56, pl. 9, ®gs. 5±8.
S. Shen, J. Yugan / Journal of Asian Earth Sciences 17 (1999) 547±559
1981 Bullarina rostrata Jin and Sun, p. 154, pl. 9, ®gs. 17±20, 22±25. 1996 Cleiothyridina a. royssii (Phillips); Jin et al., pl. V. 2, ®gs. 13±16. Remarks. The present specimens resemble Reticularia lineatus Diener from the Chitichun Limestone in external characters, which was reassigned into this species by Jin and Sun (1981). They are slightly larger than the type specimens in size and probably represent a new species. The generic state of these specimens is still pending because the direction of spiralia and the spinal types are unknown. Family Spiriferellidae Waterhouse, 1966 Genus Spiriferella Tschernyschew, 1902 Spiriferella rajah (Salter, 1865) Fig. 3Ð17±20
1865 Spirifer rajah Salter in Salter and Blanford, pp. 59, 111. 1866 Spirifer rajah Salter; Davidson, p. 40, pl. 2, ®g. 4. 1903 Spirifer rajah Salter; Diener, pp. 105, 131, 186, pl. 4, ®gs. 3±5. 1941 Spirifer rajah Salter; Muir-Wood and Oakley, p. 36, pl. 2, ®gs. 2, 3, 9±11. 1966 Spirifer rajah Salter; Waterhouse, p. 48, pl. 11, ®g. 2; pl. 12, ®g. 2 (non pl. 1, ®g. 5; pl. 3, ®g. 2; pl. 7, ®gs. 1, 2, 4). 1976 Spirifer rajah Salter; Chang and Ching, p. 215, pl. 17, ®gs. 3±12. 1976 Spiriferella a. rajah (Salter); Legrand-Blain, p. 245, pl. 2, ®gs. 4, 6. Remarks. This is one of the most abundant species in the our collection but most specimens are ventral valves, with only one complete specimen from the Waagenites Bed. The species was originally de®ned by its large size, greatest width at hinge, strong fascicular ornamentation and groove on the dorsal fold, which has been used to contain the specimens departing from the types since then. The specimens from Selong reveal that the hinge line can range from just equal to slightly shorter than the greatest width. The folds of two dorsal valves have a coarse median costa. Spiriferella nepalensis Legrand-Blain, 1976 Fig. 4Ð4
1976 Spiriferella nepalensis Legrand-Blain, p. 242, pl. 1, ®gs. 7, 11. 1976 Spiriferella qubuensis Chang in Chang and Ching, p. 212, pl. 18, ®gs. 1±5.
557
Remarks. Four ventral valves are referable to the species de®ned with the specimens from the Nyi district of Nepal (Legrand-Blain, 1976). Similar specimens from Selong were assigned to the species Spiriferella qubuensis by Chang in Chang and Ching (1976), which is here considered as a junior synonym of S. nepalensis Legrand-Blain. Family Spiriferidae King, 1848 Genus Neospirifer Fredericks, 1919 Neospirifer sp. Fig. 4Ð7, 8 Remarks. An incomplete ventral valve bears the strongly convex pro®le and strong fasciculate costation of Neospirifer. The posterior part of the valve shows that the hinge line is fairly wide and perhaps equals to the maximum width of the shell. The costation of this specimen closely resembles that of Neospirifer moosakhaiensis (Davidson) and N. kubeiensis Ting.
Family Spiriferinidae Davidson, 1884 Genus Spiriferellina Fredericks, 1919 Spiriferellina sp. Fig. 4Ð11, 12
Remarks. Spiriferellina is characterized by its typically small size, relatively few plications with fastigum and many low pustules. Our two ventral valves have a wide sulcus and 2±3 plications on each ¯ank and numerous pustules on shell surface that identify them as a species of Spiriferellina. The transverse outline, medium size and the absence of reverse plication in the sulcus suggest a close resemblance to those of Spiriferina cristata var. octoplicata ®gured by Diener (1897a) and Spiriferina octoplicata var. fastigata by Diener (1903). Family Dielasmatidae Schuchert, 1913 Genus Girtyella Weller, 1911 Girtyella? sp. Fig. 3Ð9±12 Remarks. A complete specimen with an etched beak reveals a pair of well developed dental plates in the ventral valve and a median septum in the dorsal valve. It has an elongate and equally moderately biconvex pro®le. The sulcus and fold are completely absent and the anterior commissure is rectimarginate. The surface is entirely smooth, but the loop is totally unknown. The foregoing mentioned characters suggest that this
558
S. Shen, J. Yugan / Journal of Asian Earth Sciences 17 (1999) 547±559
specimen is probably a species of Girtyella, most possible G. nyalamensis Ching.
Acknowledgements We thank Dr G.R. Shi of School of Ecology and Environment, Deakin University, for his critical reading of this paper and discussions concerning the Selong fauna. This paper is supported by Chinese Academy of Science (Grant K2951-B1-409) and the National Nature Science Foundation of China (Grant 49672092). References Archbold, N.W., Bird, P.R., 1989. Permian Brachiopoda from near Kasliu Village, West Timor. Alcheringa 13 (12), 103±123. Broili, F., 1916. Die Permischen Brachiopoden von Timor. In: Wanner, J. (Ed.), Palaeontologie von Timor Stuttgart, pp. 1±104. Buckman, S.S., 1906. Brachiopod nomenclature: Epithyris, Hypothyris, Cleiothyris Phillips, 1841. Annals and Magazine of Natural History, Ser. 7, 18, 321±327. Chang (Zhang) Shouxin, Ching (Jin) Yugan, 1976. Upper Paleozoic Brachiopoda from the Mount Jolmolangma region. In: A Report of Scienti®c Expedition in the Mount Jolmolangma Region (1966±1968), Paleontology, fasc. 2 (Edited by Chinese Academy of Science), Science Press, Beijing, pp. 159±242 (in Chinese). Conrad, T.A. 1839 Second annual report on the Palaeontological Department of the Survey, New York Geological Survey, Annual Report 3, 57±66. Davidson, T., 1862. Notes on the Carboniferous Brachiopoda collected in India by A. Fleming and W. Purdon. Quarterly Journal of the Geological Society of London 18, 25±35. Davidson, T., 1866. On the Carboniferous rocks of the valley of Kashmere. With notes on the Brachiopoda collected by Capt. Godwin-Austin in Thibet and Kashmere. Quarterly Journal of the Geological Society of London 22, 29±45. Diener, C., 1897a. The Permo-Carboniferous fauna of Chitichun No. 1. Palaeontologica Indica, Ser. 15, 1 (3), 1±105. Diener, C., 1897b. The Permian fossils of the Productus Shales of Kumaon and Gurhwal. Palaeontologica Indica, Ser. 15, 1 (4), 1± 54. Diener, C., 1899. Anthracolithic fossils of Kashmir and Spiti. Palaeontologica Indica, Ser. 15, 1 (2), 1±95. Diener, C., 1903. Permian fossils of the central Himalayas. Palaeontologia Indica, Ser. 15, 1 (5), 1±204. Fredericks, G.N., 1928. Materialy dlya klassi®katsii roda Productus Sow (contribution to the classi®cation of the genus Productus ). Izvestiia Geologicheskogo Komiteta 46 (7), 773±792 (in Russian). Grabau, A.W., 1931. The Permian of Mongolia. A report on the Permian fauna of the Jisu Honguer Limestone of Mongolia and its relations to the Permian of other parts of the world. Natural History of Central Asia 4, 1±665. Grabau, A.W., 1934. Early Permian fossils of China, Part I: Early Permian brachiopods, pelecypods, and gastropods of Kueichow. Palaeontologia Sinica, Ser. B, 8 (3), 1±168. Grant, R.E., 1965. The brachiopod Superfamily Stenoscismatacea. Smithsonian Miscellaneous Collections 148 (2), 1±192. Grant, R.E., 1970. Brachiopods from Permian±Triassic boundary
