The affinities of Notocetus vanbenedeni, an early Miocene platanistoid (Cetacea, Mammalia) from Patagonia, southern Argentina. American Museum novitates ; no. 2904

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New York, N.Y. : American Museum of Natural History
"The study of previously undescribed material of the early Miocene odontocete cetacean Notocetus vanbenedeni allows a new interpretation of its relationships, and a reevaluation of the taxon Platanistoidea. The new specimen consists of a well preserved auditory region (periotic, tympanic, malleus, stapes, squamosal, and partial occipital) associated with several teeth and some postcranial elements (scapula, vertebrae, and rib fragments). The presence of an articular rim on the periotic and the morphology of the tympanic demonstrate the close relationship of Notocetus with the Platanistidae. Notocetus is referable to the family Squalodelphidae, which also includes the genera Squalodelphis and Phocageneus. This family is the sister-group of the Platanistidae, which consists of the genera Platanista, Zarachis, and Pomatodelphis. Platanistidae and Squalodelphidae are regarded as the sister-groups of the Squalodontidae on the basis of two synapomorphies of the scapula: the loss of the coracoid process and the acromion located on the anterior edge. These three families (Platanistidae, Squalodelphidae, and Squalodontidae) constitute the Platanistoidea. The Squalodontidae, however, may be poly- or paraphyletic as they are defined by symplesiomorphies only; they are not analyzed here and the group is tentatively regarded as monophyletic. The phylogenetic relationships of this family will be considered elsewhere. The ziphiid affinities of Notocetus vanbenedeni, assumed by some previous workers, are rejected. The Ziphiidae could, however, have their origin in some squalodont-like odontocetes, a statement which favors a possible polyphyletism of the Squalodontidae. Notocetus is an Argentinian genus, but the occurrence of a periotic and a partial tympanic from the Calvert Formation of Maryland extends the distribution of the genus to the Middle Miocene of North America"--P. [1].
27 p. : ill. ; 26 cm.
Includes bibliographical references (p. 25-27).