613:
surface area, which increases the propulsive drag the animal can generate with each stroke of its foot. This is a drag-based mode of propulsion. However, some waterfowl also utilize lift-based modes of propulsion, where their feet generate hydrodynamic lift due to the angle of attack of the foot and the relative water velocity. For example, great-crested grebes use solely lift-based propulsion due to their lateral foot stroke and asymmetric, lobated toes. Most waterfowl use a combination of these two modes of propulsion, where the first third of their foot stroke generates propulsive drag and the last two-thirds of the stroke generates propulsive lift.
210:. BMP signaling molecules (BMPs) are expressed in the tissue regions between digits during development. In experiments with chickens, mutations to a BMP receptor disrupted the apoptosis of interdigital tissue and caused webbed feet similar to ducks to develop. In ducks, BMPs are not expressed at all. These results indicate that in avian lineages, the disruption of BMP signaling in interdigital tissue caused webbed feet to arise. The magnitude of attenuation in this pathway is correlated with the amount of interdigital tissue preserved. Other genetic changes implicated in webbed feet development in avians include reduction of
249:
665:, which is determined by their body length. In order to achieve speeds higher than hull speed, some ducks, like eider ducks, use distinctive modes of locomotion that involve lifting the body out of the water. They can hydroplane, where they lift part of their body out of the water and paddle with their webbed feet to generate forces that allow them to overcome gravity; they also use paddle-assisted flying, where the whole body is lifted out of the water, and the wings and feet work in concert to generate lift forces. In extreme cases, this type of behavior is used for
73:
27:
628:. Fully aquatic mammals and animals typically have flippers instead of webbed feet, which are a more heavily specialized and modified limb. It is hypothesized that an evolutionary transition between semiaquatic and fully aquatic higher vertebrates (especially mammals) involved both the specialization of swimming limbs and the transition to underwater, undulatory modes of motion. However, for semiaquatic animals that mainly swim at the surface, webbed feet are highly functional; they trade-off effectively between efficient
2267:
109:
183:
688:, the Namib sand gecko, their webbed feet may serve as sand shoes that enable them to move atop sand dunes. However, some ecologists believe that their webbed feet do not aid aboveground locomotion, but are mainly utilized as shovels for burrowing and digging in the sand. In salamanders, most species do not benefit from the increased surface area of their feet. However, some, like the bigfoot splayfoot salamander (
158:. Paddles generate less lift than hydrofoils, and paddling is associated with drag-based control surfaces. The roughly triangular design of webbed feet, with a broad distal end, is specialized to increase propulsive efficiency by affecting a larger mass of water over generating increased lift. This is in contrast to a more hydrofoil-like flipper of many permanently aquatic animals.
130:. The webbing can consist of membrane, skin, or other connective tissue and varies widely in different taxa. This modification significantly increases the surface area of the feet. One of the consequences of this modification in some species, specifically birds, is that the feet are a major location for heat loss. In birds, the legs utilize
92:. These mutations were beneficial to many semiaquatic animals because the increased surface area from the webbing allowed for more swimming propulsion and swimming efficiency, especially in surface swimmers. The webbed foot also has enabled other novel behaviors like escape responses and mating behaviors. A webbed foot may also be called a
560:
179:, or programmed cell death, in development is mediated by a variety of pathways, and normally causes the creation of digits by death of tissue separating the digits. Different vertebrate species with webbed feet have different mutations that disrupt this process, indicating that the structure arose independently in these lineages.