beds and age of Chhidru Formation, West Pakistan. In: Kummel, B., Teichert, C. (Eds.), Stratigraphic Boundary Problems: Permian and Triassic of West Pakistan. University of Kansas, Department of Geology, Special Publication 4. The University Press of Kansas, Lawrence/Manhattan/Wichita/London, pp. 117± 151. Hayasaka, I., Gan, S., 1940. A note on Camarophoria `purdoni' from the Permian of Timor. Journal of the Geological Society of Japan 47 (558), 127±132. Jin Yugan, 1985. Permian Brachiopoda and paleogeography of the Qinghai±Xizang (Tibet) Plateau. Palaeontologia Cathayana 2, 19±71. Jin Yugan, Shen Shuzhong, Zhu Zhili, Mei Shilong, Wang Wei, 1996. The Selong Xishan section, candidate of the global stratotype section and point of the Permian±Triassic boundary. In: Yin Hongfu (Ed.), The Palaeozoic±Mesozoic Boundary Candidates of the Global Stratotype Section and Point of the Permian±Triassic Boundary. China University of Geosciences Press, Wuhan, pp. 127±137. Jin Yugan, Sun Dongli, 1981. Paleozoic brachiopods from Xizang (Tibet). In: Paleontlogy of Xizang, Book III, The Series of the Sscienti®c Expedition to the Qinghai±Xizang Plateau (Edited by Nanjing Institute of Geology and Palaeontology), Science Press, Beijing (in Chinese), pp. 127±171. Legrand-Blain, M., 1976. Repartition du groupe de Spiriferella rajah (Salter, 1865) et description de Spiriferella nepalensis, nov. sp., appartenant a ce groupe. Centre National de la Recherche Scienti®que, Colloques Internationaux, France 268 (2), 237±250. L'Eveille, C., 1835. Apercu geologique de quelques localites tres riches en coquilles sur les frontieres de France et de Belgique. Societe geologique de France, Memoires, Ser. 1, 2, 29±40. Liao Zhouting, 1980. Brachiopod assemblages from the Upper Permian and Permian±Triassic boundary beds, South China. Canadian Journal of Earth Science 17 (2), 289±295. McCoy, F., 1844. In: A Synopsis of the Characters of the Carboniferous Limestone Fossils of Ireland. Dublin, London. Muir-Wood, H.M., Oakley, K.P., 1941. Upper Paleozoic faunas of North Sikkim. Palaeontologica Indica, new series 31 (1), 1±91. Muir-Wood, H.M., 1962. On the Morphology and Classi®cation of the Brachiopod Suborder Chonetoidea. British Museum, London, pp. 1±132. Muir-Wood, H.M., Cooper, G.A., 1960. Morphology, classi®cation and life habits of the Productoidea (Brachiopoda). Geological Society of America, Memoir 81, 1±447. Nakazawa, K., Kapoor, H.M., Ishii, K., Bando, Y., Okimura, Y., Tokuoka, T., 1975. The Upper Permian and Lower Triassic in Kashmir, India. Memoirs of the Faculty of Science, Kyoto University, Geology and Mineralogy 42 (1), 1±106. Oehlert, D.P., 1887. Brachiopodes. In: Fischer, P. (Ed.), Manuel de Conchyliologie et de Paleontologie Conchyliologue, ou Histoire Naturelle des Mollusques Vivants et Fossiles. F. Savy, Paris, pp. 1189±1334. Orchard, M.J., Nassichuk, W.W., Rui Lin, 1994. Conodonts from the lower Griesbachian Otoceras latilobatum Bed of Selong, Tibet and the position of the Permian±Triassic boundary. In: Pangea: Global Environments and Resources, Memoirs of the Canadian Society of Petroleum Geologists, vol. 17, pp. 823±843. Paeckelmann, W., 1930. Die fauna des deutschen Unterkarbons 1. Teil. Die brachiopoden, 1. Teil: Die orthiden, strophomeniden und choneten des mittleren und oberen Unterkarbons. Koenigliche-Preussiche geologische Landesanstalt, Abhandlungen 122, 143±326. Rao Rongbiao, Zhang Zhenggui, 1985. A discovery of PermoTriassic transitional fauna in the Qomolangma Feng area: its implications for the Permo-Triassic boundary. Xizang Geology 1, 19±31 (in Chinese). Salter, J.W., Blanford, F.G.S., 1865. Paleontology of Niti in the
S. Shen, J. Yugan / Journal of Asian Earth Sciences 17 (1999) 547±559 Northern Himalaya I, Description and Figures of the Palaeozoic and Secondary Fossils. O.T. Cutter, Military Orphan Press, Calcutta, pp. 1±112. Shi, G.R., Shen Shuzhong, 1997. A Late Permian brachiopod fauna from Selong, southern Xizang (Tibet), China. Proceedings of the Royal Society of Victoria 109 (1), 37±56. Ting (Ding) Peizhen, 1962. Several Late Permian brachiopod fossils from Tibet. Acta Palaeontologica Sinica 10 (4), 451±464 (in Chinese). Tschernyschew, T.N., 1902. Verkhnekamennougol'nye brakhiopody Urala i Timana. (Upper Carboniferous brachiopods of the Urals and the Timan). Trudy Geologicheskogo Komiteta 16 (2), 17±49 (in Russian). Ustritsky, V.I., 1963. Permian stratigraphy and faunas of western Gansu. In: Memoir of the Geological Institute, Minister of Geology and Mineralogy, Ser. B, Stratigraphy and Palaeontology, vol. 5. China Industry Publishing House, Beijing, pp. 1±49 (in Chinese). Waagen, W., 1883. Productus Limestone fossils. Palaeontologica Indica, Ser. 13 1 (pt. 4, fasc. 2), 391±546. Wang Wei, Shen Shuzhong, Zhu Zhili, 1997. Carbon isotope characters of the Permian Triassic boundary section at Selong, Xizang (Tibet), China and their signi®cance. Chinese Science Bulletin 4, 406±408 (in Chinese). Wang Yu, Jin Yugan, Fang Dawei, 1964. Brachiopod fossils of China 1 (2), 1±777 Science Press, Beijing (in Chinese). Wang Yigang, Chen Chuzhen, Rui Lin, Wang Zhihao, Liao Zhouting, He Jinwen, 1989. A potential global stratotype of Permian±Triassic boundary. In: Developments in Geoscience, Chinese Academy of Sciences, Contribution to 28th International Geological Congress 1989, Washington, D.C. USA. Science Press, Beijing, pp. 221±229. Wang Zhihao, Chen Chuzhen, Liao Zhouting, 1993. Some queries about the paper ``Age of the Selong Group in Xishan, Selong of Xizang (Tibet) and the Permian±Triassic boundary''. Journal of Stratigraphy 17 (3), 223, 237±239 (in Chinese).
559
Wang Zhihao, Wang Yigang, 1995. Permian±Lower Triassic conodonts from Selong Xishan of Nyalam, S. Tibet, China. Acta Micropalaeontologica Sinica 12 (4), 333±348. Wardlaw, B.R., Pogue, K.R., 1995. The Permian of Pakistan. In: Scholle, P.A., Peryt, T.M., Ulmer-Scholle, D.S. (Eds.), The Permian of Northern Pangea 2, Sedimentary Basins and Economic Resources. Springer-Verlag, Berlin, pp. 215±224. Waterhouse, J.B., 1966. Lower Carboniferous and Upper Permian brachiopods from Nepal. Geologische Bundesanstalt, Jahrbuch 12, 5±99. Waterhouse, J.B., 1978. Permian Brachiopoda and Mollusca from north-west Nepal. Palaeontographica Abt. A 160, 1±175. Waterhouse, J.B., 1983a. Permian brachiopods from Pija Member, Senja Formation in Manang district of Nepal, with new brachiopod genera and species from other regions. Indian Geologists' Association, Bulletin 16 (2), 111±151. Waterhouse, J.B., 1983b. A Late Permian Lyttoniid fauna from northwest Thailand. University of Queensland, Department of Geology, Papers 10 (3), 111±153. Weller, S., 1911. Genera of Mississippian loop-bearing Brachiopoda. Journal of Geology 19 (5), 439±448. Xia Fengsheng, Zhang Binggao, 1992. Age of the Selong Group in Xishan, Selong of Xizang (Tibet) and the Permian-Triassic boundary. Journal of Stratigraphy 16 (4), 256±363 (in Chinese). Yin Jixiang, Guo Shizeng, 1979. Stratigraphy of the Mt. Jolmolangma and its northern slope, with a discussion about correlation of Sinian±Cambrian and Carboniferous-Permian with adjacent areas. In: A Report of the Scienti®c Expedition in the Mt. Jolmolangma Region (1975) (Geology) (Edited by Xizang expedition team of Chinese Academy of Science), Science Press, Beijing, pp. 1±71 (in Chinese). Zhang Binggao, 1974. The Permian System. In: A Report of Scienti®c Expedition in the Mt. Jolmolangma Region (Geology), 1966±1968, (Edited by Xizang expedition team of Chinese Academy of Science), Science Press, Beijing, pp. 66±80 (in Chinese).
