Gracanicanetta
Gracanicanetta is a genus of extinct duck that lived on in Bosnia and Herzegovina during the middle Miocene epoch. It currently contains only one species which is Gracanicanetta happi. It lived in swamp environments and was probably a diving duck. It has the record of being the first documented fossil of a duck with gastroliths. Theses appear as smooth stones in clusters of around a dozen in the approximate location of the gizzard.