Rock or Fossil?

[fossilisa]

I found the item pictured a couple of weeks ago in Big Brook in Colts Neck, NJ.  

I have seen photos of Pychodontid fish teeth online and am wondering if this could possibly be one, or if it is just a rock with a similar shape.  

Hoping an expert can let me know.

 

  

[Lone Hunter]

Looks like ironstone.

[fossilisa]

@Lone Hunter I thought so initially as well, but the size and shape were in keeping with what I have seen represented in photos, and the bottom concave (though not as deep as what I've seen in pictures - so I thought it was worth getting an opinion.  Thanks!

[Rockwood]

I don't think fish have a problem with cavities ,so I agree that it looks like an ironstone concretion, which are common in the brooks. The holes are likely pockets where an iron carbonate mineral has weathered away.

[Fossildude19]

I have to agree, the concretions in Big Brook are great impersonators of fossils. 

This looks like one of those.  We've all picked them up thinking they were something else.