The first Oligocene sea turtle (Pan-Cheloniidae) record of South America

The evolution and occurrence of fossil sea turtles at the Pacific margin of South America
is poorly known and restricted to Neogene (Miocene/Pliocene) findings from the
Pisco Formation, Peru. Here we report and describe the first record of Oligocene
(late Oligocene, ∼24 Ma) Pan-Cheloniidae sea turtle remains of South America. The
fossil material corresponds to a single, isolated and well-preserved costal bone found at
the Montañita/Olón locality, Santa Elena Province, Ecuador. Comparisons with other
Oligocene and extant representatives allow us to confirm that belongs to a sea turtle
characterized by: lack of lateral ossification, allowing the dorsal exposure of the distal
end of ribs; dorsal surface of bone sculptured, changing from dense vermiculation at
the vertebral scute region to anastomosing pattern of grooves at the most lateral portion
of the costal. This fossil finding shows the high potential that the Ecuadorian Oligocene
outcrops have in order to explore the evolution and paleobiogeography distribution of
sea turtles by the time that the Pacific and the Atlantic oceans were connected via the
Panama basin.