Membranes of skin between fingers and toes of animals
Interdigital webbing refers to the presence of skin membranes between the digits. Normally, in mammals, webbing is present in the embryo but resorbed later in development, but in various mammal species, it occasionally persists in adulthood.[1] In humans, it can be found in those suffering from LEOPARD syndrome and from Aarskog–Scott syndrome.[2]
Interdigital webbing is not to be confused with syndactyly, which is a fusing of digits and occurs rarely in humans. Syndactyly specifically affecting feet occurs in birds (such as ducks), amphibians (such as frogs), and mammals (such as the kangaroo).
Among shrews, the members of the genera Chimarrogale of southeastern Asia and Neomys of western Eurasia have interdigital webbing, as does the American water shrew (Sorex palustris) of North America, but it is more well-developed in Nectogale elegans of montane Asia. Webbing is also present in the Pyrenean desman (Galemys pyrenaicus).[3]
All otters have interdigital webbing, in the fore or hind limbs or both, to aid in aquatic propulsion. In sea otters, the webbing is covered with hair, at a density of 3300 hairs per square centimeter.[15]
Whales
Pits present on the sides of fossil proximal phalanges of pakicetids, ancestral whales, suggest that these animals had interdigital webbing,[16] a development hypothesized to lead to the fluke,[17] spurred by FGF8, a fibroblast growth factor.[18]
Braun, J.K. and Díaz, M.M. 1999. Key to the native mammals of Catamarca Province, Argentina. Occasional papers of the Oklahoma Museum of Natural History 4:1–16.
Cooper, L.N., and J.G.M. Thewissen. 2009 The role of FGF-8 in the origin of interdigital webbing in cetaceans. Presentation, Society of Integrative and Comparative Biology, Boston, Massachusetts.
Harding, Larisa E.; Smith, Felisa A. (2009). "Mustela or Vison? Evidence for the taxonomic status of the American mink and a distinct biogeographic radiation of American weasels". Molecular Phylogenetics and Evolution. 52 (3): 632–42. doi:10.1016/j.ympev.2009.05.036. PMID19501660.
Kerbis Peterhans, J.C.; Patterson, B.D. (1995). "The Ethiopian water mouse Nilopegamys Osgood, with comments on the evolution of semi-aquatic adaptations in African Muridae". Zoological Journal of the Linnean Society. 113 (3): 329–349. doi:10.1111/j.1096-3642.1995.tb00937.x.
Rodhocetus is an extinct genus of protocetid early whale known from the Lutetian of Pakistan. The best-known protocetid, Rodhocetus is known from two partial skeletons that taken together give a complete image of an Eocene whale that had short limbs with long hands and feet that were probably webbed and a sacrum that was immobile with four partially fused sacral vertebrae. It is one of several extinct whale genera that possess land mammal characteristics, thus demonstrating the evolutionary transition from land to sea.
A flipper is a broad, flattened limb adapted for aquatic locomotion. It refers to the fully webbed, swimming appendages of aquatic vertebrates that are not fish.
Oryzomys is a genus of semiaquatic rodents in the tribe Oryzomyini living in southern North America and far northern South America. It includes eight species, two of which—the marsh rice rat (O. palustris) of the United States and O. couesi of Mexico and Central America—are widespread; the six others have more restricted distributions. The species have had eventful taxonomic histories, and most species were at one time included in the marsh rice rat; additional species may be recognized in the future. The name Oryzomys was established in 1857 by Spencer Fullerton Baird for the marsh rice rat and was soon applied to over a hundred species of American rodents. Subsequently, the genus gradually became more narrowly defined until its current contents were established in 2006, when ten new genera were established for species previously placed in Oryzomys.
Cerradomys marinhus, also known as Marinho's rice rat, is a rodent species from South America. It is found in Minas Gerais, Brazil. It was formerly known as Oryzomys marinhus, but was transferred to the new genus Cerradomys in 2006.
Hylaeamys perenensis, formerly Oryzomys perenensis, also known as the western Amazonian oryzomys, is an oryzomyine rodent of the family Cricetidae.
Lundomys molitor, also known as Lund's amphibious rat or the greater marsh rat, is a semiaquatic rat species from southeastern South America.
Pseudoryzomys simplex, also known as the Brazilian false rice rat or false oryzomys, is a species of rodent in the family Cricetidae from south-central South America. It is found in lowland palm savanna and thorn scrub habitats. It is a medium-sized species, weighing about 50 grams (1.8 oz), with gray–brown fur, long and narrow hindfeet, and a tail that is about as long as the head and body. The IUCN has assessed its conservation status as being of least concern, although almost nothing is known about its diet or reproduction.
The Ethiopian amphibious rat, also known as the Ethiopian water mouse, is an insectivorous and semiaquatic species of rodent in the monotypic genus Nilopegamys of the family Muridae. There has only been one known specimen. It was found along the Lesser Abay River near its source at an altitude of 2600 m in the highlands of northwestern Ethiopia in 1928. N. plumbeus is considered to be the most aquatically adapted African murid; its unusually large brain is thought to be one consequence of this lifestyle. The species is considered to be critically endangered or possibly extinct, since its habitat has been severely damaged by overgrazing and monoculture.
Nephelomys albigularis, also known as the white-throated oryzomys or Tomes's rice rat, is a species of rodent in the genus Nephelomys of family Cricetidae. Described in 1860, it was the first Nephelomys species to be discovered. It was originally described in the defunct genus Hesperomys as Hesperomys albigularis and considered related to the much smaller H. longicaudatus. By 1894, it was placed in Oryzomys, as Oryzomys albigularis, and associated with what is now Nephelomys meridensis. In the early 1960s, the scope of the species was considerably expanded to include most of the species that are now in Nephelomys, as well as a single name, boliviae, that is currently a synonym of Euryoryzomys nitidus. From 1976 on, several of these were reinstated as separate species.
