This week I probably won’t be able to respond to comments on the mystery object as I’m in Liverpool at a conference about Dinosaurs (yay!), but I have a feeling you’ll get this without any help from me, as it’s pretty distinctive:
Good luck!
Zygoma
Adventures in natural history collections
Zygoma 
It’s a juvenile. Did it say farewell to the big top ?
Awww look at its widdle tusk!
Infant elephant or perhaps dwarf elephant
Foetal Heffalump.
Baby/fetal female african?
tiny narwal?
Juvenile indian elephant? I think i remember this one…
I agree with everyone else that this pachyderm is a juvenile. How about Loxodonta cyclotis?