Shark Caudal Fin, Form and Function

Description

Many shark caudal fin illustrations show only 4-6 types and ignore the huge variety that exists, along with the reasons for the difference in shapes. Once you know the internal anatomy, it makes a lot more sense. Sharks are different from bony fishes in that they are cartilaginous and their vertebral column extends into the upper lobe of their caudal (tail) fin. They have fine collagen-like supporting filaments that extend out from the vertebral column, making up the shape of their caudal fin. The
muscles surrounding the vertebral column control the directional force of the shark’s propulsion. Sharks that feed on prey located on the sea floors tend to have a lower angle to their upper lobe. This is contrary to sharks that feed on faster moving prey in open water, which need to be capable of
maintaining or producing sudden bursts of speed, hence the steeper angle of the upper lobe.

Process

I wanted to make this illustration as clear as possible without oversimplifying. After studying the shark families, I picked out a few species in each, and after some sifting, I narrowed them down to a representative sample not only of caudal fins shape but also encompassing as wide a variety of sharks as possible. After studying numerous descriptions of each species and accumulating sufficient reference material, I created an average caudal fin for each shark family. I scanned my pencil sketched outlines, which I electronically traced using the software program ‘Illustrator’ and filled in using ‘Photoshop’. I selected the caudal fin of a Silky Shark for the anatomy diagrams as I wanted one with exaggerated shapes clearly showing the external anatomy. The vertebral column in the skeletal anatomy diagram was created using the same process as before (pencil, Illustrator and Photoshop), applying layer effects for improved volume and readability. The final layout was created using the software program ‘InDesign’.