Koristocetus pescei gen. et sp. nov., a diminutive sperm whale (Cetacea: Odontoceti: Kogiidae) from the late Miocene of Peru

Alberto Collareta, Olivier Lambert, Christian de Muizon, Mario Urbina, Giovanni Bianucci
2017 Fossil Record  
<p><strong>Abstract.</strong> Among odontocetes, members of the family Kogiidae (pygmy and dwarf sperm whales) are known as small-sized and in many respects enigmatic relatives of the great sperm whale <i>Physeter macrocephalus</i>. Most of the still scanty fossil record of Kogiidae is represented by isolated skulls and ear bones from Neogene deposits of the Northern Hemisphere, with the significant exception of <i>Scaphokogia</i>, a highly autapomorphic genus from late Miocene deposits of the
more » ... isco Formation exposed along the southern coast of Peru. Here we report on a new fossil kogiid from Aguada de Lomas, a site where the late Miocene beds of the Pisco Formation are exposed. This specimen consists of an almost complete cranium representing a new taxon of Kogiidae: <i>Koristocetus pescei</i> gen. et sp. nov. <i>Koristocetus</i> mainly differs from extant <i>Kogia</i> spp. by displaying a larger temporal fossa and well-individualized dental alveoli on the upper jaws. Coupled with a relatively elongated rostrum, these characters suggest that <i>Koristocetus</i> retained some degree of raptorial feeding abilities, contrasting with the strong suction feeding specialization seen in Recent kogiids. Our phylogenetic analysis recognizes <i>Koristocetus</i> as the earliest branching member of the subfamily Kogiinae. Interestingly, <i>Koristocetus</i> shared the southern coast of present-day Peru with members of the genus <i>Scaphokogia</i>, whose unique convex rostrum and unusual neurocranial morphology seemingly indicate a peculiar foraging specialization that has still to be understood. In conclusion, <i>Koristocetus</i> evokes a long history of high diversity, morphological disparity, and sympatric habits in fossil kogiids, thus suggesting that our comprehension of the evolutionary history of pygmy and dwarf sperm whales is still far from being exhaustive.</p>
doi:10.5194/fr-20-259-2017 fatcat:u5v54x4mlzfjxeumh5qs5hnguy