Dino Bone or Petrified Wood? Options

[swizz]

I found this over 20yrs ago south of Denver. At the time I was working on a very large construction project. One day while I was walking around having a smoke during break I found this in the wake of an earth-mover. I had already found various sizes of petrified wood at this site and several sites nearby during heavy equipment excavations but this piece was different.
It's only a busted up piece so I doubt anyone can put the rest of the dinosaur together with it, but might be worth cabbing? It would be virtually impossible to return to the area and prospect for many reasons, the foremost being - the entire area for miles is now clustered with office buildings (Tech Ctr area).
Have a look, hopefully someone here knows how to tell if it is... or knows of a resource that might. I could be WAY off on this.

Looks like petrified wood from this side SIDE A


The other side (inside) is concave and has many brittle tube-like cavities SIDE B


Standing it on end... there are no tree-growth rings (or grain) where there should be, or anywhere on the piece


A closer look at a small exposed area of tubular cavities on the inside


A closer look at more of the exposed tubular cavities


Here is a closeup some curious raised markings on SIDE A


Any thoughts?

[swizz]

Thanks Dan, it crossed my mind that it could be petrified wood-rot because it does kinda look like that on the inside. It's also chalkier and much lighter than all of my petrified pieces although it has some crystallization (minimal) running through it.
I'm thinking it's dead wood petrified as you suggested. I just got off the phone with GB. He's going to do a cross-section of it when it warms up enough here. I'll post pics in this thread after he cuts it... could be cool looking!
hmmmmm..... maybe some petrified termite-a-saursus rex's still in there.