The Order Acipenseriformes: Sturgeons and Paddlefishes

What species are included in the order Acipenseriformes?

A) Paddlefishes

B) Cichlids

C) Darters

D) Piranhas

Answer:

The order Acipenseriformes includes sturgeons and paddlefishes.

The order Acipenseriformes includes fishes that are known for having elongated bodies and being primarily cartilaginous, despite being classified as bony fishes. This order specifically includes sturgeons and paddlefishes. Characteristically, fishes in this group possess a notochord, a cartilaginous skeletal rod that supports the body during larval development.

Although not in the same order as cichlids, darters, and piranhas, which are also bony fishes (Osteichthyes), sturgeons and paddlefishes share the same taxonomic class, Actinopterygii, which is represented by the ray-finned fishes. These ray-finned fishes are so named due to the fan of slender bones that support their fins.

It is important to note that neither sturgeons nor paddlefishes are closely related to sharks or rays, which are cartilaginous fishes (Chondrichthyes), despite being cartilaginous themselves. The order Acipenseriformes thus specifically includes sturgeons and paddlefishes, making the correct answer to the initial question "Paddlefishes" (Option A).