Brachiopods from the Permian±Triassic boundary beds at the Selong Xishan section, Xizang (Tibet), China Shuzhong Shen a,*, Jin Yugan b a
School of Ecology and Environment, Deakin University, Rusden Campus, 662 Blackburn Road, Clayton, Victoria, 3168, Australia b Nanjing Institute of Geology and Palaeontology, Academia Sinica, Nanjing, Jiangsu, 210008, People's Republic of China Accepted 22 January 1999
Abstract The brachiopods from the Waagenites Bed and the upper part of the Coral Bed above and below the Permian±Triassic sequence boundary at the Selong Xishan section of southern Xizang suggest a rich brachiopod fauna existing in Selong, and a rapid invasion of Tethyan brachiopods into the Himalayas at the very end of the Permian. A transgression beginning from the Waagenites Bed and a rapid ¯ooding at the beginning of the Triassic is re¯ected by changes in composition of the Permian brachiopod assemblages in Selong. However, the dominant forms in the Permian±Triassic sequence boundary beds, including Krotovia, Spiriferella and Neospirifer, extend from the underlying beds of the Selong Group without signi®cant evolutionary change. A brief discussion of each taxon and descriptions of two new species, Stenoscisma selongensis and Martinia attenuatelloides, are presented. # 1999 Elsevier Science Ltd. All rights reserved.
1. Introduction The Selong Xishan section is one of a number of candidates for the global boundary stratotype for the Permian±Triassic boundary. This boundary sequence is entirely composed of carbonates. The biostratigraphical boundary level is indicated by the ®rst appearance of both Otoceras and Hindeodus parvus which have been respectively proposed as the key indicators (Wang et al., 1989; Xia and Zhang, 1992; Wang et al., 1993; Orchard et al., 1994; Jin et al., 1996). Increasing data from systematic studies on the section also made it valuable in understanding better the end-Permian mass extinction in the eastern Himalayas. This section is situated near the second highest peak in the world, the Xixiabangma Mount (8012 m above sea level) in Nyalam County of southern Xizang, and lies on the western side of the main road from Lhasa, the * Corresponding author. Tel.: +61-3-9244-7428; fax: +61-3-92447480. E-mail address: [email protected] (S. Shen)
provincial capital of Xizang, to Kathmandu in Nepal (Fig. 1). 2. Stratigraphic succession Permian carbonate-dominated beds at the Selong Xishan section reach a thickness of 9 m. These beds were commonly assigned to the upper part of the Selong Group (Jin et al., 1996) or an independent lithostratigraphic unit, the Baka Formation (Rao and Zhang, 1985). The carbonates are characterized by a dominance of poorly sorted, angular biogenic debris. The topmost 1.08 m of the Selong Group is named the Coral Bed because it is distinguished by the occurrence of abundant tabulate and solitary rugose corals along with some bryozoans. It was assigned to Unit 3 of ``the Prechanghsingian Bed'' by Wang et al. (1989). This bed is composed of medium bedded grainstone and seams mainly formed in a high-energy shoal environment. The contact between the Selong Group and the overlying Kangshare Formation is marked by the Caliche Bed, a thin layer of pedogenic calcrete which
1367-9120/99/$ - see front matter # 1999 Elsevier Science Ltd. All rights reserved. PII: S 1 3 6 7 - 9 1 2 0 ( 9 9 ) 0 0 0 0 4 - 8
548
S. Shen, J. Yugan / Journal of Asian Earth Sciences 17 (1999) 547±559
Fig. 1. Map showing the location of the Selong Xishan Section and the brachiopod horizons for this study (data and locality map after Jin et al., 1996).
varies laterally in thickness (Fig. 2). A rapid negative excursion of d13C value in this bed and signi®cant lowering d13C value in the basal levels of the Kangshare Formation has been detected (Wang et al., 1997). This
unusual negative excursion of d13C value indicates that the Caliche Bed is coincident with the Permian± Triassic sequence boundary. The Kangshare Formation is 7.0 m thick and is
S. Shen, J. Yugan / Journal of Asian Earth Sciences 17 (1999) 547±559
549
Fig. 2. A, Permian±Triassic strata at the Selong Xishan section; B, C, close-up views of the Permian±Triassic boundary beds with laterally-varietied Caliche Bed. 1, the Coral Bed; 2, the Caliche Bed. 3; the Waagenites Bed; 4, the Otoceras Bed.
divided into three beds (Jin et al., 1996). The Waagenites Bed at the base contains coarse bioclastics, which are strikingly similar in composition to those of the Coral Bed of the Selong Group. The Waagenites Bed, however, contains greater amounts of ostracod and gastropod shells within the bioclastics in additional more micritic lime in the matrix. This bed represents lag carbonate deposits formed in shallow, medium-energy shoal and in inter-shoal depressions. The Otoceras Bed consists of stylo-compacted corroded packstone. The boundary between this bed and the Waagenites Bed is indistinct on a polished surface as well as in thin sections. Instead, there is a thin tran-
sitional bed with mixed dolomitized bioclastic wackstone, packstone and lime mudstone. No apparent depositional gap can be documented based on petrographic evidence. The Ophiceras Bed is separated from the underlying Otoceras Bed by a distinct erosional surface. This bed consists of shell debris packstone, of which most shell fragments are of ammonoids, bivalves and gastropod coquina. Crinoid debris is sparse. This bed represents a sequence ranging from proximal to distal tempestite formed above wave base. These upward-®ning cycles are likely formed in the response to a gradual reduction in the impact of seaward currents.
550
S. Shen, J. Yugan / Journal of Asian Earth Sciences 17 (1999) 547±559
In summary, the Permian±Triassic deposits at the Selong Xishan section represent a rapid transgression at the very end of the Permian. This Permian transgression probably started from the Waagenites Bed. The latest Permian transgression rapidly ¯ooded in the Triassic Otoceras Zone and reached a maximum in the Ophiceras Zone. There is no traceable depositional gap between the Waagenites Bed and the Otoceras Bed. 3. Brachiopod composition, preservation and age problems Brachiopod faunas of this region have been frequently reported [Ting (Ding in present spelling), 1962; Chang and Ching (Zhang and Jin in present spelling), 1976; Jin, 1985; Wang et al., 1989]. Chang and Ching (1976) grouped the brachiopods from the Selong Group into three assemblages, namely the Taeniothaerus, the Callimarginatia and the Chonetella nasuta Assemblage in ascending order. Among them, the Taeniothaerus and the Chonetella nasuta Assemblages were found in Selong. Recently, Shi and Shen (1997) recognized an assemblage which is similar to those of the Lamnimargus himalayensis Zone in the Himalayan region from the middle part of the Selong Group. Estimated ages for the Chonetella nasuta Assemblage range from Guadalupian to Wuchiapingian (Jin, 1985) or from late Guadalupian (Midian) to Wuchiapingian (Shi and Shen, 1997). It seems hardly possible to narrow down the age estimation because most of the stratigraphic ranges of brachiopod taxa are fairly long. Wang et al. (1989) and Wang et al. (1993) divided the topmost part of the Selong Group into two parts, ``the Prechanghsingian Bed'' and ``the Changhsingian Bed'' or Unit 4 (6±17 cm in thickness). Brachiopods such as Waagenites cf. barusiensis (Davidson), Paracrurithyris pigmaea (Liao), Phricodothyris sp., Martinia sp. and Araxathyris sp. from ``the Changhsingian Bed'' were reported and were named as the Waagenites barusiensis±Paracrurithyris pigmaea Assemblage. Among them, Paracrurithyris pigmaea is a guide to the brachiopod faunas usually occurring in the topmost part of the Changhsingian beds in South China (Liao, 1980). However, it has long been debated whether the brachiopod shells from the Waagenites Bed of the Permian±Triassic boundary beds in Selong are reworked or simply agitated by contemporaneous wave action (Zhang, 1974, p. 77; Yin and Guo, 1979, p. 41; Wang et al., 1989, p. 221, etc.). Evidently, Permian brachiopods from Selong pose two long-standing major problems as do those from other areas of the Himalayas: (1) How to identify the diagnostic features of the Lopingian fauna? (2) Are the brachiopods from the Waagenites Bed reworked?
