Review of the fossil pufferfish genus Archaeotetraodon (Teleostei, Tetraodontidae), with description of three new taxa from the Miocene of Italy.

Three new species of the extinct pufferfish genus Archaeotetraodon are described from the Middle to Upper Miocene of Italy (A. bannikovi sp. nov, A. dicarloi sp. nov., A. zafaranai sp. nov.), and compared in detail with the three previously described taxa of the genus [A. jamestyleri (Bannikov, 1990), A. winterbottomi Tyler & Bannikov, 1994, A. cerrinaferoni Carnevale & Santini, 2006], which are known, respectively, from the Miocene of Ukraine, the Oligocene of Russia, and the Miocene of Algeria. The three new species described herein bring the number of known Archaeotetraodon species to six, thereby making it by far the most speciose extinct genus of the order Tetraodontiformes. The monophyly of Archaeotetraodon is supported by two derived conditions: bifid scale spinules (versus single spinules in all other tetraodontids), and the fusion of the haemal spine of the penultimate vertebra to the centrum (versus autogenous in all other tetraodontids). We compare a large suite of morphological features of Archaeotetraodon to those found within the group of more basal tetraodontid genera to which we believe it belongs, but we are unable to determine the closest relationships of Archaeotetraodon within that group. Morphofunctional and paleoenvironmental considerations suggest that the species of the genus Archaeotetraodon were adapted to a pelagic or deep-sea lifestyle and were probably able to tolerate relatively low oxygen concentrations. The entire fossil record of the family Tetraodontidae is discussed.