Here's a better pic. The spine is about 1" long, and in most of the way. If he lays flat on the bottom, the end of the spine is at about a 30 degree angle.
That thing is right in the middle of his body, don't try to mess with it (vital internal organs).
I see a couple of possible outcomes. They way that they are barbed, they often move and come out on the opposite side of the rays body. If that happens, you can either wait for it to work itself out or pull it out.
It may also find a decent place to sit inside the rays body cavity. The spine (from a 5 month old pup) is relatively short and thin. It may not do any damage internally if it did not hit anything vital on the way in.
It looks like the spine has be pushed completely in now. I can't see the end sticking out, but there is a bulge under the skin. He still eats but is not as active as usual. There will probably be some tissue (something like scar tissue) that will grow around the spine. Maybe some day it will work its way out.
Found the stinger from the pup in the sand tonite Noticed earlier in the week that the wound site looked like it started to heal over. I figured the stinger was well embedded. Guess it worked its way out.