四川华蓥山地区长兴期腕足动物

CHANGXINGIAN BRACHIOPODS FROM HUAYINGSHAN, SICHUAN

四川华蓥山地区二叠纪长兴期地层中共采获腕足动物90种44属,其中10新种,1新亚种.根据这些丰富的化石材料,文章分析了该区长兴期腕足动物群的性质面貌,并与国内同期灰岩相腕足动物群进行了对比.同时对本区长兴期腕足动物的古生态进行了初步探讨,识别出两个腕足动物群落,即Acosarina-Araxathyis群落和Pertgeyerella群落.

Here studied are the features of paleoecology and braehiopod fauna from the Changxingian of Huayingshan, Sichuan, with a correlation of limestone facies Changxingian brachiopod faunas between Huayingshan and other regions. The brachiopods under study were obtained from the Changxingian limestone at Liziya, Mulongdong and Daijiagou, consisting of 44 genera and 90 species (including 10 new species and 2 new subspecies). Description of new species and subspecies Enteletes transversus sp. nov. (Pl. I, fig. 3) Description Shell medium-sized, very wide (30mm), 21.8mm in length. Fold and sulcus marked; costae numbering 4 on either flank; costellae covering entire valves. Remarks This specimen resembles E. tschernyschewi Diener (Wang Yu, 1964, Pl. 19, fig. 20) in the external features, but differs in the width to length ratio which is 1.45 in the former and 1.22 in the latter. In addition, the hinge-line is short, with a length equal to 1/3 of the shell width in the former, but it is equal to 1/2 of the shell width in the latter. Horizon and Locality Changxing Formation; Mulongdong. Neochonetes mirabilis sp. nov. (Pl. I, figs. 1, 2) Description Shell small, Ventral valve very convex; ears lower and flattened; beak partly convex; costellae covering ventral valve, numbering 40 in anterior part; sulcus scarcely marked. Remarks This new species differs from N. convexa Liao in having a small shell and a very convex ventral valve, with sulcus scarcelv marked. Horizon and Locality Changxing Formation; Liziya and Mulongdong. Haydenella nasuta sp. nov. (Pl. I, figs. 4, 5) Description Shell medium-sized, elongate-oval in outline; ears small and flattened; an- terior part convexly nosedrop-shaped, occupying nearly 1/4 of shell length. Remarks This new species resembles H. yonganensis in the shell shape, but in the latter, the shell is large and subtriangular in outline, and the anterior part is less convexly nosedrop-shaped. Horizon and Locality Changxing Formation; Mulongdong and Daijiagou. Oldhamina ovata sp. nov. (Pl. I. figs. 9, 10) Remarks This new species in characterized by its very small shell, oval outline, umbonal angle (about 70°-80°), and less (7-8) lateral septa. Evidently, it differs from other species of the genus. Horizon and Locality Changxing Formation; Mulongdong. Neowellerella multiplicata sp. nov. (Pl. I. figs. 6, 11) Description Shell small, subpentagonal in outline, with a smaller convexity; costae numbering 4, 2 and 3 on either flank, sulcus, and fold respectively. Remarks This new species differs from N. pseudoutah (Huang in having 4 plications on either flank, instead of 2 in the Iatter. It is similar to N. triplicata Liao in the shell shape, but the Iatter has 3 plications on sulcus and 4 on folds. Horizon and Locality Changxing Formation; Liziya. Terebratuloidea triquetra sp. nov. (Pl, I. fig. 8) Description Shell small and rounded-trigonal in outline, both sides forming an acute angle in shape and extending abruptly. Plications numbering 4, 5 and 3 on sulcus, fold, and either flank respectively. Remarks The new species is similar to T. depressa Waagen, but the latter has more plications on sulcus and folds with lateral commissure in the form of a projecting acute angle. Horizon and Locality Changxing Formation; Mulongdong. Terebratuloidea minor aculeata subsp. nov. (Pl. I. fig. 7) Description Ventral beak acute and slightly incurved; brachial beak strongly incurved; brachial lateral commissure acute angle-shaped. Plications numbering 2, 3 and 3-4 on sulcus, fold, each flank respectively. Remarks The new subspecies resembles T. minor Waagen in having an acute and slightly incurved ventral beak, and an acute angle-shaped brachial lateral commissure. It resembles T. minor alpha in the shape of shell, but it differs in the straight lateral commis- sure, and the plieations numbering 2 on sulcus, not thickening toward anterior part, but dis-appearing anteriorly. Horizon and Locality Same as the preceding species. Uninunellina multicostata sp. nov. (Pl. II, figs. 1, 2) Description Shell medium to large, elliptical in outline. Brachial convexity much higher than ventral; costae usually exceeding 50 in number (9-10 on sulcus, and 20 on either flank). Remarks The new species is similar to U. timorensts(Beyrich), but differs in the larger size, the higher convexity and the more numerous transverse costae on sulcus. Horizon and Locality Same as the preceding species. Martinia latilinguigormis sp. nov. (Pl. II. fig, 3) Description Shell medium; outline subcircular; ventral beak erect, slightly incurved; sulcus absent, but anterior margin turning tongue-like toward brachial valve, occupying about 1/2 of shell width. Ventral valve with sulcus. Brachial fold not apparent, but brachial valve with a higher convexity. Remarks The new species differs from M. sereiplana Waagen in the relatively large size, the relatively higher convexity, the erect and slightly incurved ventral beak and the wider tongue. The new species is similar to M. orbicularis Liao in the shape of shell, but in the latter, the tongue is wider and flatter, the interspace of each beak is wider, and the brachial valve is strongly convex. Horizon and Locality Changxing Formation, Liziya. Dielasma angustaeformis sp. nov. (Pl. II. figs. 5,6) Description Shell medium, rhomboid, with the widest part nearly at midvalve, biconvex; ventral convexity slightly higher; ventral sulcus occurring in anterior part, slightly tongue-shaped. Brachial valve with low and wide fold. Anterior commissure sulcate. Remarks This new species is similar to D. subtriagulatumi, but, the latter has subtriangular outline, strongly incurved ventral beak, bigger umbonal angle and bigger shell. Horizon and Locality Same as the preceding species. Qinglongia gigantea sp. nov. (Pl. II. fig. 7) Description Shell large, spindle-shaped in outline, biconvex; brachial convexity much higher than ventral; lateral commissures nearly parallel. Fold of brachial valve with ventral furrow. Brachial interior with divergent crural plates of about 14mm in length. Surface with concentric lings. Anterior commissure rectimarginate. Remarks This new species differs from other species of the genus Qinglongia Liao in having much higher brachial convexity than ventral, nearly parallel lateral commissures and a large shell. Horizon and Locality Same as the preceding species.