Correction – 05/10/2014
Much to my disappointment, and I’m sure your own, I have to put my hands up to having made a bit of a blooper here. Thank god it wasn’t on the internet for all to see. The bone fragment below is in fact part of a birds sternum, species still unknown, not as first suspected shark fin cartilage. In my defence the shape is damned close but alas my inner child will have to accept reality though it’s still a fascinating specimen to add to my burgeoning collection. I’ll keep the blurb below as at the very least I learned something new about shark physiology and hopefully I can help prevent anyone else from making the same glaring error.
Another of my prized finds from many hours spent beachcombing is this Shark Fin bird sternum discovered on Gower just a couple of weeks ago.
Unlike you or I the skeleton of a shark is made up almost entirely from cartilage. This has the principle advantage of being lighter than bone meaning that the shark need exert far less energy to propel itself through the water. The animal loses no structural strength however as its skin is so thick that it acts almost like an external skeleton to which all the muscles are attached. This direct connection between muscle and skin is more efficient than typical physiology and is no doubt just another reason for the groups success.
All that said it means that any remains are rarely washed up intact so to find this complete fin is something rather special. Sizewise it measures approximately four centimetres tall but the jury is still out on an exact species.