Jonoichthys is an extinct genus of marine ray-finned fish from the Upper Jurassic of Argentina. The type and only known species is Jonoichthys challwa. The fossil remains of J. challwa were recovered from the Vaca Muerta Formation, in Neuquén province, Argentina. It belongs to the family Aspidorhynchidae, within Aspidorhynchiformes. References Prehistoric ray-finned fish genera Tithonian life Jurassic Argentina Fossils of Argentina Neuquén Basin Fossil taxa described in 2015