Introduction
In February 2010, Gandhi, in responding to an inquiry from Dr. Travis Columbus, noticed that the name Piptochaetium setosum (Trin.) Arechav. was superfluous and illegitimate at the time of publication because its basionym, Urachne setosa Trin., was itself superfluous and illegitimate at the time of publication, Trinius having included in it two older and validly published names, Stipa panicoides Lam. and Oryzopsis setacea Rich. Stipa panicoides is the basionym of Piptochaetium panicoides (Lam.) Desv., a taxon that is now considered distinct from Piptochaetium setosum (Parodi 1944; Cialdella and Arriaga 1998; Peña et al. 2008). In addition, Parodi, who examined the types of all the names involved, stated that the type of Oryzopsis setacea was evidently based on the same material as that of Stipa panicoides (Parodi 1944, p. 299). Thus neither of the names Trinius treated as synonyms of Urachne setosa can be used as the basionym for Piptochaetium setosum when this taxon is considered to be distinct from Piptochaetium panicoides.
Columbus and Smith have published a new name for the taxon, but they placed it in Stipa L. as Stipa purpurata (Phil.) Columbus & J.P. Sm. (Columbus and Smith 2010). We strongly disagree with their generic interpretation. Piptochaetium J. Presl, as interpreted by Parodi (1944; Parodi and Freier 1945; Thomasson 1978, 1979; Cialdella and Arriaga 1998; Cialdella and Guissani 2002; Cialdella et al. 2007; Jacobs et al. 2007; Barber et al. 2009) has been shown to be morphologically, anatomically, and molecularly distinct from other genera of the Stipeae as well as monophyletic. The purpose of this paper is to provide a valid combination in Piptochaetium for the taxon hitherto known as Piptochaetium setosum in Piptochaetium.
Parodi (1944), in his revision of Piptochaetium, listed four synonyms for Piptochaetium setosum: Urachne fusca Steud. (Steudel 1854) (the basionym of Piptochaetium fuscum), Piptochaetium purpuratum Phil. (Philippi 1857), Piptochaetium pallidum Phil. ex Griseb. (Grisebach 1879), and Piptochaetium macrocarpum Phil. (Philippi 1896). In describing Urachne fusca, Steudel cited a specimen collected by Cuming near Valparaiso, Chile. Parodi stated that he had examined a specimen in B that Nees had annotated as Piptatherum fuscum, Valparaiso, Cuming, Herb. Lindley. He also examined two other specimens, one from K and one from CGE, that were labeled Cuming 453. He stated that all three specimens were identical to each other and to the type material of Urachne setosa Trin.