Eotetraodon

Eotetraodon is an extinct genus of miniature prehistoric pufferfish that lived in Europe from the early to mid-late Eocene. It is the earliest pufferfish known from fossil remains.
The following species are known:

†E. gornylutshensis Bannikov & Tyler, 2008 - mid-late Eocene of the North Caucasus, Russia
†E. pygmaeus - early Eocene of Italy
†E. tavernei Tyler & Bannikov, 2012 - early Eocene of Italy

As the name of the type species suggests, Eotetraodon was a very small fish that reached only. Despite this very small size, fossil specimens are fully ossified, suggesting that they are of adult individuals.
Although generally considered an early pufferfish, some recent studies have placed it as part of an evolutionary grade, containing several other Bolca tetraodontiforms, leading to the threetooth puffer, a different tetraodontiform fish.