A new fossil dolphin with tusk-like teeth from New Zealand and an analysis of procumbent teeth in fossil cetaceans

Abstract

Studies involving anatomical description and taxonomy of fossil odontocetes offer insights into their evolutionary history and diversity. This study analyses tusk-like teeth in odontocetes including the description of a new species, Nihoroa reimaea, from the Waitaki valley, North Otago, New Zealand. Dental features of Nihoroa reimaea, a gracile, longirostrine odontocete with procumbent tusk-like anterior teeth and slightly denticulate cheek teeth, are described in detail. A comparative analysis of tusk-like teeth from New Zealand specimens and from elsewhere in the world was performed allowing a classification of tusk-like teeth in odontocetes and highlighting the differences between true tusks and rooted procumbent teeth. Correlation analyses revealed significant associations between rostrum proportions and tooth crown morphology. This study contributes to the understanding of tusk-like teeth and illuminates their significance in odontocete evolution. Nihoroa reimaea expands our knowledge of fossil cetaceans and highlights the importance of New Zealand's exceptional fossil record of odontocetes with tusk-like teeth.