THE EVOLUTIONARY HISTORY AND PHYLOGENETIC RELATIONSHIPS OF THE SUPERFAMILY PLATANISTOIDEA - Biology, Evolution and Conservation of River Dolphins Within South America and Asia - page 445

Chapter 23
T HE E VOLUTIONARY H ISTORY AND
P HYLOGENETIC R ELATIONSHIPS OF THE
S UPERFAMILY P LATANISTOIDEA
Lawrence G. Barnes 1  , Toshiyuki Kimura 2 + ,
and Stephen J. Godfrey 3 ±
1 Curator of Vertebrate Paleontology, Department of Vertebrate Paleontology, Natural
History Museum of Los Angeles County, Los Angeles, California, USA
2 Assistant Curator of Paleontology, Gunma Museum of Natural History,
Kamikuroiwa, Tomioka, Gunma, JAPAN
3 Curator of Paleontology, Department of Paleontology, Calvert Marine Museum,
Solomons, Maryland, USA
A BSTRACT
The fossil record demonstrates that in the past the ―river dolphin‖ superfamily,
Platanistoidea, was much more widespread geographically, and more diverse ecologically
and taxonomically than it is now, and that most of its early members lived in salt water,
not fresh water. Families in the Platanistoidea comprise a significant initial radiation of
dolphin-like toothed whales (suborder Odontoceti). Platanistoids were predominant
odontocetes in some late Oligocene and early Miocene age fossil assemblages, from
approximately 25 to 15 million years ago. However, the Platanistoidea gradually declined
in abundance and diversity approximately 15 million years ago, and they were gradually
replaced, largely by another rapidly diversifying odontocete superfamily, the
Delphinoidea. During their evolutionary histories, these two superfamilies have had an
inverse relationship of diversity and abundance. Among the archaic groups of
Platanistoidea, the essentially cosmopolitan Oligocene and Miocene family
Squalodontidae is the most primitive dentally, having heterodonty (teeth still
recognizable as incisors, canines, premolars, and molars), large and projecting anterior
 e-mail [e-mail].
+ [e-mail].
± e-mail [e-mail].