Old sea dog

We found the carcase  of a dogfish thrown up on a shingle bank. Birds had pecked out its eyes but the rest of it was intact, if smelly. Son Huw  decided it would be ideal for a foray into Nordic cuisine.  He carried it the next couple of miles, attracting some odds looks, and it came home with us, although even the actual dog declined to sample it. Now it's been cut into chunks with a Chinese chopper, heavily salted and  securely packed for the train journey to Manchester. (With any luck the smell should get them a carriage to themselves.*)

What took my interest was the skin. Examined close up it appears to be  covered with tiny backward-pointing fangs - which is exactly what they are: dermal denticles made of the same material as fish teeth.  Stroked  tailwards the skin feels smooth  as glass but rubbed in the opposite direction it's as rough and rasping as coarse sandpaper. Which is exactly what it has been used for over the centuries by woodworkers and musical instrument makers. Sharkskin's abrasive but flexible surface is ideal for burnishing delicate surfaces. Amazingly,  a single microscopic dogfish  denticle has been found embedded in a Stradivarius violin from 1711 which proves the worth of this extraordinary stuff.

*Regarding the smell. Dogfish and other members of the shark family don't have a urinary system. Instead they excrete waste liquid, mainly urea, through their skins.

Edit
ppatrick has blipped the discovery here!