Daunting dentitions: Relationships and functional morphology of three new Oligocene dolphins with tusk-like teeth from New Zealand

The focus of this thesis is the description of three new species represented by specimens OU 22397, OU 22126 and OU 22262. Specimen OU 22397 has a near-complete skull, uniquely preserved teeth and some post-cranial material which form the basis for the description of a new species and genus of Oligocene dolphin. Through the use of Micro-CT scans, scanning electron microscopy and visual observations the feeding apparatus of this dolphin is studied. The flattened rostrum and laterally-oriented teeth, amongst other features, support the hypothesis that this dolphin fed in a fashion previously undescribed for cetaceans. This involves lateral slashing of prey, as seen in sawfish, followed by raptorial feeding and consumption of the animal much in the way seen in Platanista gangetica. Specimen OU 22126 also represents a new species and genus of its own which is smaller and more gracile than OU 22397. Though no post-cranial material or mandible is preserved it has several unique characteristics of interest – in particular the crown of its first incisors are not fully erupted from the premaxilla. Though this specimen alone does not provide sufficient evidence to support the hypothesis of sexual dimorphism, the possibility is discussed, and this dolphin provides data for further studies on the topic. The prior classification of OU 22126 as a dalpiazinid is discussed and it is concluded that these animals are more closely related to waipatiids than these Italian dolphins. Specimen OU 22262 represents a new species belonging to the same genus as OU 22397. It is composed of a heavily damaged skull missing most of its rostrum, a fragment of left mandible, pristine periotics and bullae and a selection of post-cranial axial and limb elements. This post-cranial material allows for further investigation of the locomotion and neck mobility of these dolphins. A phylogenetic analysis of all three specimens is presented using a matrix of 98 taxa and 284 characters. Both an unweighted and a weighted (K=3) parsimony analysis were carried out. The results suggest that all three specimens belong to a single clade containing them and Ediscetus osbornei. This clade plots well within waipatiids and is near the base of a monophyletic Platanistoidea clade. Altogether this thesis provides formal descriptions of three new species of dolphin as well as suggesting a new feeding style, previously undescribed in cetaceans. With further study further detail regarding these animals could be discovered and this thesis begins that process