FOSSIL RECORD AND THE EVOLUTIONARY HISTORY OF INIODEA - Biology, Evolution and Conservation of River Dolphins Within South America and Asia - page 198

The most important differences from Prosqualodon are in the postorbital processes of the
frontal, the postglenoid process and the lower part of the lambdoid crest. The first are thinner
and sharper that those of Prosqualodon . The postglenoid process is very thin and posteriorly
directed. As the lambdoid crest is almost nonexistent in its lower course, the temporal fossa
has no posterior limit. However the first two differences could be due to secondary distortion,
and the third could represent a juvenile character.
We conclude based on the above observations, that Proinia patagonica is not an Iniidae,
but a junior synonym of Prosqualodon a ustralis .
Other Supposed Iniodea
Several other odontocetes were related to Inia . All of them exhibit some characteristics
actually found in Inia, but almost invariable are plesiomorphic or common convergent
features between odontoceti. Hesperocetus californicus True, 1912, Lophocetus spp, and
K ampholophos serrulus Rensemberg, 1969 are the better known odontoceti and all of them
are presently related to the basal delphinoid (possibly para or polyphyletic) family
Kentriodontiofdae (Barnes, 1978; Barnes et al., 1985).
The Position of Parapontoporia
Family PARAPONTOPORIIDAE Barnes, 1984
Genus Parapontoporia
The genus Parapontoporia Barnes, 1984 presently includes three species of exceptionally
long snouted fossil odontocetes recovered from late Tertiary sediments along the west coast
of California and Mexico. Parapontoporia pacifica Barnes, 1984 was collected from the well
preserved assemblage of vertebrate fossils of the latest Miocene Almejas formation, exposed
at the southeastern end of Cedros Island, off the west coast of Baja California. The holotype
and only known specimen is a skull with teeth, lacking a brain case, a partial mandible that is
the most complete known for the genus, and the entire rostrum, also the most complete
known for this genus. Parapontoporia wilsoni Barnes, 1985 is a single incomplete skull
recovered from sea cliffs in Santa Cruz county, California, corresponding to the lower part of
the Purisima formation. This section is correlated with the Hemphillian North American land
mammal age, latest Miocene, approx 6-8 Ma, and with the Almejas formation, where P.
pacifica is found. Parapontoporia sternbergi (Gregory & Kellogg, 1927) is the geologically
youngest parapontoporiid. Originally described as Stenodelphis sternbergi , the holotype
section of mandibular symphysis comes from the San Diego Formation, San Diego County,
California, which is correlated with the Blancan Land Mammal Age, 2-4 mya. Many
additional fossils have been referred to this species, including several nearly complete skulls
and mandibles, rostra lacking braincases, cranial vertices, and periotics. Barnes (1984)
compared the available material and suggested the mandibular morphology of Stenodelphis
sternbergi was sufficiently similar to assign this species to his newly described genus
Parapontoporia , noting that S. sternbergi had needed a new generic allocation for some time.
While each of the described parapontoporiids is known primarily by incomplete skulls that