Mites Solenoplatilobus taiwanensus (Huang 2006) com. nov. (transferred from Sierraphytoptus) of the new monotypic genus Solenoplatilobus n. gen. (Phytoptidae: Sierraphytoptinae: Sierraphytoptini) possess a thin broad frontal lobe of prodorsal shield as well as the tibial solenidion I which were missed by previous authors. Sierraphytoptine mites Austracus havrylenkonisKeifer, 1944, studied in parallel and based on fresh material from Chile, have uniquely organized dorsal annuli which form thin imbricating cuticle plates overlapping one above another resembling roof tiles. The two studied early-derivative sierraphytoptine species inhabit relict eudicots from the families Nothofagaceae and Trochodendraceae which had wider geographic distribution in previous geological epochs. Early-diverging eriophyoids with a complete set of plesiomorphies inhabit arboreous plant species. Combination of plesiomorphic morphology and association with relict hosts justifies treating at least some of the phytoptids as relicts. Searching eriophyoids on relict vascular plants in refugia and biodiversity hotspots may result in finding new representatives of early-derivative taxa of Eriophyoidea which would be important for understanding early steps of evolution of these eriophyoid mites on plants.