A recent study details the first-ever free-swimming shark lacking skin-related structures found off Cape Carbonara, Sardinia. Interestingly, the shark is missing an epidermis, stratum laxum, dermal denticles, and teeth.
Last July, trawlers fishing at a depth of 1,640 feet (500 meters) caught a blackmouth catshark, Galeus melastomus. The anglers were shocked to find that the shark was missing its skin and teeth. This morphological abnormality seems potentially fatal. However, the Journal of Fish Biology finds the specimen in good health.
Here is a link to the scientific journal reporting this discovery.