Kem Kem Abelisaurid Ulna?

[LordTrilobite]

I found this rather interesting piece on our favourite auction site. It's being sold as a croc vertebra. But it looks a lot like the ulna of an Abelisaurid from the Kem Kem beds. The resemblance with the ulna of Majungasaurus is pretty close. It's a little shorter, but the single bump on the one side seems to fit. While if it was a vertebra, it seems to lack a neural canal.

 

 

Majungasaurus left ulna

[Troodon]

Very interesting and I can see the similarity but I'm in the vertebra camp.  I believe what you are looking at is the ventral side of the vertebra.  If you look at his pictures he is very cagy intentional or not but does not show you the dorsal side of that item and that's where your neural canal would sit.  The picture I added is the closest to a dorsal view you have and there a possible signs of a sutures or flat surface.  I also see ligament pits on the side, typical of what you see on vertebra not arm bones.   There are other features but will leave it at that.  You can ask him for additional photos which would put your question to rest or not.

 

[LordTrilobite]

Good point, didn't see that.

[Renaud]

I am wondering if it's not a sacred vertebra? You can see the contact with the sacred rib on the proximal edge. 

 

For me it's not a crocodile, I found a sacral vertebra of ornithopod a few years ago in the Tithonian, she looked like this, but I'm not a dinosaur specialist.

[Troodon]

I'm more inclined to think its a Croc but the Kem Kem is a real mystery so who knows.  Not a lot of comparative material around.  The obtuse angles and missing dorsal views increase the complexity. I've seen that ventral keel on other Crocs like the picture I added of Deinosuchus so it could be a very anterior dorsal. The curvature of the front face would assist in the articulation of the cervical.  All guess work.

 

[LordTrilobite]

I think you might be right. Looking at the photos again, it looks like there are some articular surfaces where the ribs would fit on the two sides.

[Seguidora-de-Isis]

Some years ago I bought this bone of Kem Kem, and today reading your post, I remembered my bone. What do you think @LordTrilobite? Croc vertebra or an ulna of an Abelisaurid?

 

 

 

 

[LordTrilobite]

Absolutely a vertebra. Likely croc.