Redescription of Prognathodon waiparaensis and comments on its phylogenetic position

Prognathodon waiparaensis was a large-bodied mosasaurine mosasaur known from the latest Cretaceous of New Zealand. The holotype and only described specimen of the species has remained on display at the Canterbury Museum for more than 50 years after its initial description in 1971, during which time mosasaur systematics has substantially changed, and the generic placement of P. waiparaensis has come into question. Following 3D surface scanning of the holotype material, a redescription and comparison with more recently described species has revealed some minor changes to its initial description, including the identification of additional cranial material. Additional autapomorphies have been identified in a posterolateral pit on the coronoid and a large posterior projection on the axis intercentrum. The orientation of the two carinae on the marginal dentition ranges from anterior–posterior to anterior–labial throughout the jaw in a pattern that does not appear to have been previously reported in other taxa. An updated and rescored character dataset for P. waiparaensis has been inserted into a recently published phylogenetic character matrix, producing phylogenetic results that find P. waiparaensis to be sister to Prognathodon solvayi. The results also find polyphyly amongst Prognathodon species, and potential homoplasy amongst some of the characters diagnostic for the genus. Despite bearing many cranial morphological similarities with other Prognathodon members often related to a generalist diet that includes durophagy, the teeth of P. waiparaensis do not show the morphology or wear that is observed with other durophagous taxa, suggesting a difference in palaeoecology from many of its recognized congeners.George Young* [george.young@my.jcu.edu.au], College of Science and Engineering, James Cook University, Townsville, QLD, 4811, Australia; Al Mannering [alman@slingshot.co.nz], Canterbury Museum, 11 Rolleston Avenue, Christchurch, 8013, New Zealand; Mark Fraser [mfraser@canterburymuseum.com], Canterbury Museum, 11 Rolleston Avenue, Christchurch, 8013, New Zealand; Paul Scofield [pscofield@canterburymuseum.com], Canterbury Museum, 11 Rolleston Avenue, Christchurch, 8013, New Zealand.