List of semiaquatic tetrapods

This is a list of tetrapods that are semiaquatic; that is, while being at least partly terrestrial, they spend part of their life cycle or a significant fraction of their time in water as part of their normal behavior, and/or obtain a significant fraction of their food from an aquatic habitat. The very earliest tetrapods, such as Ichthyostega, were semiaquatic, having evolved from amphibious lobe-finned fish.

Some marine mammals, such as the marine otter, the polar bear and pinnipeds, are semiaquatic, while others, such as the sea otter, cetaceans and sirenians, are fully aquatic. The only fully aquatic nonmarine mammals are several manatees (the Amazonian manatee and some populations of African manatee) and certain small cetaceans (river dolphins, the tucuxi, and some populations of Irrawaddy dolphin and finless porpoise). No bird species is fully aquatic, as all must lay and incubate their amniotic eggs, as well as begin raising their young, on land or ice. Similarly among marine reptiles, sea turtles are almost fully aquatic, but must come ashore to lay eggs. Marine iguanas and partly marine crocodiles (such as the saltwater crocodile and the American crocodile) are all semiaquatic. Most sea snakes are ovoviviparous (live-bearing) and fully aquatic (the exceptions being the oviparous, semiaquatic sea kraits). A few freshwater snakes are also ovoviviparous and fully aquatic (e.g., Erpeton tentaculatum and Acrochordidae), but the majority are semiaquatic. Most amphibians have an aquatic larval stage and are at least semiaquatic for that reason, but there are many exceptions to this generalization.

The aquatic component of a semiaquatic species' lifestyle may be either obligatory or facultative to varying degrees (examples of the latter are the Arctic fox, jaguar and green iguana).

Note: dagger symbols, "†", have been used to indicate a listed taxon is extinct.

Ichthyostega BW
Restoration of Ichthyostega, an early tetrapod from the Devonian
Marine otter of the west coast of South America
Monachus schauinslandi
Hawaiian monk seal, off Kaʻula Island


All extant fully aquatic mammals except the sea otter are found in two clades of exclusively aquatic species, Cetacea and Sirenia; the extinct desmostylians are also thought to have been fully aquatic (these groups are thought to have become fully aquatic about 45, 40 and 30 Ma ago, respectively). In contrast, semiaquatic mammals are widely distributed throughout the class. However, extant semiaquatic swimming marine mammals are restricted to Carnivora (among which, pinnipeds apparently appeared about 20 Ma ago). Semiaquatic (carnivorous) rodents have been noted as having larger than normal brains for their size, possibly as a consequence of using their vibrissae for acoustic detection of prey.[1][2]

Wild Platypus 4
Platypus, a semiaquatic monotreme, Tasmania
Asiatic Elephant swimming in Bandipur
Asian elephant using its trunk as a snorkel, India
Nutria (Myocastor coypus) in a partially frozen river Ljubljanica
Invasive coypu, Europe
Muskrat swimming Ottawa
Muskrat, Ontario
2173175660 38299e9cb4 o
Male waterbuck, Kenya
Moose in Grand Teton National Park 2 (7994780433)
Female moose, Wyoming
Hippopotamus in San Diego Zoo
Hippopotamus underwater
Penguin in Antarctica jumping out of the water
Emperor penguins, Antarctica
Pelecanus Occidentalis KW 1
Brown pelican, Florida
The deployed wings wood duck
Male wood duck, Quebec


The great majority of semiaquatic birds are found within three clades whose members are mostly semiaquatic: Aequorlitornithes, Anseriformes and Gruiformes, thought to be about 64, 47 and 41 Ma old, respectively.[17][note 2]

Nonavian dinosaurs

Hesperornis BW
Hesperornis restoration
Spinosaurus durbed
Spinosaurus restoration

Only a few nonavian dinosaurs are thought to have been semiaquatic. While the Mesozoic had many types of marine reptiles, the combination of being oviparous and endothermic seems to have prevented the evolution of fully aquatic dinosaurs, as in birds.


Eudimorphodon NT small
Eudimorphodon restoration
Pterodaustro BW
Pterodaustro restoration, showing its bristle-like modified teeth, likely used for filter feeding as in flamingos

A number of types of pterosaurs are thought to have been piscivores, and a few are suspected of being molluscivores.

Other reptiles

Nile crocodile swimming sequence
Marine iguana (4202531062)
Marine iguana, Galápagos Islands
Laticauda laticaudata
Blue-lipped sea krait, Java; note paddle-like tail

Semiaquatic forms are widely distributed among extant and extinct reptiles, and extinct semiaquatic or fully aquatic marine forms were once ecologically prominent.

