Finger of Pachycephalosaurus sp.
This is a specimen of the foot, claw, and phalanx (finger bone) of the pachycephalosaur Pachycephalosaurus. Found in the Hell Creek Formation, Montana. They were excavated together from the same location and are highly likely to be from the same individual.
It is common to see claws and phalanges of Pachycephalosaurus sold separately, but it is rare for them to be available together.