Tsuga shimokawaensis, a new species of permineralized conifer leaves from the middle miocene Shimokawa group, Hokkaido, Japan
1995
Matsumoto, M. (Chiba Univ. (Japan). Faculty of Science) | Ohsawa, T. | Nishida, M.
Silicitied pinaceous leaves from the late Middle Miocene bed of Shimokawa Town, central Hokkaido, Japan are described as Tsuga shimokawaensis sp. nov. Comparisons with leaves of extant species of Tsuga show that the new species is assigned to sect. Tsuga, resembling the extant species T. heterophylla in having usually one-cell-layered hypodermis, and T. sieboldii in having mesophyll cells between the resin canal and the hypodermis. From cladistic analyses we infer that Tsuga shimokawaensis is positioned the basal in sect. Tsuga and that sect. Tsuga comprises four species groups
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