Editing Orcaella (section)

==Taxonomy and evolution==
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.<ref name=Ross>Ross, G. J. (2006). Review of the conservation status of Australia's smaller whales and dolphins. Department of the Environment and Water Resources.</ref> 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.<ref>Beasley, I., Robertson, K. M. and Arnold, P.. 2006. Description of a New Dolphin, the Australian Snubfin Dolphin ''Orcaella heinsohni'' sp. n. (Cetacea, Delphinidae). Marine Mammal Science 21: 365 -400</ref> 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 [[Orcaella#Australian snubfin dolphin|Australian snubfin dolphin]], consists of the Australian/New Guinea population.<ref>Beasley, Isabel L. (2007). Conservation of the Irrawaddy dolphin, ''Orcaella brevirostris'' (Owen in Gray, 1866) in the Mekong River: biological and social considerations influencing management. PhD thesis, James Cook University.</ref>

The '''snubfin dolphins''' (''Orcaella'') contain two of the 35 species of oceanic dolphins that make up the [[Cetacean]] family of [[Delphinidae]].<ref>Evans, Peter G.H. (1984). Macdonald, D., ed. The Encyclopedia of Mammals. New York: Facts on File. pp. 180–185. {{ISBN|0-87196-871-1}}</ref> The phylogenetic status of ''Orcaella'' has long been confused. Although the snubfin dolphins share similar external features with the [[Monodontidae]] (narwhal),<ref name=Ross /> 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.<ref>Arnason U., Gretarsdottir S.. 1992. Evolution of the common cetacean highly repetitive DNA component and the systematic position of ''Orcaella brevirostris''. Journal of Molecular Evolution 34: 201-208.</ref>

Some [[Molecular phylogeny|molecular analyses]] indicate that the genus ''Orcaella'' is closely related to the [[orca]] of the genus ''Orcinus'', the two of them together forming the subfamily Orcininae.<ref>LeDuc, R.G., Perrin, W.F., Dizon, A.E. (1999). Phylogenetic relationships among the delphinid cetaceans based on full cytochrome ''b'' sequences. Marine Mammal Science 15, 619–648.</ref><ref>May-Collado, L., Agnarsson, I. (2006). Cytochrome ''b'' and Bayesian inference of whale phylogeny. Molecular Phylogenetics and Evolution 38, 344-354.</ref> However, more recent studies have firmly found that ''Orcaella'' belongs in the [[Globicephalinae]].<ref>{{Cite journal|last=McGowen|first=Michael R|last2=Tsagkogeorga|first2=Georgia|last3=Álvarez-Carretero|first3=Sandra|last4=dos Reis|first4=Mario|last5=Struebig|first5=Monika|last6=Deaville|first6=Robert|last7=Jepson|first7=Paul D|last8=Jarman|first8=Simon|last9=Polanowski|first9=Andrea|last10=Morin|first10=Phillip A|last11=Rossiter|first11=Stephen J|date=2019-10-21|title=Phylogenomic Resolution of the Cetacean Tree of Life Using Target Sequence Capture|url=https://doi.org/10.1093/sysbio/syz068|journal=Systematic Biology|volume=69|issue=3|pages=479–501|doi=10.1093/sysbio/syz068|issn=1063-5157|pmc=7164366|pmid=31633766}}</ref>