Biltnerites is an ammonite (s.l.) genus from the lower Triassic included in the ceratitacean

Ceratitaceae

The Ceratitaceae is a superfamily in the ammonoid cephalopod order Ceratitida characterised in general by highly ornamented or tuberculate shells with ceratitic sutures that may become goniatitic or ammonitic s some offshoots....

 family Tirolitidae of the order Ceratitida, characterized by a flat, evolute shell with moderately compressed, rounded whorls. The spinose stage characteristic of the Tirolitidae is absent, but the outer whorl does have indistinct ribs that cross the venter.

Biltnerites has been found in Lower Triassic sediments is S.E. Europe