Tangasaurid eosuchians are represented by hundreds of specimens from the Permo-Triassic strata of Madagascar and Africa. The confusion surrounding the identification and anatomy of these reptiles is resolved by comparative anatomy and relative measurements, and three genera, Thadeosaurus, Tangasaurus and Hovasaurus, are described. Extensive growth series present a unique opportunity to study differences in growth strategies in two closely related Permian genera, one that was terrestrial (Thadeosaurus) and the other aquatic (Hovasaurus). The vertebrae of Youngina have a derived character state that indicates close relationship with the tangasaurids. A new genus and species of eosuchian, Acerosodontosaurus piveteaui, has a specialized feature in the carpus that is found in the Tangasauridae. The relationships between tangasaurids and other eosuchians are considered.

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