Biology Reference
In-Depth Information
Platanistidae is Araeodelphis natator, an early Middle Miocene fossil from the
western North Atlantic, whose more precise relationships are not yet known.
9. Two subfamilies are recognized in the Platanistidae, the fossil (Miocene only)
subfamily Pomatodelphininae, and the extant (Miocene to Recent) subfamily
Platanistinae.
10. The platanistid subfamily Pomatodelphininae includes late Early Miocene
Prepomatodelphis korneuburgensis from shallow marine deposits of Austria, and
more highly derived, long-snouted species of the genera Zarhachis and
Pomatodelphis of Middle and Late Miocene age from the North Atlantic realm
(France, Maryland, Virginia, North Carolina, Florida, and Alabama), all of which
have very elongate snouts and dorsoventrally flattened rostra and symphyseal
portions of their mandibles. Derived members of the Pomatodelphininae have
dorsoventrally thickened frontal bones forming eminences dorsal to their orbits, and
in at least one species, Zarhachas flagellator, these eminences were invaded by
dorsal extensions of the supraorbital lobe of the pterygoid sinus, which extended
dorsally through the anterior maxillary foramina.
11. The subfamily Platanistinae is extant, and includes the extant genus Platanista,
whose living species are the fresh water susus of south Asia, Platanista gangetica.
Fossils that appear to belong to the Platanistinae from the eastern margin of the North
Pacific basin (Oregon, Washington) suggest that the Platanistinae formerly had a
wider geographic range and were originally marine in habitat. The Platanistinae are
comparatively highly derived odontocete taxa, having among their derived characters
small size, enlarged and anteriorly extended zygomatic process of squamosal,
atrophied eye, extreme left-skew asymmetry of the cranial vertex, reduced nasal
bones, greatly enlarged supraorbital crests (formed by maxillary bones and
pneumaticized by extensions from the middle ear air sinus system), extremely narrow
supraoccipital-nuchal crest area, reduced lambdoidal crests, secondarily thickened
zygomatic process of the jugal, transversely flattened rostrum and symphyseal part of
the mandible, secondary heterodonty (crowns of anterior teeth greatly elongated,
crowns of posterior teeth widened), and paedomorphism (which accounts for some of
their derived characters).
A CKNOWLEDGMENTS
For many hours of discussion about platanistoid dolphins we are indebted to Mr. David J.
Bohaska, Dr. Robert L. Brownell, Jr., Dr. R. Ewan Fordyce, Dr. Samuel A. McLeod, Dr.
Gary S. Morgan, Dr. Christian de Muizon, Dr. Olivier Lambert, and Dr. Frank C. Whitmore,
Jr. For access to collections under their care we thank the staff of the Natural History
Museum in Vienna (Dr. Ortwin Schultz, Dr. Gudrun Daxner-Höck), United States National
Museum of Natural History (Mr. David J. Bohaska, Dr. James G. Mead), Calvert Marine
Museum, Yale Peabody Museum (the late Dr. John H. Ostrom), University of California
Museum of Paleontology at Berkeley (Dr. J. Howard Hutchison, Dr. Patricia Holroyd), and
the Muséum National d'Histoire Naturelle in Paris (Dr. Christian de Muizon). This study was
made possible by support and assistance from the Natural History Museum of Los Angeles
Search WWH ::




Custom Search