This paper examines the status and geographic distribution of the genera Hypenetes Loew and Tillobroma Hull; the status of the latter was shifted to generic level by Artigas & Papavero 1991. The genus Clavator Philippi, which is preoccupied, becomes synonymous to Tillobroma Hull, this has been proposed by Artigas & Papavero (1991), and is confirmed here. Hypenetes and Tillobroma have a possible common Gondwanan origin of approximately 180 millions years ago. Even though the external characters barely allow separation between the two genera, the obvious differences in spermathecae structures permit the inference of other internal differences and reinforce the independent status of the genera. This conclusion is also supported by 180 million years of interrupted genetic drift and the 8,500 km distance between the populations. A key to separate the species of Tillobrama is provided. Of a total of 21 species, ten are new for science: aconcaguana, angulata, fucosoides, huasquina, leucoptera, leucotrica, nahuelbutae, purpurea, spinipes and tregualemuensis. The species belonging to this genus are distributed in Argentina, Bolivia, Brazil, Paraguay, Peru and especially Chile (where 19 of 21 are found). A phylogenetic study for the species in the genus was performed. Two South African species, Hypenetes grisescens Engel and Hypenetes stigmatias Loew, were used as external group. The software used was NONA 2.0 (heuristic search). The tree of strict consensus separated the out group by nine synapomorphies from the species H. stigmatias with four autopomorphies.