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teeth, and serrated and broad-crowned cheek teeth, but well-telescoped crania with their
nares moved posteriorly, and relatively primitive body skeletons showing them to have
been medium-size whales compared to living species. The Miocene family
Allodelphinidae comprises strictly marine North Pacific odontocetes that had primitive
braincases, with relatively small nares, and very long and dorsoventrally flattened rostra
and symphyseal portions of their mandibles, which contained numerous small teeth. Late
Oligocene and Early Miocene marine members of the family Waipatiidae from the South
Pacific and northern hemisphere were smaller than squalodontids, and had smaller teeth
with less recognizable heterodonty. Platanistoids in the more derived clade that ultimately
culminated in the recent family Platanistidae have a modified zygomatic process of the
squamosal that is compressed from side to side. Within this clade of Platanistoidea, the
Atlantic and Southern Ocean family Squalodelphinidae includes the more primitive,
small to medium-size species that have tuberosities superior to the orbits that are not
invaded by the pterygoid sinuses, and teeth that still retained remnants of heterodonty.
The more highly derived Miocene to Recent family Platanistidae includes two named
subfamilies, the Miocene Pomatodelphininae, and the Miocene to Recent Platanistinae.
Species of the North Atlantic subfamily Pomatodelphininae are relatively large, long-
snouted dolphins that had many small teeth, rostra and symphyseal parts of the mandibles
that are compressed dorsoventrally, and many species in this subfamily, but not all of
them, have enlarged bony tuberosities over the orbits that are invaded by extensions of
the pterygoid air sinuses. These dolphins have been found in near shore marine, estuarine,
and fresh water deposits, and these are the first indications of any fresh water-dwelling
Platanistoidea. The more derived species of Platanistidae, those in the subfamily
Platanistinae, have fenestrations within the supraorbital crest caused by invasion of the
pterygoid sinus, and have a transversely flattened rostrum and symphyseal part of the
mandible. Miocene members of the subfamily Platanistinae are known from North
Pacific marine deposits, but the living members of the genus
Platanista
live only in rivers
of south Asia. A cladistic analysis provides a framework for a classification of the
Platanistoidea that is presented here.
I
NTRODUCTION
Among the cetacean suborder Odontoceti, or echolocating toothed whales, species of the
superfamily Platanistoidea constitute an early evolutionary radiation of small to medium-size
dolphin-like animals that diversified during the Oligocene and early part of the Miocene
epochs. The Platanistoidea reached the apex of their diversity during Late Oligocene and
Early Miocene time, approximately 28 to 16 million years ago. Subsequently platanistoids
gradually declined in both abundance and diversity. They were gradually replaced
ecologically by the now very diverse and numerous members of the superfamily
Delphinoidea, which includes, in addition to such extinct families as the generalized
Kentriodontidae, the Albireonidae, and the very strange and large-tusked Odobenocetopsidae,
and the fossil and Recent pelagic dolphins, killer whales, true porpoises, belugas, and
narwhals (families Delphinidae, Phocoenidae, and Monodontidae) (Barnes, 2002a).
The taxon Platanistoidea, first recognized at the superfamily level by Simpson (1945),
has had a convoluted history in cetacean taxonomic studies (for example see Kellogg, 1926:2;
Messenger & McGuire, 1998; Hamilton et al., 2001). In some previous classifications
(including that of Simpson, 1945) this superfamily included other so-called ―river dolphins‖
of the families Iniidae, Lipotidae, and Pontoporiidae, but these groups are now usually
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