These fins have a concave front edge with rounded posterior corners. Like sharks, it has a boneless skeleton made of cartilage, a tough, elastic substance composed of collagenous and/or elastic fibers, cells, and a firm, gel-like substance called the matrix.
These fins have a concave leading edge with rounded trailing edges. Similar to sharks, their skeleton is made up of cartilage, which is a tough, flexible material containing collagenous and/or elastic fibers, cells, and a solid, jelly-like substance known as the matrix.