Middle Eocene Pinus Remains from British Columbia

Abstract

Two types of Pinus cones and leaves have been identified in the Middle Eocene Allenby Formation of Princeton, British Columbia. A new permineralized ovulate cone, P. princetonensis sp. n., 4 8 cm long and 1.5- 2 cm in diameter, shows helically arranged ovuliferous scales with inflated apices. The parenchymatous pith of the cone axis is surrounded by a vascular cylinder containing two prominent rows of resin canals that remain distinct into the oval cone-scale complex trace and out into the discrete bundles of the ovuliferous scale. Two winged ovules, 8 mm long with wings up to 1 cm long, are present on the adaxial surface of each ovuliferous scale. This cone most closely resembles P. arnoldii Miller and cones from the subgenus Pinus, section Pinus, subsection Sylvestres. The diagnosis of P. arnoldii has been emended, based on the discovery of 121 new specimens, and includes important seed characters that were not present for its original description. Two new leaf types are described from permineralized specimens Pinus allisonii sp.n. leaves, borne in fascicles of two, contain two vascular strands separated by a band of fibers, an endodermis with radial and tangential wall thickenings, six to nine medial resin canals, a uniform hypodermis one to five cells thick, rectangular epidermal cells, and sunken adaxial and abaxial stomata. The leaves most closely resemble leaves of the subgenus Pinus, section Pinus, subsection Sylvestres Pinus andersonii sp. n. leaves, borne in fascicles of three, contain two vascular strands separated by a band of fibers, five medial resin canals, an endodermis with thickened radial and tangential walls, elliptical epidermal cells, and sunken adaxial and abaxial stomata. These leaves most closely resemble those of the subgenus Pinus, section Pinus, subsection Ponderosae. These remains are compared with the seven previously described permineralized cones and other Eocene remains assignable to the genus Pinus. This study adds to our knowledge of the variation within the genus and provides new alternatives for regarding these remains in the context of whole plants.