620:
that aid propulsion. During the transition from drag-based to lift-based propulsion in ducks, leading edge vortices formed on the front of the foot are shed, which creates a flow of water over the foot that likely aids lift production. Other species also create these vortices during their webbed foot
612:
In many species, webbed feet likely evolved to aid in generation of propulsion during swimming. Most webbed-footed animals utilize paddling modes of locomotion where their feet stroke backwards relative to their whole body motion, generating a propulsive force. The interdigital membrane increases the
244:
Webbed feet have arisen in all major vertebrate lineages with limbed animals. Most webbed-footed species spend part of their time in aquatic environments, indicating that this homologous structure provides some advantage to swimmers. Some examples from each class are highlighted here, but this is not
198:
expressions of syndactyly. While these conditions are disorders in humans, the variability in genetic cause of webbed digits informs our understanding of how this morphological change arose in species where webbed feet were selectively advantageous. These conditions also demonstrate a variety of
673:
utilize their lobated feet to generate nearly 50% of the force required to allow them to walk on water in elaborate sexual displays; they are likely the largest animal to "walk" on water, and are an order of magnitude heavier than the well-known lizards that exhibit a similar behavior.
236:(bigfoot splayfoot salamander), their webbed feet are morphologically unique from other salamanders and may serve a functional purpose. This demonstrates that webbed feet arise from developmental changes, but do not necessarily correlate with a selective advantage functionally.
229:
Webbed feet could also arise due to being linked to other morphological changes, without a selective advantage. In salamanders, webbed feet have arisen in multiple lineages, but in most do not contribute to increased function. However, in the cave salamander species
695:
increase their body size to foot surface area ratio enough to provide increased suction. This species lives in cave environments where they often encounter wet, slick surfaces. Therefore, their webbed feet may enable them to move on these surfaces with ease.
640:
can swim underwater to forage. These ducks expend more than 90% of their energy to overcome their own buoyancy when they dive. They can also achieve higher speeds underwater due to surface speeds being limited to their
621:
stroke. Frogs also create vortices that shed off their feet when swimming in water. The vortices from the two feet do not interfere with each other; therefore, each foot is generating forward propulsion independently.
329:
are typically classified as a sub-group of reptiles, but they are a distinct class within vertebrates, so are discussed separately. Birds have a wide span of representatives with webbed feet, due to the diversity of
146:
in many taxa, and is also used in aircraft to allow for high lift forces at high attack angles. This shape allows for the production of large forces during swimming through both drag-based and lift-based propulsion.
252:
A phylogenetic tree of vertebrate taxa. The classes highlighted in red contain species with webbed feet. In all these cases, webbed feet arose homologously and independently of other classes through
138:, the webbing can even be discontinuous, as seen in lobate-footed birds like grebes. However, one of the most common is the delta (Δ) or triangular shape seen in most waterfowl and frogs. This
283:), have webbed feet. Salamanders in arboreal and cave environments also have webbed feet, but in most species, this morphological change does not likely have a functional advantage.
194:
can arise from as many as nine unique subtypes with their own clinical, morphological, and genetic fingerprints. In addition, the same genetic mutations can underlie different
199:
genetic targets for mutation resulting in webbed feet, which may explain how this homologous structure could have arisen many times over the course of evolutionary history.
34:. Here, the delta (triangular) shape of the foot is clearly visible. This shape allows for the formation of leading edge vortices and lift-based propulsion during swimming.
2141:
Research for this
Knowledge (XXG) entry was conducted as part of a Locomotion Neuromechanics course (APPH 6232) offered in the School of Biological Sciences at Georgia Tech
2168:
134:
so that blood reaching the feet is already cooled by blood returning to the heart to minimize this effect. Webbed feet take on a variety of different shapes; in
118:, the common frog. Here, the foot has a delta (triangular) shape that allows for the formation of leading edge vortices and likely increases swimming efficiency.
682:
While webbed feet have mainly arisen in swimming species, they can also aid in terrestrial locomotors by increasing contact area on slick or soft surfaces. For
319:
2105:
Proctor, Noble S.; Lynch, Patrick J. (1993). "Chapters: 6. Topography of the foot, 11. The pelvic girdle, and 12. The bones of the leg and foot Family".
753:
Johansson, L. Christoffer; Norberg, R. Ake (2003-07-03). "Delta-wing function of webbed feet gives hydrodynamic lift for swimming propulsion in birds".
