Abstract:
This thesis describes an early odontocete, here named Perditicetus yaconensis, gen. et.
sp. nov., from the latest Oligocene-earliest Miocene Nye Formation in Oregon. I assign it
to the Platanistoidea, a large superfamily of odontocetes whose sole surviving member is
Platanista gangetica, the Ganges river dolphin. Despite the diversity of the
Platanistoidea, it remains poorly understood and in need of revision. As one of the
earliest-diverging clade of crown odontocetes, understanding their distribution,
morphology, and phylogeny is crucial to understanding the radiation of basal crown
odontocetes in the late Oligocene to the middle Miocene. P. yaconensis, represented by
the holotype USNM 335224, possesses several synapomorphies of the Platanistoidea;
however, similarity between P. yaconensis and other basal crown odontocetes suggests
that these early odontocetes may be closer to the Platanistoidea than initially thought,
especially those in the “Chilcacetus clade”. The specimen’s probable location in the lower Nye Formation suggests that P. yaconensis is one of the older platanistoids known
in the fossil record.