North American eastern newt as a gilled aquatic larva, aposematic terrestrial juvenile ("red eft") and aquatic adult

Circ1258 plates 17b
Young Eastern Newt - Flickr - pellaea
Redspotted newt


Amphibians differ from other semiaquatic tetrapods in that their semiaquatic lifestyle is ancestral, rather than being the result of a secondary evolutionary trend from a terrestrial state back towards an aquatic environment. Thus, they are the only tetrapods to possess gills. All extant amphibians that are semiaquatic or fully aquatic inhabit freshwater habitats, with the exception of the crab-eating frog, which also exploits brackish habitats.

Most amphibians have an aquatic larval stage and thus are at least semiaquatic by virtue of this fact. Many adult amphibians are also semiquatic (while others are fully aquatic or terrestrial). However, some amphibians lack an aquatic larval stage. Some frogs, such as most leiopelmatids, most ranixalids, some leptodactylids, some myobatrachids, Darwin's frog and the Seychelles frog, have nonaquatic tadpoles. Some caecilians, many frogs such as saddleback toads, most sooglossids and the greenhouse frog,[20] and most plethodontid salamanders lay eggs on land in which the larvae develop into adult form before they hatch. The alpine salamander[21] and African live-bearing toads (Nectophrynoides and Nimbaphrynoides)[22] are ovoviviparous and give birth on land. Additionally, about 75% of caecilians are viviparous.

See also


  1. ^ Elephants have a system of cracks in their skin which retains water and mud for purposes of thermoregulation and protection from insect parasites and UV radiation. This system is less developed in Asian elephants than in African bush elephants; the former generally live in more mesic habitats.[5]
  2. ^ These dates are without calibration based on the putative late Cretaceous fossil crown avian Vegavis; its inclusion would push back the date for Anseriformes to ~69 Ma.
  3. ^ Although all extant crocodilians are semiaquatic, some recently extinct mekosuchine genera, Mekosuchus and Quinkana, were mostly or entirely terrestrial.


  1. ^ Voss, R. S. (1988). "Systematics and ecology of ichthyomyine rodents (Muroidea) : patterns of morphological evolution in a small adaptive radiation". Bulletin of the American Museum of Natural History. 188: 259–493 (see p. 410). hdl:2246/927.
  2. ^ Peterhans, J. C. K.; Patterson, B. D. (1995). "The Ethiopian water mouse Nilopegamys Osgood, with comments on semi-aquatic adaptations in African Muridae". Zoological Journal of the Linnean Society. 113 (3): 329–349 (see pp. 341–346). doi:10.1111/j.1096-3642.1995.tb00937.x.
  3. ^ Canadian Museum of Nature – Kangaroo. Retrieved 6 January 2007.
  4. ^ Domning, D. P. (2001-10-11). "The earliest known fully quadrupedal sirenians". Nature. Nature Publishing Group. 413 (6856): 625–627. doi:10.1038/35098072. PMID 11675784.
  5. ^ Lillywhite, H. B.; Stein, B. R. (1987). "Surface sculpturing and water retention of elephant skin". Journal of Zoology. 211 (4): 727–734. doi:10.1111/j.1469-7998.1987.tb04483.x.
  6. ^ Nedelman, M. (2018-04-19). "Diving deep on one breath could be in a 'sea nomad's' DNA". CNN. Retrieved 2018-04-20.
  7. ^ Zimmer, Carl (2018-04-19). "Bodies Remodeled for a Life at Sea". The New York Times. ISSN 0362-4331. Retrieved 2018-04-23.
  8. ^ Ilardo, M. A.; Moltke, I.; Korneliussen, T. S.; Cheng, J.; Stern, A. J.; Racimo, F.; de Barros Damgaard, P.; Sikora, M.; Seguin-Orlando, A.; Rasmussen, S.; van den Munckhof, I. C. L.; ter Horst, R.; Joosten, L. A. B.; Netea, M. G.; Salingkat, S.; Nielsen, R.; Willerslev, E. (2018-04-18). "Physiological and Genetic Adaptations to Diving in Sea Nomads". Cell. 173 (3): 569–580.e15. doi:10.1016/j.cell.2018.03.054. PMID 29677510.
  9. ^ a b Walker, M. (2009-07-07). "Aquatic deer and ancient whales". BBC News. Retrieved 2010-03-26.
  10. ^ Stadelmann, B.; Herrera, L. G.; Arroyo-Cabrales, J.; Flores-Martínez, J. J.; May, B. P.; Ruedi, M.; Miller, E. H. (2004). "Molecular Systematics of the Fishing Bat Myotis (Pizonyx) vivesi". Journal of Mammalogy. 85 (1): 133–139. doi:10.1644/1545-1542(2004)085<0133:MSOTFB>2.0.CO;2.
  11. ^ de Mello Beiseigel, B.; Zuercher, G.L. (2005). "Speotheos venaticus". Mammalian Species. 783: 1–6. doi:10.1644/783.1.
  12. ^ Fox, M. W. (1984). The Whistling Hunters: Field Studies of the Asiatic Wild Dog (Cuon Alpinus). Albany: State University of New York Press. p. 67. ISBN 978-0-9524390-6-6.
  13. ^ "Panthera onca, Jaguar". North American Mammals. Smithsonian Natural History Museum. Retrieved 2018-01-30.
  14. ^ Seymour, K. L. (26 October 1989). "Panthera onca" (PDF). Mammalian Species. 340 (340): 1–9. doi:10.2307/3504096. JSTOR 3504096.
  15. ^ Meijaard, E.; Umilaela; de Silva Wijeyeratne, G. (September 2010). "Aquatic escape behaviour in mouse-deer provides insight into tragulid evolution". Mammalian Biology. 75 (5): 471–473. doi:10.1016/j.mambio.2009.05.007. Retrieved 2016-04-12.
  16. ^ Lambert, O.; Bianucci, G.; Salas-Gismondi, R.; Di Celma, C.; Steurbaut, E.; Urbina, M.; de Muizon, C. (2019). "An Amphibious Whale from the Middle Eocene of Peru Reveals Early South Pacific Dispersal of Quadrupedal Cetaceans". Current Biology. doi:10.1016/j.cub.2019.02.050.
  17. ^ a b Prum, R. O.; et al. (22 October 2015). "A comprehensive phylogeny of birds (Aves) using targeted next-generation DNA sequencing". Nature. 526 (7574): 569–573. doi:10.1038/nature15697. PMID 26444237.
  18. ^ Swanson, Paul L. (1950), "The iguana: Iguana iguana iguana (L)", Herpetologica, 6 (7): 187–193, JSTOR 3890004
  19. ^ Coles, William (2002), "Green Iguana" (PDF), U.S.V.I. Animal Fact Sheet #08, Department of Planning and Natural Resources US Virgin Islands Division of Fish and Wildlife, archived from the original (PDF) on 2007-12-11
  20. ^ "Eleutherodactylus planirostris". AmphibiaWeb. 2012. Retrieved 2016-04-09.
  21. ^ Wikisource Chisholm, Hugh, ed. (1911). "Salamander" . Encyclopædia Britannica. 1 (11th ed.). Cambridge University Press.
  22. ^ Channing, A.; Howell, K. (January 2006). Amphibians of East Africa. Comstock Pub. Associates/Cornell University Press. pp. 104–117. ISBN 978-0-8014-4374-9. OCLC 60650905.
  23. ^ Vitt, L. J.; Caldwell, J. P. (25 March 2013). Herpetology: An Introductory Biology of Amphibians and Reptiles. Academic Press. p. 453. ISBN 978-0-12-386920-3. OCLC 898295183.
Amphibious fish

