Diversity and significance of late cretaceous permineralized plant remains from Hokkaido,Japan

Middle to Late Cretaceous permineralized plants hitherto described from Hokkaido, Japan are summarized. The fossil flora comprises fungi, ferns, gymnosperms and angiosperms. Many modern fern families have been recognized including Anemiaceae, Cyatheaceae, Dennstaedtiaceae, Gleicheniaceae Loxsomaceae, Lygodiaceae and Matoniaceae. Gymnosperms are most abundant in the flora. Some recently-found materials are tentatively introduced with brief comments emphasizing their morphological and taxonomical significance. A bisporangiate flower ofCycadeoidella japonica Ogura shows fine internal anatomy and provides evidence that the cycadeoidalean ovule was a cupulate, unitegmic structure. Vascular tracheids in the synangial wall support the evolution of cycadeoidalean synangia from Paleozoic seed-fern synangia. A new gymnosperm female fructification has a thick envelope comparable to an angiosperm carpel around a large seed. The angiosperms contain various morphologies that require further extensive study.     

Permineralized rhizomes of the Osmundaceae (Filicales): Diversity and tempo-spatial distribution pattern

The family Osmundaceae is among the most primitive ferns of the Filicales, with an extensive fossil record dating back to the Late Paleozoic. Numerous fossil osmundaceous rhizomes have been documented in the geological history. However, the diversity, variation and distribution pattern of permineralized rhizomes remain poorly known. Here we intend to analyze the fossil records with regard to the diversity and distribution pattern of the osmundaceous rhizomes based on available data. To date, about 83 species ascribed to 14 genera of fossil osmundaceous rhizomes have been described worldwide, assigned to two subfamilies, namely, Thamnopteroideae and Osmundoideae. Geologically, two groups (i.e., Thamnopteroideae and Palaeosmunda) have been reported in the Permian. All the Triassic taxa are from the southern hemisphere. Jurassic osmundaceous rhizomes are abundant and widespread throughout the world, most dominant in the southern hemisphere. During the transition of Jurassic to Cretaceous, the diversity of osmundaceous rhizomes declined rapidly. In the Cretaceous, however, the osmundaceous rhizomes from the northern hemisphere surpass those from the southern hemisphere in generic level for the first time. The Cenozoic taxa diversified in the northern hemisphere with the rise of angiosperms. Geographically, the osmundaceous fossil rhizomes have been found in both hemispheres; the major localities include Ural area of the former USSR, Tasmania of Australia, southern Argentina, Antarctica, northern India, central and western part of North America and northern China. We discuss the origin, radiation, and development of the Osmundaceae based on rhizomes, to help further understand the systematic relation and evolutionary history of the family Osmundaceae.     

The Occurence of Xenoxylon ellipticum in the Late Triassic from North Guangdong,China

Xenoxylon ellipticum has been found in Hongweikeng Formation (probably Middle Keuper-Rhoetic), Gengkou Group of the Late Triassic from the North of Guangdong Province and is described in this paper. The species was first found in the Early Jurassic from West Germany in 1960. It is the fifth species of Xenoxylon Gothan ever found in China.     

Protomonimia kasai-nakajhongii gen. et sp. nov.: A permineralized magnolialean fructification from the mid-Cretaceous of japan

Protomonimia kasai-nakajhongii gen. et sp. nov., is an angiosperm fructification with numerous helically arranged follicles attached to a concave receptacle. It was obtained from the mid-Cretaceous (Turonian) of Hokkaido, Japan. Each follicle is a conduplicate carpel with an adaxial stigmatic crest. It shows many primitive features of early angiosperms, especially of the Magnoliales.Protomonimia is thought to represent a member of a mid-Cretaceous group of magnolioid ancestors from which a major part of Recent Magnoliales may have been derived. Contributions from the Laboratory of Phylogenetic Botany, Chiba University, no. 118.