Stramineopteris aureopilosus gen. et sp. nov.: Reevaluating the Role of Vegetative Anatomy in the Resolution of Leptosporangiate Fern Phylogeny

The discovery of two anatomically preserved rhizomes with attached stipe bases and adventitious roots contributes to our knowledge of filicalean fern diversity and evolution. Specimens are preserved in marine carbonate nodules at the Lower Cretaceous (Valanginian to Hauterivian) Apple Bay locality onVancouver Island, British Columbia, Canada. They represent a previously unknown filicalean fern with transitional solenostelicdictyostelic stelar architecture and are described as Stramineopteris aureopilosus gen. et sp. nov. Rhizomes range from 2.5 to 5.5 mm in diameter and are amphiphloic. Arc-shaped leaf traces display a slightly asymmetrical divergence pattern and radiate from all sides of the stele. Primary xylem maturation is exarch. Multicellular trichomes are present throughout but are produced in greater numbers at rhizome dichotomies. Both pith and cortex are of a distinctive heterogeneous construction.Acomparison of this distinctive combination of characters to previously described fern rhizomes reveals that vegetative anatomymaybe more taxonomically diagnostic for a broader range of ferns than is commonly thought. This realization provides the impetus to explore more closely the distribution of several anatomic characters among leptosporangiate ferns and to reexamine the value of vegetative anatomy for developing a clearer understanding of fern systematics.