Permineralized Pine Cones from the Cretaceous of Vancouver Island, British Columbia

Abstract

Two abraded, cylindrical cone specimens found in calcareous concretions from the Cretaceous Spray Formation (Late Campanian) of Vancouver Island, British Columbia, were sectioned using the cellulose acetate peel technique and characterized anatomically. Their sclerenchymatous pith is surrounded by a ring of separate secondary xylem bundles that lack resin canals. The outer cortical zone is sclerenchymatous and covered in a dense ramentum of trichomes that is also present on ovuliferous scale and bract bases. Vascular traces to the ovuliferous scales and bracts arise independently. The bract, with a terete trace and two lateral resin canals, lacks a distinct abaxial lobe. Ovuliferous scales are sclerotic with resin canals adaxial, abaxial, and between the vascular bundles. The ovuliferous scales have an interseminal ridge that is prominent and thick near the micropylar end of the seed, thins out near the seed chalaza, and attaches to the seed wing tissue. There are two winged seeds per scale, and the edges of the ovuliferous scale turn upward and partly enclose the seeds near the micropylar end. Seeds have a ridged sclerotesta; nucellus, megagametophyte, and embryos with eight cotyledons are preserved. Cone structure most closely resembles fossil Pinaceae of the genus Pityostrobus. These cones have a unique combination of characters that distinguish them from the previously described taxa and are described as Pityostrobus beardii sp. nov. A phylogenetic analysis using morphological data from the ovulate cones of extant and fossil taxa of Pinaceae with Cryptomeria japonica (L. f.) D. Don and Sciadopitys verticillata (Thunb.) Siebold et Zucc. as outgroups was undertaken to assess the phylogenetic position of P. beardii within Pinaceae. Pityostrobus beardii appears to be most closely related to Pityostrobus hokodzensis from the Cretaceous of Russia. These cones provide further evidence that the Pinaceae, like the angiosperms, were undergoing a rapid Cretaceous radiation.