【摘要】 <正> 一前言青海省中部玛多县黑海公社闹仓坚沟,发育一套自 Olenikian 期至 Anisian 期的地层,地层分区属于昆仑区布尔汉布达山南坡分区.这套地层岩性主要为灰、灰绿色中厚层粉砂岩及硬砂质长石砂岩,上部夹薄层钙质粉砂岩及薄层灰岩,厚约2,600米,腕足动物化石主要产于上部 Anisian 阶的薄层灰岩,尤以第46层最为丰富.本文所描述的腕足动物化石主要产自此层,共计17属、24种,其中新属7、新种16.与更多还原

【Abstract】 The braehiopod fossils described in this paper were collected from the Naocanjiekou Formation (Middle Triassic) at Naocanjiekou of Madoi County, central Qinghai. They contain 17 genera and 24 species (including 7 new genera and 16 new species) belonging to Rhynchonellida, Spiriferida, Athyrida and Terebratulida. With the exception of some special elements, the brachiopod assemblage may be compared with those from the Qingyan Formation (Guizhou), the Tienjun Formation (Mt. Qilian) and the lower part of Muschelkalk (Southern Tibet, Nepal and Spiti of India). The systematic classification of these brachiopods is also briefly discussed in this paper. Description of new genera Genus Paranudirostralina Sun et Ye gen. nov. Genotype: Paranudirostralina bifurcata Sun et Ye, gen. et sp. nov. Shell small to medium in size, roundly triangular to roundly pentagonal, equally biconvex, with the greatest convexity at the posterior part. Anterior part marked by ventral sulcus and dorsal fold; anterior commissure uniplicate. Beak small, slightly incurved; pedicle opening small, mesothyrid or permesothyrid; delthyrium open; pedicl collar present or absent. Shell smooth posteriorly, but marked by subangular plicae at the anterior half; plicae increasing by bifurcation or intercalation, with 4-5 on fold, 3-4 in sulcus and 3-4 on lateral sides. Dental plates long, extending to the hinge band, inclined toward symmetry plane; hinge plates flat, merged with socket ridge; median septum high and stout; septalium deep; crural base triangular; crura strongly curved ventrally. Comparison: This genus is very similar to Nudirostralina Yang et Xu, but differs from the latter in the open delthyrium, the depressed anterior shell, the smooth posterior and the anterior plicae which increase by bifurcation or intercalation. Geological, and Geographical distribution: Middle Triassic, Anisic; Qinghai, China. Genus Uniplicatorhynchia Sun et Ye, gen. nov. Genotype: Uniplicatorhynchia trigona Sun et Ye, gen. et sp. nov. Shell medium in size, roundly triangular to roundly pentagonal; biconvex in lateral profile. Ventral sulcus and dorsal fold wellmarked; anterior commissure uniplicate; shell smooth, ornamented with concentric lines, but without plication. Ventral beak small, incurved; pedical foramen small, permesothyrid; delthyrium open; pedical collar absent. Dental plates long and parallel, extending to the hinge-band; cardinal process absent; hinge plates flat, differentiated from low socket ridges; hinge sockets wide and flat; septalium V-shaped; median septum high and stout, nearly half the length of dorsal shell. Crura depressed in primitive part, triangular in middle part and plate-form at the end. Discussion: This new genus, as one of the Triassic rhynchonellids, closely resembles athyrids in the outline but differs markedly in the internal structures. It is also similar in outline to some species of Austriellula Strand 1928, but the latter is an indeterminate and wide genus in definition. Ager (1960, 1965, 1972) pointed out that the type species A. dilatata (Suess) from the upper Triassic of Alps, has a smooth and wide shell. He also stated that in the section of the type species no diverged dental plates were seen and that some species have short crura and dorsal median septum. A. Z. Dagis (1974) described the genus Austriellula as follows: "shell smooth; anterior commissure rectimarginate or sulcate; dental plates recessive or merged with lateral wall; delthyrium open; pedical collar absent; hinge plates narrow; crura short and flat, arc-shaped." Based on the characters just mentioned above, they both assigned this genus to the Norellidae. This new genus resembles the type species of Austriellula in the external features, but