Phytologia (February 1997) 82(2): 107-1 13. SYNOPSIS OF STEPHANODORIA (ASTERACEAE: ASTEREAE) Guy L. Nesom Texas Regional Institute for Environmental Studies, Sam Houston State University, Huntsville, Texas 77341 U.S.A. ABSTRACT A full description and citation of specimens are provided for the monotypic Mexican genus Stephanodoria. Stephanodoria tomentella is restricted to a small area of northeastern San Luis Potosi, where it is rare and in danger of extinction. The species is part of the "Xanthocephalum group" of the subtribc Machaerantherinae, but its phylogenetic position within the Xanthocephalum group is not clearly resolved. Some aspects of possible relationships among other genera of this group also are discussed. KEY WORDS: Stephanodoria, Asteraceae, M6xico, taxonomy The single species that comprises Stephanodoria E. Greene was first described by Robinson (1892) as a species of Xanthocephalum Willd. It was formally excluded from the latter by Greene (1895), who created the new genus for it. After that, it was not discussed or included in published studies evaluating relationships among Astereae until the recent dissertation by Suh (1989) and its publication by Suh & Simpson (1990), who substantiated Greene's rationale for placing Stephanodoria as a monotypic genus closely related to Xanthocephalum. Stephanodoria tomentella (B.L. Rob.) Greene is represented in herbaria by only a few specimens, including the type material collected by Pringle and a few much more recent collections from near the type locality. Because Stephanodoria is poorly known and endangered in its continued existence, a full description and citation of specimens are provided. STEPHANODORIA TOMENTELLA (B.L. Robinson) E. Greene Stephanodoria tomentella (B.L. Rob.) E. Greene, gen. & comb. nov. Erythea 3:12. 1895. BASIONYM: Xanthocephalum tomentellum B.L. Rob., Proc. Amer. Acad. Arts 27:172. 1892. TYPE: MEXICO. San Luis Potosi: alkahne 107
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