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Chapter 10
F OSSIL R ECORD AND THE E VOLUTIONARY
H ISTORY OF I NIODEA
M. A. Cozzuol
Departamento de Biologia Geral, ICB, Universidade Federal de Minas Gerais,
ICB - UFMG, Belo Horizonte, MG, Brazil.
A BSTRACT
This chapter discusses the possible phylogenetic relationships within the superfamily
Inioidea (using fossil record data) and provides detailed descriptions of Brachydelphidae,
Pontoporiidae and Iniidae (including Goniodelphis, Ischyrhorhynchus, Saurocetes,
Plicodontinia and a possible new species of Inia that is estimated to have arisen
approximately 45,000 years ago). Some previously related taxa to Iniidae are also
discussed such as Proinia patagonica. Additionally, the chapter discusses the Lipotoidea
and their relationship with Inioidea, the phylogenetic position of Parapontoporia , and the
evolutionary process (and paths) that originated the inioid clades .
I NTRODUCTION
South American river dolphins, grouped in the superfamily Inioidea (sensu Muizon,
1988a), comprise two families, Iniidae and Pontoporiidae, with only one living genus each.
Genus Inia, strictly freshwater, has two living species, I. geofrensis and I. boliviensis. Genus
Pontoporia is monotypic ( P. blainvilei ) and lives in shallow marine environments, with some
of its distribution in proximal riverine systems.
The interrelationships of this species were obscured for a long time by their inclusion in a
polyphyletic group informally called ―river dolphins‖ with the formal name Platanistoidea
(sensu Simpson, 1945). Besides the South American species, this superfamily included the
Ganges and Indus dolphins (genus Platanista , two species) and the Baiji from China (genus
Lipotes , one species).
Gray (1863) was the first to propose a systematic arrangement for the 'river' dolphins, at
that time limited to Platanista , Inia , and Pontoporia, ( Lipotes was described only in the next
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