Table 1 Brachiopods recorded from the upper part of the Coral Bed and the Waagenites Bed of the Selong Xishan section Species Waagenites sp. Krotovia arcuata Waterhouse Stenoscisma timorense Hayasaka and Gan Stenoscisma selongensis n. sp. Martinia attenuatelloides n. sp. Martinia spp. Bullarina cf. rostrata Jin and Sun Cleiothyridina deroyssii (L'Eveille) Spiriferella rajah (Salter) S. nepalensis Legrand-Blain Neospirifer sp. Spiriferellina sp. Girtyella? sp.
Coral Bed Waagenites Bed
The brachiopods reported in this paper were collected by the senior author in April, 1994, from the upper part of the Coral Bed and the Waagenites Bed of Jin et al. (1996), which correspond to the upper part of Unit 3 and Unit 4 of Wang et al. (1989) of the Selong Group (Fig. 1). Further visits were made in 1996 and 1998. Despite careful search for brachiopods from the boundary beds, particularly those from the Otoceras Bed, no brachiopods from the Otoceras Bed were found. In total, 13 species of 10 genera were recognized (Table 1). 3.1. Coral bed The brachiopods from the basal levels of the carbonate-dominated part of the Selong Xishan section were re-studied (Shi and Shen, 1997) recently. They were correlated with the Lamnimargus himalayensis Zone in the Himalayas, including Chonetella nasuta (Waagen), Cleiothyridina sp., Gruntina grunti (Shi and Shen), Taeniothaerus? sp., Neospirifer kubeiensis Ting, Spiriferella rajah (Salter) and spiriferinacean. The specimens are abundant but mostly disarticulated and fragmentary. Among the others, Cleiothyridina sp., N. kubeiensis and S. rajah are dominant and extend upward into the Coral Bed. The Coral Bed is composed of medium bedded grainstone with up to 80% skeletal debris, of which over 65% are subrounded, separated segments of crinoid stems and less than 15% abraded fragments of brachiopods, bivalves and bryozoans. They are well sorted and closely compacted. The matrix is mostly micritic, but occasionally calcite spar or oxidized dolomite are found. Abundant terrigenous clastics such as quartz silts and feldspar appear in the topmost 10 cm. Brachiopod fossils from the upper part of the Coral Bed are of relatively low diversity and include seven species of ®ve genera. These brachiopods are also dis-
S. Shen, J. Yugan / Journal of Asian Earth Sciences 17 (1999) 547±559
551
Fig. 3. 1, Stenoscisma timorense Hayasaka and Gan; posterior view, 2, 129358, Coral Bed; 2±8, Stenoscisma selongensis n. sp.; 2±5, ventral, dorsal, side and anterior views of a complete specimen, 2, 129359; 6±8, ventral, posterior and dorsal views, beak of ventral valve cut and etched to show the spondylium supported by a septum, holotype, 2, 129360; 9±12, Girtyella? sp.; side, anterior, ventral and dorsal views of a complete specimen with etched beak showing two dental plates in ventral valve and a median septum in dorsal valve, 2, 129361; 13±16, Bullarina cf. rostrata Jin and Sun; anterior, side, ventral and dorsal views of a complete specimen with etched beak, 2, 129362; 17±20, Spiriferella rajah (Salter); anterior, ventral, side and dorsal views of a small complete specimen, 1.5, 129363. (All specimens are from the Waagenites Bed unless otherwise stated.)
552
S. Shen, J. Yugan / Journal of Asian Earth Sciences 17 (1999) 547±559
articulated and fragmentary. They are characterized by abundant thick-shelled ventral valves of Spiriferella and Neospirifer, which are abraded and similar to those from the underlying beds. Most shells were broken by strong wave action, leaving few articulated shells for re-deposition in the Waagenites Bed. The age of the Coral Bed was considered to be either Guadalupian±Wuchiapingian (Chang and Ching, 1976; Jin, 1985) based on the brachiopods or Chihsian (Wang et al., 1993; Xia and Zhang, 1992). Conodonts indicate ages no later than Wuchiapingian (Wang and Wang, 1995). This suggests that most of the Changhsingian is missing here. Following the age estimation of Waterhouse (1978), Shi and Shen (1997) suggested a Midian±Wuchiapingian age for the Lamnimargus himalayensis Zone of the Himalayas. Since there is no signi®cant dierence between the brachiopods from the Coral Bed and those of the overlying Waagenites Bed, their age is probably either late Wuchiapingian or early Changhsingian.
3.2. Waagenites bed Preservation of brachiopod and bryozoan fossils in the Waagenites Bed is appreciably better than that in the Coral Bed. Although a majority of the brachiopod shells in this bed are not well preserved, many more shells from the Waagenites Bed are articulated, complete in outline (Fig. 3) and exhibit very ®ne surface ornaments. Bioclastics are ®ner in size and form around 35%, and sometimes less than 10%, of the rock. Bioclastics are usually well sorted, ranging from 0.5 mm to 2.0 mm in diameter. Packstone with poorly sorted bioclastics is also observed where the diameter of bioclastics may be up to 20 mm with slightly abraded unbroken crinoid stems. No quartz grains and other intra-clastics, coated grains and other reworked deposits have been found (Jin et al., 1996, pl. V.1, Fig. 3). The better preservation indicates that the brachiopods of the Waagenites Bed were unlikely to have been reworked from the underlying beds. Brachiopods from the Waagenites Bed tend to be smaller in size and contain more stalked forms. Largesized and thick-shelled forms such as Neospirifer kubeiensis Ting and Taeniothaerus etc., which are common in the underlying beds, do not extend upward into the Waagenites Bed. On the other hand, such smaller forms as Martinia, Waagenites and some terebratulids have not been found from the underlying beds. The species of the genus Stenoscisma are speci®cally dierent between the Waagenites Bed and the underlying Beds. The beds below the Caliche Bed are dominated by large-sized S. gigantea (Diener), whereas Stenoscisma selongensis n. sp. from the Waagenites
Bed is characterized by its small size. This size dierence is shown even for the same species. For example, Spiriferella rajah (Salter) from the Coral Bed is generally about 60 mm in width and only represented by abraded ventral valves, but specimens from the Waagenites Bed are more complete and less than 26 mm in width. All these dierences prove the brachiopods of the Waagenites Bed are not reworked from the underlying beds. However, these species belong to the same suite of the brachiopods from the Selong Group and thus cannot provide a precise age. Echinauris and Krotovia arcuata Waterhouse were ®rst reported in the Pija Shale±Siltstone Member of the Senja Formation in north-west Nepal, and assigned a Baisalian or late Djhul®an (Wuchiapingian) age by Waterhouse (1978). Cleiothyridina deroyssii (L'Eveille) is widespread in the Carboniferous and Permian in the Boreal and Gondwanan Realms. Stenoscisma timorense Hayasaka and Gan was recorded from the beds ranging from the early Guadalupian to the Changhsingian in Timor (Broili, 1916), Kashmir (Diener, 1899), Zhongba and Nyalam of Xizang (Chang and Ching, 1976) and probably the Salt Range, Pakistan (Grant, 1965). Bullarina rostrata Jin and Sun was recorded from the Goqoi Limestone of the Changhsingian and the Lasila Limestone of the Late Guadalupian (Jin and Sun, 1981). Spiriferella rajah (Salter) is one of the most common species in our collection and has a relatively long stratigraphic range. It has been reported in the lower Senja Formation of possibly Changhsingian age in Nepal (Waterhouse, 1966, 1978), Lamnimargus himalayensis Zone of probable Late Permian age (Muir-Wood and Oakley, 1941), and the Kuling Shale (Diener, 1903). Spiriferella nepalensis Legrand-Blain (=S. qubuensis Chang) is also a common element in the upper part of the Selong Group (Chang and Ching, 1976). It was recorded from the Upper Permian of Qubu, Xizang (Ting, 1962) and the Marginalosia kalikotei Zone of supposed Changhsingian age in Northwest Nepal (Waterhouse, 1966, 1978). The elements of a small brachiopod association, the Waagenites barusiensis±Paracrurithyris pigmaea Assemblage, is presumed to be from Unit 4 (Wang et al., 1989) which corresponds with the Waagenites Bed (Jin et al., 1996). This assemblage, however, has not been con®rmed by our repeated collection. In addition to Waagenites cf. barusiensis (Davidson), Paracrurithyris pigmaea Liao, Phricodothyris sp., Martinia sp. and Araxathyris sp., it also contains Hustedia (Z.Q. Chen, personal communication) and some terebratulids. All brachiopods of this association are rather small in size and mostly stalked. A close study of this collection shows that Paracrurithyris pigmaea is represented only by an incomplete ventral valve (Wang et al., 1989, pl. 1, Fig. 2). The character-
S. Shen, J. Yugan / Journal of Asian Earth Sciences 17 (1999) 547±559
istic outline and hinge line do indicate an ambocoeliid anity, but diculty arises in identifying its generic state.
