Biology Reference
In-Depth Information
(1927), Fraser & Purves (1960), and Barnes (1978, 1985), and authorships and nomenclature
of family groups and of modern taxa follow Hershkovitz (1966) and Rice (1998).
A S YNOPSIS OF THE S UPERFAMILY P LATANISTOIDEA
Not included in this review is the problematic family Dalpiaziniidae. It was originally
proposed with the name Dalpiazinidae by Muizon (1988a), its spelling was subsequently
emended by Muizon (1994: Figure 1), and includes only Dalpiazina ombonii (Longhi, 1898).
Muizon (1988a, 1991) suggested that Dalpiazina has close relationships with Squalodontidae,
but he later (Muizon 1994:141) stated it has ―…. none of the platanistoid synapomorphies.‖
Also not included in this analysis is the problematic and poorly characterized family
Acrodelphinidae (originally named Acrodelphidae by Abel, 1905; and its spelling emended
by Rice, 1998, to Acrodelphinidae). This family has sometimes been discussed in relationship
to odontocetes that are now included in the Platanistoidea, but Muizon (1988a) relegated the
family to Odontoceti, incertae sedis, and restricted it to the type species of the type genus,
because it was based on non-diagnostic material. Abel (1905) based the family Acrodelphidae
on the genus Acrodelphis Abel, 1900. The type species of Acrodelphis is Champsodelphis
denticulatus Probst, 1886 (see Probst, 1886:124), and the type material of C. denticulatus is
four isolated teeth (see Probst, 1886:pl. III, figs. 18-21; and Pilleri, 1986:36, Table 35, pl. 21,
Figures 5-7). These four teeth do not necessarily belong to the same individual cetacean, and
they definitely do not belong to the same species, and such isolated odontocete teeth are not
considered to be diagnostic.
Therefore, on the basis of the above observations and facts, we do not include the
families Dalpiaziniidae or Acrodelphinidae in our review of the superfamily Platanistoidea.
General
No phylogenetic study has definitively determined the origin of the Platanistoidea, but
the group must have originated from archaic odontocetes that were at least as primitive as
Agorophius pygmaeus (see Fordyce, 1981). The time of origin of the Platanistoidea must have
been at least by the early part of the Oligocene, because platanistoids were diverse at the
family levels by late Oligocene time.
All species of the Platanistoidea share the presence of a pointed process, or spine, on the
anterior end of the tympanic bulla. This spine in life partly surrounds the ventral side of the
Eustachian tube. This may seem like an inconsequential structure, (and if a fossil is not
properly cleaned from the rock, or not properly handled in collections, this small spine can be
easily destroyed), however, platanistoids have this structure to the exclusion of all other
Cetacea, and it is a shared derived (synapomorphic) character that is diagnostic for the
superfamily (see Fordyce, 1994: 1776; Barnes, 2006; and see Character number 32 in the
following text).
Platanistoids have in their skull a thick, vertically-oriented, bony lamina that extends
from the posterior part of the palate, across the medial side of the orbit, to the anterior part of
the ear region (see Character number 31 in following text). This bony lamina is composed, in
Search WWH ::




Custom Search