Protoglobicephala mexicana, a new genus and species of Pliocene fossil dolphin (Cetacea; Odontoceti; Delphinidae) from the Gulf of California, Mexico

Resumen

The Delphinidae is the
most diverse living family of odontocete cetaceans and includes
modern oceanic dolphins and their fossil relatives. In contrast, the
world-wide fossil record of this family is sparse when compared to
that of several other cetacean groups, and relatively few extinct
delphinids have been formally named. Most of the known fossil
Delphinidae are of Pliocene age, and most of these are from Europe.
We describe a new genus and new species of extinct Delphinidae,
Protoglobicephala mexicana, based on a cranium of Pliocene age,
between approximately 2 and 3 million years old, from Isla San Jose
in the Gulf of California, Baja California Sur, Mexico. This species
shares with Recent species of Globicephala wide exposures of the
premaxillae on the dorsal surface of the rostrum and rugose areas on
the distal ends of the premaxillae. Like other Globicephalinae
members, it is a relatively large animal and has a wide cranium,
short and broad rostrum, and relatively few teeth that are of
relatively large size. It also shares some similarities with the
generalized delphinine delphinid Tursiops. These similarities and
the geochronologically relatively young occurrence of this new
species reinforce previous notions that the present taxonomic
diversity of the family Delphinidae is the result of rapid
evolutionary diversification since Miocene time, or within
approximately the past five million years. The ability of living
species of Delphinidae in different genera, and in different nominal
subfamilies, to mate and to produce viable hybrid offspring, offers
additional support for the idea of rapid and recent evolutionary
diversification of this family