Bonafide

Don't read this if you are a bit squeamish.
On my regular walk round the Thames south and north banks, I noticed that the tide was out. At one point on the walk, you can get down to the edge of the river. I always think of the various crime programmes whenever I go take a look but on this occasion, something caught my eye. You can see it here. In the centre of the picture is a bone. About 30cms long. Definitely a leg bone of some kind. Weathered and stained by the Thames, it's difficult to tell if it's human or animal or even roughly how old, but it's a bone. No bones about it.
About a metre away was another flat bone that resembled a shoulder blade and several rib-like bones.
Nice lunch time treat eh?