View source for Iniidae

{{Short description|Family of dolphins}}
{{Multiple issues|
{{More citations needed|date=June 2025}}
{{Inline|date=June 2025}}
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{{Automatic Taxobox
| fossil_range = [[Miocene]]-[[Holocene]] 
| image = Inia.jpg
| image_caption = An [[Amazon river dolphin]] at [[Duisburg Zoo]] holding an Armored catfish in the mouth.
| image2 = Amazon river dolphin size.svg
| image2_caption = Size compared to an average human
| taxon = Iniidae
| authority = [[John Edward Gray|Gray]], 1846
| subdivision_ranks = Genera
| subdivision = ''[[Inia]]''
}}

'''Iniidae''' is a [[Family (biology)|family]] of [[river dolphin]]s containing one living genus, ''[[Inia]]'', and four extinct genera. The extant genus inhabits the river basins of [[South America]], but the family formerly had a wider presence across the [[Atlantic Ocean]]. 

Iniidae are highly morphologically different from [[Oceanic dolphin|marine dolphins]] by way of adaptations suited to their freshwater riverine habitat.<ref name=Hamilton2001/> They also display a high amount of [[sexual dimorphism]] in the form of color and size.<ref name=Martin2006>{{cite journal |author1=Martin, A.R. |author2=Silva, V.M. |year=2006 |title=Sexual dimorphism and body scarring in the boto (Amazon river dolphin) ''Inia geoffrensis'' |journal=Marine Mammal Science |volume=22 |issue=1 |pages=25–33 |doi=10.1111/j.1748-7692.2006.00003.x|bibcode=2006MMamS..22...25M }}</ref> Seasonal movement between flooded plains and rivers is common, due to the variation of seasonal rain.<ref name=Rice1998>{{cite book |author=Rice, Dale W. |year=1998 |title=Marine Mammals of the World: Systematics and distribution |series=Society for Marine Mammalogy Special Publication |place=Lawrence, KS |publisher=Society for Marine Mammalogy |volume=4 |pages=1–231 |isbn=978-189127603-3}} {{isbn|1891276034}}</ref> There has been little research done on the family, in particular the species aside from the [[Amazon river dolphin]].<ref name=Martin2006/>

==Evolution==
The South American river basins were flooded by marine waters,{{When|date=May 2019}} creating a new brackish habitat that allowed marine mammals to move into them. During the Miocene era, the sea level began to recede, trapping the mammals within the continent.<ref name="Hamilton2001">{{cite journal |author1=Hamilton, Healy |display-authors=etal |year=2001 |title=Evolution of river dolphins |journal=Proceedings of the Royal Society of London B: Biological Sciences |volume=268 |issue=1466 |pages=549–556|doi=10.1098/rspb.2000.1385 |pmid=11296868 |pmc=1088639 }}</ref>

== Morphology ==
Their necks are flexible, since their cervical vertebra are movable; this is remarkable since nearly all cetaceans' neck vertebra are fused, which rigidly aims most other cetaceans' heads forward.<ref name=Gomez2011/> The Iniidae have other morphology common to species adapted to freshwater riverine habitats;<ref name=Gutstien2011>{{cite journal |last1=Gutstien |first1=Carolina |year=2014 |title=The antiquity of riverine adaptations in Iniidae (Cetacea, Odontoceti) documented by a humerus from the Late Miocene of the Ituzaingo Formation, Argentina |journal=The Anatomical Record |volume=297 |issue=6 |pages=1096–1102 |doi=10.1002/ar.22901 |doi-access=free |pmid=24585575 |s2cid=42361824}}</ref> which include highly reduced or absent dorsal fins, so they do not become entangled in vegetation from the flooded terrestrial plains; and large, wide, paddle-like pectoral fins that allow maneuverability in confined areas cramped by vegetation.<ref name=Gomez2011>{{cite journal |author=Gomez-Salazar, C. |year=2011 |title=Photo-identification: A reliable and noninvasive tool for studying pink river dolphins (Inia geoffrensis) |journal=Aquatic Mammals |volume=37 |issue=4 |pages=472–485 |doi=10.1578/am.37.4.2011.472|bibcode=2011AqMam..37..472G }}</ref> Other riverine adaptations including a long [[Rostrum_(anatomy)|rostrum]], skull and jaw and reduced orbits.<ref>{{cite journal |author1=Pyenson, N.D. |author1-link=Nicholas Pyenson |author2=Vélez-Juarbe, J. |author3=Gutstein, C.S. |author4=Little, H. |author5=Vigil, D. |author6=O'Dea, A. |date=1 September 2015 |title=''Isthminia panamensis'', a new fossil Inioid (Mammalia, Cetacea) from the Chagres Formation of Panama and the evolution of 'river dolphins' in the Americas |journal=PeerJ |volume=3 |page=e1227 |publisher=PeerJ Inc |pmid=26355720 |pmc=4562255 |doi=10.7717/peerj.1227 |doi-access=free }}</ref>

Iniidae share many other characteristics in common with their marine [[odontocete]] relatives: Their stomachs include a fore-stomach, singled chambered main stomach, and a pyloric stomach with connecting channels. Like most other cetaceans Iniidae have lost their fur and lack true vocal cords.<ref name=Kaiya-1982>{{cite journal |author=Kaiya, Zhou |year=1982 |title=Classification and phylogeny of the superfamily Platanistoidea, with notes on evidence of the monophyly of the Cetacea |journal=Sci. Rep. Whale Res. Inst. |volume=34 |pages=93–108}}</ref> They share the similar structure of the tympanic bulla and lung shape, the position of their diaphragm and the position of the blowhole to the back of the head with their marine ancestors.

