Some may be (especially if they are in cabinets behind glass) but most of the time plaster casts are taken of the actual bones and these are then used to make articulated skeletons (you would not...
there are certain features dinosaurs have, including: legs straight under their body, bird or lizard like hips and two extra openings in their skull.
Bone
skin,bones and guw in side there body
i really dont know but thats a really good guestion