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 6.7 meters (22 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.
Research history
Recognized species
T. oweni
The first known species, Taniwhasaurus oweni, was discovered in the 1860s in the cliffs of Haumuri Bluff, located in the Conway Formation, eastern New Zealand. This formation is dated from the Upper Cretaceous, more precisely from the lower and middle Campanian stage. The first fossils formally attributed to this taxon were described by the Scottish naturalist James Hector in 1874. The skeletal material of T. oweni consisted of a skull, vertebrae and paddles, divided into three distinct sections. In 1888, noting that the fossils are incomplete, Richard Lydekker uncertainly placed T. oweni within the genus Platecarpus, being renamed Platecarpus oweni. In 1897, in his revision of the distribution of mosasaurs, Samuel Wendell Williston put Taniwhasaurus back as a separate genus, but considered it to still be close to Platecarpus. As Hector did not designate a holotype fossil for this taxona, Samuel Paul Welles and D. R. Gregg designate specimen NMNZ R1536, a fragmented skull consisting of frontal and parietal bone accompanied by partial dentary bone, as the lectotype of T. oweni in 1971. The genus name Taniwhasaurus is made up of the Māori word Taniwha, and the Ancient Greek word σαῦρος (saûros, "lizard"), all literally meaning "lizard of Taniwha", in reference to a supernatural aquatic creature from Māori mythology. The specific epithet oweni is named in honor of the famous English paleontologist Richard Owen, who was the first to describe the Mesozoic marine reptiles of New Zealand. In his article, Hector describes several skeletal remains which he attributes to another mosasaur, which he names Leiodon haumuriensis. In 1897, Williston suggested to transfer this taxon within the genus Tylosaurus, a proposal that was carried out in 1971, being renamed Tylosaurus haumuriensis. Welles and Gregg also referred to specimen NMNZ R1532 as the lectotype of Tylosaurus haumuriensis in the article. Although most of these remains have been lost since the 1890s, it's in 1999 that new cranial and postcranial material was discovered in the cliffs of Haumuri Bluff and that these findings were formalized by Michael W. Caldwell and his colleagues in 2005. Based on extensive analyzes of these fossils, researchers found that there are in fact few morphological differences between the two mosasaur taxa from this locality, the differences being mainly due to the larger size of specimen NMNZ R1532, making Tylosaurus haumuriensis a junior synonym of T. oweni.
T. antarcticus
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