Gamerabaena sonsalla, a baenid freshwater turtle that lived at the very end of the Cretaceous (~66 mya) in North Dakota, USA. Known only from a single skull, its full size is uncertain, but it may have reached lengths of around 50cm (1′7″).
Baenids first appeared in the mid-Cretaceous (~112 mya) – although their ancestry may go as far back as the Late Jurassic (~150 mya) – and were part of an early lineage of the cryptodiran turtles, the grouping which includes most freshwater turtles and terrapins, all terrestrial tortoises, and all sea turtles. However, unlike many of the their modern cousins, they weren’t capable of fully retracting their heads inside their shells.
They survived well through the K-Pg mass extinction, with several species found on both sides of the boundary, but eventually went extinct in the mid-Eocene (~42 mya).