4. A comparison with other similar faunas in the Peri± Gondwanan region The faunal succession of brachiopods from the Permian±Triassic boundary beds in the Salt Range of Pakistan (Grant, 1970) is closely comparable with that at Selong despite dierences in preservation. Those from both the White Sandstone in the upper part of the Chhidru Formation and the Dolomite Unit of the Kathwai Member, Mianwali Formation, are not only scarce, but also poorly preserved and patched in rare fossiliferous lenses. A close analysis shows that the brachiopods from the White Sandstone and other parts of the Chhidru Formation are ``much or all correlative with the Guadalupian'' (Grant, 1970). The faunal relation is comparable with that between the Coral Bed and rest of the Selong Xishan section. Brachiopods from the Kathwai Member, Mianwali Formation, include some elements of the underlying Chhidru Formation such as Linoproductus, Martinia and Spirigerella in additional to small brachiopods such as Crurithyris? extima Grant, Ombonia sp., Orthothetina sp., Lingula sp. and Spinomarginifera sp. Grant (1970, pp. 124, 148) precluded the possibility that these brachiopods were reworked from the underlying Chhidru Formation and considered that the fauna of the Dolomite Unit of the Kathwai Member is younger than that of the Chhidru Formation and contains latest Guadalupian, Wuchiapingian and Triassic elements. However, many more Tethyan forms invaded the Salt Range during the Lopingian. These include such characteristic brachiopods as Oldhamina, Enteletina, Spinomarginifera, Ombonia etc. The occurrence of the Tethyan foraminifer Colaniella (Nakazawa et al., 1975), and the Tethyan conodont Clarkina (Wardlaw and Pogue, 1995) prove that the Chhidru Formation ranges in age from latest Wuchiapingian to Changhsingian. This invasion probably re¯ected a rapid expansion of the tropical belt and an anti-tropical immigration of brachiopods into the Peri± Gondwanan region along the west coast of the Palaeotethys by the end of the Permian. It did not reach to the Selong area until the latest Changhsingian so that very few Tethyan forms appeared in the Waagenites Bed of the Selong Xishan section. In Kashmir, the brachiopod fauna from Unit E1 (2.6 m in thickness) of the Khunamuh Formation (Nakazawa et al., 1975, p. 38) is similar to that from the Waagenites Bed. This fauna comprises the brachiopods Linoproductus cf. lineatus (Waagen),
553
Lissochonetes morahensis (Waagen), Dielasma? sp., Waagenoconcha purdoni (Waagen), Athyris? sp., Schellwienella sp., Derbyia sp., Marginifera himalayensis Diener and Pustula sp.; bivalve Palaeoneilo sp., Etheripecten haydeni Nakazawa, E. cf. hiemalis (Salter), Cyrtorostrata a. lunwalensis (Reed), Nuculopsis sp., Claraia bioni Nakazawa as well as foraminifer Nodosinella longissima M-Maklay and Lunucammina sp. Some Claraia are preserved in an articulated state and considered to have been buried nearly in situ. Other fossils are more or less transported from elsewhere, such as shallower sea-bottom, before burial (Nakazawa et al., 1975, p. 38). The brachiopod elements such as Linoproductus, Lissochonetes, Waagenoconcha, and Marginifera himalayensis are long ranging and are not substantially dierent in composition from those in the underlying Division IV of the Zewan Formation. Judging from the evidence presented, the situation is somewhat analogous to that of the Selong Xishan section. All of the above-mentioned brachiopod faunas seem to share some general characteristics. For instance, they are all found within a horizon tens of centimeters to several meters in thickness near the Permian± Triassic sequence boundary. This horizon also contains brachiopods from the underlying beds coexisting with some small brachiopods. This situation seems to ®t the interpretation that the continental shelf in the Peri± Gondwanan region may have received very few sediments from greater Gondwanaland during the latest Permian. A ``starved'' deposit, which is very thin but represents a relatively long duration, may therefore be present. All fossils described in this paper are housed in the Nanjing Institute of Geology and Paleontology, Academia Sinica.
5. Systematics and descriptions Family Rugosochonetidae Muir-Wood, 1962 Genus Waagenites Paeckelmann, 1930 Waagenites sp. Fig. 4Ð5, 6 Remarks. The two ventral valves display smooth ears, costellate surface, shallow sulcus and short median septum that characterize the genus Waagenites. They are closer to the Waagenites specimens of South China rather than those of the Salt Range in their less convex pro®le and more costellate. These valves closely resemble W. sureshanensis Ching in costellation and outline, but the latter has two elevated parallel ridges in the vascular marking areas. They are also similar to
554
S. Shen, J. Yugan / Journal of Asian Earth Sciences 17 (1999) 547±559
Fig. 4. 1±3, Krotovia arcuata Waterhouse; 1±2, anterior and side views of a complete ventral valve, 2, 129342, Coral Bed; 3, anterior view of another ventral valve showing the inconspicuous elongated spine bases, 2, 129343, Waagenites Bed; 4, Spiriferella nepalensis Legrand-Blain; ventral valve, 2, 129344, Waagenites Bed; 5±6, Waagenites sp.; 5, ventral valve, 3, 129345; 6, ventral valve, 2, 129346, Waagenites Bed; 7±8, Neospirifer sp.; ventral and anterior views of an incomplete ventral valve, 1, 129347, Coral Bed; 9±10, Cleiothyridina deroyssii (L'Eveille); 9, ventral view, 1, 129348, Waagenites Bed; 10, dorsal view, 1, 129349, Waagenites Bed; 11±12, Spiriferellina sp.; ventral view, 2, 129350; ventral view, 2, 129351, Coral Bed; 13±15, Martinia spp.; 13, ventral valve, 2, 129352; 14, ventral valve, 1, 129353; 15, ventral valve, 1, 129354, Waagenites Bed; 16±20; Martinia attenuatelloides n. sp.; 16, ventral view of a ventral valve, 2, 129355, Waagenites Bed; 17±19, dorsal, ventral and side views, holotype, 2, 129356, Waagenites Bed; 20, ventral view, 2, 129357, Waagenites Bed; 21±24, Stenoscisma timorensis Hayasaka and Gan; ventral, dorsal, side, and anterior views, 2, 129358, Coral Bed.
