Wildlife Spotting

That right angle should give it away, you'd think. The only thing I've seen so far to approach it is the pectoral girdle (modified scapula or shoulder blade) of a turtle http://campus.murraystate.edu/academic/faculty/tderting/anatomyatlas/turtappenskelamy-becky.html . But I haven't really looked at other vertebrates...yet.

If so it would be among the more bizarre advertisements ever. :) Anyway it does give a sense of scale... The size and shape of the bone make me think it might come from a turtle.

Maybe it's undergone some abrasion. I'll think about it. While it is good to put in an object to give a sense of scale probably better to use a coin, pocket knife ballpoint pen. This might be mistaken for an advert.