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1967:
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Ancel, A.; Starke, L. N.; Ponganis, P. J.; Van Dam, R.; Kooyman, G. L. (2000-12-01). "Energetics of surface swimming in Brandt's cormorants
346:
all have webbed feet. They utilize different foraging behaviors in water, but use similar modes of locomotion. There is a wide variety of
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1582:
1557:
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122:
A webbed foot has connecting tissue between the toes of the foot. Several distinct conditions can give rise to webbed feet, including
186:
Bats have also developed interdigital webbing for flight. Reductions in the BMP-induced apoptosis likely allowed this trait to arise.
1636:
1609:
1068:
636:. In addition, some waterfowl can also use paddling modes for underwater swimming, with added propulsion from flapping their wings.
248:
517:
have a vestigial hind toe (1), and sandpipers and their allies have a reduced and raised hind toe barely touching the ground. The
2154:
1626:
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277:(salamanders) have representative species with webbed feet. Frogs that live in aquatic environments, like the common frog (
1208:
Zou, Hongyan; Niswander, Lee (1996-01-01). "Requirement for BMP Signaling in
Interdigital Apoptosis and Scale Formation".
690:
624:
Most fully aquatic vertebrates do not use paddling modes of locomotion, instead using undulatory modes of locomotion or
232:
131:
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72:
26:
1481:]. Mały słownik zoologiczny (in Polish). Vol. I (I ed.). Warsaw: Wiedza Powszechna. pp. 383–385.
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2216:
625:
203:
1086:"Interdigital webbing retention in bat wings illustrates genetic changes underlying amniote limb diversification"
1058:
870:
1653:
171:
Webbed feet are the result of mutations in genes that normally cause interdigital tissue between the toes to
1975:
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2458:
2443:
1057:
Sadava, David E.; Orians, Gordon H.; Heller, H. Craig; Hillis, David M.; Purves, William K. (2006-11-15).
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527:: the anterior digits (2–4) are edged with lobes of skin. Lobes expand or contract when a bird swims. In
2534:
2110:
318:
351:
88:
It likely arose from mutations in developmental genes that normally cause tissue between the digits to
1654:"Propulsive force calculations in swimming frogs. II. Application of a vortex ring model to DPIV data"
2473:
2385:
1764:
1712:
Fish, Frank E. (1994-01-01). "Association of
Propulsive Swimming Mode with Behavior in River Otters (
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1217:
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253:
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Webbed feet are a compromise between aquatic and terrestrial locomotion. Aquatic control surfaces of
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66:
47:
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661:. Surface swimmers are speed-limited due to increasing drag as they approach a physically defined
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Weatherbee, Scott D.; Behringer, Richard R.; Rasweiler, John J.; Niswander, Lee A. (2006-10-10).
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1319:"Developmental processes underlying the evolution of a derived foot morphology in salamanders"
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Gañan, Yolanda; Macias, Domingo; Basco, Ricardo D.; Merino, Ramón; Hurle, Juan M. (1998).
955:
Johansson, L. C.; Norberg, U. M. (2000-10-05). "Asymmetric toes aid underwater swimming".
654:
482:
182:
645:; at this speed, the wave drag increases to the point where the duck cannot swim faster.
1768:
1753:"Drag-based 'hovering' in ducks: the hydrodynamics and energetic cost of bottom feeding"
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on the hallux (1). Grebes have more webbing between the toes than coots and phalaropes.
540:
418:
215:
207:
43:
653:
In ducks, webbed feet have also enabled extreme forms of propulsion that are used for
2555:
2549:
2335:
2251:
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2134:
1447:] (in German) (1st ed.). Leipzig-Jena-Berlin: Urania-Verlag. pp. 72–77.
596:
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1043:
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also have a lobed hind toe (1), and gulls, terns and allies have a reduced hind toe.
2400:
2018:
1997:
992:
798:
1439:
Kalbe, Lothar (1983). "Besondere Formen für spezielle
Aufgaben der Wassertiere ".
