Boletín de la Sociedad Geológica Mexicana

Volumen 69, núm. 1, 2011, p. 149 ‒ 173

Oligocene cetaceans from Baja California Sur, Mexico

Atzcalli Ehécatl Hernández Cisneros1,2,*, Gerardo González Barba1, Robert Ewan Fordyce2

1 Museo de Historia Natural de la Universidad Autónoma de Baja California Sur, Universidad Autónoma de Baja California Sur, Carretera al Sur Km 5. 5, Apartado Postal 19-B, C. P. 23080, La Paz, Baja California Sur, México.
2 Instituto Politécnico Nacional, Centro Interdisciplinario de Ciencias Marinas (CICMAR), Av. Instituto Politécnico Nacional s/n, Col. Playa Palo de Santa Rita, Apartado Postal 592, 23096, La Paz, Baja California Sur, Mexico.
3 Department of Geology, University of Otago, PO Box 56, Dunedin 9054, New Zealand.

atz_nemesis@hotmail. com

 

Abstract

Baja California Sur has an important Cenozoic marine fossil record which includes diverse but poorly known Oligocene cetaceans from Mexico. Here we review the cetacean fossil record including new observations from materials that elucidate the evolution of the Neoceti in the Pacific basin. Fossils were collected from outcrops of the El Cien Formation (Oligocene-Early Miocene) and from San Gregorio Formation (Late Oligocene). The specimens belong to the paleontological collection of Museo de Historia Natural de la Universidad Autónoma de Baja California Sur. An estimated 26 unnamed species include toothed cetaceans: possible “archaeocetes” (?Kekenodontidae); archaic Odontoceti; and the basal group Aetiocetidae, toothed mysticetes (Mysticeti). Toothless mysticetes (Chaeomysticeti) include the basal group Eomysticetidae, and balaenopterids-like forms. The Oligocene cetaceans from Baja California Sur, Mexico are diverse and represent the most southern such assemblages known from North America.

Keywords: Mysticeti, Odontoceti, Mexico, fossils, Late Oligocene