Orcaella
| Snubfin dolphins | |
|---|---|
 |
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| Orcaella brevirostris | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | Artiodactyla |
| Infraorder: | Cetacea |
| Family: | Delphinidae |
| Genus: |
Orcaella Gray, 1866 |
| Species | |
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|
| Distribution of genus Orcaella | |
Orcaella brevirostris
Orcaella heinsohni
The snubfin dolphins (Orcaella) are a genus of Cetaceans containing two members: the Irrawaddy dolphin (Orcaella brevirostris) and the Australian Snubfin dolphin (Orcaella heinsohni). The genus was long believed to be monotypic with the only species being the Irrawaddy dolphin; however, in 2005, supposed Irrawaddy dolphin populations inhabiting the Australian/New Guinean regions were found to be significantly different and were declared a separate new species named the Australian Snubfin dolphin.
Until 2005, Orcaella brevirostris was the only recognized species in the genus Orcaella. However, comparisons within the populations of Orcaella inhabiting the Asia region and populations inhabiting the Australia/New Guinea region show distinctions in habitat, morphology, and genetics. Morphological differences include skull shape, presence or absence of a median dorsal groove in front of the dorsal fin, height of dorsal fin, and coloration. Genetic analysis constitutes a 5.9% difference between the two populations. In 2005, these significant distinctions considered by Beasley, Arnold and Robertson warranted a taxonomic split of the genus Orcaella into two separate species, Orcaella brevirostris and Orcaella heinsohni . Orcaella brevirostris known as the Irrawaddy Dolphin consists of the Asian population. The newly recognized species, known as the Australian Snubfin dolphin, consists of the Australian/New Guinea population.
The Snubfin dolphins (Orcaella) contain two of the 35 species of Oceanic dolphins that make up the Cetacean family of Delphinidae. The phylogenetic status of Orcaella has long been confused. Although the Snubfin dolphins share similar external features with the Monodontidae (narwhal), a genetic study conducted by Arnason and Gretarsdottir identified the 'Irrawaddy Dolphin' as a Delphinid. In their study, phylogenetic information obtained from a highly repetitive DNA (hrDNA) component characteristic of all cetaceans show that Orcaella share close relationships with the Delphinidae rather than the Monodontidae.
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Wikipedia