Elonichthys hypsilepis (Giebel 1848; Schultze and Bardack 1987; Middle Pennsylvanian, Mazon Creek, adults 8cm) are small taxa nesting at the base of the spiny sharks.
Elonichthys peltigerus (Giebel 1848; Schultze and Bardack 1987; Middle Pennsylvanian, adults 5cm) is a larger species with distinct skull sutures.
Palaeoniscum macropomus (Blainville 1818, 30cm; Guadalupien, Permian) gave its name to the Palaeonisciformes, a basal ray-fin clade. Elonichthys is a smaller relative.
de Blainville HMD 1818. Sur les ichthyolites, ou, Les poissons fossiles
Giebel CG 1848. Fauna d. Vorwelt, 1 (3).
Schultze H-P and Bardack D 1987. Diversity and size changes in palaeonisciform fishes
(Actinopterygii, Pisces) from the Pennsylvanian Mazon Creek fauna, Illinois, U.S.A., Journal of Vertebrate Paleontology, 7:1, 1-23, DOI: 10.1080/02724634.1987.10011635
