The cartilaginous part of the metapterygoid ( wing bone of the fish) is double-headed in the basal orders Cypriniformes and Characiformes, in the Siluriformes it ends in a single end.
The first supraneuralia (parts of the vertebrae), in the tetras and catfish, or, in the carp-like species, the first two supraneuralia are widened downwards and connected to the neural arches of the third and fourth vertebrae.
Parts of the neural arch of the first vertebra are converted to the scaphium and caustrum.
The neural arch of the second vertebra is converted to the intercalarium.
The first four vertebral centers show some shortening compared to vertebral centers further back.
The foremost parapophyses, processes on the underside of vertebrae, are, if present, fused with the central vertebral body (could also be a synapomorphism of the ostariophysi).
The tripus, a special ossicle of Weber's apparatus , was formed from the rib and parapophysis of the third vertebra.
The shortened ribs of the fourth vertebra, called the suspensorium, enclose the front section of the swim bladder on both sides .
The following cladogram shows the systematic position of the otophysa:
Wilfried Westheide , Reinhard Rieger: Special Zoology. Part 2: Vertebrae and Skull Animals. 1st edition, Spektrum Akademischer Verlag, Heidelberg • Berlin 2004, ISBN 3-8274-0307-3 .
EO Wiley & G. David Johnson: A teleost classification based on monophyletic groups. Page 134 in Joseph S. Nelson, Hans-Peter Schultze & Mark VH Wilson: Origin and Phylogenetic Interrelationships of Teleosts. 2010, Verlag Dr. Friedrich Pfeil, Munich, ISBN 978-3-89937-107-9 .