thanks to Jackie and Bob at pompeiiinpictures there is some talk about an urban myth that I had not heard before. Remember that pompeiiinpictures is a great resource and a link to it is also found on the History Teachers Association of NSW website in the links section.
Delta the dog of (Pompeii or) Herculaneum
There is a reference to this myth or truth in a book of 1822 but there is no source information quoted to prove this as myth or fact. There are references to the dog being found in Herculaneum and the the collar, with a Greek inscription, being (then) in the Gallery of the Grand Duke of Tuscany. (Other versions elsewhere refer simply to the excavations at Pompeii and Herculaneum).
The story is not about the dog that was chained up. It's about the dog who was protecting a child that day in 79 AD. The story reads that a dogs skeleton was found laying over the body of a child about the age of ten or twelve. The dog had a silver collar that was engraved with his name "Delta" and it also recounted how he had saved his master, Severinus (Severino) from death on three occasions. Some accounts say the child was Severinus, and some say he was the son of Severinus.
A rather touching story although it didn't end well for either the dog or the child.
A researcher is currently trying to prove the story by finding the collar which seems to have vanished over time. I'll let you know if any more comes of this.