I don't know very much about fossils, but we found this one in a boulder at the base of the cliffs in Mewslade Bay on the Gower. It seemed to have lots of tiny bones coming off a backbone but really didn't remind us of anything. I've had a look at a fossil identification chart but it doesn't seem to resemble anything I've seen. I'd be very grateful if you could identify it for me please. Many thanks!
I agree with Thomas. This is a transverse cross section through a coral. Corals consist of a soft polyp, similar to a sea anemone, which secretes a hard limestone skeleton of calcium carbonate for support. The remains of the skeleton are often fossilised, as in this specimen which has been preserved in hard limestone rock. What you can see in your photographs is a slanted cross section across the coral cup (corallite) where the polyp would have sat when alive.
Coral fossils like this are common in Carboniferous Limestone rocks which occur widely in Britain and Ireland, including the Gower Peninsula where you found this, so it is almost certainly of this age, roughly 300 million years old!
Like you did, most people think of bones first, but most fossils are animals without bones but with other hard parts, like shells and coral. I have to say that, as an invertebrate fan! Also, cross sections and preservation throw up tricks and the guides usually only show perfect whole specimens which don't help!