Anatomically Preserved Ferns from the Late Cretaceous of Western North America: Dennstaedtiaceae

Abstract

Rhizomes and stipe bases of dennstaedtiaceous ferns occur within a rich assemblage of permineralized plant fossils in the Upper Cretaceous Horseshoe Canyon Formation of southern Alberta, Canada. Two dennstaedtiaceous species are represented by procumbent rhizomes that branch frequently and produce closely spaced fronds. The dorsiventral rhizomes produce fronds from the top and sides and produce adventitious roots from the lower surface. Both species are assigned to the morphogenus Microlepiopsis gen. nov. on the basis of distinctive solenostelic rhizomes, with sclerenchymatous pith and cortex and relatively simple frond trace anatomy. In one species, Microlepiopsis bramanii sp. nov., the trace diverges as two \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewco...