Moanasaurus

Abstract: New mosasaur specimens of Piripauan-Haumurian (Campanian-Maastrichtian) age are described from the Mangahouanga Stream, North Island, New Zealand. These include two distinctive adult skulls and one incomplete cranial and postcranial specimen. A new genus and species Rikisaurus tehoensis is recognised and a new species of Mosasaurus, M.flemingi, is described. A further specimen is identified as aff. Prognathodon overtoni. Two fragmentary specimens are also described (as aff. Moanasaurus mangahouangae and gen. and sp. indet.), along with an isolated adult limb bone (gen. and sp. indet.) of a type not previously collected in New Zealand.

Abstract: Novas et al. (2002. Ameghiniana 39:245–249) described and named a new mosasaur as Lakumasaurus antarcticus from the Late Cretaceous marine deposits of the Antarctic Peninsula. The specimen was recovered from the late Campanian Santa Marta Formation on James Ross Island. A number of characters indicate the affinities of Lakumasaurus with the Tylosaurinae. However, other characters of Lakumasaurus are unusual among tylosaurines, particularly the dentition bearing fine striae, teeth with non-serrated anterior carinae, anterior teeth without posterior carinae, relatively straight lateral margins on frontal and relatively small size. Investigation of mosasaurs from New Zealand confirms that these characters occur in the type specimen of Taniwhasaurus oweni Hector 1874, collected from the late Campanian Conway Formation of Haumuri Bluff. Size and similar morphological characters indicate the synonymy of Lakumasaurus with Taniwhasaurus. The synonymy of Lakumasaurus with Taniwhasaurus adds significantly to the evidence of endemism among marine reptiles in Antarctica, New Zealand and Patagonia (Weddellian Province) during the Late Cretaceous. Taniwhasaurus along with the possible co-occurrence of Moanasaurus are the first mosasaurs at a generic level to indicate Gondwanan endemism. The mosasaur evidence is complemented by the plesiosaur Aristonectes, which occurs in the Maastrichtian of Argentina and Antarctica and appears similar to Kaiwhekea from the Maastrichtian of New Zealand, and by Mauisaurus, an elasmosaurid which occurs in the Maastrichtian of Antarctica and medial Campanian-Maastrichtian of New Zealand. Copyright © 2007 John Wiley & Sons, Ltd.

Abstract: Fossil organic-walled dinoflagellate cysts (dinocysts) have been used to constrain the age of the Maungataniwha Sandstone and associated phosphatic and calcareous concretions from the Mangahouanga Stream, northwest Hawke's Bay, New Zealand. These concretions often contain dinosaur and marine reptile fossils, including the mosasaur Moanasaurus mangahouangae, first discovered within the study area in a calcareous concretion. The Maungataniwha Sandstone contains low to moderately diverse dinocyst assemblages corresponding to the Vozzhennikovia spinulosa – Isabelidinium pellucidum zonal interval (lower to upper Haumurian). Recovered dinocyst assemblages from in situ concretions are similar to those from the surrounding sediments, suggesting that the concretions have grown in place. Calcareous float concretions containing the mosasaur Moanasaurus mangahouangae, as well as the two phosphatic concretions (one of which also contained a mosasaur fossil), are all of a lower Haumurian age. Plesiosaur fossil...