Upper cretaceous araucarian cones from Hokkaido: Araucaria nihongii sp. nov.

Abstract

Ten small, permineralized cones 3.0–4.2 cm in diameter are described from the Late Cretaceous Upper Yezo Group of Hokkaido, Japan. Cones are spherical with prominent winged bracts and thin ovuliferous scales, and bear one seed per cone-scale complex. Internally the pith of the cone axis is parenchymatous grading into plates and nests of sclereids in the peduncle. Numerous resin canals occur in the pith and cortex but are absent in the wood of the cone axis. Bracts display an abcission layer at the base of sharply upturned laminar tips. Integumentary layers of crushed sarcotesta and endotesta and a prominent thick sclerotesta with a zig-zag pattern of sclereids indicate that these cones were probably near maturity at the time of transport and burial. The nucellus is free from the integument except at the chalaza and shows a prominent wavy apex. Megagametophyte and dicotyledonous embryo tissues are well-preserved. These cones represent a single type of araucarian cone that closely resembles those of the section Eutacta of the genus Araucaria. Embryo structure, however, compares most favorably with those of the section Intermedia. These remains are described as representing a new species, Araucaria nihongii Stockey, Nishida et Nishida sp. nov. A reassessment of the fossil record of the sections within the genus Araucaria is given with respect to these and other previously described fossil araucarian remains.