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styles in bird feet, including birds with all digits joined in webbing, like the
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114:
81:
62:
20:
1323:
Proceedings of the
National Academy of Sciences of the United States of America
1090:
Proceedings of the
National Academy of Sciences of the United States of America
358:. Palmations and lobes enable swimming or help walking on loose ground such as
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2226:
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715:
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362:. The webbed or palmated feet of birds can be categorized into several types:
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139:
127:
58:
2027:
1945:
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1843:
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1682:
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1176:
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1006:
Fish, F.E. (2004). "Structure and
Mechanics of Nonpiscine Control Surfaces".
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Kowalska-Dyrcz, Alina (1990). "Entry: noga ". In Busse, Przemysław (ed.).
1298:
1269:"Morphological Diversity of the Avian Foot Is Related with the Pattern of
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856:
839:
818:
2422:
2345:
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2231:
1918:
Clifton, Glenna T.; Hedrick, Tyson L.; Biewener, Andrew A. (2015-04-15).
1867:"Aquatic burst locomotion by hydroplaning and paddling in common eiders (
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394:
151:
55:
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774:
2350:
1936:
1919:
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1601:
The
Emergence of Whales: Evolutionary Patterns in the Origin of Cetacea
1237:
514:
510:
448:
440:
291:
211:
2048:
National
Audubon Society: The Sibley Guide to Bird Life & Behavior
1920:"Western and Clark's grebes use novel strategies for running on water"
1673:
1502:
Fish, F. E.; Baudinette, R. V.; Frappell, P. B.; Sarre, M. P. (1997).
2308:
968:
617:
588:
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506:
498:
494:
466:
432:
410:
398:
295:
2044:
Elphick, John B.; Dunning, Jack B. Jr.; Sibley, David Allen (2001).
1729:
19:
This article is primarily about non-human animals. For humans, see
1865:
Gough, William T.; Farina, Stacy C.; Fish, Frank E. (2015-06-01).
670:
592:
558:
528:
502:
436:
374:
355:
339:
317:
302:. While turtles with webbed feet are aquatic, most geckos live in
299:
247:
181:
107:
77:
71:
819:"Mechanics, power output and efficiency of the swimming muskrat (
369:: only the anterior digits (2–4) are joined by webbing. Found in
2504:
2372:
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1406:
1404:
580:
544:
532:
406:
402:
386:
382:
378:
370:
343:
335:
326:
270:
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465:: a small web between the anterior digits (2–4). Found in some
2193:
2177:
390:
359:
1153:"Syndactyly: phenotypes, genetics and current classification"
2140:
1751:
Ribak, Gal; Swallow, John G.; Jones, David R. (2010-09-07).
1384:
1382:
1380:
294:
have webbed-footed representatives that include freshwater
459:. Some gannets have brightly colored feet used in display.
1998:"Substrate excavation in the Namibian web-footed gecko,
616:
The stroke of the foot through the water also generates
431:: all four digits (1–4) are joined by webbing. Found in
202:
One pathway implicated in interdigital necrosis is the
2107:
1652:
Stamhuis, Eize J.; Nauwelaerts, Sandra (2005-04-01).
521:
is the only sandpiper having 3 toes (tridactyl foot).
2071:(2nd ed.). New York: W.H. Freeman and Company.
1461:
1422:
1396:
16:
Animal feet with non-pathogenic interdigital webbing
2492:
2431:
2371:
2274:
2192:
2045:
1575:The Beaver: Natural History of a Wetlands Engineer
2002:Andersson 1908, and its ecological significance"
1573:Muller-Schwarze, Dietland; Sun, Lixing (2003).
1577:. Comstock Publishing Associates. p. 12.
2162:
1317:Jaekel, Martin; Wake, David B. (2007-12-18).
8:
1418:
1392:
1996:Russell, A. P.; Bauer, A. M. (1990-12-01).
1552:. Discovery Publishing House. p. 124.