Amphibious fish are fish that are able to leave water for extended periods of time. About 11 distantly related genera of fish are considered amphibious. This suggests that many fish genera independently evolved amphibious traits, a process known as convergent evolution. These fish use a range of terrestrial locomotory modes, such as lateral undulation, tripod-like walking (using paired fins and tail), and jumping. Many of these locomotory modes incorporate multiple combinations of pectoral, pelvic and tail fin movement.

Many ancient fish had lung-like organs, and a few, such as the lungfish, still do. Some of these ancient "lunged" fish were the ancestors of tetrapods. However, in most recent fish species these organs evolved into the swim bladders, which help control buoyancy. Having no lung-like organs, modern amphibious fish and many fish in oxygen-poor water use other methods such as their gills or their skin to breathe air. Amphibious fish may also have eyes adapted to allow them to see clearly in air, despite the refractive index differences between air and water.

Aquatic animal

An aquatic animal is an animal, either vertebrate or invertebrate, which lives in the water for most or all of its lifetime. Many insects such as mosquitoes, mayflies, dragonflies and caddisflies have aquatic larvae, with winged adults. Aquatic animals may breathe air or extract oxygen that dissolved in water through specialised organs called gills, or directly through the skin. Natural environments and the animals that live in them can be categorized as aquatic (water) or terrestrial (land). This designation is paraphyletic.

Aquatic mammal

Aquatic and semiaquatic mammals are a diverse group of mammals that dwell partly or entirely in bodies of water. They include the various marine mammals who dwell in oceans, as well as various freshwater species, such as the European otter. They are not a taxon and are not unified by any distinct biological grouping, but rather their dependence on and integral relation to aquatic ecosystems. The level of dependence on aquatic life varies greatly among species. Among freshwater taxa, the Amazonian manatee and river dolphins are completely aquatic and fully dependent on aquatic ecosystems. Semiaquatic freshwater taxa include the Baikal seal, which feeds underwater but rests, molts, and breeds on land; and the capybara and hippopotamus which are able to venture in and out of water in search of food.

