Is it a spiral (I think so, but it could be separate rings, going just on the photo)?
Please could we have a photo from each end as well.
It would be useful to know its density, as a means of determining whether it is made of rock (ie. a fossil) or not. You can determine its volume by water displacement, weight on kitchen scales, preferably ending up with density in g/ml (=g/cc).
Any details on location would also be useful (Northern Somalia being quite large).