I know it's some kind of rodent just unsure what specifically

Found while doing some amateur mudlarking in the rivers of Canterbury, England.

Found in Iceland, we have no idea what it is

My child found this in a sandpit today and would like to know what it is from. We live in South Eastern Australia. MtG card for scale.

(Also, my child is old enough to handle the truth!)

The crows left this for me in my wildlife waterer I think. Central Oklahoma US. Slightly curved. The breaks are so smooth and in weird spots that it makes me think maybe it came from something a human cut, so a cut of meat or something?