Aethalionopsis is an extinct genus of prehistoric freshwater bony fish from the Early Cretaceous (Barremian to early Aptian, with possible earlier or later occurrences) of western Europe.[1] Formerly classified as a species of the elopiformAnaethalion, it is now known to be a relative of the modern milkfish (Chanos) in order Gonorhynchiformes. It was previously placed as a basal member of the suborder Chanoidei, but is now more often placed as a basal member of the subfamily Chaninae of the family Chanidae, placing it closer to the extant Chanos.[2][3][4][5]
Only a single species is presently accepted, A. robustus from the famous Iguanodon dinosaur locality of the Sainte-Barbe Clays Formation in Bernissart, Belgium. However, potential localities are also known from the Berriasian-Hauterivian of Sussex, England (classified in the genus Anaethalion as A. valdensis), and the Aptian-Albian of southern Italy (possibly an undescribed species). However, more recent studies have only accepted and commented on A. robustus, with no mention of these other occurrences.[2][6]