PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 114(1):34-4I. 2001. A remarkable new species of small falcon from the Quaternary of Cuba (Aves: Falconidae: Falco) William Suarez and Storrs L. Olson (WS) Museo Nacional de Historia Natural; Obispo 61, Plaza de Armas, La Habana CH 10100, Cuba; (SLO) Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560, U.S.A. Abstract. — An enigmatic small falcon, Falco kurochkini, new species, is de-scribed from postcranial bones from several Quaternary sites in western and central Cuba. It was approximately intermediate in size between F. sparverius and F. columbarius but had proportionately longer and more slender leg ele-ments than any living species of Falco. It is hypothesized that F. kurochkini may have been terrestrial, pursuing prey on foot, and that its extinction could have been related to terrestrial nesting habits as well. Falcons of the genus Falco are poorly represented in the West Indies today. Two species, the Merlin (F. columbarius) and the Peregrine (F. peregrinus) are migrant or wintering birds from North America, al-though there are single breeding records of the latter from Cuba (Regalado & Cables 2000) and Dominica (Raffaele et al. 1998). Thus, the only truly resident Falco is the American Kestrel (F. sparverius), the smallest New World falcon, which is found throughout the Antilles. There are three en-demic subspecies, of which by far the most distinctive is the Cuban F. s. sparverioides, which has three plumage phases — dark, light, and intermediate (Berovides & Fer-nandez 1984), whereas the other taxa have no phases and are all more similar to the light phase of the Cuban bird. The Cuban subspecies has expanded relatively recently into the southern Bahamas and possibly to Jamaica and Hispaniola (Wotzkow 1998), although its occurrence on the last two is-lands does not appear to have been docu-mented by specimens. Considering this dearth of Antillean fal-cons, the discovery of a highly distinctive new fossil species in Cuba, also of small size, assumes considerable interest. We first learned of the existence of such a falcon in 1981, when E. N. Kurochkin showed one of us (SLO) a tarsometatarsus that he had collected in Camagiiey eight years before. This specimen was so long and slender that it clearly could not be referred to any known species (Fig. 2E). Recently, Suarez was able to collect a considerable series of bones of this species representing most of the major postcranial elements, so that there is now sufficient material to characterize the new species. Materials and Methods Material examined. — Skeletons of the following species of Falconidae in the col-lections of the National Museum of Natural History, Smithsonian Institution (USNM): Herpetotheres cachinnans, Caracara plan-cus, C. cheriway, Milvago chimango, M. chimachima, Daptrius americanus, D. ater, Phalcoboenus australis, Spiziapteryx cir-cumcinctus, Polihierax insignis, Microhier-ax caerulescens, Falco mexicanus, F. rus-ticolus, F. peregrinus, F. rufigularis, F. biannicus, F. cherrug, F. tinnunculus, F. vespertinus, F. rupicoloides, F. femoralis, F. cuvieri, F. eleonorae, F. subbuteo, F.