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

• Published in: Fossil Record
• Main Authors: Collareta, Alberto, Lambert, Olivier, De Muizon, Christian, Urbina, Mario, Bianucci, Giovanni
• Other Authors: Dipartimento di Scienze della Terra Pisa, University of Pisa - Università di Pisa, Royal Belgian Institute of Natural Sciences (RBINS), Centre de Recherche en Paléontologie - Paris (CR2P), Muséum national d'Histoire naturelle (MNHN)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Museo de Historia Natural de Lima (MHN), Universidad Nacional Mayor de San Marcos (UNMSM)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2017
• Subjects: [SDU.STU.PG]Sciences of the Universe [physics]/Earth Sciences/Paleontology; Fossa; Koris; Pisco; Physeter macrocephalus; Sperm whale
• Online Access: https://hal.archives-ouvertes.fr/hal-02612072; https://hal.archives-ouvertes.fr/hal-02612072/document; https://hal.archives-ouvertes.fr/hal-02612072/file/186-2017%20Collareta%20et%20al.pdf; https://doi.org/10.5194/fr-20-259-2017

International audience Among odontocetes, members of the family Kogi-idae (pygmy and dwarf sperm whales) are known as small-sized and in many respects enigmatic relatives of the great sperm whale Physeter macrocephalus. 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 Scaphoko-gia, a highly autapomorphic genus from late Miocene deposits of the Pisco 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 Kogi-idae: Koristocetus pescei gen. et sp. nov. Koristocetus mainly differs from extant Kogia 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 Koristocetus retained some degree of raptorial feeding abilities, contrasting with the strong suction feeding specialization seen in Recent kogiids. Our phyloge-netic analysis recognizes Koristocetus as the earliest branching member of the subfamily Kogiinae. Interestingly, Koris-tocetus shared the southern coast of present-day Peru with members of the genus Scaphokogia, whose unique convex rostrum and unusual neurocranial morphology seemingly indicate a peculiar foraging specialization that has still to be understood. In conclusion, Koristocetus 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.