Many marine fossils described in previous research have been from long-recognized temperate regions such as South Carolina, off the coast of Oregon, Hokkaido and New Zealand. Few equatorial and polar fossils are currently known.

Skull, Urkudelphis chawpipacha MO-1 (holotype) in right lateral view.Credit: Tanaka et al (2017)

While in the tropical region of Santa Elena Province, Ecuador, the authors of this study found a small dolphin skull, which they identified as representing a new species, Urkudelphis chawpipacha, based on facial features. The dolphin skull had a bone crest front and center on its face, above the eye sockets. This species stands apart from other Oligocene dolphins with its shorter and wider frontal bones located near the top of the head and the parallel-sided posterior part of its jaw. The authors also conducted a phylogenetic analysis which revealed that the new species may be the ancestor of the nearly-extinct Platanistoidea, or river dolphin, and may have lived during the Oligocene era.

The fossil is one of the few fossil dolphins from the equator, and is a reminder that Oligocene cetaceans may have ranged widely in tropical waters.

This study was supported by an UPSE project IN-P5-2016-1 for equipment at UPSE, and YT thanks support of a trip to Ecuador. This work has also been supported by the Agencia Estatal de Investigación (AEI) from Spain and the European Regional Development Fund of the European Union (CGL2016-76431-P) and the project CGL2015-68333 (MINECO/FEDER, UE).

1. Yoshihiro Tanaka, Juan Abella, Gabriel Aguirre-Fernández, Maria Gregori, R. Ewan Fordyce. A new tropical Oligocene dolphin from Montañita/Olón, Santa Elena, Ecuador. PLOS ONE, 2017; 12 (12): e0188380 DOI: 10.1371/journal.pone.0188380