Seed cones of Metasequoia milleri from the Middle Eocene of southern British Columbia

Abstract

Permineralized ovulate cones of Metasequoia milleri Rothwell and Basinger (Taxodiaceae) are preserved in silicified peats of the Middle Eocene Allenby Formation near Princeton, B.C., Canada. Cones are about 17 mm wide and 25 mm long and are borne terminally on sparsely leaved stalks or peduncles. Twenty to 30 cone scales are arranged decussately on the cone axis. Externally, cone scales are broadly hexagonal and labiate in appearance owing to a medial cleft. Several ovules, with micropyles directed toward the cone axis, are attached to the adaxial surface of the cone scale. Seeds are 3–4 mm wide and about 5 mm long, with two lateral wings each approximately equal in size to the central seed body. Anatomical similarity to and close association with pollen cones and vegetative remains of M. milleri indicate that all organs belong to a single species. The vegetative body and pollen cones of M. milleri differ in few respects from those of living Metasequoia glyptostroboides Hu and Cheng. The seed cones of M. milleri cannot be distinguished from those of the living species. The close resemblance of the two species indicates evolutionary near stasis, at least structurally, throughout the Tertiary.