樺太産Desmostylus mirabilisの骨格 : IV. 中手骨

概要

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The metacarpus of Desmostylus mirabilis NAGAO from Keton is described, and critical review is discussed about the morphology of the related specimens. The specimen in question has been misregarded as the left first rib by NAGAO (1941) and SHIKAMA (1966), but in this article, it is referred to the left fifth metacarpus to be compared with that of Paleoparadoxia tabatai. The characteristics of the fifth metacarpus are as follows: long and thin in general, proximal articular surface triangular with lateral angle, lateral margin recurved, the body depressed fore-and-aft in the middle, but thick in distal in cross section. The fifth metacarpus fairly longer and thinner than the fifth metatarsus (the longest among metatarsi), and longer than any proximal phalanges. Compared with the Izumi specimen of Paleoparadoxia tabatai, followings are distinguishable: stout relating to the length, proximal lateral projection feeble, dorsal surface in proximal half more inclined laterally, lateral margin less recurved, distal part less flat.
地学団体研究会の論文
1981-09-25