Associated Vertebrae?

[Nanotyrannus35]

I'd came across an sale listed as an associated pair of juvenile Hadrosaur Dorsal vertebrae - from the Judith River Formation.

I had been wondering, are they really associated, and how can you tell if fossils are associated? Here are the pictures from the seller. 

 

 

[connorp]

Since the specimens have been removed from matrix, it is impossible to prove they are associated unless the seller can provide pictures of the discovery process. Any time you see specimens described as associated, it's probably safest to assume otherwise as it's one of those things sellers tack on to inflate price.

[Troodon]

You have to be careful like connorp mentioned.

This is where trust in a digger or seller becomes important.  They need provide you the provenance that supports them being associated.   Just saying that is a weak argument.   Photos are the best but diggers rarely take them.  See what they say.   The other factor that supports the association is their preservation.. these look very similar and would have to be in close proximity to become that way, but does not guarantee it.