The first material known from the genus were the prominent fin spines that curve anteriorly over the head of the animal. When first described in 1883 from the St. Louis Limestone, these remains were given the name Physonemus falcatus.
The initial specimens recognized from the genus exhibited distinctive fin spines that curved forward over the animal's head, a characteristic also seen in related species. Initially described in 1883 from the St. Louis Limestone, these fossils were initially designated as Physonemus falcatus.