Tangasaurus mennelli (Haughton 1924; Late Permian) was known from only two specimens collected in 1922. Later, Currie (1982) reported over 300 partial specimens were attributed to Tangasaurus, but reattributed most of them elsewhere.
The large reptile tree nested Tangasaurus betwee Acerosodontosaurus and Claudiosaurus. Hovasaurus and Thadeosaurus are sister taxa.
Haughton (1924) described a long, powerful, flattened tail and presumed an aquatic existence. The great size of the transverse processes at the base of the tail are notable. So is their anterior curvature. These reflect the size of the caudofemoralis muscles driving the large hind limbs. Note the large coracoid, central sternum, short ribs, massive humerus (especialy distally) and high caudal spines creating a sculling tail ideal for swimming.