秋田県田代産デスモスチルスの歯について

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Four Desmostylus teeth here described were procured by the senior writer in 1949 from the middle Miocene bed at Karuisawa, Tashiro, Ugo-machi, Akita Prefecture. They were donated by the founders Saito and Shida to be Stored in the Mining Museum, Akita University. Specimen a (LM 2), subquadrate in occlusal view, 64mm in maximum length, 42mm in fore width and 30mm in aft width, consists of eight columns arranged in three transverse rows (3, 2, 2+1); median three columns are largest and subpentagonal; lingual side is higher than buccal; there are two roots of smaller fore and larger aft; anterior and posterior enamel wall carry polished surfaces due to contact with the neighbouring teeth; teeth are much worn and dentine islets relatively large sized and depressed; basal cingulum is indistinct. Specimen b (RM 2), quadrate in crown view, 63mm in maximum length and 38mm in maximum width, consists of seven columns arranged in three columns (2, 2, 2+1); median two columns are largest; buccal side is higher than lingual; 33mm high at the former and 28mm at the latter just above root branching; lingual column of third row is much sloped down inward; there are two anterior and posterior roots. Specimen c (RM 3) is preserved only in two columns of first row which is 34mm wide and 36mm high at fore side; transverse width of dentine islet of lingual column (3mm)/ditto of lingual column (17mm) is 0.18 and maximum thickness of enamel wall is 9mm. In RM 2 they are 0.38 and 7mm of lingual column of first row. Specimen d (LM 3) is fragmental, consisting of two columns and part of two columns, which correspond to lingual column of second row and two columns of third row and median posterior accessory column; transverse width of dentine islet of lingual column of second row (21mm)/ditto of the column (5mm) is 0.24 and enamel wall is 8mm in maximum thickness. The Keton specimen reported by Nagao, Iziri and Kamei from South Saghalien, the Nagakura specimen described by Tokunaga from Fukushima Prefecture and the Togari specimen (type) described by Tokunaga and Iwasaki from Gihu Prefecture have been compared with those specimens in question. Specimen a is rather like RM 2 of Togari and RM 2 of Nagakura. Specimen b is also like RM 2 of Nagakura. Anything like specimen c can not be found amog Japanese specimens of Desmostylus. The writers are going to use the specific name of hesperus japonicus Tokunaga & Iwasaki.
横浜国立大学の論文
1965-11-30

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鹿間時夫
チバラギ・ボーリング

秋田県田代産デスモスチルスの歯について

スポンサーリンク

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