Taniwhasaurus

Taniwhasaurus is an extinct genus of mosasaurs (a group of extinct marine lizards) that lived during the Campanian stage of the Late Cretaceous. It is a member of the subfamily Tylosaurinae, a lineage of mosasaurs characterized by a long toothless conical rostrum. Two valid species are attached to the genus, T. oweni and T. antarcticus, known respectively from the fossil record of present-day New Zealand and Antarctica. T. 'capensis' from present-day South Africa represents a chimera of two different mosasaur genera, potentially Prognathodon and Taniwhasaurus, but not identifiable at the species level. The other formerly assigned species, T. 'mikasaensis' from present-day Japan, remains problematic due to the fragmentary state of the attributed fossils. The generic name literally means "taniwha lizard", referring to a supernatural aquatic creature from Māori mythology.

Taniwhasaurus is a medium-sized mosasaurid, with maximum size estimates putting it at around 5 to 8 meters (16 to 26 ft) in length. The rare fossils of the axial skeleton indicate that the animal would have had great mobility in the vertebral column, but the tail would generate the main propulsive movement, a method of swimming proposed for other mosasaurids. The constitution of the forelimb of Taniwhasaurus indicates that it would have had powerful paddles for swimming. CT scans performed on the snout foramina of T. antarcticus show that Taniwhasaurus, like various aquatic predators today, would likely have had an electro-sensitive organ capable of detecting the movements of prey underwater.

The fossil record shows that both officially recognized species of Taniwhasaurus were endemic to the seas of the ancient supercontinent Gondwana, nevertheless living in different types of bodies of waterbodies. Indeterminate specimens including the holotype of T. 'mikasaensis' have also been found in Eurasia, but they are not diagnostic to the species level. The concerned geological formations shows that the genus shared its habitat with invertebrates, bony fishes, cartilaginous fishes, and other marine reptiles, including plesiosaurs and other mosasaurs.