Iniidae
Iniidae | |
---|---|
An Amazon river dolphin at Duisburg Zoo holding an Armored catfish in the mouth. | |
Size compared to an average human | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Order: | Artiodactyla |
Infraorder: | Cetacea |
Superfamily: | Inioidea |
Family: | Iniidae Gray, 1846 |
Genera | |
Iniidae is a family of river dolphins 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 marine dolphins by way of adaptations suited to their freshwater riverine habitat.[1] They also display a high amount of sexual dimorphism in the form of color and size.[2] Seasonal movement between flooded plains and rivers is common, due to the variation of seasonal rain.[3] There has been little research done on the family, in particular the species aside from the Amazon river dolphin.[2]
Evolution
The South American river basins were flooded by marine waters,[when?] 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.[1]
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.[4] The Iniidae have other morphology common to species adapted to freshwater riverine habitats;[5] 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.[4] Other riverine adaptations including a long rostrum, skull and jaw and reduced orbits.[6]
Iniidae share many other characteristics in common with their marine
The dentition of Iniidae dolphins is heterodont,[citation needed] 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.[8][9][3] Martin in 2004 found supporting evidence that genetic exchange occurs between multiple sites on the Amazon, even places hundreds of kilometres apart.[citation needed]
Taxonomy
The family was described by John Edward Gray in 1846.[10]
Current classifications include a single living genus, Inia, with one to four species and several subspecies.[11][12] The family also includes three extinct genera described from fossils found in South America, Florida, Libya, and Italy.[10]
- 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
- Genus †Goniodelphis
- Family Iniidae
References
- ^ PMID 11296868.
- ^ .
- ^ ISBN 1891276034
- ^ .
- S2CID 42361824.
- PMID 26355720.
- ^ Kaiya, Zhou (1982). "Classification and phylogeny of the superfamily Platanistoidea, with notes on evidence of the monophyly of the Cetacea". Sci. Rep. Whale Res. Inst. 34: 93–108.
- ^ Gravena, Waleska; et al. (2014). "Looking to the past and the future: Were the Madeira River rapids a geographical barrier to the boto (Cetacea: Iniidae)?". Conservation Genetics. 15 (3): 619–629.
- S2CID 22868836.
- ^ a b "Inia taxon description". The Paleobiology Database. Archived from the original on 2012-10-12. Retrieved 2022-09-21.
- ^
Hrbek, Tomas; da Silva, Vera Maria Ferreira; Dutra, Nicole; Gravena, Waleska; Martin, Anthony R.; Farias, Izeni Pires (2014-01-22). "A new species of river dolphin from Brazil or: How little do we know our biodiversity?". PMID 24465386.
- ^ "Inia". ASM Mammal Diversity Database. American Society of Mammalogists. Retrieved 2021-09-05.