First question-is that soapstone??
Yes-Definitely needs to be pinned
If you can fit the pieces tight together(that's the key) and the breaks become hairline or tighter.
Sometimes you can fit them together they become invisible.
I would do the following.
Using a flowing epoxy or a combination of epoxy and ca glue.
Put the trunk together by pinning the pieces together.
Provided there is room to work from behind the trunk.
Drill 2/3 holes in the face of trunk that broke off (slightly downward if possible)
Then using clamps fit the piece back together -drill thru the holes in the broken trunk to the elephant.
Take it apart and set the pins on the elephant.
Mount the broken piece -I would use bonstone express epoxy.
Then clamp together tight-clean off any excess-color and fill the holes in the back.
Clean off any excess-
I might do it a bit different for the tusk-fit the pieces together tightly-then use thin ca glue placed on top of the tight crack-it will penetrate .
It will drip out the bottom so be mindful of that-you will get a nice tight strong fit-then you can decide if you need to pin it. (probably a good idea)
The ca glue that drips can be shaved off with a razor.