FOSSIL RECORD AND THE EVOLUTIONARY HISTORY OF INIODEA - Biology, Evolution and Conservation of River Dolphins Within South America and Asia - page 202

Pontoporia (Muizon, 1988c) and emphasizes the difference with Brachydelphinae. Removing
Brachydelphis and allied, Parapontoporia and Lipotes from Pontoporiidae makes

Pontoporiinae and Pontoporiidae equivalent.
Pontistes was recorded in the Bahia Inglesa formation, Chile (Canto et al., 2002), and it is
also probably present in Denmark (Pyenson & Hoch, 2007, see below).

Pliopontos littoralis Muizon, 1983

From the early Pliocene Sud-Sacaco level in the Pisco formation, dated at approximately
5 Ma, Muzion (1983) described Pliopontos littoralis as a large pontoporiid that he considered
close to the living La Plata dolphin. The holotype is an incomplete skull, with partial rostrum
and one tympanic bulla. Additional referred material includes other incomplete skulls, a
sternum with almost all caudal vertebrae, other cervical and lumbar vertebrae, and other
partial rostra and mandibles. The principal differences between Pliopontos and Pontoporia
are the body size, orbit size, and maxillary crests.

Pontoporia sp

Remains of Pontoporia are relatively common in the Quaternary coastal deposits in
Argentina and Brazil (Ribeiro et al., 1998; MAC, pers.obs.). Older records of this genus are
reported from South America, mainly on the basis of isolated periotics (Cozzuol, 1985, 1996).

Non South American Pontoporiidae

Pyenson & Hoch (2007) reported remains of Pontoporiidae of Tortonian age from
Denmark. They noted that those specimens have a symmetrical vertex, being closer to
Pontoporiidea, and referred to as the best preserved specimen as cf Pontistes , a South
American genus, and being the only pontoporids to be reported outside of South America.
This is especially significant because it shows a wide distribution of pontoporids at the origin
of the clade and, if the assignment to Pontistes is confirmed, it will also be the only South
American genus recorded outside the continent.

The Interrelationships of the Pontoporiidae

The phylogenetic relationships among Pontistes , Pliopontos and Pontoporia are
unresolved. Muizon (1984) does not consider that Pliopontos could be the direct ancestor of
Pontoporia , due to the existence of several complex functional characters indicative of
specialization for existence in the littoral environment. Rather, he suggested that the two are
sister taxa, united by the apomorphic development of a crest affecting the maxillary only, and
that Pontistes is the sister to the clade of Pliopontos and Pontoporia. Pontistes, although it