Natatory fringes are rows of stiff hairs that occur along the margins of the hindfeet in some

rodent Rodents (from Latin , 'to gnaw') are mammals of the Order (biology), order Rodentia ( ), which are characterized by a single pair of continuously growing incisors in each of the upper and Mandible, lower jaws. About 40% of all mammal specie ...

s. They occur along the

plantar Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position provi ...

margins and in some cases also between the toes. Among sigmodontines, a mostly South American groups, natatory fringes are present in

Ichthyomyini Ichthyomyini is a tribe of New World rats and mice in the subfamily Sigmodontinae. The species within this tribe share the characteristics of all being carnivorous semiaquatic rodents. The following genera are recognized in this tribe: * Subtribe ...

and some

Oryzomyini Oryzomyini is a tribe of rodents in the subfamily Sigmodontinae of the family Cricetidae. It includes about 120 species in about thirty genera,Weksler et al., 2006, table 1 distributed from the eastern United States to the southernmost parts of S ...

.Weksler, 2006, p. 25 Among ichthyomyines, the fringes are poorly developed in ''

Neusticomys ''Neusticomys'' is a genus of semiaquatic, animalivorous South American rodents in the family Cricetidae. The term ''Neusticomys'' derives from the two ancient greek words (), meaning "able to swim", and (), meaning "mouse, rat". ''N. monticol ...

'' but well-developed in other genera, and in ''

Rheomys mexicanus The Mexican water mouse, Mexican fishing mouse or Goodwin's water mouse (''Rheomys mexicanus''), is a species of semiaquatic rodent in the family Cricetidae. It has a restricted range in the state of Oaxaca in southern Mexico, Threatened by def ...

'' the hairs of the fringes may exceed in length. ''

Amphinectomys ''Amphinectomys savamis'', also known as the Ucayali water ratMusser and Carleton, 2005 or amphibious rat,Duff and Lawson, 2004 is a rodent from the Peruvian Amazon. It is placed as the only member of genus ''Amphinectomys'' in the tribe Oryzomyi ...

'', ''

Holochilus ''Holochilus'' is a genus of semiaquatic rodents in the tribe Oryzomyini of family Cricetidae,* sometimes called marsh rats. It contains five living species, '' H. brasiliensis'', '' H. chacarius'', '' H. nanus'', '' H. oxe'', and '' H. sciureus ...

'', ''

Lundomys ''Lundomys molitor'', also known as Lund's amphibious ratMusser and Carleton, 2005, p. 1124 or the greater marsh rat, is a semiaquatic rat species from southeastern South America. Its distribution is now restricted to Uruguay and nearby Ri ...

'', and ''

Nectomys ''Nectomys'' is a genus of rodent in the tribe Oryzomyini of family Cricetidae. Musser and Carleton, 2005. It is closely related to '' Amphinectomys'' and was formerly considered congeneric with '' Sigmodontomys''. It consists of five species, wh ...

'' are the only oryzomyines with natatory fringes, but have them only weakly developed; one study also records them in ''

Oryzomys ''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 ...

''. In oryzomyines, the fringes are an adaptation for a

semiaquatic In biology, being semi-aquatic refers to various macroorganisms that live regularly in both aquatic and terrestrial environments. When referring to animals, the term describes those that actively spend part of their daily time in water (in ...

lifestyle that appeared convergently in the ''Holochilus-Lundomys'' and ''Nectomys-Amphinectomys'' lineages. The term was introduced in 1993 by Voss and Carleton in describing ''

''.Voss and Carleton, 1993, p. 13

References

Literature cited

*Sánchez H., J., Ochoa G., J. and Voss, R.S. 2001
Rediscovery of ''Oryzomys gorgasi'' (Rodentia: Muridae) with notes on taxonomy and natural history
{dead link, date=February 2018 , bot=InternetArchiveBot , fix-attempted=yes (subscription required). ''Mammalia'' 65:205–214. *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. *Voss, R.S. and Carleton, M.D. 1993
A new genus for ''Hesperomys molitor'' Winge and ''Holochilus magnus'' Hershkovitz (Mammalia, Muridae) with an analysis of its phylogenetic relationships
''American Museum Novitates'' 3085:1–39. *Weksler, M. 2006
Phylogenetic relationships of oryzomyine rodents (Muroidea: Sigmodontinae): separate and combined analyses of morphological and molecular data
''Bulletin of the American Museum of Natural History'' 296:1–149. Rodent anatomy