S. Shen, J. Yugan / Journal of Asian Earth Sciences 17 (1999) 547±559
the species Waagenites barusiensis (Davidson) in size, conspicuous ears, shallow sulcus and subtrapezoid outline, but the amount of costellae are more than twenty ®ve. W. barusiensis (Davidson) usually has thirteen simple costellae on the ventral valve. Family Overtoniidae Muir-Wood and Cooper, 1960 Genus Krotovia Fredericks, 1928 Krotovia arcuata Waterhouse, 1978 Fig. 3Ð1±3 1978 Krotovia arcuata Waterhouse, pp. 52±54, pl. 6, ®gs. 2±10. 1983a Krotovia arcuata Waterhouse, pp. 122±123, pl. 2, ®gs. 9±18. Remarks. This species are represented by 15 specimens, including two complete specimens with conjoined shells. They are essentially identical in external characters, except for the slightly transverse outline, with those described by Waterhouse (1978). The external ornamentation is particularly characteristic and consists of elongated elevations and pustules with spines about 1 mm in diameter. Spines arise from the pustules and are mostly arranged in quincunx, but irregularly developed on trail. Pustules are elongated and form inconspicuous costellae numbering about 4 in 5 mm. Nevertheless, the internal features of our specimens are completely unknown. Family Stenoscismatidae Oehlert, 1887 Genus Stenoscisma Conrad, 1839 Stenoscisma timorense Hayasaka and Gan, 1940 Fig. 4Ð21±24, Fig. 3Ð1 1940 Camarophoria timorensis Hayasaka and Gan, p. 129, pl. 9, ®gs. 1±7. 1965 Camarophoria purdoni Davidson; Grant, p. 149, pl. 20, ®gs. 1±4. 1976 Stenoscisma timorensis Hayasaka and Gan; Chang and Ching, p. 193, pl. 11, ®gs. 20±27, text®g. 7. 1989 Stenoscisma timorense (Hayasaka and Gan); Archbold and Bird, p. 110, ®g. 5A±Z, AA±BB. Remarks. This species shows a wide range of variations in shell shape and costation. Its costae commonly originate from midvalve or only develop on the anterior part of the shell and range from 1 to 6 in number on the sulcus (Hayasaka and Gan, 1940, p. 19). The present specimen, which is complete with articulate valves, agrees in outline and costation with the type-specimens from the Permian of Timor. This species has been considered as the synonym of Stenoscisma purdoni (Davidson) (Ustritsky, 1963, p. 22). However, the shell size of S. purdoni is usually
555
smaller, and the costae are much stronger and begin nearly from the beak. Stenoscisma selongensis n. sp. Fig. 3Ð2±8 1996 Stenoscisma a. globulina (Phillips); Jin et al., pl. V. 2, ®gs. 1±8. Holotype. A conjoined shell (129360) from the Waagenites Bed. Other material. A complete conjoined shell (129359) from the Waagenites Bed. Etymology. Referring to Selong, the type locality of this species. Diagnosis. Stenoscisma with pentagonal outline, variable costation, distinct convexity and anterior tongue. Description. Small to medium in size for genus, pentagonal in outline, biconvex in pro®le; maximum width nearly at midvalve; lateral sides nearly parallel; anterior margin truncated. Ventral valve ¯atly convex in anterior and lateral pro®le; beak obtuse, suberect; interarea inconspicuous; sulcus wide, beginning near midvalve, deepening abruptly; bottom generally ¯at, extended into long truncated tongue dorsally; ¯anks gently convex; surface costate except for smooth umbonal region, 1±3 in sulcus, if 3, with the middle one much stronger than the outer 2, each ¯ank with 1±2 weak costae. Dorsal valve strongly convex in anterior pro®le, but ¯atly convex in lateral pro®le, ¯anks sharply inclined, fold highly elevated with a deep groove along midline; costae 2±4 on fold, but fairly uneven in size, the middle 2 much higher than the outer 2, each ¯ank with 1±2 weak costae. Ventral interior with a spondylium supported by a median septum; dorsal interior with a median septum. Other characters unknown. Measurements (in mm). Registration no.
Length
Width
Thickness
129359 129360 (holotype)
10.5 15.7
9.5 14.5
7.5 11.5
Comparison. This species was tentatively referred to Stenoscisma a. globulina (Phillips) by Jin et al. (1996). Although only two complete specimens are available, the authors consider that there are sucient evidence, such as the distinct convexity, outline, anterior tongue and peculiarly arranged costae, to dierentiate it from existing species of Stenoscisma. The new species diers from S. globulina (Phillips) in its pentagonal outline, relatively large size and costation.
556
S. Shen, J. Yugan / Journal of Asian Earth Sciences 17 (1999) 547±559
Family Martiniidae Waagen, 1883 Genus Martinia McCoy, 1844 Martinia spp. Fig. 4Ð13±15 Remarks. A complete specimen with conjoined valves and nine ventral valves show the characters of the genus Martinia but possibly belong to more than one species. The subcircular outline, even biconvex pro®le and well-developed sulcus of some specimens recall the typical features of Martinia orbicularis Gemmellaro that occur widely in the Permian of the Tethyan Realm.
Remarks. The peculiar outline of the ventral valve, lateral and anterior pro®le, strongly incurved umbo and well-de®ned sulcus of this species shows a general resemblance with the genus Attenuatella, especially the species A. piyasini Waterhouse from Thailand (Waterhouse, 1983b, p. 134, pl. 4, Figs. 13±18). Lack of the crural plates inside the dorsal valve and very short hinge line exclude the possibility of belonging to this genus. On the other hand, these Attenuatella-type external features distinguish it from other species of Martinia.
Family Athyrididae McCoy, 1844 Genus Cleiothyridina Buckman, 1906 Cleiothyridina deroyssii (L'Eveille, 1835) Fig. 4Ð9, 10
Martinia attenuatelloides n. sp. Fig. 4Ð16±20 Holotype. A complete conjoined shell (129356) from the Waagenites Bed. Other material. Four ventral valves. Among them two are registered (129355, 129357). Etymology. Attenuatella, a generic name of brachiopods; -oides (Greek), similar. Diagnosis. Small Martinia with Attenuatella-type outline and pro®le, but very short and curved hinge line. Description. Small in size, elongately triangular in outline, unevenly biconvex in pro®le; maximum width near anterior commissure; hinge-line fairly short; cardinal extremities inconspicuous. Surface smooth, no regular ornament visible. Ventral valve of adults strongly convex in lateral pro®le and younger individuals usually less convex; lateral slopes sharply inclined outwards, but median region ¯attening in anterior pro®le; beak perhaps pointed but usually not preserved; sulcus shallow but distinct, originating from beak, slightly widening but not deepening anteriorly. Dorsal valve much less convex than ventral valve in pro®le, elongate with strongly merging umbo in outline; lateral slopes gently inclined. Ventral interior without dental plates; dorsal interior without crural plates. Other features unknown. Measurements (in mm). Registration no.
Length
Width
Thickness
129355 129356 (holotype) 129357
11.5 9.0 7.3
9.5 7.4 6.1
5.6 5.0 3.5
1835 Spirifer deroyssii L'EveilleÂ, p. 39, pl. 2, ®gs. 18±20. 1862 Athyris royssii (L'EveilleÂ); Davidson, p. 27, pl. 1, ®g. 6. 1883 Athyris royssii (L'EveilleÂ); Waagen, p. 475, pl. 39, ®g. 10; pl. 40, ®gs. 6±12. 1897a Athyris royssii (L'EveilleÂ); Diener, p. 59, pl. 10, ®gs. 1±3, 6. 1897b Athyris royssii (L'EveilleÂ); Diener, p. 47, pl. 5, ®g. 5. 1931 Athyris royssii (L'EveilleÂ); Grabau, pp. 120± 121, pl. 6, ®gs. 7a±d, 8a±c. 1934 Athyris (Cleiothyridina ) royssii (L'EveilleÂ); Grabau, pp. 110±111, pl. 7, ®gs. 9±10. 1964 Cleiothyridina royssii (L'EveilleÂ); Wang et al. p. 622, pl. 122, ®gs. 8±13. 1976 Cleiothyridina royssii (L'EveilleÂ); Chang and Ching, pp. 195±196, pl. 15, ®g. 8. Remarks. This well de®ned species is characterized by its subpentagonal outline, medium size, inconspicuous sulcus and fold on the anterior part. The present specimens usually have a medium size, subpentagonal outline, well-formed concentric lamellae and the medially placed muscle marks, which all recall the species of C. deroyssii. Family Elythidae Fredericks, 1919 Genus Bullarina Jin and Sun, 1981 Bullarina cf. rostrata Jin and Sun, 1981 Fig. 3Ð13±16
1897a Reticularia lineatus Diener, p. 56, pl. 9, ®gs. 5±8.