322:Webbing and lobation in a bird's right foot
2169:
2155:
2147:
1508:: Metabolic Effort Associated with Rowing"
1434:
1432:
1430:
1273:Gene Expression in the Developing Autopod"
96:to contrast it from a more hydrofoil-like
2525:Tradeoffs for locomotion in air and water
2090:. Birds. Mechanicsburg: Stackpole Books.
2017:
1935:
1886:
1794:
1776:
1672:
1604:. Springer Science & Business Media.
1360:
1342:
1288:
1184:
1127:
1109:
1060:Life (Loose Leaf): The Science of Biology
838:
726:Tradeoffs for locomotion in air and water
1504:"Energetics of Swimming by the Platypus
61:. This adaptation is primarily found in
25:
736:
2135:Liquid Life Laboratory, Dr. Frank Fish
1457:
1414:
1388:
1312:
1310:
1308:
571:have webbed feet. Most of these have
7:
2113:. pp. 70–75, 140–141, 142–144.
1548:Yadav, P. R.; Khanna, D. R. (2005).
1410:
950:
948:
812:
810:
808:
748:
746:
744:
742:
740:
583:. Some notable examples include the
69:many times across vertebrate taxa.
1924:The Journal of Experimental Biology
1875:The Journal of Experimental Biology
1824:The Journal of Experimental Biology
1661:The Journal of Experimental Biology
1515:The Journal of Experimental Biology
1008:IEEE Journal of Oceanic Engineering
827:The Journal of Experimental Biology
84:has webbed feet, and can swim well.
1598:Thewissen, J. G. M. (1998-10-31).
1462:Elphick, Dunning & Sibley 2001
1423:Elphick, Dunning & Sibley 2001
1397:Elphick, Dunning & Sibley 2001
1157:European Journal of Human Genetics
509:, and some domesticated breeds of
354:and birds with lobed digits, like
14:
551:The palmate foot is most common.
2265:
1625:Lulashnyk, Lorne (2016-12-19).
928:"Why Don't Ducks' Feet Freeze?"
2019:10.1080/03946975.1990.10539462
1:
2052:. New York: Alfred A. Knopf.
142:shape is a solution that has
1778:10.1371/journal.pone.0012565
1230:10.1126/science.272.5262.738
132:countercurrent heat exchange
1820:(Phalacrocorax penicillatus
1151:Malik, Sajid (2017-04-27).
389:, and other aquatic birds (
2572:
2381:Flying and gliding animals
2217:Fin and flipper locomotion
817:Fish, F. E. (1984-05-01).
204:bone morphogenetic protein
54:, present in a variety of
18:
2263:
691:Chiropterotriton magnipes
233:Chiropterotriton magnipes
2109:. New Haven and London:
2086:Kochan, Jack B. (1994).
1506:Ornithorhynchus anatinus
1419:Proctor & Lynch 1993
1393:Proctor & Lynch 1993
543:and some palmate-footed
50:(webbings) that aids in
2067:Gill, Frank B. (2001).
1836:10.1242/jeb.203.24.3727
1527:10.1242/jeb.200.20.2647
1344:10.1073/pnas.0710216105
1111:10.1073/pnas.0604934103
1028:10.1109/joe.2004.833213
894:Gill, Frank B. (1994).
479:semipalmated sandpipers
265:Of the three orders of
152:non-piscine vertebrates
2520:Terrestrial locomotion
2464:Evolution of cetaceans
2459:Origin of avian flight
2444:Evolution of tetrapods
1628:Understanding Surfaces
1290:10.1006/dbio.1997.8843
678:Terrestrial locomotion
669:. Western and Clark's
564:
323:
273:(frogs and toads) and
257:
187:
119:
85:
48:interdigital membranes
35:
2535:Undulatory locomotion
2484:Homologous structures
2111:Yale University Press
1445:Wildlife by the Water
1277:Developmental Biology
840:10.1242/jeb.110.1.183
562:
505:(only two toes), all
321:
251:
185:
111:
75:
29:
2479:Analogous structures
2474:Convergent evolution
1881:(Pt 11): 1632–1638.
