Common Name: round-tailed muskrat, Florida water rat
This large aquatic rodent is a relative of voles and lemmings.
Although today restricted to Florida and southern Georgia, in the Pleistocene the species lived as far north as South Carolina and possibly West Virginia.
- Middle Pleistocene to Holocene Epochs; late Irvingtonian to present land mammal age
- About 600,000 years ago to present
Scientific Name and Classification
Neofiber alleni True, 1884
Source of Species Name: This species was named after Professor J. A. Allen, a prominent zoologist and friend of Frederick W. True, curator of mammology at the then U.S. National Museum, who originally named this species.
Classification: Mammalia, Eutheria, Euarchontoglires, Rodentia, Myomorpha, Muroidea, Cricetidae, Avricolinae, Neofibrini
Alternate Scientific Names: none
Overall Geographic Range
Currently, the round-tailed muskrat is found in much of peninsular Florida and in southeastern Georgia (Birkenholz, 1972). Fossils of Neofiber alleni have been identified from many localities in Florida, as well as from the Ladds Cave, northwestern Georgia (Frazier, 1977), the Isle of Hope Site in coastal Georgia (Hulbert and Pratt, 1998), two localities in coastal South Carolina (Saunders, 2002), and possibly Trout Cave in West Virginia (Grady and Garton, 2000). The type locality of this species is Georgiana, Brevard County, Florida (True, 1884b).
Florida Fossil Occurrences
- Alachua County—Arredondo 1A; Arredondo 2A; Haile 2A; Haile 13A; Haile 14A; Haile 14B; Hornsby Springs; Surprise Cave
- Brevard County—Melbourne
- Citrus County—Lecanto 2A; Sabertooth Cave
- Columbia County—Ichetucknee River (including 2B and 3B sites); Santa Fe River 2
- Dade County—Cutler Hammock Site; Monkey Jungle Hammock 2; Nichols Hammock
- Hardee County—Riverview
- Hillsborough County—Leisey Shell Pit 2
- Indian River County—Vero Canal Site
- Levy County—Devil’s Den; Waccasassa River (general); Waccasassa River 2; Waccasassa River 2B; Waccasassa River 4; Waccasassa River 5A; Waccasassa River 7A
- Manatee County—Bradenton 51st Street
- Marion County—Eureka Lock; Oklawaha River 2; Orange Lake 2A; Rainbow River; Reddick 1; Reddick 1A; Reddick 1B; Reddick 1C; Withlacoochee River 4A; Withlacoochee River 5E
- Palm Beach County—West Palm Beach
- Pinellas County—Catalina Gardens; Maximo Moorings; Millenium Park; Seminole Field; St. Petersburg; Tierra Verde Island; Zeta Pond Site
- Polk County— Palmetto Mine Pleistocene Bog Site
- Putnam County— St. Johns Lock
- Sarasota County— Warm Mineral Springs
- Seminole County—Wekiwa River 1
- St. Johns County— Wilson Quarry
- Sumter County—Coleman 2A; Coleman 3C
- Taylor County—Aucilla River 3E; Aucilla River 3J
- Volusia County—Daytona Beach Bone Bed
- Wakulla County—St. Marks River
Rodentia is an order of mammals comprising a large diversity of animals such as rats, mice, squirrels, capybaras, porcupines, and beavers. Neofiber alleni is an extant species of rodent commonly known as the round-tailed muskrat or the Florida water rat. Generally, the Florida water rat is a brown-furred, semi-aquatic inhabitant of wet enivornments rich in vegetation such as swamps and marshes, where it feeds on aquatic grasses. Unlike the muskrat Ondatra zibethicus, which has a flattened tail, the Florida water rat has a tail that is round in cross-section. It is approximately 26 cm (10.2 in) to 38 cm (15.0 in) long from the tip of the nose to the tail, and is intermediate in size between the muskrat and the meadow vole, Microtus pennsylvnicus (Meade, 1952; Birkenholz, 1972; Frazier, 1977). More information about the extant species can be found here.
