Astragalus tortipes is a new species from the southern flank of Sleeping Ute Mountain in southwestern Colorado that grows with mixed desert scrub on Mancos Shale badlands overlain by pediment gravel. Based on phylogenetic estimations using parsimony, the new species is placed as a member of Barneby's sect. Lonchocarpi subsect. Lonchocarpi and is compared morphologically to other astragali. Astragalus tortipes is characterized by its hyper-reflexed pod, a character unique in North American Astragalus. The genus Astragalus (Fabaceae), with over 2500 species worldwide, is one of the largest genera of flowering plants (Airy Shaw 1973; Polhill 1981; Sanderson 1989). Western North America, where there has been a remarkable radiation in the genus, contains nearly 600 species and varieties of Astragalus. This area has undergone large-scale climatic and topographic change throughout the Tertiary. These changes, coupled with great physiographic and edaphic variability, especially on the Colorado Plateau, have resulted in population isolation (Welsh 1978). Subsequent edaphic specialization and restricted seed dispersal have contributed to a high rate of allopatric speciation (Sanderson 1989). Present patterns of distribution suggest that many of these species occur in small isolated populations (Barneby 1964). Thus, it is not surprising that new species of Astragalus are still being discovered. To the growing list of species of Astragalus, we add another from desert badlands on the Ute Mountain Ute Indian Reservation in extreme southwestern Colorado, near the Four Corners of Colorado, New Mexico, Arizona, and Utah. This Astragalus was first noted in 1985 on the lower flank of the southern end of Sleeping Ute Mountain by Richard Fleming and Porter who collected a fragmentary specimen (Porter 1902, SJNM) in late phenology with only one, albeit distinctive, pod. In 1989 Anderson discovered an entire population 3 mi from the previous site, collected additional material, and conducted an inventory for the new species in the surrounding area. Recent environmental legislation (the National Environmental Policy Act of 1969 and the Endangered Species Act of 1973, as Amended) is responsible for requisite rare and endangered plant species inventories on projects involving federal lands or federal funding, and/ or federal permitting. The discovery of this species was the result of inventories for rare and endangered plants in association with work on seismic lines and an irrigation canal system. Astragalus tortipes J. L. Anderson & J. M. Porter, sp. nov. (Fig. 1)-TYPE: U.S.A., Colorado, Montezuma Co., Ute Mountain Ute Reservation, toe slope of southern end of Sleeping Ute Mountain, 2.5 mi (4 km) S of Towaoc, T33 1/2N, R17W, S19 NWSW, 1720 m, on small hill of Mancos Shale ovarlain with pediment gravel, 25 April 1989, J. L. Anderson 89-16 (holotype: BRY; isotypes: ARIZ, ASU, COLO, CS, NMC, NY, SJNM, UTC).