S. Shen, J. Yugan / Journal of Asian Earth Sciences 17 (1999) 547±559
1981 Bullarina rostrata Jin and Sun, p. 154, pl. 9, ®gs. 17±20, 22±25. 1996 Cleiothyridina a. royssii (Phillips); Jin et al., pl. V. 2, ®gs. 13±16. Remarks. The present specimens resemble Reticularia lineatus Diener from the Chitichun Limestone in external characters, which was reassigned into this species by Jin and Sun (1981). They are slightly larger than the type specimens in size and probably represent a new species. The generic state of these specimens is still pending because the direction of spiralia and the spinal types are unknown. Family Spiriferellidae Waterhouse, 1966 Genus Spiriferella Tschernyschew, 1902 Spiriferella rajah (Salter, 1865) Fig. 3Ð17±20
1865 Spirifer rajah Salter in Salter and Blanford, pp. 59, 111. 1866 Spirifer rajah Salter; Davidson, p. 40, pl. 2, ®g. 4. 1903 Spirifer rajah Salter; Diener, pp. 105, 131, 186, pl. 4, ®gs. 3±5. 1941 Spirifer rajah Salter; Muir-Wood and Oakley, p. 36, pl. 2, ®gs. 2, 3, 9±11. 1966 Spirifer rajah Salter; Waterhouse, p. 48, pl. 11, ®g. 2; pl. 12, ®g. 2 (non pl. 1, ®g. 5; pl. 3, ®g. 2; pl. 7, ®gs. 1, 2, 4). 1976 Spirifer rajah Salter; Chang and Ching, p. 215, pl. 17, ®gs. 3±12. 1976 Spiriferella a. rajah (Salter); Legrand-Blain, p. 245, pl. 2, ®gs. 4, 6. Remarks. This is one of the most abundant species in the our collection but most specimens are ventral valves, with only one complete specimen from the Waagenites Bed. The species was originally de®ned by its large size, greatest width at hinge, strong fascicular ornamentation and groove on the dorsal fold, which has been used to contain the specimens departing from the types since then. The specimens from Selong reveal that the hinge line can range from just equal to slightly shorter than the greatest width. The folds of two dorsal valves have a coarse median costa. Spiriferella nepalensis Legrand-Blain, 1976 Fig. 4Ð4
1976 Spiriferella nepalensis Legrand-Blain, p. 242, pl. 1, ®gs. 7, 11. 1976 Spiriferella qubuensis Chang in Chang and Ching, p. 212, pl. 18, ®gs. 1±5.
557
Remarks. Four ventral valves are referable to the species de®ned with the specimens from the Nyi district of Nepal (Legrand-Blain, 1976). Similar specimens from Selong were assigned to the species Spiriferella qubuensis by Chang in Chang and Ching (1976), which is here considered as a junior synonym of S. nepalensis Legrand-Blain. Family Spiriferidae King, 1848 Genus Neospirifer Fredericks, 1919 Neospirifer sp. Fig. 4Ð7, 8 Remarks. An incomplete ventral valve bears the strongly convex pro®le and strong fasciculate costation of Neospirifer. The posterior part of the valve shows that the hinge line is fairly wide and perhaps equals to the maximum width of the shell. The costation of this specimen closely resembles that of Neospirifer moosakhaiensis (Davidson) and N. kubeiensis Ting.
Family Spiriferinidae Davidson, 1884 Genus Spiriferellina Fredericks, 1919 Spiriferellina sp. Fig. 4Ð11, 12
Remarks. Spiriferellina is characterized by its typically small size, relatively few plications with fastigum and many low pustules. Our two ventral valves have a wide sulcus and 2±3 plications on each ¯ank and numerous pustules on shell surface that identify them as a species of Spiriferellina. The transverse outline, medium size and the absence of reverse plication in the sulcus suggest a close resemblance to those of Spiriferina cristata var. octoplicata ®gured by Diener (1897a) and Spiriferina octoplicata var. fastigata by Diener (1903). Family Dielasmatidae Schuchert, 1913 Genus Girtyella Weller, 1911 Girtyella? sp. Fig. 3Ð9±12 Remarks. A complete specimen with an etched beak reveals a pair of well developed dental plates in the ventral valve and a median septum in the dorsal valve. It has an elongate and equally moderately biconvex pro®le. The sulcus and fold are completely absent and the anterior commissure is rectimarginate. The surface is entirely smooth, but the loop is totally unknown. The foregoing mentioned characters suggest that this
558
S. Shen, J. Yugan / Journal of Asian Earth Sciences 17 (1999) 547±559
specimen is probably a species of Girtyella, most possible G. nyalamensis Ching.
Acknowledgements We thank Dr G.R. Shi of School of Ecology and Environment, Deakin University, for his critical reading of this paper and discussions concerning the Selong fauna. This paper is supported by Chinese Academy of Science (Grant K2951-B1-409) and the National Nature Science Foundation of China (Grant 49672092). References Archbold, N.W., Bird, P.R., 1989. Permian Brachiopoda from near Kasliu Village, West Timor. Alcheringa 13 (12), 103±123. Broili, F., 1916. Die Permischen Brachiopoden von Timor. In: Wanner, J. (Ed.), Palaeontologie von Timor Stuttgart, pp. 1±104. Buckman, S.S., 1906. Brachiopod nomenclature: Epithyris, Hypothyris, Cleiothyris Phillips, 1841. Annals and Magazine of Natural History, Ser. 7, 18, 321±327. Chang (Zhang) Shouxin, Ching (Jin) Yugan, 1976. Upper Paleozoic Brachiopoda from the Mount Jolmolangma region. In: A Report of Scienti®c Expedition in the Mount Jolmolangma Region (1966±1968), Paleontology, fasc. 2 (Edited by Chinese Academy of Science), Science Press, Beijing, pp. 159±242 (in Chinese). Conrad, T.A. 1839 Second annual report on the Palaeontological Department of the Survey, New York Geological Survey, Annual Report 3, 57±66. Davidson, T., 1862. Notes on the Carboniferous Brachiopoda collected in India by A. Fleming and W. Purdon. Quarterly Journal of the Geological Society of London 18, 25±35. Davidson, T., 1866. On the Carboniferous rocks of the valley of Kashmere. With notes on the Brachiopoda collected by Capt. Godwin-Austin in Thibet and Kashmere. Quarterly Journal of the Geological Society of London 22, 29±45. Diener, C., 1897a. The Permo-Carboniferous fauna of Chitichun No. 1. Palaeontologica Indica, Ser. 15, 1 (3), 1±105. Diener, C., 1897b. The Permian fossils of the Productus Shales of Kumaon and Gurhwal. Palaeontologica Indica, Ser. 15, 1 (4), 1± 54. Diener, C., 1899. Anthracolithic fossils of Kashmir and Spiti. Palaeontologica Indica, Ser. 15, 1 (2), 1±95. Diener, C., 1903. Permian fossils of the central Himalayas. Palaeontologia Indica, Ser. 15, 1 (5), 1±204. Fredericks, G.N., 1928. Materialy dlya klassi®katsii roda Productus Sow (contribution to the classi®cation of the genus Productus ). Izvestiia Geologicheskogo Komiteta 46 (7), 773±792 (in Russian). Grabau, A.W., 1931. The Permian of Mongolia. A report on the Permian fauna of the Jisu Honguer Limestone of Mongolia and its relations to the Permian of other parts of the world. Natural History of Central Asia 4, 1±665. Grabau, A.W., 1934. Early Permian fossils of China, Part I: Early Permian brachiopods, pelecypods, and gastropods of Kueichow. Palaeontologia Sinica, Ser. B, 8 (3), 1±168. Grant, R.E., 1965. The brachiopod Superfamily Stenoscismatacea. Smithsonian Miscellaneous Collections 148 (2), 1±192. Grant, R.E., 1970. Brachiopods from Permian±Triassic boundary
