THE EVOLUTIONARY HISTORY AND PHYLOGENETIC RELATIONSHIPS OF THE SUPERFAMILY PLATANISTOIDEA - Biology, Evolution and Conservation of River Dolphins Within South America and Asia - page 456

Figure 6. Cranium of a member of the platanistoid family Squalodelphinidae, Notocetus vanbenedeni
(Moreno, 1892), of earliest Miocene age from the southwestern Atlantic coast of South America ; A,
dorsal view; B , right lateral view; modified from Lydekker (1894:pl. 6, figs. 1, 1b).
Platanistidae
The monophyly of the platanistoid crown group, the family Platanistidae, is supported by
the phylogenetic analysis herein. The family is represented by fossils from Miocene marine,
brackish, and fresh water deposits of the Northern Hemisphere, but it is today represented
only by the living dolphins called the susus, members of the genus Platanista Wagler, 1830,
which live in fresh water environments of south Asia.
Members of the Platanistidae have a cranium with an asymmetrical cranial vertex that is
skewed to left side, posterior ends of premaxillae much expanded posterolaterally, frontals
exposed between the mesethmoid and the nasal bones on the posterior wall of dorsal naris, a
sheath of bone present in the medial part of the orbit formed by combination of the lateral
lamina of the pterygoid (formed as an outer lamina or bony plate of the pterygoid within the
orbit that extends posteriorly from the palate and contacts with the styliform process of the
squamosal) and a posterior extension of the palatine bone. They also have a highly modified
zygomatic process of the squamosal that is compressed transversely (and that has a concave
medial surface and a broad connection to the postorbital process of the frontal), and an
elongated and narrow rostrum and symphyseal portion of the mandible, especially elongated
in some of the geochronologically earlier Miocene species. The anterior teeth, when
preserved in the fossil species, are larger than the posterior teeth, as is the case also with the
living species, Platanista gangetica. In most odontocetes, including members of all of the
other families of Platanistoidea, the posterior maxillary foramen is located posterolateral to