Pseudephedrus chilensis n.sp., a parasite of Neuquenaphis schlingeri H. R. Lambers on Nothofagus obliqua, and P. lambersi n.sp., a parasite of N. similis H. R. Lambers on Nothofagus pumilo in South America are described. A key to the ♀♀ of the three known species of Pseudephedrus is provided. Taxonomical affinities, distribution, and host range of the aphidiid genera Parephedrus Starý & Carver, 1971, Pseudephedrus Starý, 1972, and Vanhartenia Starý & v. Harten, 1972 are examined and discussed. These aphidiids are found to be specific parasites of ancient Callaphidid aphids, viz. Sensoriaphis furcifera in South Australia, Neolizerius acunai Holman in Cuba, Neuquenaphis spp. in Chile, and Paoliella monotuberculata in West Africa, respectively. The distribution of the aphids could be connected with Gondwanaland, and thus the aphidiids possibly provide further evidence of continental drift and for the former existence of such a continent.