Pinus haboroensis sp. nov. and the affinities of permineralized leaves from the Upper Cretaceous of Japan

Abstract

A new species of Pinus is described based on permineralized needles from the Sankebetsugawa, Haboro, and the Koyanosawa, Ikushumbetsu, Mikasa City, Hokkaido, Japan. Leaf fragments were discovered in calcium carbonate nodules with abundant ammonites dated as Santonian–Senonian (Upper Cretaceous). The leaves, borne in fascicles of three or four, are 0.9–1.1 mm in radial and 1.5–1.8 mm in tangential diameters, and fragments up to 0.5 cm long have been recovered. The vascular strand is double and bundles are separated by a large anchor-shaped band of sclerenchyma fibers. Transfusion tissue up to four cells wide and a long-base triangular endodermis with an irregular outline surround the vascular tissues. Six to eight medial and external resin canals occur within the band of small plicate mesophyll cells three or four cells wide. The uniform hypodermis from one to four cells thick lies beneath thick-walled elliptical epidermal cells. These amphistomatic leaves with deeply sunken stomata most closely resemble those of Pinus coulteri D. Don, subgenus Pinus, section Pinus, subsection Sabinianae and have added significantly to our knowledge of permineralized Cretaceous pine needles. Pinus haboroensis sp. nov. is closely compared anatomically with the other Upper Cretaceous pines from Japan and North America and primitive needle characters are discussed. Emended diagnoses for P. flabellifolia Ogura and P. bifoliata Ueda and Nishida are presented, including a description of their possible affinities to sections and subsections of the genus Pinus.