The genus Cyriocosmus Simon, 1903 is revised based on most types and additional material from Argentina, Brazil, Colombia, Tobago Island and Venezuela. Two species are newly described from Brazil: Cyriocosmus nogueira-netoi and Cyriocosmus fernandoi. The species Cyriocosmus fascia-tus (Mello-Leitão, 1930), formerly synonymized with Cyriocosmus elegans, is revalidated. Metrio-pelma nigriventris (Mello-Leitão, 1939) and Cyriocosmus butantan Pérez-Miles, 1998 are transferred to Hapalopus Ausserer, 1875, proposing Hapalopus nigriventris (Mello-Leitão, 1939) new combination and Hapalopus butantan (Pérez-Miles, 1998) new combination. The female of Hapalopus butantan is described for the first time. All 11 species of Cyriocosmus are diagnosedand keyed. A cladistic analysis with 28 characters and 19 taxa was carried out. Searches using three phylogenetic packages found a single, totally resolved tree with the same topology.
Zootaxa 846: 1-31