Iniopterygiformes (Originally spelled Iniopterygia and sometimes informally abbreviated as "iniops")[1][2][3] is an extinct order of cartilaginous fish known only from the Carboniferous period of the United States.

Iniopterygians are also noted to possess proportionally large skulls and eyes, armor plates composed of dentin, and "tooth-whorls" of fused teeth.

Their elongated pectoral fins bore large, denticle-covered spines, and they are thought to have used them to swim using a "flying" motion.

[1][4] The iniopterygians were comparatively small chondrichthyans, with the largest species reaching only 50 cm (20 in) in length.

[1] The group is regarded as a relative of modern chimaeras, and is placed in the subclass Holocephali.