The Chondrostei are a sub-class of ray-finned fish, the Actinopterygii. They include the sturgeons, huge fish which provide caviar.
The Chondrostei are mainly cartilaginous fish with some ossification. There are 52 species divided among two orders. The orders are the Acipenseriformes (sturgeons and paddlefishes), and the Polypteriformes (reedfishes and bichirs).
This group has at times been classified with the sharks: the similarities are obvious, not only do the chondrosteans mostly lack bone, the structure of the jaw is more akin to that of sharks than other bony fish. Both lack scales (except the Polypteriforms). Additional shared features include spiracles and, in sturgeons, a heterocercal tail (the vertebrae extend into the larger lobe of the caudal fin). However the fossil record suggests that these fish have more in common with the Teleostei than their external appearance might suggest.