Ungual tuft

In mammals, ungual tufts are tufts of hairs at the base of claws of the forefeet and hindfeet. Their presence has been used as a character in cladistic studies of the Cricetidae, a large family of rodents.
Rice rats.
Members of the tribe Oryzomyini ("rice rats"), in the Cricetidae subfamily Sigmodontinae, normally have ungual tufts, but they may be reduced or absent in semiaquatic species (i.e. those adapted to life in the water). "Lundomys molitor", "Nectomys apicalis", the marsh rice rat ("Oryzomys palustris"), and species of "Holochilus" lack ungual tufts on their forefeet. On the hindfeet, most species have well-developed ungual tufts only on the second to fifth toes, but "Sooretamys angouya" and "Eremoryzomys polius" also have thick tufts on the first toe. "Pseudoryzomys simplex", "Mindomys hammondi", "Nectomys squamipes", "Sigmodontomys alfari", "Oryzomys couesi", the marsh rice rat, and species of "Melanomys" have sparse ungual tufts only, and "Lundomys molitor", "Nectomys apicalis", "Sigmodontomys aphrastus", and species of "Holochilus" have very reduced tufts or lack them entirely.
Other examples.
Among other South American cricetids, "Abrothrix lanosus" has white ungual tufts that are shorter than the claws. "Akodon paranaensis" has long ungual tufts. "Calomys cerqueirai" has silvery tufts on the second through fifth digits of the forefeet and all digits of the hindfeet. "Abrawayaomys" has long, dense ungual tufts. The Tylomyinae are characterized by the presence of ungual tufts on their hindfeet.
White ungual tufts are also present in the Philippine murine genus "Batomys". "B. hamiguitan" and "B. russatus" have short tips, not extending to the tips of the claws, but those of "B. granti" and "B. salomonseni" have tufts longer than the claws. The Malagasy "Monticolomys" has long ungual tufts, extending beyond the claws, whereas the related "Macrotarsomys" has shorter tufts. The Brazilian spiny rat "Phyllomys sulinus" has long, light gray ungual tufts.
The tenrec "Microgale jobihely" has long, dark brown ungual tufts. The opossum "Monodelphis handleyi" has short ungual tufts.