The dentition of Iniidae dolphins is [[heterodont]],{{citation needed|date=November 2017}} having conical, small teeth that differ slightly in the front of the mouth. The teeth extend lingually in the back and in the front they have a small depression on the side of each. These mammals are carnivorous, finding prey by using echolocation.

==Speciation==
There is scientific debate on the number of species within the genus ''Inia'': The main issue is whether there are two or three species, or whether those can be considered sub-species. According to some researchers
* ''Inia geoffrensis''
* ''Inia humboldtiana''
* ''Inia boliviensis'' 

are three separate species, while many consider ''I. geoffrensis'' and ''I. boliviensis'' to be the only two.<ref name=Gravena2014>{{cite journal |author1=Gravena, Waleska |display-authors=etal |year=2014 |title=Looking to the past and the future: Were the Madeira River rapids a geographical barrier to the boto (Cetacea: Iniidae)? |journal=Conservation Genetics |volume=15 |issue=3 |pages=619–629}}</ref><ref>{{cite journal |author1=Ruiz-García, M. |author2=Banguera, E. |author3=Cardenas, H. |year=2006 |title=Morphological analysis of three Inia (Cetacea: Iniidae) populations from Colombia and Bolivia |journal=Acta Theriologica |volume=51 |issue=4 |pages=411–426 |doi=10.1007/bf03195188|s2cid=22868836 }} </ref><ref name=Rice1998/> Martin in 2004 found supporting evidence that genetic exchange occurs between multiple sites on the Amazon, even places hundreds of kilometres apart.{{cn|date=September 2022}}

==Taxonomy==
The family was described by [[John Edward Gray]] in 1846.<ref name=TPBDB>{{cite web |title=''Inia'' taxon description |website=The Paleobiology Database |url=https://paleobiodb.org/classic/checkTaxonInfo?taxon_no=53142 |url-status=live |access-date=2022-09-21 |archive-date=2012-10-12 |archive-url=https://web.archive.org/web/20121012212849/http://paleodb.org/cgi-bin/bridge.pl?action=checkTaxonInfo&taxon_no=53142&is_real_user=1 }}</ref>

Current classifications include a single living genus, ''Inia'', with one to four species and several subspecies.<ref name=Hrbek2014>
{{cite journal
 | last1 = Hrbek  | first1 = Tomas      | last2 = da Silva | first2 = Vera Maria Ferreira
 | last3 = Dutra  | first3 = Nicole     | last4 = Gravena  | first4 = Waleska
 | last5 = Martin | first5 = Anthony R. | last6 = Farias   | first6 = Izeni Pires
 | date = 2014-01-22
 | title = A new species of river dolphin from Brazil or: How little do we know our biodiversity?
 | journal = [[PLOS ONE]]
 | volume = 9 | issue = 1 | page = e83623
 | pmid =  24465386 | pmc = 3898917 | bibcode = 2014PLoSO...983623H
 | doi = 10.1371/journal.pone.0083623 | doi-access = free
<!-- | editor1-last = Turvey | editor1-first = Samuel T. -->
}}
</ref><ref>
{{cite mdd
 |genus=Inia
 |access-date=2021-09-05
}}
</ref>
The family also includes three extinct genera described from fossils found in [[South America]], [[Florida]], [[Libya]], and [[Italy]].<ref name=TPBDB/>

*Superfamily [[Inioidea]]
**Family Iniidae
***Genus †''[[Goniodelphis]]''
**** ''G. hudsoni''
***Genus ''[[Inia]]''
**** ''Inia araguaiaensis'' - [[Araguaian river dolphin]]
**** ''Inia boliviensis'' - [[Bolivian river dolphin]]
**** ''Inia geoffrensis'' - [[Amazon river dolphin]]
****''Inia humboldtiana'' - [[Orinoco river dolphin]]
***Genus †''[[Isthminia]]'' 
****†''[[Isthminia panamensis]]''
***Genus †''[[Meherrinia]]''
***Genus †''[[Ischyrorhynchus]]'' (syn. ''Anisodelphis'')
**** ''I. vanbenedeni'' (syn. ''Anisodelphis brevirostratus'')
***Genus †''[[Saurocetes]]'' (syn. ''Saurodelphis'', ''Pontoplanodes'')
**** ''S. argentinus'' (syn. ''Pontoplanodes obliquus'') 
**** ''S. gigas''

==References==
{{reflist|25em}}

{{Cetacea|O.}}
{{Odontoceti|D.}}
{{Taxonbar|from=Q54873}}

[[Category:Iniidae| ]]
[[Category:Mammals of South America]]
[[Category:Mammals of Brazil]]
[[Category:Mammals of Peru]]
[[Category:Mammal families]]
[[Category:Taxa named by John Edward Gray]]