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The ears of river dolphins have specific adaptations to their aquatic environment. In humans, the middle ear works as an impedance equalizer between the outside air's low impedance and the cochlear fluid's high impedance. In river dolphins, and other cetaceans, there is no great difference between the outer and inner environments.
According to a study in 1971, Peale's dolphin and the Cephalorhynchus species are the only dolphins that do not whistle (no acoustic data are available for the hourglass dolphin). Peale's dolphin also shares with several Cephalorhynchus species the possession of a distinct white "armpit" marking behind the pectoral fin.
River dolphins are thought to have relictual distributions, that is, their ancestors originally occupied marine habitats, but were then displaced from these habitats by modern dolphin lineages. [ 17 ] [ 18 ] Many of the morphological similarities and adaptations to freshwater habitats arose due to convergent evolution ; thus, a grouping of all ...
Articles relating to the river dolphins, a polyphyletic group of fully aquatic mammals that reside exclusively in freshwater or brackish water. They are an informal grouping of dolphins, which itself is a paraphyletic group within the infraorder Cetacea. Extant river dolphins are placed in two superfamilies, Platanistoidea and Inioidea.
Studies [34] have found there to be two different types of cochlea in the dolphin population. Type I has been found in the Amazon river dolphin and harbour porpoises. These types of dolphin use extremely high frequency signals for echolocation. Harbour porpoises emit sounds at two bands, one at 2 kHz and one above 110 kHz.
Watch: Rare 'super pod' of Risso's dolphins enjoy California waters. Monterey Bay Whale Watch said on Facebook that their scouting boat spotted the dolphins when it went out to "perform a survey ...
8. Corgi. The corgi—aka, everyone’s favorite short-legged pup—is one of the most recognizable dogs with pointy ears. Beloved by Queen Elizabeth II, these dogs have been favored by the kings ...
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.