Two new species of a new genus, Postopsyllidium rebeccae and P. emilyae, are described, which are preserved in amber from northern Myanmar and central New Jersey, USA (100-90 myo), respectively. These are the first specimens of the hemipteran family Protopsyllidiidae found in amber and the latest occurrence of the family, some 50 my later than previous records; all others are compressions in rocks (many of them just wings) from the Late Permian to the Early Cretaceous. Postopsyllidium emilyae is also the first record of the group from the Western Hemisphere. A catalogue of Protopsyllidiidae is provided as well as an hypothesis of phylogenetic relationships among genera, though monophyly of the family is ambiguous. Postopsyllidium appears to be a recently derived genus, and four genera are removed from the family. Complete preservation in amber allows new insight into relationships, specifically that Postopsyllidium, and perhaps most or all Protopsyllidiidae, represent an extinct sister group to the Sternorrhyncha that retain features of some Auchenorrhyncha. Radiations of true Sternorrhyncha began in the Jurassic and Cretaceous, by which time the Protopsyllidiidae were apparently already relicts.