Think this is a skull? but of what animal I don't know
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I had thought that after seeing spring watch a moment ago (tahat's what reminded me to post it), but wasn't too sure.
Correctly, this is the synsacrum - the pelvic bones fused to most of the lower vertebrae. In the second picture you can clearly see the fused chain of vertebrae in the middle on the underside. It provides rigidity to the skeleton in flight. This structure that causes more puzzlement than almost anything else posted on iSpot, usually assumed to be the skull of some strange beast.
recording wildlife with The Recorder's Year on www.hbrg.org.uk/TRY.html.
Lat/Lng: 51.1, -1.5
OS grid ref: SU3544