西南日本の豊浦層群歌野層および西中山層(ジュラ紀初期)の植物化石 (I)

概要

論文の詳細を見る
Fossil plants are very abundant in the Middle Jurassic Utano Formation mainly of marine origin distributed to the south of the Tabe Fault, Yamaguchi Prefecture. In this paper we revised previous palaeobotanical works and described 50 plant-species belonging to 29 genera based mainly on a number of specimens newly obtained. The florula of the upper Liassic Nishinakayama Formation directly underlying the Utano Formation consists all of southern-type elements. On the contrary, the flora of the Utano Formation characterized by the mixture of such northern elements as Coniopteris, Onychiopsis elongata, Dictyozamites, Ginkgoites and Czekanowskia and of such southern elements as Phlebopteris, Acrostichopteris, Pachypteris, Otozamites sp. cf. O. klipsteinii, Zamites, Ptilophyllum, Nilssonia sp. cf. N. densinervis, Brachyphyllum and Araucarites. The geological age of this flora is presumed to be not older than late Toarcian and no coeval flora has been found in the Japanese Islands. In addition we made in this paper detailed comparison of floristic features between the Utano flora and its coeval floras in China and other regions. Moreover we described five forms collected from the Nishinakayama Formation equvalent in this area.
国立科学博物館の論文