Hell Creek Mystery - Ungual, Osteoderm?

[GPayton]

I spent two weeks in the badlands of the world-famous Hell Creek Formation in South Dakota this June with @Jared C after being graciously invited by the trip leader Harrison Duran. While there we made several amazing discoveries (check out the impending whopper of a trip report by Jared to hear all about it soon), but I also found a couple smaller things that I need some help identifying. This bone is one of them. 

When I first came across it I thought it might be a hadrosaur or ceratopsian ungual because of the silhouette, but the weird texture on the bottom and the ridge on the top seem to rule that out. Then I thought it might be an osteoderm of some sort, maybe from a nodosaur like Denversaurus or the rare Ankylosaurus itself, yet it doesn't seem to quite match any of the examples from those taxa that I've seen online. Any guesses are welcome as I've completely given up on finding out what this thing might be on my own! 

@ThePhysicist @hadrosauridae

 

Edited September 4 by GPayton

[Mikrogeophagus]

Sounds like you guys had a good time in the Hell Creek! I'm terrified to see what you two brought back... please tell me it's just a handful of gar scales... 

[ThePhysicist]

The symmetry of the bone suggests it came from the midline of the animal. I suspect the neural arch of a vertebra.

 

(Note most ankylosaurian osteoderms are asymmetrical and possess a single, non-branching keel on the dorsal surface.)

Edited September 4 by ThePhysicist

[GPayton]

9 hours ago, ThePhysicist said:

The symmetry of the bone suggests it came from the midline of the animal. I suspect the neural arch of a vertebra.

 

I never would have even considered that as a possible ID, but I think you're right! The texture of the bone reminded me of other crocodilian limb bones and vertebrae that I came across so I looked up a few pictures of what the neural arches look like and found a match. Probably a partial neural arch from a thoracic vertebra, although I still don't really know how it would have joined with the rest of the neural arch and the centrum. 

For comparison:

 

Edited September 4 by GPayton

[ThePhysicist]

Cool, I was going to guess the animal, but figured I'd just point you in that general direction and let you do the hard work. 

 

13 hours ago, GPayton said:

although I still don't really know how it would have joined with the rest of the neural arch and the centrum

Keep in mind that it's broken and worn quite a bit.