A really tiny cut & polished ammonite from Madagascar. It is discreetly glued onto a base so that it stands nicely. I think that these are the centres of larger fossils which have been worked down to this size. They can work in any of the miniature scales.
Ammonites are extinct relatives of modern day nautiloids and squid. The largest known ammonite in the world would have been 8 1/2 feet (2.59 metres) across if it were complete.
5/16 inch (0.8 cm) wide, 7/16 inch (1.1 cm) tall.