There is only one photo of the smooth handfish: an image of a withered, yellowing specimen with pectoral fins that extend like arms, and a triangular crest attached to the top of its head. Sometime between 1800 and 1804, French zoologist François Péron plucked this fish out of the ocean while voyaging through Australia, presumably in the shallow coastal waters of southeastern Tasmania.

Since then, no other smooth handfish (Sympterichthys unipennis) has ever been spotted, and the fish that Péron collected became the holotype for the entire species. In March 2020, the IUCN officially declared the species to be extinct.