Tirnovella

Tirnovella is an extinct subgenus of ammonoid cephalopod, from the early Cretaceous.

Use in Stratigraphy
The group is often used as an index fossil, with Tirnovella alpillensis being used to define border between the Berriasian and the Valanginian stages of the Cretaceous, and Tirnovella subalpina defining the border between the Middle and Lower substages of the Berriasian. The Middle Berriasian is the defined as the Tirnovella occitanica zone.

Distribution
Fossils of the genus are relatively common throughout Europe, with fossils from Morocco to Crimea.