Dear Guys,
I recently collected three examples of interesting small bones that have the cavities in the same area, I found them in flint erratics of South Lithuania.
One scientist (Jens Koppka) told be that one time the occasional bird bone in flint was found by his colleagues in Lithuania.
I recenly found the link with very similar shape of bone known as Enantiophoenix in the middle picture of one publication that I share with you now :
https://peerj.com/articles/1032/
Open this link and look for "Comparison of scapulocoracoid between the dromaeosaurid Balaur and other paravians", the cavity in the second scapulocoracoid picture is named as "snf".
Please look at my fossil pictures and this link and help with confirmation if you could.
Best Regards
Domas