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Two subfamilies have been recognized (Barnes, 2002b) within the family Platanistidae;
the Pomatodelphininae and the Platanistinae. Araeodelphis, discussed above, cannot be
assigned to either of these. The subfamily Pomatodelphininae, named by Barnes (2002b),
includes extinct species of the North Atlantic realm belonging to the genera
Prepomatodelphis Barnes, 2002b, Zarhachis Cope, 1868, and Pomatodelphis Allen, 1921.
Members of the subfamily Pomatodelphininae have dorsoventrally flattened rostra and
symphyseal portions of their mandibles (Figure 8).
Figure 8. Schematic cross sections of the rostra and mandibles, at approximately mid-length, of
representatives of the two different subfamilies of the family Platanistidae. The example for the
subfamily Pomatodelphininae is based upon USNM 10485, a specimen that was referred by Kellogg
(1924) to Middle Miocene Zarhachis flagellator Cope, 1868, from the Calvert Formation in Maryland.
The example for the subfamily Platanistinae is based upon CAS 16340, an adult female individual of
Recent Platanista gangetica (Roxburgh, 1801) from Pakistan; after Barnes (2006: Figure 8). Images are
diagrammatic and are not to scale.
The geochronologically earliest named pomatodelphinine is the late Early Miocene
Prepomatodelphis korneuburgensis Barnes, 2002b, from the Karpatian age (late Burdigalian
correlative) Korneuburg Formation in the Korneuburg Basin, Austria, and is between
approximately 16.5 Ma and 16.7 Ma in age. The Korneuburg Basin was a small, sometimes
brackish-water estuary that was connected in Miocene time to the larger Vienna Basin.
P repomatodelphis korneuburgensis , and Araeodelphis, demonstrate that a supraorbital
maxillary crest is not a diagnostic character of the family Platanistidae. A maxillary crest does
occur in some of the more derived taxa, and in some of the taxa that have the crest, it is
fenestrated by extensions of the supraorbital lobe of the pterygoid sinus (Fraser and Purves,
1960; Bohaska et al., 2007).
Zarhachis flagellator Cope, 1868, was originally named on the basis of a vertebra.
Kellogg (1924, 1926) referred more complete specimens to this species (see Figure 9) from
the Calvert Formation in Maryland, U. S. A., and these are of middle Middle Miocene age
(Gottfried et al., 1994:233), approximately 13 to 15 Ma. Zarhachis flagellator differs from P.
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