Hernández Cisneros, A.E. & E.H., Nava Sánchez (2022). Oligocene Dawn Baleen Whales in Mexico (Cetacea, Eomysticetidae) and Palaeo¬biogeographic Notes. J.A., Moreno Bedmar (Eds.), Paleontología Mexicana. 11(1): 1 - 12. URL.
Atzcalli Ehecatl Hernández Cisneros 1 y Enrique Hiparco Nava Sánchez 2
Eomysticetids are an extinct basal taxon of baleen whales (Mysticeti: Chaeomysticeti - ‘true whales’), which appeared during the Oligocene and reflected a transitional stage between the origin of baleen and the loss of teeth, a trait that characterizes extant baleen whales. The eomysticetids are recognized as a diverse and widely distributed lineage with a rich record in the Australasia region (Australia and New Zealand). Several features of their palaeobiology, such as ontogenetic growth and ecological feeding, have been discussed; however, traits related to their biogeography and inherent speciation (origin and extinction) have only been briefly reviewed. In this context, the present study addresses biogeographic aspects based on a new fossil from the eastern North Pacific belonging to the records of the El Cien Formation of Baja California Sur, Mexico. Our description and phylogenetic analysis classify this new specimen of eomysticetid within the genus Eomysticetus (cf. Eomysticetus sp.). In addition, we identify the biogeographic relationship between the (eastern) North Pacific and the (western) North Atlantic, which indicates a possible exchange of their Oligocene cetacean faunas. Furthermore, the presence of the Gaarlandia terrestrial arc during the Oligocene indicate vicariance events, which likely led to allopatric speciation within Eomysticetidae in the North Hemisphere. Lastly, the Oligocene cetacean fossil record from Baja California Sur, unique in Mexico, might explain several aspects of the eomysticetids palaeobiology, considering the several unnamed specimens housed in the local collections.
Palabras clave: Baja California Sur; El Cien Formation; Eomysticetidae; Gaarlandia; Palaeobiogeography
Para obtener una copia del documento contacta la personal de la biblioteca a través del correo bibliocicimar{a}ipn.mx