chondrostelean

Chondrostean is a term used to describe a group of ray-finned fishes that are primitive in their evolutionary lineage. These fishes belong to the infraclass Chondrostei, which is part of the subclass Actinopterygii. The most distinctive characteristic of chondrosteans is their largely cartilaginous skeleton, although they possess dermal bones. This feature reflects their ancestral condition, as the skeletons of more derived bony fishes are predominantly ossified.

Modern chondrosteans are represented by a very small number of species, most notably the sturgeons and paddlefishes. Sturgeons are large, bottom-dwelling fish found in the Northern Hemisphere, known for their elongated bodies, scutes (bony plates) along their sides, and barbels used to detect prey. Paddlefish are also large fish, characterized by a long, flattened snout called a rostrum. Historically, the group was much more diverse, but it has undergone significant decline, with many species now endangered or extinct.

Chondrosteans are considered an important group for understanding the evolution of bony fishes. Their anatomical features, such as the structure of their fins and skull, provide insights into the transition from cartilaginous skeletons to fully ossified ones seen in teleost fishes, which constitute the vast majority of living fish species today. Their ecological roles vary, with sturgeons often being important predators in their aquatic environments.