beds and age of Chhidru Formation, West Pakistan. In: Kummel, B., Teichert, C. (Eds.), Stratigraphic Boundary Problems: Permian and Triassic of West Pakistan. University of Kansas, Department of Geology, Special Publication 4. The University Press of Kansas, Lawrence/Manhattan/Wichita/London, pp. 117± 151. Hayasaka, I., Gan, S., 1940. A note on Camarophoria `purdoni' from the Permian of Timor. Journal of the Geological Society of Japan 47 (558), 127±132. Jin Yugan, 1985. Permian Brachiopoda and paleogeography of the Qinghai±Xizang (Tibet) Plateau. Palaeontologia Cathayana 2, 19±71. Jin Yugan, Shen Shuzhong, Zhu Zhili, Mei Shilong, Wang Wei, 1996. The Selong Xishan section, candidate of the global stratotype section and point of the Permian±Triassic boundary. In: Yin Hongfu (Ed.), The Palaeozoic±Mesozoic Boundary Candidates of the Global Stratotype Section and Point of the Permian±Triassic Boundary. China University of Geosciences Press, Wuhan, pp. 127±137. Jin Yugan, Sun Dongli, 1981. Paleozoic brachiopods from Xizang (Tibet). In: Paleontlogy of Xizang, Book III, The Series of the Sscienti®c Expedition to the Qinghai±Xizang Plateau (Edited by Nanjing Institute of Geology and Palaeontology), Science Press, Beijing (in Chinese), pp. 127±171. Legrand-Blain, M., 1976. Repartition du groupe de Spiriferella rajah (Salter, 1865) et description de Spiriferella nepalensis, nov. sp., appartenant a ce groupe. Centre National de la Recherche Scienti®que, Colloques Internationaux, France 268 (2), 237±250. L'Eveille, C., 1835. Apercu geologique de quelques localites tres riches en coquilles sur les frontieres de France et de Belgique. Societe geologique de France, Memoires, Ser. 1, 2, 29±40. Liao Zhouting, 1980. Brachiopod assemblages from the Upper Permian and Permian±Triassic boundary beds, South China. Canadian Journal of Earth Science 17 (2), 289±295. McCoy, F., 1844. In: A Synopsis of the Characters of the Carboniferous Limestone Fossils of Ireland. Dublin, London. Muir-Wood, H.M., Oakley, K.P., 1941. Upper Paleozoic faunas of North Sikkim. Palaeontologica Indica, new series 31 (1), 1±91. Muir-Wood, H.M., 1962. On the Morphology and Classi®cation of the Brachiopod Suborder Chonetoidea. British Museum, London, pp. 1±132. Muir-Wood, H.M., Cooper, G.A., 1960. Morphology, classi®cation and life habits of the Productoidea (Brachiopoda). Geological Society of America, Memoir 81, 1±447. Nakazawa, K., Kapoor, H.M., Ishii, K., Bando, Y., Okimura, Y., Tokuoka, T., 1975. The Upper Permian and Lower Triassic in Kashmir, India. Memoirs of the Faculty of Science, Kyoto University, Geology and Mineralogy 42 (1), 1±106. Oehlert, D.P., 1887. Brachiopodes. In: Fischer, P. (Ed.), Manuel de Conchyliologie et de Paleontologie Conchyliologue, ou Histoire Naturelle des Mollusques Vivants et Fossiles. F. Savy, Paris, pp. 1189±1334. Orchard, M.J., Nassichuk, W.W., Rui Lin, 1994. Conodonts from the lower Griesbachian Otoceras latilobatum Bed of Selong, Tibet and the position of the Permian±Triassic boundary. In: Pangea: Global Environments and Resources, Memoirs of the Canadian Society of Petroleum Geologists, vol. 17, pp. 823±843. Paeckelmann, W., 1930. Die fauna des deutschen Unterkarbons 1. Teil. Die brachiopoden, 1. Teil: Die orthiden, strophomeniden und choneten des mittleren und oberen Unterkarbons. Koenigliche-Preussiche geologische Landesanstalt, Abhandlungen 122, 143±326. Rao Rongbiao, Zhang Zhenggui, 1985. A discovery of PermoTriassic transitional fauna in the Qomolangma Feng area: its implications for the Permo-Triassic boundary. Xizang Geology 1, 19±31 (in Chinese). Salter, J.W., Blanford, F.G.S., 1865. Paleontology of Niti in the
S. Shen, J. Yugan / Journal of Asian Earth Sciences 17 (1999) 547±559 Northern Himalaya I, Description and Figures of the Palaeozoic and Secondary Fossils. O.T. Cutter, Military Orphan Press, Calcutta, pp. 1±112. Shi, G.R., Shen Shuzhong, 1997. A Late Permian brachiopod fauna from Selong, southern Xizang (Tibet), China. Proceedings of the Royal Society of Victoria 109 (1), 37±56. Ting (Ding) Peizhen, 1962. Several Late Permian brachiopod fossils from Tibet. Acta Palaeontologica Sinica 10 (4), 451±464 (in Chinese). Tschernyschew, T.N., 1902. Verkhnekamennougol'nye brakhiopody Urala i Timana. (Upper Carboniferous brachiopods of the Urals and the Timan). Trudy Geologicheskogo Komiteta 16 (2), 17±49 (in Russian). Ustritsky, V.I., 1963. Permian stratigraphy and faunas of western Gansu. In: Memoir of the Geological Institute, Minister of Geology and Mineralogy, Ser. B, Stratigraphy and Palaeontology, vol. 5. China Industry Publishing House, Beijing, pp. 1±49 (in Chinese). Waagen, W., 1883. Productus Limestone fossils. Palaeontologica Indica, Ser. 13 1 (pt. 4, fasc. 2), 391±546. Wang Wei, Shen Shuzhong, Zhu Zhili, 1997. Carbon isotope characters of the Permian Triassic boundary section at Selong, Xizang (Tibet), China and their signi®cance. Chinese Science Bulletin 4, 406±408 (in Chinese). Wang Yu, Jin Yugan, Fang Dawei, 1964. Brachiopod fossils of China 1 (2), 1±777 Science Press, Beijing (in Chinese). Wang Yigang, Chen Chuzhen, Rui Lin, Wang Zhihao, Liao Zhouting, He Jinwen, 1989. A potential global stratotype of Permian±Triassic boundary. In: Developments in Geoscience, Chinese Academy of Sciences, Contribution to 28th International Geological Congress 1989, Washington, D.C. USA. Science Press, Beijing, pp. 221±229. Wang Zhihao, Chen Chuzhen, Liao Zhouting, 1993. Some queries about the paper ``Age of the Selong Group in Xishan, Selong of Xizang (Tibet) and the Permian±Triassic boundary''. Journal of Stratigraphy 17 (3), 223, 237±239 (in Chinese).
559
Wang Zhihao, Wang Yigang, 1995. Permian±Lower Triassic conodonts from Selong Xishan of Nyalam, S. Tibet, China. Acta Micropalaeontologica Sinica 12 (4), 333±348. Wardlaw, B.R., Pogue, K.R., 1995. The Permian of Pakistan. In: Scholle, P.A., Peryt, T.M., Ulmer-Scholle, D.S. (Eds.), The Permian of Northern Pangea 2, Sedimentary Basins and Economic Resources. Springer-Verlag, Berlin, pp. 215±224. Waterhouse, J.B., 1966. Lower Carboniferous and Upper Permian brachiopods from Nepal. Geologische Bundesanstalt, Jahrbuch 12, 5±99. Waterhouse, J.B., 1978. Permian Brachiopoda and Mollusca from north-west Nepal. Palaeontographica Abt. A 160, 1±175. Waterhouse, J.B., 1983a. Permian brachiopods from Pija Member, Senja Formation in Manang district of Nepal, with new brachiopod genera and species from other regions. Indian Geologists' Association, Bulletin 16 (2), 111±151. Waterhouse, J.B., 1983b. A Late Permian Lyttoniid fauna from northwest Thailand. University of Queensland, Department of Geology, Papers 10 (3), 111±153. Weller, S., 1911. Genera of Mississippian loop-bearing Brachiopoda. Journal of Geology 19 (5), 439±448. Xia Fengsheng, Zhang Binggao, 1992. Age of the Selong Group in Xishan, Selong of Xizang (Tibet) and the Permian-Triassic boundary. Journal of Stratigraphy 16 (4), 256±363 (in Chinese). Yin Jixiang, Guo Shizeng, 1979. Stratigraphy of the Mt. Jolmolangma and its northern slope, with a discussion about correlation of Sinian±Cambrian and Carboniferous-Permian with adjacent areas. In: A Report of the Scienti®c Expedition in the Mt. Jolmolangma Region (1975) (Geology) (Edited by Xizang expedition team of Chinese Academy of Science), Science Press, Beijing, pp. 1±71 (in Chinese). Zhang Binggao, 1974. The Permian System. In: A Report of Scienti®c Expedition in the Mt. Jolmolangma Region (Geology), 1966±1968, (Edited by Xizang expedition team of Chinese Academy of Science), Science Press, Beijing, pp. 66±80 (in Chinese).