Iniopterygiformes

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 characterized by large, superficially wing-like pectoral fins positioned upwards behind the head, from which the name of the group (translated as "nape fin")^[1] is derived. 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]

3D scan of the skull and pectoral region of the sibyrinchid Iniopera richardsoni

Iniopterygiformes Temporal range: Carboniferous
Life restoration of Iniopteryx
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Subclass:	Holocephali
Order:	†Iniopterygiformes Zangerl & Case, 1973
Families
Sibyrhinchidae Iniopterygidae

The group is regarded as a relative of modern chimaeras, and is placed in the subclass Holocephali. Two families of iniopterygians are recognized; the Sibyrhynchidae and the Iniopterygidae, with the former containing the genera Sibyrhynchus, Iniopera, and Inioxyele and the latter housing all other named genera.^[3][5] The classification of the iniopterygians, both with each other and with other groups of holocephalan, has been considered problematic.^[5]

Genera

• Cervifurca
• Iniopera
• Iniopteryx
• Inioxyele
• Papilionichthys
• Promexyele
• Rainerichthys
• Sibyrhynchus