Pachyceras Xylophagorum Ratzeburg, 1844:218 - As Roptrocerus xylophagorum: - 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 1. Symphyta and Apocrita (Parasitica). Smithsonian Institution Press, Washington D.C. 1-1198. (distribution); De Santis, 1981De Santis, L. 1981. Catalogo de los himenopteros calcidoideos de America al Sur de los Estados Unidos. - Primer suplemento. Revista Peruana de Entomologia 24 (1):1-38. (distribution); Ruíz et al., 2004Ruíz Cancino, E., J.M. Coronado Blanco, S.N. Myartseva & J.F. Luna Salas 2004. Adenda a Chalcidoidea (Hymenoptera). In: Bousquets, J.L., J.J. Morrone, O.Y. Ordóñez & I.V. Fernández (Ed.). Biodiversidad, Taxonomía y Biogeografía de artrópodos de México: Hacia una síntesis de su conocimiento. Volumen IV. 725-734. (distribution); Noyes, 2019Noyes, J.S. 2019. Universal Chalcidoidea Database. World Wide Web electronic publication. :. (distribution).
Pachyceras Eccoptogastri Ratzeburg, 1844:218 - 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 1. Symphyta and Apocrita (Parasitica). Smithsonian Institution Press, Washington D.C. 1-1198.:764 ( listed as synonym of Roptrocerus xylophagorum (Ratzeburg, 1844)).
Roptrocerus rectus Provancher, 1887:202 - 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 1. Symphyta and Apocrita (Parasitica). Smithsonian Institution Press, Washington D.C. 1-1198.:764 ( listed as synonym of Roptrocerus xylophagorum (Ratzeburg, 1844)). - As Rhoptrocerus rectus: - Dalla Torre, 1898Dalla Torre, C.G. 1898. Catalogus Hymenopterorum hucusque descriptorum systematicus et synonymicus, V. Chalcididae et Proctotrupidae. Sumptibus Guilelmi Engelmann, VII + 598. (distribution).
Platygerrhus scolyti Ashmead, 1894:335, ♀. Holotype ♀, Morgantown, W. Va. (leg. Prof. A.D. Hopkins). - 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 1. Symphyta and Apocrita (Parasitica). Smithsonian Institution Press, Washington D.C. 1-1198.:764 ( listed as synonym of Roptrocerus xylophagorum (Ratzeburg, 1844)).