Calliopsis bakeri Cockerell, 1896:221, ♂. Holotype ♂, Colorado: Chamber's Lake, Larimer County, 9500 feet, July 18, 1895 (leg. C.F. Baker). - As Heterosarus bakeri: - Krombein et al., 1979Krombein, K.V., P.D. Hurd, D.R. Smith & B.D. Burks 1979. Catalog of Hymenoptera in America North of Mexico. Volume 2. Apocrita (Aculeata). Smithsonian Institution Press, Washington D.C. 1199-2209. (distribution). - As Panurginus bakeri: - Cockerell, 1912Cockerell, T.D.A. 1912. New records of bees (Hymen.). Entomological News 23:444-447. (distribution); Cockerell, 1918Cockerell, T.D.A. 1918. Some bees of the genus Panurginus (Hym.). Entomological News 29:169-171. (distribution); Cockerell, 1919Cockerell, T.D.A. 1919. The bees of the Rocky Mountain National Park (Hymenop.). Entomological News and Proceedings of the Entomological Section of the Academy of Natural Sciences of Philadelphia 30 (10):286-294. (distribution); Cockerell, 1922Cockerell, T.D.A. 1922. Bees of the genus Panurginus obtained by the American Museum Rocky Mountain Expeditions. American Museum Novitates 36:1-10. (distribution). - As Protandrena bakeri: - Sagot et al., 2018Sagot, P, J. Mérida, R. Ayala & R. Vandame 2018. Situación actual del conocimiento de la fauna de abejas (Apoidea: Anthophila) del estado de Chiapas, México. In: (Ed.). Memorias X Congreso Mesoamericano sobre Abejas Nativas. 191-2011. (distribution); Nava-Bolaños & Osorio-Olvera, 2022Nava-Bolaños, A. & L. Osorio-Olvera 2022. Estado del arte del conocimiento de biodiversidad de los polinizadores de México. Revista Mexicana de Biodiversidad 93:1-77. (distribution). - As Pseudopanurgus bakeri: - Timberlake, 1964Timberlake, P.H. 1964. Some new species of Pseudopanurgus of the subgenus Heterosarus Robertson (Hymenoptera, Apoidea). American Museum Novitates 2185:1-26. (distribution).