HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Jud, N. A. Articles by Stockey, R. A. PubMed Articles by Jud, N. A. Articles by Stockey, R. A. Agricola Articles by Jud, N. A. Articles by Stockey, R. A.

Todea from the Lower Cretaceous of western North America: implications for the phylogeny, systematics, and evolution of modern Osmundaceae¹

² Department of Environmental and Plant Biology, Ohio University, Athens, Ohio 45701 USA ³ Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9

ABSTRACT

The first fossil evidence for the fern genus Todea has been recovered from the Lower Cretaceous of British Columbia, Canada, providing paleontological data to strengthen hypotheses regarding patterns of evolution and phylogeny within Osmundaceae. The fossil consists of a branching rhizome, adventitious roots, and leaf bases. The dictyoxylic stem has up to eight xylem bundles around a sclerenchymatous pith. Leaf traces diverge from cauline bundles in a typical osmundaceous pattern and leaf bases display a sheath of sclerenchyma around a C-shaped xylem trace with 2–8 protoxylem strands. Within the adaxial concavity of each leaf trace, a single sclerenchyma bundle becomes C-shaped as it enters the cortex. The sclerotic cortex is heterogeneous with an indistinct outer margin. The discovery of Todea tidwellii sp. nov. reveals that the genus Todea evolved by the Lower Cretaceous. A phylogenetic analysis combining morphological characters of living and extinct species with a previously published nucleotide sequence matrix confirms the taxonomic placement of T. tidwellii. Results also support the hypothesis that Osmunda s.l. represents a paraphyletic assemblage and that living species be segregated into two genera, Osmunda and Osmundastrum. Fossil evidence confirms that Osmundaceae originated in the Southern Hemisphere during the Permian, underwent rapid diversification, and species extended around the world during the Triassic. Crown group Osmundaceae originated by the Late Triassic, with living species appearing by the Late Cretaceous.

Key Words: Cretaceous • fern phylogeny • Osmundaceae • Osmundastrum • rhizome • Todea