Please indicate at least some data about locality / suggested age of the discussed specimen.
In my opinion this is not ammonite fossil, as ammonites are characterized by fluted septa, while septa of this specimen are looks like those of nautiloid cephalopods.
Well, the fossil occurs in the Xiukang melange of the Yarlung Zangbo suture, Tibet. The Xiukang melang has a long age range with olistoliths, likely from the Permian to the Paleogene. Dating them is the main hope for geologists.
I agree with Rogov. Nautiloids have concave septa towards the aperture, whereas ammonoids have convex septa towards the aperture. The specimen on the photo has concave septa, hence a nautiloid.
Not necessarily. Nautiloids are not extinct. However, it looks Palaeozoic to me (gut feeling), but nautiloids are not my field. I would hesitate a lot from making conclusions from the photo.
Based on your photograph, I agree with Rogov and Alsen. It's a nautilods, but further identification is impossible, unless you can collect more well preserved specimens.
To date, I know some isolated nautiloids occurrence in Triassic and Jurassic, at South Tibet. So it is not scarce to find some of them.
You can take some samples for conodont study, if the age is older than Jurassic.