Neofiber alleni is closely related to Ondatra zibethicus, and the two species are considered to be more closely related to each other than to any other living species. They belong to a subfamily of rodents known as Avricolinae which comprises of some 30 genera and 150 species commonly called voles, lemmings, and muskrats (Robovsky et al., 2007).
The genus Neofiber first appears in the fossil record in the middle Pleistocene of North America in the form of the extinct Leonard’s muskrat, Neofiber leonardi (Hibbard, 1943; Frazier, 1977). Neofiber leonardi is known from fossils in Texas, the Great Plains, Virginia, and Florida (Frazier, 1977; Kasper, 1992). The oldest fossils of Neofiber alleni are from the late Irvingtonian Coleman 2A locality in Sumter County, Florida (Matin, 1974). Based on the similarity and overlapping degrees of variation in the morphology of the teeth through time, it is thought that Neofiber alleni evolved from Neofiber leonardi sometime in the middle Pleistocene (Frazier, 1977; Kasper, 1992). Currently, Neofiber is restricted to Florida and southeastern Georgia, possibly due to their reliance on warm aquatic habitats (Frazier, 1977). But its range was much wider in the Pleistocene.
Like other cricetid rodents, Neofiber alleni does not have any premolar teeth in its upper and lower dentition. Like other avricoline rodents, Neofiber alleni has molar teeth that are characterized by an occlusal surface that looks like a series of triangles (Hulbert, 2001). The skull of Neofiber alleni is similar to that of the common muskrat, Ondatra zibethicus, but is smaller (Frazier, 1977). Neofiber alleni may be differentiated from Neofiber leonardi on the basis of the morphology of their molar teeth. Neofiber leonardi have molars with relatively antero-posteriorly compressed triangular occluding surfaces and antero-posteriorly wider reentrant angles. Furthermore, the anteroexternal column on the lower third molar is better defined in Neofiber leonardi compared to Neofiber alleni.
- Original Author: Arianna Harrington
- Original Completion Date: May 15, 2015
- Editor: Richard C. Hulbert Jr. and Natali Valdes
- Last Updated On: May 29, 2015
Birkenholz, D.E. 1972. Neofiber alleni. Mammalian Species 15:1-4.
Frazier, M.K. 1977. New records of Neofiber leonardi (Rodentia: Cricetidae) and the Paleoecology of the genus. Journal of Mammology 58(3):368-373.
Grady, F., and E. R. Garton. 2000. Paleontology and historic field trip of the John Guilday Cave Preserve (Trout Rock). Bulletin – West Virginia Speleological Survey 14:241-244.
Hulbert Jr., R. C. 2001. The Fossil Vertebrates of Florida. University Press of Florida: Gainesville, FL. Pp. 232-236.
Hulbert Jr., R. C. , and A. E. Pratt. 1998. Pleistocene (Rancholabrean) vertebrate faunas from coastal Georgia. Journal of Vertebrate Paleontology 18(2):412-429.
Kasper, S. 1992. Mammals from the Late Pleistocene Carrol Creek Local Fauna, Donley Co., Texas. The Southwestrn Naturalist 37(1):54-64.
Meade, G.E. 1952. The water rat in the Pleistocene of Texas. Journal of Mammology 33(1):87-89.
Robovsky, J., Ricankova, V., Zrzavy, J. 2008. Phylogeny of Arvicolinae (Mammalia, Cricetidae): utility of morphological and molecular data sets in a recently radiating clade. Zoologica Scripta 37(6):571-590. [Download PDF]
True, F.W. 1884a. A muskrat with a round tail. Science 75(4):34.
True, F.W. 1884 b. A new muskrat, Neofiber alleni, from Florida. Proceedings of the United States National Museum 7:170-172.
This material is based upon work supported by the National Science Foundation under Grant Number CSBR 1203222, Jonathan Bloch, Principal Investigator. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.