Oryzomys dimidiatus, also known as the Nicaraguan oryzomys, Thomas's rice rat, or the Nicaraguan rice rat, is a rodent in the family Cricetidae. It is known from only three specimens, all collected in southeastern Nicaragua since 1904. Placed in Nectomys upon its discovery, it was later classified in its own subgenus of Oryzomys and finally recognized as closely related to other species now placed in Oryzomys, including the marsh rice rat and Coues' rice rat, which occurs in the same region.
Oryzomys gorgasi, also known as Gorgas's oryzomys or Gorgas's rice rat, is a rodent in the genus Oryzomys of family Cricetidae. First recorded in 1967, it is known from only a few localities, including a freshwater swamp in the lowlands of northwestern Colombia and a mangrove islet in northwestern Venezuela. It reportedly formerly occurred on the island of Curaçao off northwestern Venezuela; this extinct population has been described as a separate species, Oryzomys curasoae, but does not differ morphologically from mainland populations.
Oryzomyini is a tribe of rodents in the subfamily Sigmodontinae of the family Cricetidae. It includes about 120 species in about thirty genera, distributed from the eastern United States to the southernmost parts of South America, including many offshore islands. It is part of the clade Oryzomyalia, which includes most of the South American Sigmodontinae.
Noronhomys vespuccii, also known as Vespucci's rodent, is an extinct rat species from the islands of Fernando de Noronha off northeastern Brazil. Italian explorer Amerigo Vespucci may have seen it on a visit to Fernando de Noronha in 1503, but it subsequently became extinct, perhaps because of the exotic rats and mice introduced by the first explorers of the island. Numerous but fragmentary fossil remains of the animal, of uncertain but probably Holocene age, were discovered in 1973 and described in 1999.
Cerradomys maracajuensis, also known as the Maracaju oryzomys, is a rodent species from South America. It is terrestrial and is found in gallery forests in Bolivia, Paraguay and nearby Brazil and Peru. It was first discovered near the Brazilian city of Maracaju.
Carletonomys cailoi is an extinct rodent from the Pleistocene (Ensenadan) of Buenos Aires Province, Argentina. Although known only from a single maxilla with the first molar, its features are so distinctive that it is placed in its own genus, Carletonomys. Discovered in 1998 and formally described in 2008, it is part of a well-defined group of oryzomyine rodents that also includes Holochilus, Noronhomys, Lundomys, and Pseudoryzomys. This group is characterized by progressive semiaquatic specializations and a reduction in the complexity of molar morphology.
Nephelomys is a genus of South American oryzomyine rodents found in the Andes from Bolivia to Venezuela, with a westward extension into the mountains of Costa Rica. Its generic name is derived from the Ancient Greek word nephelê "mist", referring to the cloud forest habitat of the members of the genus.
Nephelomys moerex is a species of rodent in the genus Nephelomys of family Cricetidae. The type locality is at Mindo in western Ecuador, where it has been recorded together with three other rodents of the oryzomyine group, Sigmodontomys aphrastus, Mindomys hammondi, and Handleyomys alfaroi, as well as three opossums, Chironectes minimus and unidentified species of Didelphis and Marmosa. Mindo is a "tiny agricultural community" located at 0°02'S, 78°48'W and 1,264 metres (4,150 ft) above sea level. It was originally described by Oldfield Thomas as a subspecies of Oryzomys albigularis. It remained synonymized under this species until it was recognized as a separate species when the genus Nephelomys was established for Oryzomys albigularis and related species in 2006.
In anatomy, posterolateral palatal pits are gaps at the sides of the back of the bony palate, near the last molars. Posterolateral palatal pits are present, in various degrees of development, in several members of the rodent family Cricetidae. Many members of the family lack them or have only simple pits, but Arvicolinae and Oryzomyini have more highly developed posterolateral palatal pits. Posterolateral palatal pits are also present in some other rodents, including Glis, Jaculus, Hystrix, Abrocoma, Ctenomys, Chinchilla, and Lagidium.
In rodent anatomy, the zygomatic plate is a bony plate derived from the flattened front part of the zygomatic arch (cheekbone). At the back, it connects to the front (maxillary) root of the zygomatic arch, and at the top it is connected to the rest of the skull via the antorbital bridge. It is part of the maxillary bone, or upper jaw, which also contains the upper cheekteeth. Primitively, rodents have a nearly horizontal zygomatic plate. In association with specializations in zygomasseteric system, several distinct morphologies have developed across the order.
Natatory fringes are rows of stiff hairs that occur along the margins of the hindfeet in some rodents. They occur along the plantar margins and in some cases also between the toes. Among sigmodontines, a mostly South American groups, natatory fringes are present in Ichthyomyini and some Oryzomyini. Among ichthyomyines, the fringes are poorly developed in Neusticomys but well-developed in other genera, and in Rheomys mexicanus the hairs of the fringes may exceed 3 millimetres (0.12 in) in length. Amphinectomys, Holochilus, Lundomys, and Nectomys are the only oryzomyines with natatory fringes, but have them only weakly developed; one study also records them in Oryzomys. In oryzomyines, the fringes are an adaptation for a semiaquatic lifestyle that appeared convergently in the Holochilus-Lundomys and Nectomys-Amphinectomys lineages. The term was introduced in 1993 by Voss and Carleton in describing Lundomys.
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