differs from the latter in the dental plates, the well-developed septalium and the dorsal medium septum. Austriellula fuchsi described by Siblik (1975) from Dolpo, northwestern Nepal, bears well-developed dental plates and dorsal median septum. In respect of these characters it may be assigned to this genus. Besides, some Cenozoic Basiliolids, namely, Basiliola Dall 1908, Eohemithyris Hartlein et Grant 1944, Streptaria Cooper 1955, Aphelesia Cooper 1959 and Aetheia Thamann 1945 also are similar in outline to the present genus, but they differ from the latter in having conjunct deltidial plates, a developed pedical collar and a wide prefalcifer crura but no septalium. Geological and Geographical distribution: Middle Triassic; Qinghai, China. Genus Nucleusorhynchia Sun et Ye, gen nov. Genotype: Nucleusorhyncchia typica Sun et Ye, gen. et sp. nov. Shell small, walnut-shaped, gently biconvex. Beak short and small. Foramen permesothyrid; deltidial plates discrete; beak ridge round; palintrope narrow and small. Sulcus and fold absent; anterior commissure rectimarginate; shell surface smooth, only marked by fine growth lines. Dental plates nearly parallel; cardinal process low; septalium wide and shallow; median septum thick and low. Crura roundly thick in the primitive part, inclined inward like plate in the anterior part and slightly curved ventrally. Discussion: The new genus belongs to a small, smooth and rectimarginate Triassic rhychonellid. A. C. Bittner (1980) described some Triassic forms from the Alps, whichbear the same external characters as the new genus, but their internal structures are unknown, and therefore the assignment of these forms are very difficult. Geological and Geographical distribution: Middle Triassic, Qinghai, China; Middle-Upper Triassic, Europe. Genus Qinghaispiriferina Sun et Ye, gen nov. Genotype: Qinghaispiriferina abovata Sun et Ye, gen. et sp. nov. Shell medium-sized, sub-circular, unequally convex; ventral valve more convex. Beak short and incurved; cardinal area low and inclined; delthyrium open; hinge line short, equal to 1/2-1/3 the shell width; cardinal extremities obtusely rounded. Ventral sulcus and dorsal fold more or less developed; shell surface smooth; plicatien rounded and low in the anterior part of the flanks; concentric lamellae well-developed, intersected with plication to form a beautiful reticulation. Dental plates discrete; ventral median septum high and stout, sometimes touching the delthyrial ridges; cardinal process low; crura long; jugum indistinct. Discussion: This new genus may be distinguished from other Triassic spiriferids by (1) shell smooth posteriorly, (2)placations on flanks low and gentle and (3) cardinal extremities obtusely rounded (or not auriculate). Some early Jurassic species (for example, S. tumida (Buch)) bear similar characters to this genus, and therefore can be assigned to the new genus. Geological and Geographical distribution: Triassic to Early Jurassic (?) Europe and Asia. Superfamily Mentzelacea Sun et Ye, superfam, nov. Shell punctate; ventral median septum connected with dental plates to form a spondylium; dorso-cardinal process low, dorsal median septum present or absent; hinge plates discrete or united, loop supports more or less developed; shell surface smooth by plication. Geological and Geographical distribution: Triassic-Jurassic, all parts of the world. Family Mentzelidae Sun et Ye, fam. nov. Ventral median septum connected with dental plates at the base or the middle part; hinge plates discrete; dorsal median septum and loop supports absent. Geological and Geographical distribu tion: Triassic: all parts of the world. Genus Madoia Sun et Ye, gen nov. Genotype: Madoia rostrata Sun et Ye, gen. et sp. nov. Shell small to medium-sized, oval to roundly pentagonal; equally biconvex: hinge line short and incurred. Ventral beak short, incurved, covering low cardinal area and open delthyrium; dorsal beak convex and incurred. Shell surface smooth, with