possible enigmatic kekenodontid (Cetacea, Kekenodontidae) from the Oligocene of Mexico

Abstract

Kekenodontidae is a taxon of unresolved affinity in Cetacea; whether it belongs to Mysticeti or archaeocetes remains uncertain, mainly due to the poor fossil record from the Oligocene. Here, we report a left periotic, identified as a kekenodontid from the Oligocene (Chattian) of Baja California Sur, Mexico. This periotic is phenetically similar to Kekenodon onamata in the presence of: broad and deep anteroexternal sulcus, broad oblique furrow on the anterior half of the ventral surface of the pars cochlearis, a transversally narrow pars cochlearis, deeply excavated mallear fossa, and present but indistinct stylomastoid fossa. In the light of the highly diagnostic periotic in Cetacea, this fossil, an isolated left periotic, is currently recognized as a kekenodontid. Thus, this fossil is the first possible kekenodontid recognized from the North Pacific, suggesting a global distribution of Kekenodontidae during the Oligocene.