Looks like just 1/2 of the abdomen of something and it looks like you can see where some of the legs were attached. I think the top (second pic in the thread) is actually the inside of whatever it was because it looks like there are some internal support structures there.
It is the underside of some sort of species of beetle including half of the thorax with the middle and rear coaxae plus most of the abdomen.
In many species of beetle such as water beetles or chafers these two sections are fused together and there is no obvious clear demarcation between thorax and abdomen. Looking at the first picture you can clearly see the hind coxal process which essentially mark the 'end' of the badomen. Probably the remains of a beetle dropped by a bat of other predator.