Dicotyledonous fossil wood flora and early evolution of wood characters in the Cretaceous of Hokkaido, Japan

Fossil woods are abundant in the Cretaceous Yezo Group in Hokkaido, Japan, in strata of Albian to Santonian ages. From 144 dicotyledonous samples, fourteen species representing 10 genera were identified: Castanoradix cretacea gen. et sp. nov., C. biseriata gen. et sp. nov., Frutecoxylon yubariense gen. et sp. nov., Hamamelidoxylon obiraense sp. nov., Icacinoxylon kokubunii sp. nov., 1. nishidae sp. nov., Magnolia-ceoxylon hokkaidoense sp. nov., Nishidaxylon jezoense gen. et sp. nov., Paraphyllanthoxylon cenomaniana sp. nov., P. obiraense sp. nov., Plataninium jezoensis sp. nov., P. ogasawarae sp. nov., Sabiaceoxylon jezoense gen. et sp. nov. and Ulminium kokubunii sp. nov. All 14 species are new and four of the 10 genera are new. Five genera (Icacinoxylon, Magnolia-ceoxylon, Paraphyllanthoxylon, Plataninium and Ulminium) already are known from the Cretaceous and Tertiary, one (Hamamelidoxylon) previously is known only from the Tertiary. The species distribution by age is: Albian: one species; Cenomanian: four species in four genera; Turonian: ten species in eight genera; Coniacian: six species in five genera; Santonian: eight species in seven genera. The two specimens of Icacinoxylon kokubunii from the Albian are the oldest records of dicotyledonous woods in Japan.