After last week’s anthropological object, I thought I’d give you a bit of a challenge:
Any idea what this is?
As usual you can put your suggestions, comments and questions below and I’ll do my best to answer. Good luck!
Zygoma
Adventures in natural history collections
Zygoma 
Well, just as a first observation, I’d say its a vertebra from something or other. I shall ponder on what…
It’s certainly an odd-looking one, with its flattened profile and lack of anything in the way of a centrum presumably being significant. My guess would be an atlas vertebra (or at least one from the neck), and, as for animal group, I’d suggest a turtle, and a pretty big one at that.
Beyond that, I’m not really sure; there are a number of turtles that would be in roughly this size range. One tends to think of sea turtles when you think large… but I’m fairly sure some of the bigger freshwater ones would be in this size range, as well.
I like your reasoning, but this is not a vertebra!
Could this be a cross-section of a turtle/tortoise carapace?
It is a cross-section, but not of a testudine.
I’m thinking it’s a cervical vertebra to a side-necked turtle, for a number of reasons, but the clincher is because it’s asymmetrical.
Most of the side-necked turtles are from Australia, South America, and Africa. Since the collection you pull most of your unusual specimens from often has an African species, I’d venture a guess that this turtle’s from Africa. Just a guess though. This bone made be wonder what cross-sections of all the os penises of the world would look like. Are they solid, or do they have ventricles and holes?
This reasoning would be spot-on if this were a vertebra, but it’s not!
As to bacula, they are solid, sometimes with a urethral groove, but not always. They tend to have quite a range of cross-sectional shapes that are species specific, so they can provide useful characters for identification.
My first thought was a large chondrichthyan skull – sawfish maybe?- , but it does seem a bit bony. But then, it looks a bit like an anterior view of a sectioned pelvis of something like a rhino, but that would make the ring in the centre a bit odd for a section of caudal vertebra, particularly as you say it’s not vertebrae. Close?
Some of what you said is very close indeed, but I’m not saying which bit!
Just did the sensible thing and looked at the scale, which pretty much rules out the rhino. Soooo… chondricthyan?
😉
Hmm. Is it a cross section through a small ray of some sort?
Narcinidae?
Not Narcinidae
The cross-section of a sawfish ‘saw’?
Oooh….
I think maybe something like this or a paddlefish but I can’t find another picture that looks like it.
Or a paddlefish/sturgeon’s snout?
Cooler
My first thought was pelvis until I spotted the asymmetry. A unicorn horn? Seriously, might it be a narwhal horn?
Narwhal tusks are upper left incisors with a twist, so they would indeed look asymmetrical. However, although they have a central pulp cavity, they don’t have the extra bits.
So not a unicorn.
are those sinus cavities?
I believe they are.
Maybe the skull of a Hammerhead shark?
I looked at pictures earlier today of a hammerhead shark skull and I don’t think it is a hammerhead shark because the bone looks too heavy and thick and not like cartilage. The nose bits don’t seem to go through the middle of the skull on a hammerhead shark either.