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previous analyses. These two authors independently concurred in their recognition of the
monophyly of the superfamily Platanistoidea, the monophyly of each of its included families,
the basal placement of the family Squalodontidae, the more derived placement of the family
Waipatiidae, the sister relationship of the family Squalodelphinidae to the family
Platanistidae, and the placement as a crown group the extant family Platanistidae.
Fordyce's (2006) study was prepared prior to description by Barnes (2006) of the family
Allodelphinidae. In our present analysis, and that of Barnes (2006), the Allodelpinidae appear
at a basal position in the tree because of their possession of a relatively primitive braincase,
on which the relatively small nares are positioned relatively anteriorly, and the nasal bones
are relatively elongate anteroposteriorly and transversely narrow. The members of the family
Squalodontidae, while being dentally the most primitive platanistoids, share with the more
crown-ward families Waipatiidea, Squalodelphinidae, and Platanistidae, a more telescoped
(sensu Miller, 1923) cranium on which the nares are enlarged and the nasal bones have
become anteroposteriorly shortened and transversely widened. The families Squalodontidae,
Waipatiidae, and Squalodelphinidae demonstrate progressive simplification of the dentition,
reduction in size of the anterior teeth, and coalescing of the roots of the premolars and molars.
The families Squalodelphinidae and Platanistidae share such derived characters as a
tuberosity or crest on the maxilla over the orbit, the location of the posterior maxillary
foramen very close to the posterolateral corner of the ascending process of the maxilla, and
the medial excavation and transverse compression of the zygomatic process of the squamosal.
The clade that is represented by the subfamily Pomatodelphininae of the family Platanistidae
is notable by the dorsoventral compression of the rostrum and the symphyseal part of the
mandible, and the clade that is represented by the subfamily Platanistinae of the family
Platanistidae is characterized by the transverse compression of the rostrum and the
symphyseal part of the mandible.
C
LASSIFICATION OF THE
P
LATANISTOIDEA
The following classification of the superfamily Platanistoidea is derived in part from the
classifications that have been proposed by Fordyce (1994), Fordyce & Barnes (1994),
Fordyce et al. (1995), and Barnes (2002b, 2006), and on some taxonomic comments by
Fordyce (2006), and has been modified on the basis of the morphological observations and
phylogenetic analysis in this study.
We place the family Allodelphinidae first, despite their long rostra and single-rooted
teeth, because they are basal in the phylogenetic tree (Figure 12), and in recognition of their
primitive cranial structures, including the anterior location of the nares on the facial part of
the cranium.
Bold text indicates new taxonomic determinations in this study. Parentheses indicate
names that originally were proposed by authors at different ranks than they are used here,
followed by the name of the reviser, and the date of publication of that revision. Names that
are in quotations (―
”
) indicate the need for additional study and probable re-assignment.
Order Cetacea Brisson, 1762
Suborder Odontoceti Flower, 1864
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