arsanatomica:These are fins from a 500lb Bluefin Tuna. Tuna are members of the Scrombrid fam
arsanatomica: These are fins from a 500lb Bluefin Tuna. Tuna are members of the Scrombrid family, a group of fast swimming, partially warm-blooded apex predators, with highly streamlined bodies and retractable fins. In the image above, the large dorsal fin, with its rigid bony rays, can disappear completely into a deep groove on the body.This gives the fish its distinctive bullet shape, as it charges forward in the water. The fin is pulled out when the fish is slowing down, or turning to keep its cylindrical body from rolling over. The distinctive little fins, or finlets in the last image are only found in this group of fish. Muscles beneath the skin allows them to move independently. There’s a few people out there researching this, but at the current time their exact function is unknown. -- source link