Mammal adaptation to an aquatic lifestyle vary considerably between species. River dolphins and manatees are both fully aquatic and therefore are completely tethered to a life in the water. Seals are semiaquatic; they spend the majority of their time in the water, but need to return to land for important activities such as mating, breeding and molting. In contrast, many other aquatic mammals, such as hippopotamus, capybara, and water shrews, are much less adapted to aquatic living. Likewise, their diet ranges considerably as well, anywhere from aquatic plants and leaves to small fish and crustaceans. They play major roles in maintaining aquatic ecosystems, beavers especially.

Aquatic mammals were the target for commercial industry, leading to a sharp decline in all populations of exploited species, such as beavers. Their pelts, suited for conserving heat, were taken during the fur trade and made into coats and hats. Other aquatic mammals, such as the Indian rhinoceros, were targets for sport hunting and had a sharp population decline in the 1900s. After it was made illegal, many aquatic mammals became subject to poaching. Other than hunting, aquatic mammals can be killed as bycatch from fisheries, where they become entangled in fixed netting and drown or starve. Increased river traffic, most notably in the Yangtze river, causes collisions between fast ocean vessels and aquatic mammals, and damming of rivers may land migratory aquatic mammals in unsuitable areas or destroy habitat upstream. The industrialization of rivers led to the extinction of the Chinese river dolphin, with the last confirmed sighting in 2004.

Marine mammal

Marine mammals are aquatic mammals that rely on the ocean and other marine ecosystems for their existence. They include animals such as seals, whales, manatees, sea otters and polar bears. They do not represent a distinct taxon or systematic grouping, but rather have a polyphyletic relation due to convergent evolution, as in they do not have an immediate common ancestor. They are also unified by their reliance on the marine environment for feeding.

Marine mammal adaptation to an aquatic lifestyle varies considerably between species. Both cetaceans and sirenians are fully aquatic and therefore are obligate water dwellers. Seals and sea-lions are semiaquatic; they spend the majority of their time in the water but need to return to land for important activities such as mating, breeding and molting. In contrast, both otters and the polar bear are much less adapted to aquatic living. Their diet varies considerably as well; some may eat zooplankton, others may eat fish, squid, shellfish, sea-grass and a few may eat other mammals. While the number of marine mammals is small compared to those found on land, their roles in various ecosystems are large, especially concerning the maintenance of marine ecosystems, through processes including the regulation of prey populations. This role in maintaining ecosystems makes them of particular concern as 23% of marine mammal species are currently threatened.

Marine mammals were first hunted by aboriginal peoples for food and other resources. Many were also the target for commercial industry, leading to a sharp decline in all populations of exploited species, such as whales and seals. Commercial hunting led to the extinction of Steller's sea cow, sea mink, Japanese sea lion and the Caribbean monk seal. After commercial hunting ended, some species, such as the gray whale and northern elephant seal, have rebounded in numbers; conversely, other species, such as the North Atlantic right whale, are critically endangered. Other than hunting, marine mammals can be killed as bycatch from fisheries, where they become entangled in fixed netting and drown or starve. Increased ocean traffic causes collisions between fast ocean vessels and large marine mammals. Habitat degradation also threatens marine mammals and their ability to find and catch food. Noise pollution, for example, may adversely affect echolocating mammals, and the ongoing effects of global warming degrade Arctic environments.

Marine reptile

Marine reptiles are reptiles which have become secondarily adapted for an aquatic or semiaquatic life in a marine environment.

The earliest marine reptiles arose in the Permian period during the Paleozoic era. During the Mesozoic era, many groups of reptiles became adapted to life in the seas, including such familiar clades as the ichthyosaurs, plesiosaurs (these two orders were once thought united in the group "Enaliosauria," a classification now cladistically obsolete), mosasaurs, nothosaurs, placodonts, sea turtles, thalattosaurs and thalattosuchians. After the mass extinction at the end of the Cretaceous period, marine reptiles were less numerous, but there was still a high variety of species in the early Cenozoic, such as "true" sea turtles, bothremydids, palaeophiid snakes, a few choristoderes such as Simoedosaurus and dyrosaurid crocodylomorphs. Various types of marine gavialid crocodilians remained widespread as recently as the Late Miocene.Currently, of the approximately 12,000 extant reptile species and sub-species, only about 100 are classed as marine reptiles: extant marine reptiles include marine iguanas, sea snakes, sea turtles and saltwater crocodiles.Some marine reptiles, such as ichthyosaurs, plesiosaurs, metriorhynchid thalattosuchians, and mosasaurs became so well adapted to a marine lifestyle that they were incapable of venturing onto land and gave birth in the water. Others, such as sea turtles and saltwater crocodiles, return to shore to lay their eggs. Some marine reptiles also occasionally rest and bask on land.

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