chondrostean

Chondrostean refers to members of the Chondrostei, a group of ray-finned fishes (Actinopterygii) that includes the living sturgeons and paddlefishes, as well as numerous extinct lineages. Chondrosteans are among the most primitive living actinopterygians, retaining several ancestral features such as a predominantly cartilaginous endoskeleton and a relatively elongate, heterocercal tail.

In sturgeons (Acipenseriformes), the body is long and covered with bony scutes; they possess four barbels near the mouth and an elongated snout; their skeleton remains largely cartilaginous though some bones may ossify. Paddlefishes (Polyodontidae) have a very elongated rostrum and a toothless, suction-feeding mouth, with electroreceptors on the rostrum aiding prey detection.

Ecology and conservation: They inhabit rivers, estuaries, and coastal waters; many species migrate between freshwater and saltwater; they are long-lived and late to mature; many populations have declined due to overfishing for caviar and meat and habitat loss; several species are endangered or critically endangered; conservation includes habitat restoration and farming programs.

Taxonomy: Chondrostei is a formal grouping within ray-finned fishes; living members are chiefly in the orders Acipenseriformes; the two widely recognized surviving lineages are sturgeons and paddlefishes; the group also includes numerous extinct families known only from fossils.