Gleichenia appianensis sp. nov. (Gleicheniaceae): A Permineralized Rhizome and Associated Vegetative Remains from the Eocene of Vancouver Island, British Columbia

Abstract

A permineralized gleicheniaceous rhizome with an attached stipe base has been identified from the Appian Way locality on Vancouver Island, British Columbia, Canada. The specimens are preserved in Middle Eocene marine calcareous concretions that are studied using the cellulose acetate peel technique. The marginally mesarch rhizome has a vitalized protostele, protoxylem elements with helical wall thickenings, and scalariform metaxylem tracheids that occur in clusters. A continuous band of phloem and pericycle surrounds the xylem. The inner cortex consists of a layer of small‐diameter sclerenchyma fibers, and the outer cortex is composed of larger parenchyma cells. A nodal island of sclerenchyma is present between the leaf trace and protostele at the level of frond‐trace divergence. Long metaxylem tracheids in the frond trace show septa in longitudinal section that likely represent tyloses. Roots diverge from all sides of the rhizome with traces that run obliquely through the cortex. Numerous associated but isolated frond segments are found in the Appian Way nodules that show a pinched and inrolled C‐shaped vascular trace and pseudodichotomous bifurcation. The frond traces have numerous protoxylem strands, and the general anatomy is comparable to that of gleicheniaceous stipes. The rhizome is described as a new species of Gleichenia, Gleichenia appianensis Mindell, Stockey, Rothwell, et Beard sp. nov., and represents the first record of Gleicheniaceae in the Tertiary of North America.