imbricate concentric lamellae; shallow sulcus and depressed fold seen only in the anterior part. Dental plates absent; ventral median septum high and thick, connecting the low spondylium near the beak; cardinal process comb-like; binge plates discrete; septalial plates absent; jugum unknown. Comparison: This new genus resembles Mentzelia Quensted 1871 in some respects, but the latter is distinguished from the former by the transverse shell, the developed cardinal area, the unequally convex valves and the lack of distinct imbricate concentric lamellae. Geological and Geographical distribution: Middle Triassic; Qinghai, China. Genus Tosuhuthyris Sun et Ye, gen.nov. Genotype: Tosuhuthyris sulcus Sun et Ye, gen. et sp. nov. Shell small cireularly rhomboidal planoconvex to unequally biconvex. Ventral beak short and incurred; pedieal opennig large.mesothyrid; beak ridge distinct; planarea small; sulcus wide and shallow in the anterior part of the dorsal valve; ventral valve swelling like roof-ridge along the middle line. Pedical collar present, dental plates discrete and not extending to the hinge band; hinge plates merged with inner socket ridges; outer hinge plates narrow; septalium V-shaped, formed by bifurcation of the median septum; median septum low and thick, nearly 1/3-1/2 the length of the dorsal valve; crural base triangular, rising from ventral side of the hinge plates; crural process high; loop short, with only descending branches, occupying 1/3-1/2 the length of the dorsal valve. Discussion: The new genus, as a terebratullids, is characterized by having a short loop resembling the crura of rhynchonellids, which have no high crural processes on the crura. Based on his study of loops of terebratullids, A. Z. Dagis (1974) proposed 10 forms of loops: (1) Dielasma form, (2) Terebratula form, (3) Aulacothyroides form, (4) Angustothyris form, (5) Zeilleria form, (6) Dallina tellina form, (9) Gefonia form and (10) form, (7) Aulacothyropsis form, (8) Terebra-Cryptacanthia form. This genus is a representative of terebratullids with no complete loop. Deslongchamp (1884) and Steinich (1965), who studied Gryphus and Chatwinothyris respectively, pointed out that in the early evolutionary stage, this loop has only short and parallel descending branches, not touching at the end, and that the connecting band is developed in the late stage. Sanqiaothyris from the Late Triassic of Guizhou also has an incomplete loop. This genus is simlar in outline to the Triassic terebratullids, such as Sulcatinella, Sulcatothyris, Cruratula, Aulacpothyris, Andyrella, etc., but differs from them in having only descending loop branches. Geological and Geographical distribution: Middle Triassic; Qinghai, China. Genus Pirithyris Sun et Ye, gen. nov. Genotype: Pirithyris pius Sun et Ye, gen. et sp. nov. Shell small, pear-shaped, equally biconvex. Beak prominent and slightly curved: pedical foramen circular, large epithyrid; beak ridge rounded; palintrope small; delthyrium covered by discrete deltidium. Fold and sulcus poorly developed, only shallow and wide dorsal sulcus appearing in the anterior part; anterior commissure sulcate; pedical collar present. Dental plates long, slightly inclined outward; hinge plates merged with inner socket ridge; septalium well-developed, wide V-shaped; median septum high and stout, nearly extending to the anterior margin; crural base triangular; crural processes unconspicuous; loop short, consisting of only plate-like descending branches. Comparison: This genus resembles Tosuhuthyris Sun et Ye in the internal structure, but differs from the latter in the long and high median septum, the unconspicuous crural processes, the stout and prominent beak and the epithyrid pedical foramen. This genus is very similar to Praecubanothyris Dagis in the external features, but in the latter, the dental plates are absent and the loop has a connecting band. Geological and Geographical distribution: Middle Triassic Anisic; Qinghai, China.更多还原