1869:Somateria mollissima
1830:(Pt 24): 3727–3731.
1718:Journal of Mammalogy
1169:10.1038/ejhg.2012.14
932:Ask a Naturalist.com
711:Interdigital webbing
575:, as opposed to the
573:interdigital webbing
348:webbing and lobation
254:convergent evolution
245:a complete listing.
144:convergently evolved
124:interdigital webbing
67:convergently evolved
2530:Rotating locomotion
2469:Comparative anatomy
2000:Palmatogecko rangei
1978:on February 7, 2010
1972:National Geographic
1968:"Web-Footed Geckos"
1930:(Pt 8): 1235–1243.
1769:2010PLoSO...512565R
1667:(Pt 8): 1445–1451.
1335:2007PNAS..10420437J
1329:(51): 20437–20442.
1222:1996Sci...272..738Z
1102:2006PNAS..10315103W
1096:(41): 15103–15107.
1020:2004IJOE...29..605F
775:10.1038/nature01695
767:2003Natur.424...65J
608:Swimming propulsion
112:The webbed foot of
2449:Evolution of birds
2202:Aquatic locomotion
1937:10.1242/jeb.118745
1888:10.1242/jeb.114140
1550:Biology of Mammals
1441:Tierwelt am Wasser
821:Ondatra zibethicus
721:Bird feet and legs
634:aquatic locomotion
626:flipper locomotion
565:
491:greater yellowlegs
471:Eurasian dotterels
352:Brandt's cormorant
324:
258:
188:
154:may be paddles or
120:
86:
52:aquatic locomotion
36:
2543:
2542:
2500:Animal locomotion
2439:Evolution of fish
2319:facultative biped
2120:978-0-300-07619-6
2097:978-0-8117-2515-6
2078:978-0-7167-2415-5
2059:978-0-679-45123-5
1674:10.1242/jeb.01530
1488:978-83-214-0563-6
1216:(5262): 738–741.
963:(6804): 582–583.
659:courtship display
567:Some semiaquatic
487:upland sandpipers
226:gene expression.
218:and reduction of
208:signaling pathway
65:species, and has
42:is a specialized
30:Webbed feet of a
2563:
2510:Robot locomotion
2284:Limb development
2269:
2242:Lobe-finned fish
2171:
2164:
2157:
2148:
2124:
2101:
2082:
2063:
2051:
2032:
2031:
2021:
2006:Tropical Zoology
1993:
1987:
1986:
1984:
1983:
1974:. Archived from
1964:
1958:
1957:
1939:
1915:
1909:
1908:
1890:
1862:
1856:
1855:
1815:
1809:
1808:
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1742:
1741:
1714:Lutra canadensis
1709:
1703:
1702:
1676:
1658:
1649:
1643:
1642:
1631:. FriesenPress.
1622:
1616:
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1589:
1588:
1570:
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1563:
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1492:
1470:
1464:
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1408:
1399:
1386:
1375:
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1364:
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1292:
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1257:
1205:
1199:
1198:
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1142:
1141:
1131:
1113:
1081:
1075:
1074:
1054:
1048:
1047:
1003:
997:
996:
969:10.1038/35036689
952:
943:
942:
940:
939:
924:
918:
917:
891:
885:
884:
882:
881:
871:"Webbed Wonders"
867:
861:
860:
842:
814:
803:
802:
750:
667:sexual selection
655:escape behaviors
483:stilt sandpipers
2571:
2570:
2566:
2565:
2564:
2562:
2561:
2560:
2546:
2545:
2544:
2539:
2488:
2454:Origin of birds
2427:
2367:
2289:Limb morphology
2270:
2261:
2247:Ray-finned fish
2212:Fish locomotion
2188:
2175:
2131:
2121:
2104:
2098:
2088:Feet & Legs
2085:
2079:
2066:
2060:
2043:
2040:
2035:
1995:
1994:
1990:
1981:
1979:
1966:
1965:
1961:
1917:
1916:
1912:
1864:
1863:
1859:
1817:
1816:
1812:
1750:
1749:
1745:
1730:10.2307/1382481
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1597:
1596:
1592:
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1572:
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1567:
1560:
1547:
1546:
1542:
1521:(20): 2647–52.
