Something (probably an injury) triggered a replacement cartilaginous tail to grow, but the original was still in tact. Anoles have "breakage planes" in place at each vertebrae in their tails which when allow them to quickly release of the rest of the tail beyond a stressed point, usually when a predator has a hold of it. After awhile, a replacement will grow in its place, but instead of having bony vertebrae, it will have cartilage.
Sometimes the original tail doesn't break off all the way and the result is a second cartilaginous tail sprouting from the spot, creating a double tail like this.
anoledouble tailsplit tailbrown anole