Late Early Cretaceous (Albian) Sasayama Flora from the Sasayama Group in Hyogo Prefecture, Japan

Abstract

Abstract. Plant fossils are reported on from the Lower Cretaceous Upper Formation of the Sasayama Group, including the new species Otozamites toshioensoi sp. nov. The Sasayama Flora proposed here is characterized by an abundance of microphyllous conifers such as Brachyphyllum spp. and Pseudofrenelopsis sp., as well as by the rare occurrence of pteridophytes. These floristic components suggest that an arid climate prevailed in the land of the Sasayama Group and that the Ryoseki-type flora, which generally represents the Outer Zone of Japan during the Late Jurassic to Early Cretaceous, flourished in the Inner Zone of Japan during the late Early Cretaceous. Albian or Cenomanian ages have previously been proposed for the Upper Formation of the Sasayama Group by radiometric datings, but an Albian age is preferred here in regards to the extremely rare occurrence of possible angiosperms.