THE EVOLUTIONARY HISTORY AND PHYLOGENETIC RELATIONSHIPS OF THE SUPERFAMILY PLATANISTOIDEA - Biology, Evolution and Conservation of River Dolphins Within South America and Asia - page 463

symphyseal part of the mandible, secondary heterodonty (crowns of anterior teeth greatly
elongated, crowns of posterior teeth widened), and what we suggest is paedomorphism
(which may account for some of the derived characters of this dolphin).
A N EW G ENUS OF F OSSIL P LATANISTOID D OLPHIN
Zarhinocetus , New Genus
Synonymy
Squalodon (part). Kellogg, 1931:373, for Squalodon errabundus Kellogg, 1931.
“Squalodon”. Barnes, 1977: 327, Table 3, for Squalodon errabundus Kellogg, 1931, as a
taxon of the family Platanistidae; Barnes, 2006:31-34, [part], for S qualodon errabundus
Kellogg, 1931, as a taxon of the platanistoid family Allodelphinidae.
Diagnosis of genus: A genus of the platanistoid family Allodelphinidae, differing from
Allodelphis Wilson, 1935, by having cranium with relatively wider facial region,
dorsoventrally higher occipital shield, transversely narrower mesorostral gutter in posterior
part of rostrum anterior to nares, ventrally depressed medial part of dorsal surface of proximal
part of rostrum, anteroposteriorly-oriented crest of maxilla on dorsal surface of supraorbital
process of maxilla, nasal bones narrower anteriorly and wider posteriorly, posterior ends of
premaxillae atrophied and retracted anteriorly, and not extending posteriorly as far as nares,
area where posterior end of premaxilla formerly existed (forming premaxillary sac fossa (or
spiracular plate)) formed of smooth, convex, and dense maxillary bone, asymmetrical cranial
vertex with mid-line between nasal and frontal bones located to left of sagittal plane of
cranium, and swollen tubercle of bone on lateral part of rostral maxilla anterior to antorbital
notch.
Type species: Squalodon errabundus Kellogg, 1931.
Included species: Zarhinocetus errabund us (Kellogg, 1931).
Etymology: The genus name is derived from za- , Greek, an intensive particle, meaning
very or exceedingly; combined with rhinos, Greek for nose, snout, beak, or bill; plus ketos,
Greek for a large sea animal or whale, here using the Latin form, cetus; and alludes to the
extremely long rostrum of this type of platanistoid cetacean. We use the suffix cetus, rather
than delphis, to intentionally emphasize that platanistoids are not in the strict sense dolphins,
as so many of the living members of the Delphinoidea are commonly called, but are in the
more broad sense toothed whales.
Geographic and geochronologic ranges: Middle and Late Miocene, eastern North Pacific
coast in the area of central and southern California, U.S.A.
Zarhinocetus Errabund us (Kellogg, 1931), New Combination
Synonymy
Squalodon errabundus Kellogg, 1931:373; as a species of Squalodontidae.
“Squalodon” errabundus Kellogg, 1931. Barnes, 1977:327, Table 3; as a species of
Platanistidae.