Earliest Mysticete from the Late Eocene of Peru Sheds New Light on the Origin of Baleen Whales

• Published in: Current Biology
• Main Authors: Lambert, Olivier, Martínez-Cáceres, Manuel, Bianucci, Giovanni, Di Celma, Claudio, Salas-Gismondi, Rodolfo, Steurbaut, Etienne, Urbina, Mario, de Muizon, Christian
• Other Authors: 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), Dipartimento di Scienze della Terra Pisa, University of Pisa - Università di Pisa, Università degli Studi di Camerino = University of Camerino (UNICAM), Museo de Historia Natural de Lima (MHN), Universidad Nacional Mayor de San Marcos (UNMSM), Catholic University of Leuven - Katholieke Universiteit Leuven (KU Leuven)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2017
• Subjects: [SDU.STU.PG]Sciences of the Universe [physics]/Earth Sciences/Paleontology; Pisco; Antarc*; Antarctica; baleen whales; toothed whales
• Online Access: https://hal.archives-ouvertes.fr/hal-02612083; https://doi.org/10.1016/j.cub.2017.04.026

International audience Although combined molecular and morphological analyses point to a late middle Eocene (38–39 million years ago) origin for the clade Neoceti (Odontoceti, echolocating toothed whales plus Mysticeti, baleen whales, and relatives), the oldest known mysticete fossil dates from the latest Eocene (about 34 million years ago) of Antarctica [1, 2]. Considering that the latter is not the most stemward mysticete in recent phylogenies and that Oligocene toothed mysticetes display a broad morphological disparity most likely corresponding to contrasted ecological niches, the origin of mysticetes from a basilosaurid ancestor and its drivers are currently poorly understood [1, 3, 4, 5, 6, 7, 8]. Based on an articulated cetacean skeleton from the early late Eocene (Priabonian, around 36.4 million years ago) of the Pisco Basin, Peru, we describe a new archaic tooth-bearing mysticete, Mystacodon selenensis gen. et sp. nov. Being the geologically oldest neocete (crown group cetacean) and the earliest mysticete to branch off described so far, the new taxon is interpreted as morphologically intermediate between basilosaurids and later toothed mysticetes, providing thus crucial information about the anatomy of the skull, forelimb, and innominate at these critical initial stages of mysticete evolution. Major changes in the morphology of the oral apparatus (including tooth wear) and flipper compared to basilosaurids suggest that suction and possibly benthic feeding represented key, early ecological traits accompanying the emergence of modern filter-feeding baleen whales’ ancestors.