1510:
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1500:
1496:
1489:
1472:
1471:
1467:
1456:
1452:
1438:
1437:
1428:
1409:
1402:
1387:
1378:
1316:
1315:
1306:
1266:
1265:
1261:
1207:
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1150:
1149:
1145:
1083:
1082:
1078:
1071:
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1005:
1004:
1000:
954:
953:
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937:
935:
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925:
921:
906:
893:
892:
888:
879:
877:
869:
868:
864:
816:
815:
806:
761:(6944): 65–68.
752:
751:
738:
734:
702:
680:
651:
649:Other behaviors
610:
605:
557:
316:
289:
280:Rana temporaria
263:
242:
169:
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115:Rana temporaria
106:
24:
17:
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2426:
2425:
2420:
2418:Pterosaur wing
2415:
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2403:
2398:
2388:
2383:
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2259:
2254:
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2207:Cephalopod fin
2204:
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2196:
2190:
2189:
2176:
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2173:
2166:
2159:
2151:
2145:
2144:
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2129:External links
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2012:(2): 197–207.
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1724:(4): 989–997.
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1063:. Macmillan.
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597:water opossum
594:
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582:
578:
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563:Platypus foot
561:
554:
552:
546:
542:
538:
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74:
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2005:
1999:
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1980:. Retrieved
1976:the original
1971:
1962:
1927:
1923:
1913:
1878:
1874:
1868:
1860:
1827:
1823:
1819:
1813:
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1283:(1): 33–41.
1280:
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1209:
1203:
1160:
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1089:
1079:
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1011:
1007:
1001:
960:
956:
936:. Retrieved
934:. 2010-04-22
931:
922:
895:
889:
878:. Retrieved
874:
865:
830:
826:
820:
758:
754:
689:
683:
681:
652:
638:Diving ducks
623:
615:
611:
566:
550:
524:
462:
453:frigatebirds
428:
423:Diving ducks
366:
325:
290:
278:
264:
243:
231:
228:
223:
219:
201:
189:
170:
149:
121:
113:
93:
87:
39:
37:
2413:Insect wing
2363:Webbed foot
2304:unguligrade
2299:plantigrade
2294:digitigrade
2069:Ornithology
1458:Kochan 1994
1415:Kochan 1994
1389:Kochan 1994
896:Ornithology
833:: 183–201.
706:Webbed toes
630:terrestrial
463:Semipalmate
457:tropicbirds
429:Totipalmate
415:shearwaters
304:terrestrial
190:In humans,
167:Development
82:pied avocet
63:semiaquatic
59:vertebrates
40:webbed foot
21:Webbed toes
2341:Cephalopod
2257:Pelvic fin
2227:Dorsal fin
2222:Caudal fin
1982:2017-04-28
1822:Brandt)".
