Big Hell Creek bone - a bit of a mystery

[Opabinia Blues]

So, this bone was collected by me earlier in the summer from the Hell Creek Formation in Montana. Upon collecting this bone I had thought that it was a Triceratops (or other Ceratopsid, I suppose) phalanx based on the shape and my memory of seeing pictures online. I was pretty confident in this ID up until a few days ago, and the following are throwing me:

 

1. This bone seems really big for a Triceratops phalanx. The other examples I can find online are not this large, but then again Triceratops was a pretty big animal and I’ve underestimated its size before.

 

2. It’s hard to tell because it is very weathered, but the shape isn’t quite a good of a fit as for a trike phalanx as I had initially thought. Also, the underside of the bone is heavily eroded, which I hadn’t noticed before as I had yet to clean all the mud/matrix off of it.

 

So, I’m posting this here in the hope of getting a few more looks from some other people. Let me know what your thoughts are, and thank you in advance!

 

 

 

 

 

 

Obligatory tag of @Troodon

 

Thanks for looking!

[Troodon]

Definitely not a phalanx, to large and boxy.   Any chance its a part of a sacrum or even more so the distal part of a ceratopsian syncervical (axis part), see photo..

 

 

 

[Opabinia Blues]

1 hour ago, Troodon said:

Definitely not a phalanx, to large and boxy.   Any chance its a part of a sacrum or even more so the distal part of a ceratopsian syncervical (axis part), see photo..

 

 

 

Possibly… if it is it’s bigger than the one in the photo, but the shape seems to be at least close to correct. Do the cervical verts display lateral compression like my bone shows?

 

A pelvic element isn’t a bad idea either.

[Troodon]

Not sure what lateral compression you are referring to.  Pelvic bones are typically flatish, nothing that boxy in that area.

Here is one in my collection, its a juvie and the distal end diameter is 7" across.

 

[Opabinia Blues]

Alright, so we’re back to square one in this one. There’s a Torosaurus syncervical vertebra on display at the Denver Museum of Nature and Science which I went to look at for comparison… and I’m pretty confident in saying that my bone is not any part of a syncervical. Not sure where to go to from here, although I will say that of all the bones on a Ceratopsid skeleton, an element near the pelvis still does seem to make the most sense (circled in the last photo is what looks familiar). But of course this is all working on the assumption that it is a ceratopsid bone, which may not be the case.

 

 

Edited September 7, 2021 by Opabinia Blues

[jpc]

This looks like a vertebra... a big one. Possibly a sacral.

[Opabinia Blues]

10 minutes ago, jpc said:

This looks like a vertebra... a big one. Possibly a sacral.

That’s what I’ve been thinking now that I’ve looked at a skeleton more closely.

[Troodon]

Well that was the first option I presented part of the sacrum

[Opabinia Blues]

15 hours ago, Troodon said:

Well that was the first option I presented part of the sacrum

Yes, and that’s why I had gotten pictures of the sacrum from the museum specimen for comparison. Thanks for the suggestion.