A new eomysticetid from the Oligocene Kokoamu Greensand of New Zealand and a review of the Eomysticetidae (Mammalia, Cetacea)

Eomysticetids represent a worldwide, short-lived radiation of archaic baleen-bearing mysticetes that elucidate morphofunctional shifts and ontogenetic change amongst early Neoceti. Fossils of eomysticetids are now recorded from Oligocene marine rocks along the margins of the North Pacific (Japan), North Atlantic (South Carolina), and the Southern Ocean (New Zealand). The assemblage from New Zealand is diverse, with five species in three genera present during the Duntroonian stage (Chattian, 27.3–25.2 Ma). A new genus and species of eomysticetid from the lower Kokoamu Greensand of New Zealand, <i>Matapa waihao</i> gen. et sp. nov., increases the known diversity of Southern Hemisphere eomysticetids. <i>Matapa</i> uniquely exhibits a rounded margin of the occipital shield, and shares a mosaic of features seen in Northern Hemisphere eomysticetids such as a large squamosal prominence, an inflated and posteriorly rounded paroccipital process, and a double-faced posterior bullar facet with longitudinal ridges. The holotype specimen of <i>Matapa waihao</i> is ontogenetically immature, but ontogenetically static tympanoperiotic characters that diagnose this new species are shared by referred adult specimens. <i>Matapa</i> is uppermost Whaingaroan (28.1–27.3 Ma) in age, the oldest eomysticetid from New Zealand. Fossils of <i>Matapa</i> are recovered from both the modern west and east coast of New Zealand which, during the Oligocene, were on the margin of the Southern Ocean. Inclusion of <i>Matapa</i> within an earlier published cladistic analysis recovers <i>Matapa</i> as the earliest diverging member of the New Zealand eomysticetid clade, and confirms eomysticetid monophyly. The taxonomy, morphology and geochronological age of all known eomysticetids are reviewed. http://zoobank.org/urn:lsid:zoobank.org:pub:EE1CB5CC-618B-4ABA-9D97-5B9DEDD3470E