A new monotypic genus of Asteraceae-Senecioneae, Caxamarca, is described from northern Peru. The single herbaceous perennial species, Caxamarca sanchezii M. O. Dillon & Sagistegui, is endemic to the seasonally dry valleys of southwestern Cajamarca. The potential relationships of the genus are discussed. RESUMEN. Un gdnero monotipico nuevo de Asteraceae-Senecioneae, Caxamarca se describe para el norte de Peri. La inica especie, la herbicea perenne, Caxamarca sanchezii M. O. Dillon et Sagistegui, es end~mica de los valles estacionalmente secos del suroeste del Departamento de Cajamarca. Se discuten las relaciones potenciales del g~nero. During continuing detailed studies on the flora of northern Peru, the following monotypic genus of Senecioneae (Asteraceae) was encountered in the seasonally dry river valleys in southwestern Cajamarca. This new genus is proposed after an exhaustive examination of all available genera within the tribe and detailed studies on many neotropical members of the large and complex genus Senecio L. While generic concepts within the Senecioneae have been reviewed (Barkley, 1985a; Barkley et al., 1996; Bremer, 1994; Nordenstam, 1978), future changes are to be expected as taxonomies are tested with data from other disciplines, such as molecular systematics. Caxamarca (Asteraceae tribe Senecioneae) M. O. Dillon & Sagistegui, gen. nov. TYPE: Caxamarca sanchezii M. O. Dillon & Sagistegui. Herba rhizomatosa usque ad 1.5 m alta, radices carnosi foetidi; caules erecti simplexalata medullosus. Folia basale 40-50 cm longa, profunde pinnatisecta. Folia caulina alterna, herbacea, sessilia, basi decurrentis; lamina plana herbacea 20-35 cm longa, 7-11 cm lata, margine distincte denticulata. Capitulescentiae corymboso-cymosae 3-20 capitulis (vulgo 3-7). Capitula heterogama radiata ca. 10 mm alta, ca 10 mm lata; phyllaria subbiseriatis 17-28 (vulgo 22-28). Flores radiati pistillati 10-22; ligulae luteae, 10-25 mm longae, 4-8 mm latae. Flores disci hermaphroditi 80-160 (vulgo 80-130); corollae tubulosae luteae, 12-15 mm longae; limbus profunde quinquelobus. Antherae basis sagittata; collum filamenti basi dilatatum. Styli rami apice conico pilis penicillum centrale. Achaenia decemcostata pilosus; pappi setae biseriate 6-7 mm longus barbellatae persistentes. Caxamarca sanchezii M. O. Dillon & Sagistegui, sp. nov. TYPE: Peru. Dept. Cajamarca: Prov. Contumazi, Alrededor de San Benito, 1200 m, 12 May 1994, A. Sagdstegui A., S. Leiva & C. Sagdstegui 15185 (holotype, HAO; isotypes, CPUN, F, MO, US). Figures 1, 2. Perennial herbs to 1.5 m tall; roots fasciculate, tuberous, malodorous, individual tubers 8-12 cm long, 2-3 cm diam., white; stems fistulose, 1-2.5 cm diam. at the base, unbranched, glabrous, winged by the decurrent leaf bases, the wings 4-7 mm wide, glabrous, reticulate-nerved, denticulate, ciliolate. Leaves basal and cauline; basal leaves rosulate, the blades profoundly dissected, odd pinnate, the rachis 40-50 cm long, 8-10 pairs of leaflets, the leaflets ovate to lanceolate, 5-10 cm long, 2-6 cm wide, the margins dentate-serrate; cauline leaves alternate, sessile, decurrent, the blades oblong-lanceolate, 20-35 cm long, 7-11 cm wide, membranous, apically acuminate, the margins irregularly dentate-serrate, reticulate-nerved, glabrous, the nerves sparsely pilose. Capitulescences cymose-corymbose. Capitula 3-7(-20), radiate; pedicels 1-8 cm long, striate, swollen apically, densely pilose; calyculus (10-)16-22-bracteolate, the bracts narrowly linear, 1-2 cm long, 0.5-1 mm wide, acuminate apically, 1-nerved, greenish purple; involucres hemispherical, ca. 10 mm tall, ca. 10 mm wide; phyllaries (17-)22-28, weakly biseriate, equal, lanceolate, 8-10 mm long, 2-3 mm wide, fused at the base, glabrous or pilose, acuminate; ray florets 10-22, pistillate, the corolla yellow, the tube 0.5-0.6 mm long, glabrous, the ligule oblong-linear, 10-25 mm long, 4-8 mm wide, glabrous, 10-12-nerved, 2-3-dentate apically; disc NovoN 9: 156-161. 1999. This content downloaded from 157.55.39.138 on Tue, 19 Apr 2016 04:43:33 UTC All use subject to http://about.jstor.org/terms Volume 9, Number 2 1999 Dillon & SagAstegui Caxamarca from Peru 157 Zmm .i ::i: ::ii li? a