938:2017-04-18
880:2017-04-17
732:References
716:Syndactyly
663:hull speed
643:hull speed
595:, and the
577:syndactyly
537:phalaropes
519:sanderling
475:sandpipers
445:cormorants
267:amphibians
261:Amphibians
196:phenotypic
192:syndactyly
156:hydrofoils
140:delta wing
128:syndactyly
104:Morphology
2432:Evolution
2391:Bird wing
2336:Arthropod
2329:quadruped
2028:0394-6975
1946:1477-9145
1897:1477-9145
1844:0022-0949
1787:1932-6203
1683:0022-0949
1411:Gill 2001
1353:0027-8424
1177:1018-4813
1120:0027-8424
1036:0364-9059
977:0028-0836
914:959809850
849:0022-0949
783:1476-4687
685:P. rangei
579:found in
395:flamingos
332:waterfowl
240:Phylogeny
214:-induced
177:Apoptosis
162:Evolution
32:mute swan
2550:Category
2423:Wingspan
2406:feathers
2401:skeleton
2386:Bat wing
2346:Tetrapod
2232:Fish fin
1954:25911734
1905:25852065
1852:11076736
1805:20830286
1757:PLOS ONE
1699:34494254
1691:15802668
1371:18077320
1254:27174863
1195:22333904
1138:17015842
1044:28802495
985:11034197
791:12840759
700:See also
618:vortices
603:Function
585:platypus
541:finfoots
515:lapwings
449:anhingas
441:pelicans
419:skimmers
308:arboreal
292:Reptiles
287:Reptiles
173:apoptose
90:apoptose
56:tetrapod
2493:Related
2351:dactyly
2237:Flipper
2038:Sources
1796:2935360
1765:Bibcode
1738:1382481
1535:9359371
1362:2154449
1331:Bibcode
1299:9527879
1246:8614838
1238:2889452
1218:Bibcode
1210:Science
1186:3400728
1129:1622783
1098:Bibcode
1016:Bibcode
993:4302176
857:6379093
799:4429458
763:Bibcode
569:mammals
555:Mammals
511:chicken
467:plovers
437:boobies
433:gannets
411:petrels
403:jaegers
399:fulmars
367:Palmate
296:turtles
275:Urodela
98:flipper
2515:Samara
2324:triped
2309:uniped
2117:
2094:
2075:
2056:
2026:
1952:
1944:
1903:
1895:
1850:
1842:
1803:
1793:
1785:
1736:
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1681:
1635:
1608:
1581:
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1485:
1369:
1359:
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1252:
1244:
1236:
1193:
1183:
1175:
1136:
1126:
1118:
1067:
1042:
1034:
991:
983:
975:
957:Nature
912:
902:
855:
847:
797:
789:
781:
755:Nature
671:grebes
591:, the
589:beaver
587:, the
529:grebes
525:Lobate
507:grouse
503:herons
499:avocet
495:willet
473:) and
455:, and
356:grebes
342:, and
300:geckos
206:(BMP)
94:paddle
80:, the
78:waders
2373:Wings
2358:Digit
2314:biped
2276:Limbs
2186:wings
2182:limbs
1734:JSTOR
1695:S2CID
1657:(PDF)
1511:(PDF)
1479:Birds
1477:[
1475:Ptaki
1443:[
1250:S2CID
1234:JSTOR
1040:S2CID
989:S2CID
795:S2CID
593:otter
581:birds
545:ducks
533:coots
407:loons
387:terns
383:gulls
379:swans
375:geese
371:ducks
344:swans
340:geese
336:Ducks
327:Birds
314:Birds
271:Anura
224:msx-2
220:msx-1
136:birds
46:with
2556:Foot
2505:Gait
2396:keel
2194:Fins
2184:and
2178:Fins
2115:ISBN
2092:ISBN
2073:ISBN
2054:ISBN
2024:ISSN
1950:PMID
1942:ISSN
1901:PMID
1893:ISSN
1848:PMID
1840:ISSN
1801:PMID
1783:ISSN
1716:)".
1687:PMID
1679:ISSN
1633:ISBN
1606:ISBN
1579:ISBN
1554:ISBN
1531:PMID
1483:ISBN
1367:PMID
1349:ISSN
1295:PMID
1242:PMID
1191:PMID
1173:ISSN
1134:PMID
1116:ISSN
1065:ISBN
1032:ISSN
981:PMID
973:ISSN
910:OCLC
900:ISBN
853:PMID
845:ISSN
787:PMID
779:ISSN
657:and
632:and
493:and
435:and
417:and
391:auks
385:and
377:and
306:and
298:and
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