樺太産Desmostylus mirabilisの骨格 : III. 肋骨・肩甲骨・寛骨

概要

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The ribs, scapula and os coxae of Desmostylus mirabilis NAGAO from Keton are described. Desmostylus appears to have 13 pairs of ribs (INUZUKA, 1980a), of which are characteristic the following features: The eighth rib the longest; the seventh the largest in curvature; costal head long medio-laterally in the anterior ones, but the largest and long foreand-aft in the middle ones; neck longest in the eighth or ninth; costal tubercle present until the twelfth; dorsal muscle area well developed in the fifth to the ninth, inclined more stronger in the more anterior ones; shaft not fiat in cross section except for the anterior ones; thorax nearly circular in cross section. Scapula long, triangular in outline; facies serrata not so rough; posterior border thick; scapular spine located at a little forward to the middle, being relatively high, not so inclined; acromion terminated at a level higher than that of the glenoid cavity; tuber spinae well developed; glenoid cavity relatively large. As to the os coxae the following characteristics are recognized: Wing of ilium not so expanded laterally; ischium well developed, making a wide ischiatic plate; pubis projected downward to horizontally and slightly backward; obturator foramen faced rather laterally than ventrally because of wide symphysis; acetabulum located at the mid-length, facing out and backward; pelvic symphysis long; sacro-iliac angle large, being about 150°.
地学団体研究会の論文
1981-01-25