Fossils of them have been found in Montana, Indiana, Illinois, and Nebraska.
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Ironically, Iniopteryx rushlaui, the type species, has not yet been assigned to a specific family, though some experts place it in its own monotypic family, "Iniopterygidae." The closest modern-day relatives of the Iniopterygii are the Chimaeras (Chimaeriformes) also known as ghost sharks, rabbit fish or rat fish.
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Iniopterygiformes ("Nape Wing Forms") is an extinct order of chimaera-like cartilaginous fish that lived from the Devonian to Carboniferous periods (345–280 million years ago).