Sacropterygii is which of the following?

• A. Lobe-finned fish
• B. Ray-finned fishes
• C. Jawless fishes
• D. Cartilaginous fishes

Answer: (A)

Sarcopterygii refers to lobe-finned fishes, a group defined by fleshy, lobed pectoral and pelvic fins that attach to the body with a robust internal skeleton and a central series of bones, more limb-like in structure. This contrasts with ray-finned fishes, whose fins are webs of skin supported by many slender bony rays rather than a solid, muscular lobe. The distinctive fin anatomy of lobe-finned fishes underpins their position as the lineage leading to tetrapods, and living examples include lungfishes and coelacanths. The other options don’t fit because jawless fishes lack jaws and have a different skeletal design, while cartilaginous fishes have skeletons made of cartilage and fins supported by cartilage rather than the fleshy, bone-backed lobes characteristic of Sarcopterygii.